Vitamins C and E and beta carotene supplementation and cancer risk: a randomized controlled trial

Association between dietary vitamin C intake/blood level and risk of digestive system cancer: a systematic review and meta-analysis of prospective studies

Experimental studies have shown that vitamin C has anti-cancer effects, but previous meta-analyses have indicated that the role of vitamin C in digestive system cancers (DSCs) is controversial. In this study, a systematic review and meta-analysis of the relationship between dietary intake/plasma concentration of vitamin C and the risk of DSC was conducted, evaluating 32 prospective studies with 1 664 498 participants. Dose-response and subgroup analyses were also performed. Systematic literature searches were performed in PubMed, EMBASE and Web of Science databases until 9th September 2023. Vitamin C intake significantly reduced DSCs risk (RR = 0.88, 95% confidence interval (CI) 0.83 to 0.93). The subgroup analyses showed the risks of oral, pharyngeal, and esophageal (OPE) cancers (0.81, 0.72 to 0.93), gastric cancer (0.81, 0.68 to 0.95), and colorectal cancer (0.89, 0.82 to 0.98) were negatively correlated with vitamin C intake, and the effect of vitamin C was different between colon cancer (0.87, 0.77 to 0.97) and rectal cancer (1.00, 0.84 to 1.19). However, plasma vitamin C concentration was only inversely associated with gastric cancer risk (0.74, 0.59 to 0.92). Dose-response analysis revealed that 250 and 65 mg day-1 vitamin C intakes had the strongest protective effect against OPE and gastric cancers respectively. These estimates suggest that vitamin C intake could significantly reduce gastrointestinal cancer incidence, including OPE, gastric, and colon cancers. Plasma vitamin C has a significant reduction effect on the incidence of gastric cancer only, but additional large-scale clinical studies are needed to determine its impact on the incidence of DSCs.

The role of vitamin C in the prevention of pancreatic cancer: a systematic-review

Introduction and aim

The aim of this systematic review was to assess the role of vitamin C in the prevention of pancreatic cancer (PC).

Methods

A comprehensive literature search was performed in PubMed, Embase and Web of Science up to August 2023, to identify randomized controlled trials (RCT), cohort studies and mendelian randomization studies based on prospective databases assessing the role of vitamin C in PC prevention.

Results

A total of twelve studies including European and North-American participants were included: two RCT, three mendelian randomization (MR) studies and seven cohort studies. Both RCT showed high quality in Cochrane risk of bias tool. Only one cohort study had <7 points in Newcastle Ottawa Scale. Both RCT found no association between the intake of 500 mg/day of vitamin C and the incidence of PC. Only one prospective cohort study found an association between vitamin C serum levels and a lower incidence of PC. The remaining cohort studies and MR studies found no association between dietary/supplements intake of vitamin C or circulating vitamin C levels and the incidence of PC.

Conclusion

There is no supporting evidence that vitamin C prevents PC development. Future prospective quality studies including high-risk populations are needed.

Comprehensive Strategies for Metabolic Syndrome: How Nutrition, Dietary Polyphenols, Physical Activity, and Lifestyle Modifications Address Diabesity, Cardiovascular Diseases, and Neurodegenerative Conditions

Several hallmarks of metabolic syndrome, such as dysregulation in the glucose and lipid metabolism, endothelial dysfunction, insulin resistance, low-to-medium systemic inflammation, and intestinal microbiota dysbiosis, represent a pathological bridge between metabolic syndrome and diabesity, cardiovascular, and neurodegenerative disorders. This review aims to highlight some therapeutic strategies against metabolic syndrome involving integrative approaches to improve lifestyle and daily diet. The beneficial effects of foods containing antioxidant polyphenols, intestinal microbiota control, and physical activity were also considered. We comprehensively examined a large body of published articles involving basic, animal, and human studie, as well as recent guidelines. As a result, dietary polyphenols from natural plant-based antioxidants and adherence to the Mediterranean diet, along with physical exercise, are promising complementary therapies to delay or prevent the onset of metabolic syndrome and counteract diabesity and cardiovascular diseases, as well as to protect against neurodegenerative disorders and cognitive decline. Modulation of the intestinal microbiota reduces the risks associated with MS, improves diabetes and cardiovascular diseases (CVD), and exerts neuroprotective action. Despite several studies, the estimation of dietary polyphenol intake is inconclusive and requires further evidence. Lifestyle interventions involving physical activity and reduced calorie intake can improve metabolic outcomes.

The Effect of Randomized Beta-Carotene Supplementation on CKD in Men

Introduction

Beta-carotene (BC) protects the body against free radicals that may damage the kidney and lead to the development of acute kidney injury and chronic kidney disease (CKD). Previous studies in animal models have demonstrated a potential protective effect of 30 mg/kg BC supplementation on renal ischemia or reperfusion injury and subsequently improved kidney function. The extension of these findings to humans, however, remains unclear.

Methods

Our study leverages previously collected data from the Physicians' Health Study I (PHS I), a large-scale, long-term, randomized trial of middle-aged and older US male physicians testing 50 mg BC every other day for primary prevention of cardiovascular disease and cancer. We examined the impact of randomized BC supplementation on self-reported incident CKD identified by self-reports stating "yes" to kidney disease from annual follow-up questionnaires from randomization in 1982 through the end of the randomized BC intervention at the end of 1995, and on CKD defined as an estimated glomerular filtration rate (eGFR) < 60 ml/min per 1.73 m2 at the end of 1995. Analyses compared incident CKD between BC supplementation and placebo using Cox proportional hazards regression models and logistic regression. We also examined whether smoking status (current vs. former or never smoker) or other factors modified the effect of randomized BC supplementation on CKD.

Results

A total of 10,966 participants were randomized to BC, and 10,952 participants were randomized to a placebo group. Baseline characteristics between randomized BC groups were similar. There was no significant benefit between BC supplementation and self-reported incident CKD after adjusting for age and randomized aspirin treatment (hazard ratio [HR] = 0.97, 95% confidence interval [CI]: 0.86-1.08, P-value = 0.56). Stratified by smoking status, there was no significant benefit of BC supplementation and self-reported incident CKD either among former or never smokers (HR = 0.95, 95% CI: 0.84-1.07, P-value = 0.41) or current smokers (HR = 1.08, 95% CI: 0.78-1.50, P-value = 0.64). Smoking status did not modify the association between BC supplementation and incident CKD (P-interaction = 0.47). In subgroup analysis among those with available serum creatinine at the study end (5480 with BC and 5496 with placebo), there was no significant benefit between BC supplementation and CKD based on eGFR < 60 ml/min per 1.73 m2 (odds ratio [OR] = 0.96, 95% CI: 0.85-1.08, P-value = 0.49).

Conclusion

Long-term randomized BC supplementation did not affect the risk of incident CKD in middle-aged and older male physicians.

Scientific opinion on the tolerable upper intake level for preformed vitamin A and β-carotene

Following two requests from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the revision of the tolerable upper intake level (UL) for preformed vitamin A and β-carotene. Systematic reviews of the literature were conducted for priority adverse health effects of excess vitamin A intake, namely teratogenicity, hepatotoxicity and endpoints related to bone health. Available data did not allow to address whether β-carotene could potentiate preformed vitamin A toxicity. Teratogenicity was selected as the critical effect on which to base the UL for preformed vitamin A. The Panel proposes to retain the UL for preformed vitamin A of 3000 μg RE/day for adults. This UL applies to men and women, including women of child-bearing age, pregnant and lactating women and post-menopausal women. This value was scaled down to other population groups using allometric scaling (body weight0.75), leading to ULs between 600 μg RE/day (infants 4-11 months) and 2600 μg RE/day (adolescents 15-17 years). Based on available intake data, European populations are unlikely to exceed the UL for preformed vitamin A if consumption of liver, offal and products thereof is limited to once per month or less. Women who are planning to become pregnant or who are pregnant are advised not to consume liver products. Lung cancer risk was selected as the critical effect of excess supplemental β-carotene. The available data were not sufficient and suitable to characterise a dose-response relationship and identify a reference point; therefore, no UL could be established. There is no indication that β-carotene intake from the background diet is associated with adverse health effects. Smokers should avoid consuming food supplements containing β-carotene. The use of supplemental β-carotene by the general population should be limited to the purpose of meeting vitamin A requirements.

Association of serum five heavy metals level with all-cause and cause-specific mortality: a large population-based cohort study

The study aimed to explore the association between five heavy metals exposure (Cadmium, Lead, Mercury, Manganese, and Selenium) and mortality [all-cause, cardiovascular disease (CVD), and cancer-related]. We integrated the data into the National Health and Nutrition Examination Survey from 2011 to 2018 years. A total of 16,092 participants were recruited. The link between heavy metals exposure and mortality was analyzed by constructing a restricted cubic spline (RCS) curve, Cox proportional hazard regression model, and subgroup analysis. The RCS curve was used to show a positive linear relationship between Cadmium, Lead, and all-cause mortality. In contrast, there was a negative linear correlation between Mercury and all-cause mortality. Additionally, Manganese and Selenium also had a J-shaped and L-shaped link with all-cause mortality. The positive linear, positive linear, negative liner, J-shaped, and L-shaped relationships were observed for Cadmium, Lead, Mercury, Manganese, and Selenium and CVD mortality, respectively. Cadmium, Lead, Mercury, and Selenium were observed to exhibit positive linear, U-shaped, negative linear, and L-shaped relationships with cancer-related mortality, respectively. There was an increase and then a decrease in the link between Manganese and cancer-related morality. This study revealed the correlation between the content of different elements and different types of mortality in the U.S. general population.

Not all carotenoids can reduce the risk of gastric cancer: a systematic review with meta-analysis

BACKGROUND

Gastric cancer is characterized by high invasiveness, heterogeneity, and late diagnosis, leading to high incidence and mortality rates. It is a significant public health concern globally. Early prevention is crucial in reducing the occurrence of gastric cancer, and dietary prevention, particularly focusing on carotenoids, has been considered a convenient and effective approach. However, the association between carotenoid intake and gastric cancer incidence remains controversial.

METHODS

A systematic search was conducted in PubMed, Ovid Embase, Web of Science, and Cochrane databases from inception to January 5, 2023. Two reviewers independently screened search results, extracted relevant data, and evaluated study quality. Statistical analysis was performed using the "metan" command in STATA 16 software. Random-effects or fixed-effects models were chosen based on the magnitude of heterogeneity among studies.

RESULTS

This study included a total of 35 publications, consisting of 23 case-control studies and 12 cohort studies. Meta-analysis of case-control studies showed that alpha-carotene (OR = 0.71, 95% CI: 0.55-0.92), beta-carotene (OR = 0.62, 95% CI: 0.53-0.72), and lutein (OR = 0.82, 95% CI: 0.69-0.97) significantly reduced the risk of gastric cancer, while beta-cryptoxanthin (OR = 0.88, 95% CI: 0.75-1.04) and lycopene (OR = 0.86, 95% CI: 0.73-1.00) showed no significant correlation. Meta-analysis of cohort studies indicated no significant associations between any of the five carotenoids and gastric cancer incidence (alpha-carotene: RR = 0.81, 95% CI: 0.54-1.23; beta-carotene: RR = 0.86, 95% CI: 0.64-1.16; beta-cryptoxanthin: RR = 0.86, 95% CI: 0.64-1.16; lutein: RR = 0.94, 95% CI: 0.69-1.29; lycopene: RR = 0.89, 95% CI: 0.69-1.14).

CONCLUSIONS

The relationship between carotenoids and gastric cancer incidence may vary depending on the type of study conducted. Considering that evidence from cohort studies is generally considered stronger than evidence from case-control studies, and high-quality randomized controlled trials show no significant association between carotenoids and gastric cancer incidence, current evidence does not support the supplementation of carotenoids for gastric cancer prevention. Further targeted research is needed to explore the association between the two.

Dietary and supplementary vitamin C intake and the risk of lung cancer: A meta‑analysis of cohort studies

Previous cohort studies reported inconsistent findings regarding the association between dietary or supplementary vitamin C intake and lung cancer risk. These associations were investigated by conducting a meta-analysis of cohort studies. The PubMed and EMBASE databases were utilized, using keywords related to the topic from inception to April 15, 2022. Pooled effect sizes, such as relative risk (RR) or hazard ratio (HR) with 95% confidence intervals (CIs), were calculated using a random-effects model. A total of 20 cohort studies from 13 articles were included in the final analysis. In a meta-analysis of all studies, there was no significant association between dietary or supplementary vitamin C intake and lung cancer risk (RR/HR, 0.90; 95% CI, 0.80-1.01; I2=56.4%; n=20). In the subgroup meta-analysis by the source of vitamin C, dietary vitamin C intake decreased the risk of lung cancer (RR/HR, 0.82; 95% CI, 0.73-0.92; I2=42.5%; n=14), whereas there was no association between supplementary vitamin C intake and lung cancer risk (RR/HR, 1.01; 95% CI, 0.84-1.22; n=4). The present meta-analysis of cohort studies found that dietary vitamin C intake is beneficial for preventing lung cancer, whereas its supplementary intake does not have a beneficial effect.

Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies

Aging accompanied by several age-related complications, is a multifaceted inevitable biological progression involving various genetic, environmental, and lifestyle factors. The major factor in this process is oxidative stress, caused by an abundance of reactive oxygen species (ROS) generated in the mitochondria and endoplasmic reticulum (ER). ROS and RNS pose a threat by disrupting signaling mechanisms and causing oxidative damage to cellular components. This oxidative stress affects both the ER and mitochondria, causing proteopathies (abnormal protein aggregation), initiation of unfolded protein response, mitochondrial dysfunction, abnormal cellular senescence, ultimately leading to inflammaging (chronic inflammation associated with aging) and, in rare cases, metastasis. RONS during oxidative stress dysregulate multiple metabolic pathways like NF-κB, MAPK, Nrf-2/Keap-1/ARE and PI3K/Akt which may lead to inappropriate cell death through apoptosis and necrosis. Inflammaging contributes to the development of inflammatory and degenerative diseases such as neurodegenerative diseases, diabetes, cardiovascular disease, chronic kidney disease, and retinopathy. The body's antioxidant systems, sirtuins, autophagy, apoptosis, and biogenesis play a role in maintaining homeostasis, but they have limitations and cannot achieve an ideal state of balance. Certain interventions, such as calorie restriction, intermittent fasting, dietary habits, and regular exercise, have shown beneficial effects in counteracting the aging process. In addition, interventions like senotherapy (targeting senescent cells) and sirtuin-activating compounds (STACs) enhance autophagy and apoptosis for efficient removal of damaged oxidative products and organelles. Further, STACs enhance biogenesis for the regeneration of required organelles to maintain homeostasis. This review article explores the various aspects of oxidative damage, the associated complications, and potential strategies to mitigate these effects.

Association between β-carotene supplementation and risk of cancer: a meta-analysis of randomized controlled trials

CONTEXT

β-Carotene, which is derived from most fruits and vegetables, is the most common type of carotenes. Existing studies have demonstrated that β-carotene is associated with some positive health outcomes. However, results about the effects of supplemental β-carotene on cancer are inconsistent.

OBJECTIVE

To determine the association between supplemental β-carotene intake and the risk of cancers.

DATA SOURCES

Eight databases (PubMed, Web of Science, Embase, Cochrane, China National Knowledge Infrastructure, Wangfang, China Science and Technology Journal Database, and Chinese Biomedical Literature Database) were systematically searched until September 2022.

DATA EXTRACTION

Only reports from randomized controlled trials in which an association between supplemental β-carotene intake and the risk of cancer was found were included in the meta-analysis.

DATA ANALYSIS

A total of 18 eligible studies based on 8 different randomized controlled trials were included in the meta-analysis, with varying sample sizes from 391 to 39 876 participants. There was no significant association between supplemental β-carotene intake and overall cancer incidence rate after synthesizing all the results (risk ratio [RR]: 1.02; 95% confidence interval [CI], 0.99-1.05). Results from subgroup analysis indicated that intake of supplemental β-carotene significantly increased the risk of lung cancer (RR: 1.19; 95%CI: 1.08-1.32), whereas no significant associations were observed for other site-specific cancers. In addition, smokers and the subgroup of participants with only low-dose β-carotene intake had a risk increment of cancer if they took supplemental β-carotene (RR: 1.16; 95%CI: 1.05-1.29).

CONCLUSION

β-Carotene supplementation has no beneficial or harmful effect on cancer incidence; moreover, it might have potentially harmful effects on lung cancer, especially for people who smoke. On the basis of the evidence from this study, supplemental intake of β-carotene is not recommended for preventing cancer, and the establishment of a tolerable upper intake level of β-carotene should be considered.

Trends in Diet and Cancer Research: A Bibliometric and Visualization Analysis

Diet plays a critical role for patients across the cancer continuum. The World Cancer Research Fund International and the American Cancer Society have published evidence supporting the role of nutrition in cancer prevention. We conducted an analysis of the literature on dietary nutrients and cancer to uncover opportunities for future research. The objective of the bibliometric analysis was to describe trends in peer-reviewed publications on dietary components and cancer and to highlight research gaps. PubMed was queried for manuscripts with diet- and cancer-related keywords and Medical Subject Headings (MeSH) terms. Metadata covering 99,784 publications from 6469 journals were analyzed to identify trends since 1970 on diet topics across 19 tumor types. Publications focused largely on breast, colorectal, and liver cancer, with fewer papers linking diet with other cancers such as brain, gallbladder, or ovarian. With respect to "unhealthy" diets, many publications focused on high-fat diets and alcohol consumption. The largest numbers of publications related to "healthy" diets examined the Mediterranean diet and the consumption of fruits and vegetables. These findings highlight the need for additional research focused on under-investigated cancers and dietary components, as well as dietary studies during cancer therapy and post-therapy, which may help to prolong survivorship.

Nutritional Metabolomics in Diet-Breast Cancer Relations: Current Research, Challenges, and Future Directions-A Review

Breast cancer is one of the most common types of cancer in women worldwide, and its incidence is increasing. Diet has been identified as a modifiable risk factor for breast cancer, but the complex interplay between diet, metabolism, and cancer development is not fully understood. Nutritional metabolomics is a rapidly evolving field that can provide insights into the metabolic changes associated with dietary factors and their impact on breast cancer risk. The review's objective is to provide a comprehensive overview of the current research on the application of nutritional metabolomics in understanding the relationship between diet and breast cancer. The search strategy involved querying several electronic databases, including PubMed, Scopus, Web of Science, and Google Scholar. The search terms included combinations of relevant keywords such as "nutritional metabolomics", "diet", "breast cancer", "metabolites", and "biomarkers". In this review, both in vivo and in vitro studies were included, and we summarize the current state of knowledge on the role of nutritional metabolomics in understanding the diet-breast cancer relationship, including identifying specific metabolites and metabolic pathways associated with breast cancer risk. We also discuss the challenges associated with nutritional metabolomics research, including standardization of analytical methods, interpretation of complex data, and integration of multiple-omics approaches. Finally, we highlight future directions for nutritional metabolomics research in studying diet-breast cancer relations, including investigating the role of gut microbiota and integrating multiple-omics approaches. The application of nutritional metabolomics in the study of diet-breast cancer relations, including 2-amino-4-cyano butanoic acid, piperine, caprate, rosten-3β,17β-diol-monosulfate, and γ-carboxyethyl hydrochroman, among others, holds great promise for advancing our understanding of the role of diet in breast cancer development and identifying personalized dietary recommendations for breast cancer prevention, control, and treatment.

Association between Dietary Inflammatory Index and Gastric Adenocarcinoma: A Multicenter Case-Control Study in Brazil

BACKGROUND

Few studies have evaluated the association between diet-related inflammation and gastric adenocarcinoma (GA) and evidence is scarce in Brazil. This study evaluated the association between a pro-inflammatory diet and GA.

METHODS

A multicenter case-control study was conducted in Brazil. A total of 1645 participants-492 cases, 377 endoscopy controls, and 776 hospital controls-were included. Energy-adjusted Dietary Inflammatory Index (E-DII^TM) scores were derived from a validated food frequency questionnaire. We used binary and multinomial logistic regression models for the analysis of total GA, and its subtypes (cardia and non-cardia, intestinal, and diffuse histological subtypes).

RESULTS

In cases versus endoscopy controls, a pro-inflammatory diet, estimated by higher E-DII scores, was associated with a higher risk GA (OR_Q4vsQ1: 2.60, 1.16-5.70), of non-cardia GA (OR: 2.90, 1.06-7.82), and diffuse subtype (OR: 3.93, 1.59-9.70). In cases versus hospital controls, higher E-DII scores were associated with a higher risk of GA (OR: 2.70, 1.60-4.54), of cardia GA (OR: 3.31, 1.32-8.24), non-cardia GA (OR: 2.97, 1.64-5.39), and both intestinal (OR: 2.82, 1.38-5.74) and diffuse GA (OR: 2.50, 1.54-5.11) subtypes.

CONCLUSIONS

This study provides evidence that a pro-inflammatory diet is associated with an increased risk of GA in Brazil. E-DII requires the inclusion of sodium due to its importance in carcinogenesis.

Effect of Melittin Complexes with Graphene and Graphene Oxide on Triple-Negative Breast Cancer Tumors Grown on Chicken Embryo Chorioallantoic Membrane

One of the components of bee venom is melittin (M), which has strong lysing properties on membranes. M has high toxicity to cancer cells, but it also affects healthy cells, making it necessary to use methods for targeted delivery to ensure treatment. This research is a continuation of previous studies using graphene nanomaterials as M carriers to breast cancer cells. The studies described below are conducted on a more organized biological structure than what is found in vitro cells, namely, cancerous tumors grown on a chicken embryo chorioallantoic membrane. Caspase 3 and 8 levels are analyzed, and the level of oxidative stress markers and changes in protein expression for cytokines are examined. The results show that M complexes with nanomaterials reduce the level of oxidative stress more than M alone does, but the use of graphene (GN) as a carrier increases the level of DNA damage to a greater extent than the increase caused by M alone. An analysis of cytokine levels shows that the use of the M and GN complex increases the level of proteins responsible for inhibiting tumor progression to a greater extent than the increase occasioned by a complex with graphene oxide (GO). The results suggest that the use of GN as an M carrier may increase the toxic effect of M on structures located inside a cell.

Association of Oral or Intravenous Vitamin C Supplementation with Mortality: A Systematic Review and Meta-Analysis

Mortality is the most clinically serious outcome, and its prevention remains a constant struggle. This study was to assess whether intravenous or oral vitamin C (Vit-C) therapy is related to reduced mortality in adults. Data from Medline, Embase, and the Cochrane Central Register databases were acquired from their inception to 26 October 2022. All randomized controlled trials (RCTs) involving intravenous or oral Vit-C against a placebo or no therapy for mortality were selected. The primary outcome was all-cause mortality. Secondary outcomes were sepsis, COVID-19, cardiac surgery, noncardiac surgery, cancer, and other mortalities. Forty-four trials with 26540 participants were selected. Although a substantial statistical difference was observed in all-cause mortality between the control and the Vit-C-supplemented groups (p = 0.009, RR 0.87, 95% CI 0.78 to 0.97, I² = 36%), the result was not validated by sequential trial analysis. In the subgroup analysis, mortality was markedly reduced in Vit-C trials with the sepsis patients (p = 0.005, RR 0.74, 95% CI 0.59 to 0.91, I² = 47%), and this result was confirmed by trial sequential analysis. In addition, a substantial statistical difference was revealed in COVID-19 patient mortality between the Vit-C monotherapy and the control groups (p = 0.03, RR 0.84, 95% CI 0.72 to 0.98, I² = 0%). However, the trial sequential analysis suggested the need for more trials to confirm its efficacy. Overall, Vit-C monotherapy does decrease the risk of death by sepsis by 26%. To confirm Vit-C is associated with reduced COVID-19 mortality, additional clinical random control trials are required.

Association between Dietary and Supplemental Antioxidants Intake and Lung Cancer Risk: Evidence from a Cancer Screening Trial

Previous studies provided inconsistent results on the effects of antioxidant nutrient intake on lung cancer prevention. We aimed to evaluate the association between antioxidant consumption from food and supplemental sources and lung cancer incidence. Data were obtained from the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial. A total of 98,451 participants were included in the data analysis. We used a multivariable Cox proportional hazards regression model to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between antioxidant intake and lung cancer risk. Dose-response assessments for individual nutrients were conducted. We also selected the model for the best combination of antioxidants for reducing lung cancer risk using machine learning methods. After the median follow-up of 12.2 years, 1642 new cases were identified. Intake of the calculated HRs indicated a trend for a higher quartile of food-based Composite Dietary Antioxidant Index (fCDAI) associated with a lower lung cancer risk after adjusting for covariates (HR_Q4vs.Q1 = 0.64, 95% CI: 0.52, 0.79; P for trend < 0.001). Protective effects of dietary antioxidant intake were observed across all individual antioxidant micronutrients except magnesium. Random forests model suggested the dietary intake group of α-carotene, magnesium, vitamin C, vitamin E, lycopene, selenium, lutein, and zeaxanthin, and β-carotene had the most favorable effects on lung cancer prevention. Higher consumption of antioxidants from food sources has a protective effect against lung cancer, while no effects were shown in the supplemental group. It is recommended to consume a combination of various antioxidants due to the potential benefits from the interaction, while more research should be performed to investigate the underlying mechanisms of antioxidant synergic effects on lung cancer risk reduction.

Circulating vitamin C and digestive system cancers: Mendelian randomization study

BACKGROUND & AIMS

Vitamin C is an antioxidant with a potential role in the prevention of digestive system cancers, but there is yet no consensus whether vitamin C has a causal role in these cancers. The aim of this study was to utilize Mendelian randomization to decipher the potential causal associations of vitamin C with risk of digestive system cancers.

METHODS

Ten genetic variants previously found to be significantly associated with circulating vitamin C were used as instrumental variables. Effect size estimates for the genetic associations of the vitamin C-associated genetic variants with six major malignancies of digestive system were obtained from the FinnGen (N = 309 154) and UK Biobank (N = 367 542) studies. Results from the two studies were combined using meta-analysis.

RESULTS

Genetically predicted higher circulating vitamin C showed a suggestive association with lower risk of small intestine and colorectal cancer after accounting for multiple testing. The odds ratio per 1 standard deviation increment in circulating vitamin C was 0.55 (95% confidence interval 0.32-0.94; P = 0.029) for small intestine cancer and 0.84 (95% confidence interval 0.73-0.96; P = 0.013) for colorectal cancer. There was a suggestive association between genetically predicted higher circulating vitamin C with lower risk of liver cancer in FinnGen but no association in the meta-analysis (odds ratio 0.69; 95% CI 0.36-1.32; P = 0.265). Genetically predicted circulating vitamin C was not associated with cancers of the esophagus, stomach, or pancreas.

CONCLUSION

This Mendelian randomization study indicates that vitamin C might play a role in the prevention of small intestine and colorectal cancer.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Plants, Plants, and More Plants: Plant-Derived Nutrients and Their Protective Roles in Cognitive Function, Alzheimer’s Disease, and Other Dementias

Background and Objectives: Alzheimer’s disease (AD) is the most common form of dementia, with the risk of developing it attributed to non-modifiable and modifiable factors. Currently, there is no cure for AD. A plant-based diet may protect against cognitive decline, due to the effects of plant-based nutrients such as vitamins, antioxidants, and fiber. The aim of the review is to summarize current literature on plant-based nutrients and their impact on cognition. Materials and Methods: A search was conducted on PubMed for clinical and murine studies, using combinations of the following words: “Alzheimer’s disease”, “dementia”, “cognition”, “plant-based diet”, “mild cognitive impairment”, “vitamin B”, “vitamin C”, “vitamin E, “beta carotene”, “antioxidants”, “fiber”, “vitamin K”, “Mediterranean diet”, “vitamin D”, and “mushrooms”. Results and Conclusions: A diet rich in vitamin B and antioxidants can benefit the cognitive functions of individuals as shown in randomized clinical trials. Vitamin K is associated with improved cognition, although large randomized controlled trials need to be done. Fiber has been shown to prevent cognitive decline in animal studies. Vitamin D may contribute to cognitive health via anti-inflammatory processes. Several medical organizations have recommended a plant-based diet for optimizing cognitive health and potentially helping to prevent dementia.

Association Between Beta-Carotene Supplementation and Mortality: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background

Aging is a phenomenon universally involving all organisms, genetically determined, and epigenetically influenced by the environment. Numerous observational studies have shown the positive impact of non-pharmacological approaches started in younger age on chronic conditions affecting the elderly health and survival. This meta-analysis aimed to investigate the effect of beta-carotene on the total and cause-specific mortality as reported by randomized controlled trials (RCTs).

Methods

We searched Medline, Scopus, Web of Science, and CENTRAL Cochrane from inception to September 2021. Studies were eligible if enrolled adults with any health condition, compared beta-carotene supplements at any dose with placebo or no intervention, provided information on deaths from any cause, and were RCTs, in English. The risk of bias was assessed by the Cochrane risk of bias tool and the GRADE. Risk ratios and their 95% confidence intervals were used and a P-value less than 0.05 was considered statistically significant.

Results

Among 3,942 articles searched, 44 articles on 31 RCTs, which included 216,734 total subjects, 108,622 in beta-carotene supplement groups, and 108,112 in the placebo or no-intervention groups, were involved in the final analyses. In a random-effects meta-analysis of all 31 trials, beta-carotene supplements were found to have no preventive effect on mortality (risk ratio 1.02, 95% confidence interval 0.98–1.05, I2 = 42%). Further, the analysis showed no preventive effect on cancer, cardiovascular, cerebrovascular, and other mortality causes. Instead, beta-carotene supplementation significantly increased the risk of lung cancer mortality (RR 1.14, 95% CI 1.02, 1.27, I2 = 3%) but decreased the risk of human immunodeficiency virus-related mortality (RR 0.55, 95% CI 0.33, 0.92, I2 = 0).

Conclusion

More studies should be performed to better define the role of beta-carotene on survival, to confirm or deny our results. Therefore, the possible beneficial or harmful effects of the beta-carotene supplementation on mortality must not be overstated.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=259354], identifier [CRD42021259354].

Mortality after multivitamin supplementation: Nearly 35-year follow-up of the randomized Linxian Dysplasia Nutrition Intervention Trial

BACKGROUND

The objective of this study was to update the association between multivitamin supplementation and total or cause-specific mortality in a population with a high prevalence of undernutrition in China.

METHODS

The Linxian Dysplasia Nutrition Intervention Trial was a randomized, double-blind, placebo-controlled trial in which 3318 persons aged 40-69 years with esophageal squamous dysplasia were assigned to receive daily multivitamin supplementation or a placebo for 6 years and were followed for 29 years. The primary outcome was esophageal/gastric cardia cancer mortality. The data were analyzed with Cox proportional hazards regression models. Subgroup analyses were performed by common characteristics such as age and gender.

RESULTS

The cumulative total mortality was 83.5%. Multivitamin supplementation did not affect total or cause-specific mortality in the participants as a whole (hazard ratio [HR], 0.96; 95% confidence interval [CI], 0.89-1.03). Subgroup analyses showed that no association between multivitamin supplementation and all-cause mortality was observed in men (HR, 0.90; 95% CI, 0.81-1.01), women (HR, 1.01; 95% CI, 0.91-1.12), younger participants (HR, 0.97; 95% CI, 0.87-1.08), or older participants (HR, 0.94; 95% CI, 0.85-1.04). Significant reductions in heart disease mortality (HR, 0.64; 95% CI, 0.47-0.87) and cerebrovascular disease mortality (HR, 0.74; 95% CI, 0.56-1.00) were seen in older men. In a subgroup of younger men and a subgroup of moderate or severe dysplasia, subjects receiving multivitamin supplementation had a lower risk of esophageal/cardia cancer mortality (HR for younger men, 0.76; 95% CI, 0.58-0.99; HR for moderate or severe dysplasia, 0.76; 95% CI, 0.58-1.00). No association between multivitamin supplementation and any cause-specific mortality was observed in a mild dysplasia population.

CONCLUSIONS

Multivitamin supplementation in a population with esophageal squamous dysplasia was not associated with the risk of total mortality in the 35-year follow-up of this randomized controlled trial. In light of this and previous trials, multivitamin supplements should be used thoughtfully to improve health status of populations with esophageal squamous dysplasia.

LAY SUMMARY

Multivitamin supplementation is common, yet its effect on mortality is unclear. The aim of this study was to update the long-term effects of multivitamin supplementation on total and cause-specific mortality during nearly 35 years of follow-up in the Linxian Dysplasia Nutrition Intervention Trial in China. Multivitamin supplementation in a population with esophageal squamous dysplasia was not associated with the risk of total mortality in the 35-year follow-up of this randomized controlled trial, and this indicates that multivitamin supplements should be used thoughtfully to improve health status.

Role of Beta-Carotene in Lung Cancer Primary Chemoprevention: A Systematic Review with Meta-Analysis and Meta-Regression

Lung cancer is one of the most common neoplasms globally, with about 2.2 million new cases and 1.8 million deaths annually. Although the most important factor in reducing lung cancer risk is lifestyle change, most patients favour the use of supplements, for example, rather than quitting smoking or following a healthy diet. To better understand the efficacy of such interventions, a systematic review was performed of data from randomized controlled trials concerning the influence of beta-carotene supplementation on lung cancer risk in subjects with no lung cancer before the intervention. The search corpus comprised a number of databases and eight studies involving 167,141 participants, published by November 2021. The findings indicate that beta-carotene supplementation was associated with an increased risk of lung cancer (RR = 1.16, 95% CI = 1.06-1.26). This effect was even more noticeable among smokers and asbestos workers (RR = 1.21, 95% CI = 1.08-1.35) and non-medics (RR = 1.18, 95% CI = 1.07-1.29). A meta-regression found no relationship between the beta-carotene supplementation dose and the size of the negative effect associated with lung cancer risk. Our findings indicate that beta-carotene supplementation has no effect on lung cancer risk. Moreover, when used as the primary chemoprevention, beta-carotene may, in fact, increase the risk of lung cancer.

Plasma Circulating Vitamin C Levels and Risk of Endometrial Cancer: A Bi-Directional Mendelian Randomization Analysis

Background

Observational studies indicated that circulating vitamin C (VitC) levels may be correlated with the risk of endometrial cancer (EC). However, the causal effects and direction between them were still unclear.

Methods

In this study, 11 single nucleotide polymorphisms (SNPs) robustly correlated with plasma VitC levels were extracted from the latest genome-wide association study (GWAS), containing 52,018 individuals. Genetic data of EC were obtained from the Endometrial Cancer Association Consortium (ECAC) (12,906 cases and 108,979 controls). An inverse-variance weighted method was utilized as the primary analysis of Mendelian randomization (MR), supplemented by the weighted median, MR Pleiotropy Residual Sum and Outlier test (MR-PRESSO), and MR-Egger methods. Additional sensitivity analyses excluding 3 SNPs with secondary phenotypes were conducted to rule out the possible pleiotropic effects. Potential impacts of several risk factors of EC, such as obesity, body mass index (BMI), hypertension, and diabetes on VitC levels, were assessed. We additionally evaluated the effects of VitC on LDL cholesterol levels, HDL cholesterol levels, and triglycerides levels to probe into the possible mediators in the VitC-EC pathway.

Results

Genetically predicted higher plasma VitC levels (per 1 SD increase, approximately 20 μmol/L) were causally associated with an increased risk of EC overall [odds ratio (OR) 1.374, 95% CI 1.128–1.674, p = 0.0016], supported by complementary sensitivity analyses. In the subgroup analyses, genetically predicted higher levels of VitC were associated with a tendency of increased risks of both endometrioid (OR_SD 1.324, 95% CI 0.959–1.829, p = 0.0881) and non-endometrioid histology (OR_SD 1.392, 95% CI 0.873–2.220, p = 0.1647) while without statistical significance. The association remained significant after the exclusion of the three pleiotropic SNPs (OR_SD 1.394, 95% CI 1.090–1.784, p = 0.0082). The confounders and mediators were unlikely to affect the VitC-EC relationship. The causal effect of EC on VitC levels was not supported (OR 1.001, 95% CI 0.998–1.004, p = 0.4468).

Conclusions

This bi-directional MR study demonstrated a causal risk role of higher circulating VitC at physiological levels on an increased risk of EC, which was independent of confounders and mediators. Further studies are warranted to elucidate the possible mechanisms.

The Role of Bioactive Compounds in Natural Products Extracted from Plants in Cancer Treatment and Their Mechanisms Related to Anticancer Effects

Cancer is one of the greatest causes of death worldwide. With the development of surgery, radiotherapy, and medical agents, the outcomes of cancer patients have greatly improved. However, the underlying mechanisms of cancer are not yet fully understood. Recently, natural products have been proven to be beneficial for various conditions and have played important roles in the development of novel therapies. A substantial amount of evidence indicates that bioactive compounds could improve the outcomes of cancer patients via various pathways, such as endoplasmic reticulum stress, epigenetic modification, and modulation of oxidative stress. Here, we review the current evidence of bioactive compounds in natural products for the treatment of cancer and summarize the underlying mechanisms in this pathological process.

Positive Aspects of Oxidative Stress at Different Levels of the Human Body: A Review

Oxidative stress is the subject of numerous studies, most of them focusing on the negative effects exerted at both molecular and cellular levels, ignoring the possible benefits of free radicals. More and more people admit to having heard of the term "oxidative stress", but few of them understand the meaning of it. We summarized and analyzed the published literature data in order to emphasize the importance and adaptation mechanisms of basal oxidative stress. This review aims to provide an overview of the mechanisms underlying the positive effects of oxidative stress, highlighting these effects, as well as the risks for the population consuming higher doses than the recommended daily intake of antioxidants. The biological dose-response curve in oxidative stress is unpredictable as reactive species are clearly responsible for cellular degradation, whereas antioxidant therapies can alleviate senescence by maintaining redox balance; nevertheless, excessive doses of the latter can modify the redox balance of the cell, leading to a negative outcome. It can be stated that the presence of oxidative status or oxidative stress is a physiological condition with well-defined roles, yet these have been insufficiently researched and explored. The involvement of reactive oxygen species in the pathophysiology of some associated diseases is well-known and the involvement of antioxidant therapies in the processes of senescence, apoptosis, autophagy, and the maintenance of cellular homeostasis cannot be denied. All data in this review support the idea that oxidative stress is an undesirable phenomenon in high and long-term concentrations, but regular exposure is consistent with the hormetic theory.

Dietary and Supplemental Vitamin C Intake and Risk of Breast Cancer: Results from the Nurses' Health Studies

BACKGROUND

Some previous studies suggested that high supplemental vitamin C intake may be associated with an increased risk of breast cancer, although evidence is inconsistent.

OBJECTIVES

Our objective was to study the association between vitamin C intake and breast cancer risks using regularly updated assessments of intake over a long follow-up.

METHODS

We prospectively followed 88,041 women aged 33 to 60 years from the Nurses' Health Study (1980-2014) and 93,372 women aged 26 to 45 years from the Nurses' Health Study II (1991-2013). A total of 11,258 incident invasive breast cancers among 181,413 women were diagnosed. Data on vitamin C intake were collected every 2-4 years via a validated FFQ and specific questions on dietary supplement use. Multivariate HRs and 95% CIs for incident invasive breast cancer were estimated with Cox models.

RESULTS

During follow-up, 82% of participants ever used supplements containing vitamin C, including multivitamins. Cumulative total vitamin C intake (HR for quintiles 5 compared with 1 = 0.97; 95% CI: 0.91-1.03; Ptrend = 0.81), dietary vitamin C intake (HR for quintiles 5 compared with 1 = 0.98; 95% CI: 0.92-1.04; Ptrend = 0.57), and supplemental vitamin C intake (HR for quintiles 5 compared with 1 in users = 1.02; 95% CI: 0.94-1.09; Ptrend = 0.77) were not associated with breast cancer risks. Results were unchanged when different exposure latencies were considered. The results did not differ by menopausal status, postmenopausal hormone therapy use, or BMI. No differences were observed by estrogen receptor status of the tumor.

CONCLUSIONS

Our results do not support any important association between total, dietary, or supplemental vitamin C intake and breast cancer risks.

Dietary Carotenoids in Head and Neck Cancer-Molecular and Clinical Implications

Head and neck cancer (HNC) is one of the most common cancers in the world according to GLOBCAN. In 2018, it was reported that HNC accounts for approximately 3% of all human cancers (51,540 new cases) and is the cause of nearly 1.5% of all cancer deaths (10,030 deaths). Despite great advances in treatment, HNC is indicated as a leading cause of death worldwide. In addition to having a positive impact on general health, a diet rich in carotenoids can regulate stages in the course of carcinogenesis; indeed, strong epidemiological associations exist between dietary carotenoids and HNS, and it is presumed that diets with carotenoids can even reduce cancer risk. They have also been proposed as potential chemotherapeutic agents and substances used in chemoprevention of HNC. The present review discusses the links between dietary carotenoids and HNC. It examines the prospective anticancer effect of dietary carotenoids against intracellular cell signalling and mechanisms, oxidative stress regulation, as well as their impact on apoptosis, cell cycle progression, cell proliferation, angiogenesis, metastasis, and chemoprevention; it also provides an overview of the limited preclinical and clinical research published in this arena. Recent epidemiological, key opinion-forming systematic reviews, cross-sectional, longitudinal, prospective, and interventional studies based on in vitro and animal models of HNC also indicate that high carotenoid content obtained from daily supplementation has positive effects on the initiation, promotion, and progression of HNC. This article presents these results according to their increasing clinical credibility.

Vitamin C and cancer risk and treatment

Vitamin C (L-ascorbic acid) works as a strong reductant, radical scavenger, and protector of cell membranes against primary peroxidative damage in tissues and in the extracellular fluid. L-ascorbic acid is involved in the synthesis of collagen and many other biologically relevant substances, enzyme activity, xenobiotic detoxification, and prevention of forming carcinogenic nitrosamines. It also plays a role in the immune system. Numerous data indicate that cancer patients suffer from vitamin C deficiency. Studies show that people with a low vitamin C intake have an increased risk of head and neck cancers as well as lung, gastric, pancreatic, cervical, rectal, or breast cancer. On the other hand, there is no clinical evidence to support the thesis that antioxidant supplements (including vitamin C) prevent cancer. Observational trials investigating high doses of intravenous L-ascorbic acid in previously treated cancer patients have shown that it allows an increase in quality of life and may improve physical, mental, and emotional functions, as well as reducing adverse effects of standard anticancer treatment, including fatigue, nausea, vomiting, and appetite loss. So far, there were a few randomized controlled trials and they have not reported any statistically significant improvements in the overall or progression-free survival with vitamin C, as compared to the control arm. However, preclinical data indicating a role of L-ascorbic acid in modulation of immune response and its involvement in epigenome remodeling suggest its new potential clinical applications in cancer patients, especially in combination with immunotherapy. It seems reasonable to further investigate the value of vitamin C as a supportive treatment or in combination with anticancer targeted therapy.

A Narrative Review of the Safety of Anti-COVID-19 Nutraceuticals for Patients with Cancer

Simple Summary

Dietary supplement use has increased more than 35% globally since the COVID-19 outbreak. While some nutraceuticals are potentially efficacious against severe disease from COVID-19, their indiscriminate use by patients with cancer without medical supervision is concerning. The aim of this narrative review was to evaluate the data on safety of “anti-COVID-19” nutraceuticals for patients with cancer. We found that the use of vitamin C, vitamin D, and selenium supplements is likely safe and even potentially beneficial at typically recommended doses. However, caution is advised regarding the use of omega-3 fatty acids and zinc, as risks from their use may outweigh the benefits.

Abstract

Interest in dietary supplements and their efficacy in treating and preventing disease has increased greatly since the outbreak of the COVID-19 pandemic. Due to the risk of severe COVID-19 in patients with cancer, we conducted a narrative review aiming to better understand the data on the safety of the most efficacious “anti-COVID-19” nutraceuticals for patients with cancer. We conducted a PubMed database search aimed at identifying the most effective nutrients for use against COVID-19. For the identified nutraceuticals, we searched PubMed again regarding their safety for patients with cancer. Fifty-four total records (52 independent studies) were retrieved, pertaining to vitamin D, vitamin C, selenium, omega-3 fatty acids, and zinc. Vitamin D results from 23 articles indicated safe use, but two articles indicated potential harm. All 14 articles for vitamin C and five out of six articles for selenium indicated the safety of use (one study for selenium suggested harm with high-dose supplementation). Results for omega-3 fatty acids (seven articles) and zinc (one article), however, were rather mixed regarding safety. We conclude that vitamin D, vitamin C, and selenium supplements are likely safe or even beneficial at typically recommended doses; however, caution is urged with omega-3 fatty acid supplements, and zinc supplements should likely be avoided. More experimental research is needed, and nutraceutical use by patients with cancer should always be under the supervision of a healthcare team.

Redox regulation by carotenoids: Evidence and conflicts for their application in cancer

Carotenoids have been constantly investigated since the early fifty for their chemical, biochemical and biological properties being presence in foods. Among the more than 1100 carotenoids synthesized by plants and microorganisms, approximately 50 are present in the human diet, and about 20 can be detected in human blood and tissues. Review articles that discuss the anticancer and cancer preventing activity of phytochemicals have often in common the difficulty to find a coherency between the results deriving from experimental studies and the controversial or weak clinical indications arising from epidemiological and interventional studies. In this scenario, the class of carotenoids does not represent an exception. In fact, according with World Cancer Research Fund, strong evidence exists that high-dose supplementation of β-carotene increases the risk of lung cancer, while for other types of cancer, the protective or harmful effects of food-containing carotenoids or carotenoid supplements have been considered limited, suggestive or unlikely. The analysis of the mechanistic evidence is complicated by the double nature of carotenoids being molecules acting either as antioxidant or pro-oxidant compounds. The present review analyzes the ambiguity and the unexpected results deriving from the epidemiological and interventional studies and discusses how the effects of carotenoids on cancer risk can be explained by understanding their capacity to modulate the cellular antioxidant response, depending on the concentration applied and the cellular metabolism. In the final part, a new global approach is proposed to study the contribution of carotenoids, but also of other phytochemicals, to disease prevention, including cancer.

Nutrition and nonmelanoma skin cancers

Nonmelanoma skin cancer (NMSC), the most widely diagnosed cancer in the United States, is rising in incidence despite public health and educational campaigns that highlight the importance of sun avoidance. It is,therefore, important to establish other modifiable risk factors that may be contributing to this increase. There is a growing body of evidence in the literature suggesting certain nutrients may have protective or harmful effects on NMSC. We review the current literature on nutrition and its effect on NMSC with a focus on dietary fat, vitamin A, nicotinamide, folate, vitamin C, vitamin D, vitamin E, polyphenols, and selenium.

Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study

BACKGROUND

Circulating vitamin C concentrations have been associated with several cancers in observational studies, but little is known about the causal direction of the associations. This study aims to explore the potential causal relationship between circulating vitamin C and risk of five most common cancers in Europe.

METHODS

We used summary-level data for genetic variants associated with plasma vitamin C in a large vitamin C genome-wide association study (GWAS) meta-analysis on 52,018 Europeans, and the corresponding associations with lung, breast, prostate, colon, and rectal cancer from GWAS consortia including up to 870,984 participants of European ancestry. We performed two-sample, bi-directional Mendelian randomization (MR) analyses using inverse-variance-weighted method as the primary approach, while using 6 additional methods (e.g., MR-Egger, weighted median-based, and mode-based methods) as sensitivity analysis to detect and adjust for pleiotropy. We also conducted a meta-analysis of prospective cohort studies and randomized controlled trials to examine the association of vitamin C intakes with cancer outcomes.

RESULTS

The MR analysis showed no evidence of a causal association of circulating vitamin C concentration with any examined cancer. Although the odds ratio (OR) per one standard deviation increase in genetically predicted circulating vitamin C concentration was 1.34 (95% confidence interval 1.14 to 1.57) for breast cancer in the UK Biobank, this association could not be replicated in the Breast Cancer Association Consortium with an OR of 1.05 (0.94 to 1.17). Smoking initiation, as a positive control for our reverse MR analysis, showed a negative association with circulating vitamin C concentration. However, there was no strong evidence of a causal association of any examined cancer with circulating vitamin C. Sensitivity analysis using 6 different analytical approaches yielded similar results. Moreover, our MR results were consistent with the null findings from the meta-analysis exploring prospective associations of dietary or supplemental vitamin C intakes with cancer risk, except that higher dietary vitamin C intake, but not vitamin C supplement, was associated with a lower risk of lung cancer (risk ratio: 0.84, 95% confidence interval 0.71 to 0.99).

CONCLUSIONS

These findings provide no evidence to support that physiological-level circulating vitamin C has a large effect on risk of the five most common cancers in European populations, but we cannot rule out very small effect sizes.

The application of feature engineering in establishing a rapid and robust model for identifying patients with glioma

The aim of the study is to evaluate the efficacy of the combination of Raman spectroscopy with feature engineering and machine learning algorithms for detecting glioma patients. In this study, we used Raman spectroscopy technology to collect serum spectra of glioma patients and healthy people and used feature engineering-based classification models for prediction. First, to reduce the dimensionality of the data, we used two feature extraction algorithms which are partial least squares (PLS) and principal component analysis (PCA). Then, the principal components were selected using the feature selection methods of four correlation indexes, namely, Relief-F (RF), the Pearson correlation coefficient (PCC), the F-score (FS) and term variance (TV). Finally, back-propagation neural network (BP), linear discriminant analysis (LDA) and support vector machine (SVM) classification models were established. To improve the reliability of the model, we used a fivefold cross validation to measure the prediction performance between different models. In this experiment, 33 classification models were established. Integrating 4 classification criteria, PLS-Relief-F-BP, PLS-F-Score-BP, PLS-LDA and PLS-Relief-F-SVM had better effects, and their accuracy rates reached 97.58%, 96.33%, 97.87% and 96.19%, respectively. The experimental results show that feature engineering can select more representative features, reduce computational time complexity and simplify the model. The classification model established in this experiment can not only increase the robustness of the model and shorten the discrimination time but also realize the rapid, stable and accurate diagnosis of glioma patients, which has high clinical application value.

Implication of Dietary Iron-Chelating Bioactive Compounds in Molecular Mechanisms of Oxidative Stress-Induced Cell Ageing

One of the prevailing perceptions regarding the ageing of cells and organisms is the intracellular gradual accumulation of oxidatively damaged macromolecules, leading to the decline of cell and organ function (free radical theory of ageing). This chemically undefined material known as "lipofuscin," "ceroid," or "age pigment" is mainly formed through unregulated and nonspecific oxidative modifications of cellular macromolecules that are induced by highly reactive free radicals. A necessary precondition for reactive free radical generation and lipofuscin formation is the intracellular availability of ferrous iron (Fe2+) ("labile iron"), catalyzing the conversion of weak oxidants such as peroxides, to extremely reactive ones like hydroxyl (HO•) or alcoxyl (RO•) radicals. If the oxidized materials remain unrepaired for extended periods of time, they can be further oxidized to generate ultimate over-oxidized products that are unable to be repaired, degraded, or exocytosed by the relevant cellular systems. Additionally, over-oxidized materials might inactivate cellular protection and repair mechanisms, thus allowing for futile cycles of increasingly rapid lipofuscin accumulation. In this review paper, we present evidence that the modulation of the labile iron pool distribution by nutritional or pharmacological means represents a hitherto unappreciated target for hampering lipofuscin accumulation and cellular ageing.

Oxidative Stress, Plant Natural Antioxidants, and Obesity

Oxidative stress is important in the pathophysiology of obesity, altering regulatory factors of mitochondrial activity, modifying the concentration of inflammation mediators associated with a large number and size of adipocytes, promoting lipogenesis, stimulating differentiation of preadipocytes to mature adipocytes, and regulating the energy balance in hypothalamic neurons that control appetite. This review discusses the participation of oxidative stress in obesity and the important groups of compounds found in plants with antioxidant properties, which include (a) polyphenols such as phenolic acids, stilbenes, flavonoids (flavonols, flavanols, anthocyanins, flavanones, flavones, flavanonols, and isoflavones), and curcuminoids (b) carotenoids, (c) capsaicinoids and casinoids, (d) isothiocyanates, (e) catechins, and (f) vitamins. Examples are analyzed, such as resveratrol, quercetin, curcumin, ferulic acid, phloretin, green tea, Hibiscus Sabdariffa, and garlic. The antioxidant activities of these compounds depend on their activities as reactive oxygen species (ROS) scavengers and on their capacity to prevent the activation of NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells), and reduce the expression of target genes, including those participating in inflammation. We conclude that natural compounds have therapeutic potential for diseases mediated by oxidative stress, particularly obesity. Controlled and well-designed clinical trials are still necessary to better know the effects of these compounds.

Demystifying Oxidative Stress

The hypothesis that reactive oxygen species (ROS) can be not just associated with but causally implicated in disease was first made in 1956, but so far, the oxidative stress theory of disease has not led to major therapeutic breakthrough, and the use of antioxidant is now confined to the field of complementary medicine. This chapter reviews the lack of high-level clinical evidence for the effectiveness of antioxidants in preventing disease and the epistemological problems of the oxidative stress theory of disease. We conclude on possible ways forward to test this hypothesis with approaches that take into account personalized medicine. The previous oxidative stress model has helped neither to diagnose nor to treat possibly ROS-related or ROS-dependent diseases. The redox balance concept that low ROS levels are beneficial or tolerable and high levels are disease triggers and best reduced is apparently wrong. Physiological ROS signalling may become dysfunctional or a disease trigger by at least five mechanisms: a physiological source may appear at an unphysiological site, a physiological source may be underactivated (less common) or overactivated (more common), a new source may appear, a physiological source may be overactivated or underactivated, and a toxifying enzyme may convert an ROS signal molecule into a more reactive molecule. The latter three mechanisms may reach a physiological or nonphysiological target. All of these dysregulations may be the direct and essential cause of a disease (rarely the case) or just a secondary epiphenomenon, which will disappear once the non-ROS-related cause of the disease is cured (much more common). Importantly, these mechanisms are the same for almost every signalling system. Causal target validation (sources, toxifiers and targets) is essential in order to identify effective drugs and therapies for ROSopathies.

Colorectal cancer in the Linxian China Nutrition Intervention Trial: Risk factors and intervention results

BACKGROUND

Colorectal cancer (CRC) is among the most common cancers in economically developed countries and developing world. While dietary factors are associated with risk of CRC in the West and urban China, little is known about risk or protective factors in rural China.

METHODS

The Linxian General Population Nutrition Intervention Trial (NIT) cohort was established over 30 years ago to test whether daily multivitamin/mineral supplements could reduce the incidence and mortality of esophageal/gastric cardia cancer. The cohort included a total of 29,553 healthy participants 40-69 years old who were randomly assigned to supplements or placebos via a 24 fractional factorial study design. We examined risk factors for the development of CRC as well as the effects of four different nutritional factors (Factor A: retinol, zinc; B: riboflavin, niacin; C: ascorbic acid, molybdenum; D: selenium, alpha-tocopherol, beta-carotene,) on CRC incidence following 5.25 years of supplementation in this randomized, placebo-controlled intervention trial.

RESULTS

CRC risk increased with age and height as well as piped water usage, family history of CRC, and consumption of foods cooked in oil, eggs, and fresh fruits. No effect on CRC was seen for any of these four intervention factors tested in both genders, but CRC was reduced 37% in females who received Factor D (selenium/alpha-tocopherol/beta-carotene) (RR = 0.63, 95% CI = 0.43-0.92, P = 0.016) compared to females who did not receive Factor D.

CONCLUSIONS

In this undernourished rural Chinese population, CRC risk factors in this Chinese cohort showed both similarities and differences compared to Western and urban Asian Chinese populations. Intervention results suggested a potential benefit for women supplemented with selenium/alpha-tocopherol/beta-carotene.

Oxidative Stress-Inducing Anticancer Therapies: Taking a Closer Look at Their Immunomodulating Effects

Cancer cells are characterized by higher levels of reactive oxygen species (ROS) compared to normal cells as a result of an imbalance between oxidants and antioxidants. However, cancer cells maintain their redox balance due to their high antioxidant capacity. Recently, a high level of oxidative stress is considered a novel target for anticancer therapy. This can be induced by increasing exogenous ROS and/or inhibiting the endogenous protective antioxidant system. Additionally, the immune system has been shown to be a significant ally in the fight against cancer. Since ROS levels are important to modulate the antitumor immune response, it is essential to consider the effects of oxidative stress-inducing treatments on this response. In this review, we provide an overview of the mechanistic cellular responses of cancer cells towards exogenous and endogenous ROS-inducing treatments, as well as the indirect and direct antitumoral immune effects, which can be both immunostimulatory and/or immunosuppressive. For future perspectives, there is a clear need for comprehensive investigations of different oxidative stress-inducing treatment strategies and their specific immunomodulating effects, since the effects cannot be generalized over different treatment modalities. It is essential to elucidate all these underlying immune effects to make oxidative stress-inducing treatments effective anticancer therapy.

Dietary iron and vitamins in association with mortality

BACKGROUND & AIMS

Although disorders of iron metabolism are among the most common diseases and dietary intakes of vitamin A, B₂, B₆, C, E, and folic acid are known to affect the absorption or oxidation of iron, limited data are available on the association of dietary iron and these vitamins with mortality in the same population. Specifically, the holistic dietary vitamins intake and its combined effect with iron on mortality are unclear. The purpose of this study was to evaluate the association of dietary iron, holistic dietary vitamins, and their interactive effect with total and cause-specific mortality.

METHODS

We evaluated the effects of dietary total/heme/non-heme iron, vitamins, and their interaction on all-cause/cardiovascular disease (CVD)/cancer mortality among 14,826 US adults in the National Health and Nutrition Examination Survey (NHANES), a population-based nationally representative study. We developed a vitamin score to represent the holistic dietary intakes of vitamin A, B₂, B₆, C, E, and folic acid.

RESULTS

A total of 2154 deaths occurred during a median follow-up of 9.3 years. Results from multivariate Cox proportional hazards models showed that higher vitamin score was associated lower risk of all-cause mortality (P-trend = 0.027). Negative interactions between dietary heme iron and vitamin score were observed on all-cause/CVD mortality. Dietary higher vitamins combined with lower heme iron was associated with lower risk of all-cause and CVD mortality (HR (95% confidence intervals (CIs)): 0.80 (0.64-0.98) and 0.55 (0.31-0.98), respectively). Higher dietary vitamins combined with higher total/non-heme iron was associated with lower risk of CVD mortality (HR (95%CIs): 0.69 (0.48-0.99) and 0.70 (0.48-0.99), respectively). These results remained significant even excluding participants with iron supplementation.

CONCLUSION

Our findings suggested that interactive effect of holistic dietary vitamins and iron play a protective role in decreasing all-cause and CVD mortality. Future studies, including cohort studies and clinical trials, are necessary to confirm these findings.

Intake of Dietary Fruit, Vegetables, and Fiber and Risk of Colorectal Cancer According to Molecular Subtypes: A Pooled Analysis of 9 Studies

Protective associations of fruits, vegetables, and fiber intake with colorectal cancer risk have been shown in many, but not all epidemiologic studies. One possible reason for study heterogeneity is that dietary factors may have distinct effects by colorectal cancer molecular subtypes. Here, we investigate the association of fruit, vegetables, and fiber intake with four well-established colorectal cancer molecular subtypes separately and in combination. Nine observational studies including 9,592 cases with molecular subtypes for microsatellite instability (MSI), CpG island methylator phenotype (CIMP), and somatic mutations in BRAF and KRAS genes, and 7,869 controls were analyzed. Both case-only logistic regression analyses and polytomous logistic regression analyses (with one control set and multiple case groups) were used. Higher fruit intake was associated with a trend toward decreased risk of BRAF-mutated tumors [OR 4th vs. 1st quartile = 0.82 (95% confidence interval, 0.65-1.04)] but not BRAF-wildtype tumors [1.09 (0.97-1.22); P difference as shown in case-only analysis = 0.02]. This difference was observed in case-control studies and not in cohort studies. Compared with controls, higher fiber intake showed negative association with colorectal cancer risk for cases with microsatellite stable/MSI-low, CIMP-negative, BRAF-wildtype, and KRAS-wildtype tumors (P trend range from 0.03 to 3.4e-03), which is consistent with the traditional adenoma-colorectal cancer pathway. These negative associations were stronger compared with MSI-high, CIMP-positive, BRAF-mutated, or KRAS-mutated tumors, but the differences were not statistically significant. These inverse associations for fruit and fiber intake may explain, in part, inconsistent findings between fruit or fiber intake and colorectal cancer risk that have previously been reported. SIGNIFICANCE: These analyses by colorectal cancer molecular subtypes potentially explain the inconsistent findings between dietary fruit or fiber intake and overall colorectal cancer risk that have previously been reported.

Association of vitamin C intake with breast cancer risk and mortality: a meta-analysis of observational studies

The association between vitamin C intake and breast cancer is unclear. This meta-analysis aimed to precisely assess the association of vitamin C intake with breast cancer risk and mortality. We searched the PubMed, Embase, and Web of Science databases up to June 2020 and found 69 studies relevant to breast cancer risk (54 studies) and survival (15 studies). Relative risks and 95% confidence intervals were calculated using the random-effects models. Pooled results suggested that the highest versus lowest vitamin C intake was significantly associated with a lower risk of breast cancer incidence (Relative Risk = 0.86; 95% confidence interval, 0.81-0.92). Dietary vitamin C but not supplements was found to reduce breast cancer risk (Relative Risk = 0.89; 95% confidence interval, 0.82-0.96). For the highest versus lowest vitamin C intake, the pooled hazard risk for breast cancer-specific mortality was 0.78 (95% confidence interval, 0.69-0.88), totality mortality was 0.82 (95% confidence interval, 0.74-0.91), and recurrence was 0.81 (95% confidence interval, 0.67-0.99). Our analysis suggests that higher vitamin C intake is significantly associated with reduced breast cancer incidence and mortality. However, the intake of vitamin C supplements has no significant effect on breast cancer prevention.

Vitamin C and Cancer: The Role of Vitamin C in Disease Progression and Quality of Life in Cancer Patients

Much attention has been put on antioxidants as potential preventive and therapeutic agents against cancer. Vitamin C, an important antioxidant with anti-inflammatory and immune system enhancement features, could provide protection against cancer. However, experimental and epidemiologic evidence on vitamin C and cancer risk are still indefinite. Substantial literature reports that cancer patients experience vitamin C deficiency associated with decreased oral intake, infection, inflammation, disease processes, and treatments such as radiation, chemotherapy, and surgery. Studies demonstrate associations between IVC and inflammation biomarkers and propose some amelioration in symptoms, with a possible advantage in quality of life (QoL) when intravenous vitamin C (IVC) alone or in combination with oral vitamin C is administered in oncologic care. While, the anticancer impact of high doses of IVC remains debatable in spite of growing evidence that high dose vitamin C shows anti-tumorigenic activity by elevating the amount of reactive oxygen species (ROS) in cancer cells without meaningful toxicities. Hence, there is an urgent requirement for rigorous and well-controlled assessments of IVC as an adjuvant therapy for cancer before clear conclusions can be drawn. Thus, more clinical trials are required to determine the additive impact of high dose vitamin C in cancer patients.

Lifestyle, Oxidative Stress, and Antioxidants: Back and Forth in the Pathophysiology of Chronic Diseases

Oxidative stress plays an essential role in the pathogenesis of chronic diseases such as cardiovascular diseases, diabetes, neurodegenerative diseases, and cancer. Long term exposure to increased levels of pro-oxidant factors can cause structural defects at a mitochondrial DNA level, as well as functional alteration of several enzymes and cellular structures leading to aberrations in gene expression. The modern lifestyle associated with processed food, exposure to a wide range of chemicals and lack of exercise plays an important role in oxidative stress induction. However, the use of medicinal plants with antioxidant properties has been exploited for their ability to treat or prevent several human pathologies in which oxidative stress seems to be one of the causes. In this review we discuss the diseases in which oxidative stress is one of the triggers and the plant-derived antioxidant compounds with their mechanisms of antioxidant defenses that can help in the prevention of these diseases. Finally, both the beneficial and detrimental effects of antioxidant molecules that are used to reduce oxidative stress in several human conditions are discussed.

Lifestyle, Oxidative Stress, and Antioxidants: Back and Forth in the Pathophysiology of Chronic Diseases

Oxidative stress plays an essential role in the pathogenesis of chronic diseases such as cardiovascular diseases, diabetes, neurodegenerative diseases, and cancer. Long term exposure to increased levels of pro-oxidant factors can cause structural defects at a mitochondrial DNA level, as well as functional alteration of several enzymes and cellular structures leading to aberrations in gene expression. The modern lifestyle associated with processed food, exposure to a wide range of chemicals and lack of exercise plays an important role in oxidative stress induction. However, the use of medicinal plants with antioxidant properties has been exploited for their ability to treat or prevent several human pathologies in which oxidative stress seems to be one of the causes. In this review we discuss the diseases in which oxidative stress is one of the triggers and the plant-derived antioxidant compounds with their mechanisms of antioxidant defenses that can help in the prevention of these diseases. Finally, both the beneficial and detrimental effects of antioxidant molecules that are used to reduce oxidative stress in several human conditions are discussed.

Lifestyle, Oxidative Stress, and Antioxidants: Back and Forth in the Pathophysiology of Chronic Diseases

Oxidative stress plays an essential role in the pathogenesis of chronic diseases such as cardiovascular diseases, diabetes, neurodegenerative diseases, and cancer. Long term exposure to increased levels of pro-oxidant factors can cause structural defects at a mitochondrial DNA level, as well as functional alteration of several enzymes and cellular structures leading to aberrations in gene expression. The modern lifestyle associated with processed food, exposure to a wide range of chemicals and lack of exercise plays an important role in oxidative stress induction. However, the use of medicinal plants with antioxidant properties has been exploited for their ability to treat or prevent several human pathologies in which oxidative stress seems to be one of the causes. In this review we discuss the diseases in which oxidative stress is one of the triggers and the plant-derived antioxidant compounds with their mechanisms of antioxidant defenses that can help in the prevention of these diseases. Finally, both the beneficial and detrimental effects of antioxidant molecules that are used to reduce oxidative stress in several human conditions are discussed.