The health effects of vitamin C supplementation: a review

Dietary diversity and nutrient adequacy among women in Bosomtwe District, Ghana

The sustainable development goals seek to end all forms of malnutrition of women of reproductive age (WRA) by 2030. As such, recent data on nutrient adequacy are needed to aid in tracking progress. However, data on specific dietary nutrient intakes includes only iron, folate, vitamin A, and vitamin B12 in Ghana. Therefore, women's dietary diversity score (W-DDS) is often used as a proxy measure of nutrient adequacy. It is hypothesised that there is no association between W-DDS and Nutrient Adequacy among WRA in peri-urban Ghana. Hence, this research evaluated the associations between W-DDS and nutrient adequacy ratio (NAR) and assessed the determinants of mean nutrient adequacy ratio (MAR) in the Bosomtwe District of Ghana. A community-based cross-sectional study was conducted, and data collected on anthropometry, food insecurity, socio-demographic characteristics and dietary intake using the 24-hour recall from 407 WRA. In all, 21 nutrients were assessed. The mean age, W-DDS, and MAR were 29.0 ± 6.7 years, 5.3 ± 1.9, and 0.65 ± 0.19 respectively. The NAR were generally high for the macronutrients as compared to micronutrients and the nutrients with low NAR included vitamin C (0.27 ± 0.19), vitamin A (0.15 ± 0.23), vitamin B12 (0.54 ± 0.32), calcium (0.28 ± 0.20), zinc (0.52 ± 0.23) and iron (0.57 ± 0.28) - signifying the WRA may be consuming monotonous carbohydrate-based diet. The hierarchical multivariable linear regression found a significant association between W-DDS and MAR after controlling for confounders (β = 0.404, p < 0.001). The determinants of MAR were ethnicity (β = 0.110, p = 0.006) and body mass index (β = 0.189, p < 0.001). This study supports the use of W-DDS as a proxy indicator of nutrient adequacy. Strategies meant to address nutrient inadequacies should be adaptable to different ethnic groups and overweight-reducing strategies should be incorporated into broader nutrition initiatives.

Ascorbic acid as serine protease inhibitor in lung cancer cell line and human serum albumin

Serine proteases (SPs) are distributed among all living cells accounting for almost one-third of all proteases. Dysregulation of SPs during inflammation and/or infection can result in devastating consequences, such as skin and lung inflammation, neuroinflammation, arthritis, as well as metastasis of cancerous cells. Such activities are tightly regulated by various inhibitors known as serine protease inhibitors (SERPIN). The thermodynamic investigations previously revealed that L-ascorbic acid binds to trypsin more firmly than pepsin and the binding force of L-ascorbic acid is driven by hydrogen bonds and van der Waals forces. However, the physiochemical effects of such interaction on trypsin and/or pepsin have not yet been reported. Ascorbic acid, also known as vitamin C, is one of the essential nutrients and most common food supplements, fortificants, and preservatives. The aim of this study was to explore the inhibitory effects of ascorbic acid on serine proteases at various concentrations on the in-vitro digestion and/or hydrolysis of intercellular matrix of cell monolayer and human serum albumin (HSA). The inhibitory effects of ascorbic on trypsin are investigated by qualitative and quantitative analysis using SDS-PAGE imaging and NIH densitometric software. Upon the addition of ascorbic acid in both indicator systems, the detachment and/or dissociation of cell monolayer and the digestion of HSA were inhibited in the presence of EDTA-Trypsin. The inhibitory effect of ascorbic acid on the digestion of intercellular matrix and/or hydrolysis of HSA showed a dose-dependent trend until it reached the maximum extent of inhibition. At an equal concentration (2.5mg/mL) ascorbic acid and EDTA-Trypsin exhibited the most potent inhibitory effect on the in vitro digestion of protein either in the form of intercellular matrix in cell monolayer and/or HSA respectively. Overall, our results based on two indicator systems strongly indicate that ascorbic acid may function as a serine protease inhibitor (SERPIN) beyond other important functions.

Diet quality as assessed by the healthy eating index-2020 among different smoking status: an analysis of national health and nutrition examination survey (NHANES) data from 2005 to 2018

BACKGROUND

Combining smoking with poor eating habits significantly elevates the risk of chronic illnesses and early death. Understanding of how dietary quality shifts post-smoking cessation remains limited. The objective of this study is to examine dietary quality - using Healthy Eating Index (HEI - 2020) and its 13 components, among current, former, and never smokers, and particularly the impact of quitting and the duration of cessation on dietary habits.

METHODS

A cross-sectional analysis of 31,569 adults from the National Health and Nutrition Examination Survey (NHANES) 2005-2018 was conducted. Dietary quality was assessed using HEI-2020 scores, which were determined by NIH developed - simple HEI scoring algorithm per person. Smoking status was categorized into current, former, and never smokers, with further subdivisions for current (heavy/light smokers) and former smokers (duration post-cessation). Descriptive analysis and multiple regression models weighted to represent the US population were performed.

RESULTS

The current smoking rate was 19.4%, with a higher prevalence in males (22.5%) than females (17.5%). Current smokers reported statistically significantly lower HEI total score than both former and never smokers. Former smokers exhibited HEI scores similar to those of never smokers. The adjusted HEI total scores for current, former, and never smokers were 49.2, 54.0, and 53.3, respectively, with a statistically significant difference (p < 0.001). Moreover, light smokers had better total HEI score than heavy smokers (46.8 vs. 50.8, p < 0.001, respectively), but former and never smokers scored even higher. Quitting smoking immediately improved dietary quality, with former smokers reaching the dietary levels of never smokers within 5-10 years (53.8 vs. 53.3, p > 0.05, respectively). Compared to current smokers, former smokers tended to consume more beneficial foods (e.g., fruits, vegetables, greens and beans, whole grains, proteins, and fatty acids), while also consuming more sodium and less added sugar.

CONCLUSIONS

Current smokers, particularly heavy smokers, exhibit poorer dietary habits than former and never smokers. The dietary quality of former smokers aligns with never smokers over time, highlighting the positive impact of smoking cessation on diet. This has implications for reducing chronic disease risks associated with poor diet and smoking.

Vitamin C fortification: need and recent trends in encapsulation technologies

The multifaceted role of vitamin C in human health intrudes several biochemical functions that are but not limited to antioxidant activity, homoeostasis, amino acid synthesis, collagen synthesis, osteogenesis, neurotransmitter production and several yet to be explored functions. In absence of an innate biosynthetic pathway, humans are obligated to attain vitamin C from dietary sources to maintain its optimal serum level (28 μmol/L). However, a significant amount of naturally occurring vitamin C may deteriorate due to food processing, storage and distribution before reaching to the human gastrointestinal tract, thus limiting or mitigating its disease combating activity. Literature acknowledges the growing prevalence of vitamin C deficiency across the globe irrespective of geographic, economic and population variations. Several tools have been tested to address vitamin C deficiency, which are primarily diet diversification, biofortification, supplementation and food fortification. These strategies inherit their own advantages and limitations. Opportunely, nanotechnology promises an array of delivery systems providing encapsulation, protection and delivery of susceptible compounds against environmental factors. Lack of clear understanding of the suitability of the delivery system for vitamin C encapsulation and fortification; growing prevalence of its deficiency, it is a need of the hour to develop and design vitamin C fortified food ensuring homogeneous distribution, improved stability and enhanced bioavailability. This article is intended to review the importance of vitamin C in human health, its recommended daily allowance, its dietary sources, factors donating to its stability and degradation. The emphasis also given to review the strategies adopted to address vitamin c deficiency, delivery systems adopted for vitamin C encapsulation and fortification.

Microwave induced thermally assisted solvent-based bonding of biodegradable thermoplastics: an eco-friendly rapid approach for fabrication of microfluidic devices and analyte detection

There is an increasing interest in low-cost, facile and versatile thermoplastic bonding for microfluidic applications that can be easily transitioned from laboratory prototyping to industrial manufacturing. In addition, owing to the surge in the usage of thermoplastic microfluidics and its adverse effect on the environment, it is prudent to source alternative materials that are biodegradable, providing a sustainable, green approach. To address the problems, here we introduce an environment friendly, low-cost and safe welding technology used in the fabrication of microcassettes from biodegradable cellulose acetate (CA) thermoplastics. The thermally assisted solvent based bonding of the thermoplastics was accomplished in a domestic microwave oven with the aid of a polyether ether ketone (PEEK) vise. To characterize the quality of the bonding, our in-house technique was compared with a conventional thermally assisted solvent bonding configuration using a heat press machine and tested under different conditions. Our microwave induced bonding of CA presents three times reduced bonding time with higher bonding strength, good reliability and does not necessitate the use of cumbersome instrumentation. Finally, we demonstrate an electrophoresis application and vitamin C detection accomplished using this biodegradable microcassette presenting comparable results with traditional techniques, illustrating the potential of this fabrication technique in different microfluidic applications.

Inhibitory Effect of Ascorbic Acid on in vitro Enzymatic Digestion of Raw and Cooked Starches

Ascorbic acid, also known as vitamin C, was previously reported to inhibit the activity of pancreatic α-amylase, the primary digestive enzyme for starch. A major implication of such inhibition is a slowed rate of starch digestion into glucose, which thereby reduces postprandial hyperglycemia. The aim of this study was to explore the inhibitory effects of ascorbic acid at various concentrations on the in vitro digestion of high amylose maize starch (HAMS) and potato starch (PS) in both raw and cooked conditions. Resistant starch (RS) content, defined as the starch that remained after 4 h of simulated in vitro enzymatic digestion, was measured for the starch samples. Upon the addition of ascorbic acid, the RS contents increased in both raw and cooked starches. Cooking significantly reduced the RS contents as compared to raw starches, and less increase in RS was observed with the addition of ascorbic acid. The inhibitory effect of ascorbic acid on the digestion of raw starches showed a dose-dependent trend until it reached the maximum extent of inhibition. At the concentrations of 12.5 and 18.75 mg/mL, ascorbic acid exhibited the most potent inhibitory effect on the in vitro starch digestion in raw and cooked conditions, respectively. Overall, our results strongly indicate that ascorbic acid may function as a glycemic modulatory agent beyond other important functions, and its effects persist upon cooking with certain concentrations applied.

Boosting the Photoaged Skin: The Potential Role of Dietary Components

Skin photoaging is mainly induced by ultraviolet (UV) irradiation and its manifestations include dry skin, coarse wrinkle, irregular pigmentation, and loss of skin elasticity. Dietary supplementation of nutraceuticals with therapeutic and preventive effects against skin photoaging has recently received increasing attention. This article aims to review the research progress in the cellular and molecular mechanisms of UV-induced skin photoaging. Subsequently, the beneficial effects of dietary components on skin photoaging are discussed. The photoaging process and the underlying mechanisms are complex. Matrix metalloproteinases, transforming growth factors, skin adipose tissue, inflammation, oxidative stress, nuclear and mitochondrial DNA, telomeres, microRNA, advanced glycation end products, the hypothalamic-pituitary-adrenal axis, and transient receptor potential cation channel V are key regulators that drive the photoaging-associated changes in skin. Meanwhile, mounting evidence from animal models and clinical trials suggests that various food-derived components attenuate the development and symptoms of skin photoaging. The major mechanisms of these dietary components to alleviate skin photoaging include the maintenance of skin moisture and extracellular matrix content, regulation of specific signaling pathways involved in the synthesis and degradation of the extracellular matrix, and antioxidant capacity. Taken together, the ingestion of food-derived functional components could be an attractive strategy to prevent skin photoaging damage.

Thermodynamic prediction of proton and hydrogen atom abstraction in dehydroascorbic acid and its bicyclic form

Conformation analysis of dehydroascorbic acid and its bicyclic form was performed using the density functional theory. For the energetically preferred conformations, ionization potentials (IP) and bond dissociation enthalpies (BDE) were calculated using the B3LYP functional and 6-311++G** basis set. The effects of aqueous solution were estimated using the solvation model based on density (SMD) and the polarizable continuum model (IEF-PCM). The obtained results were compared with available experimental data for reference L-ascorbic acid (vitamin C). Our calculations indicate that the investigated bicyclic metabolic product of vitamin C can also exhibit limited radical scavenging ability due to the thermodynamically preferred dissociation of tertiary —CH bonds.

(Ascorb)ing Pb Neurotoxicity in the Developing Brain

Lead (Pb) neurotoxicity is a major concern, particularly in children. Developmental exposure to Pb can alter neurodevelopmental trajectory and has permanent neuropathological consequences, including an increased vulnerability to further stressors. Ascorbic acid is among most researched antioxidant nutrients and has a special role in maintaining redox homeostasis in physiological and physio-pathological brain states. Furthermore, because of its capacity to chelate metal ions, ascorbic acid may particularly serve as a potent therapeutic agent in Pb poisoning. The present review first discusses the major consequences of Pb exposure in children and then proceeds to present evidence from human and animal studies for ascorbic acid as an efficient ameliorative supplemental nutrient in Pb poisoning, with a particular focus on developmental Pb neurotoxicity. In doing so, it is hoped that there is a revitalization for further research on understanding the brain functions of this essential, safe, and readily available vitamin in physiological states, as well to justify and establish it as an effective neuroprotective and modulatory factor in the pathologies of the nervous system, including developmental neuropathologies.

Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trial

INTRODUCTION

The Republic of Korea (ROK) military has a high incidence of respiratory diseases at training centres. Vitamin C has been reported to reduce the incidence of colds. For the purpose of preventing soldiers' respiratory diseases, this study aimed to investigate whether vitamin C intake can prevent common colds in the ROK Army soldiers.

METHODS

This was a randomised, placebo-controlled, and double-blind trial of soldiers who enlisted in the Korea Army Training Centre for 30 days from 12 February to 13 March 2018. The study participants were divided into groups (vitamin C vs placebo). The military medical records were searched to determine whether the participants had a common cold. Multiple logistic regression analysis was performed to identify the association between vitamin C intake and diagnosis of common colds. In addition, subgroup analysis on the relationship between vitamin C intake and common cold according to smoking status, training camp and physical rank was conducted.

RESULTS

A total of 1444 participants were included in our study. Of these participants, 695 received vitamin C (6000 mg/day, vitamin C group), while 749 participants received placebo (0 mg/day, placebo group). The vitamin C group had a 0.80-fold lower risk of getting a common cold than did the placebo group. Subgroup analyses showed that this effect was stronger among subjects in camp A, among never smokers and among those in physical rank 3.

CONCLUSION

Vitamin C intake provides evidence to suggest that reducing the common colds in Korean Army soldiers. Our results may serve as a basis for introducing military healthcare policies that can provide vitamin C supplementation for military personnel in basic military training.

Review on nutritional composition of orange-fleshed sweet potato and its role in management of vitamin A deficiency

A wide variety of the roots and tubers plays a major role in human diet, animal feed, and industrial raw materials. Sweet potatoes (SPs) play an immense role in human diet and considered as second staple food in developed and underdeveloped countries. Moreover, SP production and management need low inputs compared to the other staple crops. The color of SP flesh varied from white, yellow, purple, and orange. Scientific studies reported the diversity in SP flesh color and connection with nutritional and sensory acceptability. Among all, orange-fleshed sweet potato (OFSP) has been attracting food technologists and nutritionists due to its high content of carotenoids and pleasant sensory characteristics with color. Researchers reported the encouraging health effects of OFSP intervention into the staple food currently practicing in countries such as Uganda, Mozambique, Kenya, and Nigeria. Scientific reviews on the OFSP nutritional composition and role in vitamin A management (VAM) are hardly available in the published literature. So, this review is conducted to address the detailed nutritional composition (proximate, mineral, carotenoids, vitamins, phenolic acids, and antioxidant properties), role in vitamin A deficiency (VAD) management, and different food products that can be made from OFSP.

Ascorbic acid diminishes bone morphogenetic protein 2-induced osteogenic differentiation of muscle precursor cells

INTRODUCTION

Muscle precursor cells (MPC) are integral to the maintenance of skeletal muscle and have recently been implicated in playing a role in bone repair. The primary objective of this study was to understand better the role of oxidative stress during the osteogenic differentiation of MPCs.

METHODS

Muscle precursor cells were treated with various combinations of ascorbic acid (AA), bone morphogenetic protein (BMP)-2, and either a superoxide dismutase analog (4-hydroxy-TEMPO [TEMPOL]) or polyethyleneglycol-conjugated catalase. Muscle precursor cell proliferation and differentiation were determined, and alkaline phosphatase activity was measured as an index of osteogenic differentiation.

RESULTS

After treatment with 200 μM AA, superoxide was increased 1.5-fold, whereas AA in combination with 100 ng/ml BMP-2 did not increase alkaline phosphatase (ALP) activity. When cells were treated with TEMPOL in combination with 100 ng/ml BMP-2 and 200 μM AA, ALP activity significantly increased.

DISCUSSION

These data suggest that increasing oxidative stress with AA induces sublethal oxidative stress that prevents BMP-2-induced osteogenic differentiation of MPCs. Muscle Nerve 59:501-508, 2019.

Emerging Evidence on Neutrophil Motility Supporting Its Usefulness to Define Vitamin C Intake Requirements

Establishing intake recommendations for vitamin C remains a challenge, as no suitable functional parameter has yet been agreed upon. In this report, we review the emerging evidence on neutrophil motility as a possible marker of vitamin C requirements and put the results in perspective with other approaches. A recent in vitro study showed that adequate levels of vitamin C were needed for this function to work optimally when measured as chemotaxis and chemokinesis. In a human study, neutrophil motility was optimal at intakes ≥250 mg/day. Interestingly, a Cochrane review showed a significant reduction in the duration of episodes of common cold with regular vitamin C intakes in a similar range. Additionally, it was shown that at a plasma level of 75 µmol/L, which is reached with vitamin C intakes ≥200 mg/day, incidences of cardiovascular disease were lowest. This evidence would suggest that daily intakes of 200 mg vitamin C might be advisable for the general adult population, which can be achieved by means of a diverse diet. However, additional studies are warranted to investigate the usefulness of neutrophil motility as a marker of vitamin C requirements.

Liposomal-encapsulated Ascorbic Acid: Influence on Vitamin C Bioavailability and Capacity to Protect Against Ischemia-Reperfusion Injury

Intravenous administration of vitamin C has been shown to decrease oxidative stress and, in some instances, improve physiological function in adult humans. Oral vitamin C administration is typically less effective than intravenous, due in part to inferior vitamin C bioavailability. The purpose of this study was to determine the efficacy of oral delivery of vitamin C encapsulated in liposomes. On 4 separate randomly ordered occasions, 11 men and women were administered an oral placebo, or 4 g of vitamin C via oral, oral liposomal, or intravenous delivery. The data indicate that oral delivery of 4 g of vitamin C encapsulated in liposomes (1) produces circulating concentrations of vitamin C that are greater than unencapsulated oral but less than intravenous administration and (2) provides protection from ischemia–reperfusion-mediated oxidative stress that is similar to the protection provided by unencapsulated oral and intravenous administrations.

A Randomized Controlled Trial Evaluating a Low-Volume PEG Solution Plus Ascorbic Acid versus Standard PEG Solution in Bowel Preparation for Colonoscopy

Evaluation of polyethylene glycol electrolyte lavage solution containing ascorbic acid (PEG-ASC) has been controversial in the point of its hyperosmolarity, especially in old population. So we therefore designed the present study to compare the efficacy, acceptability, tolerability, and safety of 1.5 L PEG+ASC and 2 L standard PEG electrolyte solution (PEG-ELS), not only in the general population, but also in patients of advanced age. Randomization was stratified by age (<70 years or 70> years), and hematological and biochemical parameters were compared in each age group, especially with respect to the safety profile of each regimen. As a result, the 1.5-L PEG-ASC regimen had higher patient acceptability than the 2-L PEG-ELS regimen. Tolerability, bowel cleansing, and safety were similar between regimens. However, we demonstrated significant statistical changes in the hematological and biochemical parameters after taking bowel preparation solutions, not only in the PEG+ASC group, but also in the PEG-ELS group. No significant differences in the safety profile were found between subjects aged less than 70 years and those aged 70 years or more; nevertheless, regardless of age, proper hydration is needed throughout the bowel preparation process.

Protective effects of ascorbic acid against the genetic and epigenetic alterations induced by 3,5-dimethylaminophenol in AA8 cells

Exposure to monocyclic aromatic alkylanilines (MAAs), namely 2,6-dimethylaniline (2,6-DMA), 3,5-dimethylaniline (3,5-DMA) and 3-ethylaniline (3-EA), was significantly and independently associated with bladder cancer incidence. 3,5-DMAP (3,5-dimethylaminophenol), a metabolite of 3,5-DMA, was shown to induce an imbalance in cytotoxicity cellular antioxidant/oxidant status, and DNA damage in mammalian cell lines. This study was designed to evaluate the protective effect of ascorbic acid (Asc) against the cytotoxicity, reactive oxygen species (ROS) production, genotoxicity and epigenetic changes induced by 3,5-DMAP in AA8 Chinese Hamster Ovary (CHO) cells. In different cellular fractions, 3,5-DMAP caused alterations in the enzyme activities orchestrating a cellular antioxidant balance, decreases in reduced glutathione levels and a cellular redox ratio as well as increases in lipid peroxidation and protein oxidation. We also suggest that the cellular stress caused by this particular alkylaniline leads to both genetic (Aprt mutagenesis) and epigenetic changes in histones 3 and 4 (H3 and H4). This may further cause molecular events triggering different pathological conditions and eventually cancer. In both cytoplasm and nucleus, Asc provided increases in 3,5-DMAP-reduced glutathione levels and cellular redox ratio and decreases in the lipid peroxidation and protein oxidation. Asc was also found to be protective against the genotoxic and epigenetic effects initiated by 3,5-DMAP. In addition, Asc supplied protection against the cell cycle (G1 phase) arrest induced by this particular alkylaniline metabolite.

A meta-analysis of randomized controlled trials of low-volume polyethylene glycol plus ascorbic acid versus standard-volume polyethylene glycol solution as bowel preparations for colonoscopy

BACKGROUND

Standard-volume polyethylene glycol (PEG) gut lavage solutions are safe and effective, but they require the consumption of large volumes of fluid. A new lower-volume solution of PEG plus ascorbic acid has been used recently as a preparation for colonoscopy.

AIM

A meta-analysis was performed to compare the performance of low-volume PEG plus ascorbic acid with standard-volume PEG as bowel preparation for colonoscopy.

STUDY

Electronic and manual searches were performed to identify randomized controlled trials (RCTs) that compared the performance of low-volume PEG plus ascorbic acid with standard-volume PEG as bowel preparation for colonoscopy. After a methodological quality assessment and data extraction, the pooled estimates of bowel preparation efficacy during bowel cleansing, compliance with preparation, willingness to repeat the same preparation, and the side effects were calculated. We calculated pooled estimates of odds ratios (OR) by fixed- and/or random-effects models. We also assessed heterogeneity among studies and the publication bias.

RESULTS

Eleven RCTs were identified for analysis. The pooled OR for preparation efficacy during bowel cleansing and for compliance with preparation for low-volume PEG plus ascorbic acid were 1.08 (95% CI = 0.98-1.28, P = 0.34) and 2.23 (95% CI = 1.67-2.98, P<0.00001), respectively, compared with those for standard-volume PEG. The side effects of vomiting and nausea for low-volume PEG plus ascorbic acid were reduced relative to standard-volume PEG. There was no significant publication bias, according to a funnel plot.

CONCLUSIONS

Low-volume PEG plus ascorbic acid gut lavage achieved non-inferior efficacy for bowel cleansing, is more acceptable to patients, and has fewer side effects than standard-volume PEG as a bowel preparation method for colonoscopy.

2 L PEG plus ascorbic acid versus 4 L PEG plus simethicon for colonoscopy preparation: a randomized single-blind clinical trial

BACKGROUND

The 2 L polyethylene glycol (PEG) lavage solution has been proved to be similarly safe and effective as 4 L PEG formulations, in spite of the reduced volume.

OBJECTIVE

To compare low-volume PEG-based solution combined with ascorbic acid with high-volume PEG-based solution combined with simethicon in terms of efficacy and patient tolerability.

METHODS

This was a single-blind prospective randomized trial. Patients were randomized to receive either 2 L PEG plus ascorbic acid (PEG+Asc) or 4 L PEG plus simethicon (PEG+Sim). The primary endpoint was overall colon cleansing evaluation, assessed by blinded investigators using Aronchick score. Secondary end points included patient compliance and tolerability and adverse events.

RESULTS

Sixty patients received PEG+Asc and 60 received PEG+Sim. Overall bowel cleansing score was considered adequate in 81.67% of the PEG+Asc and 80% of the PEG+Sim groups, respectively. Excellent and good ratings were recorded in 11.6% and 38.3% receiving PEG+Asc as compared with 26.6% and 23.3% of patients receiving PEG+Sim. Patient tolerability and safety were similar with both the preparations.

CONCLUSIONS

According to our data, low-volume PEG+Asc has comparable efficacy, safety, and tolerability as high-volume PEG+Sim; therefore, it can be considered as a good alternative solution for bowel preparation. More improvements are necessary to achieve the target of a perfect preparation.

Low-volume PEG plus ascorbic acid versus high-volume PEG as bowel preparation for colonoscopy

OBJECTIVE

High volumes of polyethylene glycol (PEG)-based solutions as bowel preparation for colonoscopy are effective, but often poorly tolerated. To compare a 2 l PEG-based solution combined with ascorbic acid (PEG + Asc) with 4 l PEG-based solution (PEG).

METHODS

In a single blind, quasi-randomized, prospective study, 350 patients undergoing colonoscopy received 2 l of PEG + Asc or 4 l of PEG. For morning procedures, the total dose of PEG + Asc was taken the evening before, for afternoon colonoscopies, PEG + Asc was given as a split dose. The 4 l PEG preparation was given as a split dose. Efficacy of preparation was scored on a five-point scale in three different colon segments. Patients' experiences were evaluated using a questionnaire.

RESULTS

From 307 patients (149 PEG + Asc, 158 PEG), results were available. Successful colon cleansing was achieved in 90.6% in the PEG + Asc group compared to 96% in the PEG group (not significant). In patients prepared with PEG + Asc, bowel cleansing was worse when patients underwent colonoscopy in the morning, compared to afternoon procedures. Side-effects and patients' experiences were similar in the PEG + Asc and PEG group.

CONCLUSIONS

Low-volume PEG + ascorbic acid has comparable efficacy and tolerability as high-volume PEG solution. The cleansing results were worse if patients received the full dose PEG + Asc the evening before the procedure compared to the split dose. Our data support the administration of PEG + Asc as a split dose before the procedure.

Vitamin C: is supplementation necessary for optimal health?

BACKGROUND

Consumption of vitamin C is essential for life in humans because the body does not synthesize it. Numerous studies have demonstrated that supplementation with vitamin C enhances the immune system, avoids DNA damage, and significantly decreases the risk of a wide range of pathologies, such as cancers, and degenerative and chronic diseases. Moreover, it has been demonstrated that modern crop production, transport, and food storage severely impair the quality of food and provoke a loss in micronutrients, such as vitamin C.

OBJECTIVES

In this paper, we report that the Recommended Daily Allowance (RDA) in vitamin C is lower than the bodily needs. In fact, it does not seem to ensure true health protection and it appears difficult to reach an effective dose of vitamin C only through food consumption. Furthermore, the literature shows that vitamin C intake higher than the RDA is safe. Therefore, in order to achieve optimal health and avoid a number of diseases, we suggest that, in the present situation, vitamin C supplementation is required.

CONCLUSIONS

According to the current literature, we would like to emphasize that to ensure an optimal allowance of vitamin C, we advise 1 g daily intake of vitamin C supplementation, accompanied by a diet rich in fruits and vegetables.

Nutritional biochemistry of spaceflight

As we approach the end of the first 50 years of human space travel, much has been learned about adaptation to microgravity and the risks associated with extended-duration space exploration. As the frequency and duration of flights grew, nutrition issues became more critical and the questions to be answered became more complex: What are the nutrient requirements for space travelers? Can nutrients be used as tools to mitigate the negative effects of space travel on humans? How does nutrition interrelate with other physiological systems (such as muscle, bone, and cardiovascular system) and their adaptation to microgravity? Much research has been done over the decades in both actual spaceflight and ground-based analogs. We review here much of what is known, and highlight areas of ongoing research and concerns for future exploration of the Moon, Mars, and beyond.

Randomized trial of low-volume PEG solution versus standard PEG + electrolytes for bowel cleansing before colonoscopy

OBJECTIVES

Polyethylene glycol (PEG)-based gut lavage solutions are safe and effective, but require consumption of large volumes of fluid. We compared a new 2 L solution of PEG plus ascorbic acid (PEG + Asc) with standard 4 L PEG with electrolytes (PEG + E) for bowel cleansing before colonoscopy to determine efficacy, safety, and patient acceptability.

METHODS

Consenting adult inpatients scheduled to undergo colonoscopy were randomized to receive either 2 L PEG + Asc or 4 L PEG + E. Preparations were taken as split doses the evening before colonoscopy and the following morning. The PEG + Asc group took 1 L at each administration (i.e., total dose of 2 L). The PEG + E group took 2 L at each administration (i.e., total dose of 4 L). Bowel cleansing success was assessed via videotapes by independent, blinded raters. Statistical noninferiority was predefined as a difference of <15% in the lower limit of the 97.5% confidence interval for treatment difference. Patient views on the preparations were elicited. Adverse events were noted.

RESULTS

Successful gut cleansing was achieved in 136 of 153 (88.9%) cases of the PEG + Asc group and 147 of 155 (94.8%) cases of the 4 L PEG + E group (mean difference -5.9 [-12.0-infinity]). The difference fell within the predefined limit for noninferiority. Clinical and laboratory parameters showed no difference in safety profile. Patient ratings of acceptability and taste were better for the PEG + Asc group than for the PEG + E group (P < 0.025).

CONCLUSIONS

The combination of ascorbic acid and PEG-based bowel preparation reduces the volume patients have to drink without compromising efficacy or safety. The low-volume PEG + Asc preparation was more acceptable to patients, and should, therefore, improve effectiveness in routine practice.

Green tea catechins upregulate superoxide dismutase and catalase in fruit flies

Chinese Longjing green tea is an excellent source of polyphenol antioxidants. HPLC analysis revealed that Longjing green tea catechin extract (GTC) contained 62% epigallocatechin gallate (EGCG), 19% epigallocatechin (EGC), 9% epicatechin gallate (ECG), and 7% epicatechin (EC). Investigating the effect of GTC on the lifespan of Drosophila melanogaster, we observed that a 10 mg GTC/mL diet could prolong its 50% survival time by 36% and mean lifespan by 16%. This was consistent with 17% reduction in total body lipid hydroperoxide (LPO) level in GTC-treated flies compared to the control group. Supplementation of 10 mg GTC/mL diet increased the survival time only in wild type Oregon-R-C (OR) but not in two mutant fly lines, SOD(n108)/TM3 (gene for superoxide dismutase (SOD) was knocked out) and Cat(n1)/TM3 (gene for catalase was knocked out), when the flies were challenged with paraquat or hydrogen peroxide. Accordingly, SOD and catalase activities in OR wild type increased by 40 and 19%, respectively. RT-PCR analysis indicated that the genes for copper-zinc containing SOD (CuZnSOD), manganese containing SOD (MnSOD), and catalase were upregulated. It was concluded that prolonging lifespan by GTC in D. melanogaster was influenced, among others, by upregulation of endogenous antioxidant enzymes.

Dietary Supplements for The Prevention and Treatment of Coronary Artery Disease

PURPOSE

With the recent growth in the use of dietary supplements, it is increasingly important for clinicians to be familiar with the evidence for and against their efficacy. We set out to systematically review the dietary supplements available for the prevention and treatment of coronary artery disease.

METHODS

Between May 2004 and May 2006, we searched MEDLINE, the Cochrane Library, and Pro-Quest using the MeSH terms hypertension, hypercholesterolemia, myocardial infarction, dietary supplements, and herb-drug interactions. The MeSH terms of individual supplements identified were then added to the search. Reference lists of pertinent papers were also searched to find appropriate papers for inclusion. We included randomized controlled trials published in English of at least 1 week's duration that studied the efficacy of supplements in the treatment of hypercholesterolemia, or hypertension, or in the prevention of cardiac events. Qualifying papers were identified and assigned a Jadad quality score. In areas of uncertainty, a second investigator independently scored the trial.

RESULTS

Fifteen (15) supplements were identified. Of these, most had little data available and most of the data were of poor quality. The supplements with the most supporting data were policosanol and garlic, both for hyperlipidemia.

CONCLUSIONS

A growing body of literature exists for numerous supplements in the prevention of coronary artery disease, but much of these data are inconclusive. Clinicians should become familiar with the extent and limitations of this literature so that they may counsel their patients better.

High-dose vitamin C infusion reduces fluid requirements in the resuscitation of burn-injured sheep

Fluid resuscitation to maintain adequate tissue perfusion while reducing edema in the severely burned patient remains a challenge. Recent studies suggest that reactive oxygen species generated by thermal injury are involved in edema formation associated with burn. The present study tested the hypothesis that adding a free radical scavenger to the resuscitation fluid would reduce total fluid requirements in the treatment of severe thermal injury. Anesthetized chronically instrumented sheep received a 40% total body surface area full-thickness flame burn. At 1 h after injury, animals were resuscitated with lactated Ringer's (LR, n = 14) as control, LR containing high doses of vitamin C (VC, n = 6), 1000 mOsM hypertonic saline (HS, n = 7), or 1000 HS containing VC (HS/VC, n = 7) in coded bags so that investigators were blinded to the treatment. Fluids were infused at an initial Parkland rate of 10 mL/kg/h, adjusted hourly to restore and maintain urine output at 1 to 2 mL/kg/h. Sheep in the VC or HS/VC group received 250 mg/kg VC in the first 500 mL of LR or HS, and then 15 mg/kg/h thereafter. Hemodynamic variables and indices of antioxidant status were measured. At 48 h postburn, sheep were euthanized, and heart, liver, lung, skeletal muscle, and ileum were evaluated for antioxidant status. All fluid resuscitation regimens were equally effective in restoring cardiac output to near baseline levels; no treatment effects were apparent on arterial pressure or heart rate. VC infusion significantly reduced fluid requirements and, therefore, net fluid balance (fluid in, urine out) by about 30% at 6 h and about 50% at 48 h in comparison with the LR group (P < 0.05). HS and HS/VC reduced fluid requirements by 30% and 65%, respectively, at 6 h, but the volume-sparing effect of HS was not observed after 36 h and that of HS/VC was lost after 12 h. Plasma total antioxidant potential increased about 25-fold (P < 0.05) at 2 and 3 h in response to VC infusion compared with the LR and HS groups, and remained about 5- to 10-fold higher throughout the rest of the study. VC infusion also prevented the 4-fold increase in plasma thiobarbituric acid reactive substances seen in the LR group early after burn (P < 0.05). Tissue antioxidant status was similar between groups. In this sheep burn model, continuous high-dose VC infusion reduced net fluid balance, reduced indices of plasma lipid peroxidation, and maintained overall antioxidant status in comparison with standard-of-care LR treatment.

Vitamins inhibit oxidant-induced apoptosis of corneal endothelial cells

PURPOSE

To determine the effects of vitamins A, C, and E supplementation on lipid peroxidation and apoptosis in corneal endothelial cells.

METHODS

Murine corneal endothelial cells were maintained in tissue culture medium supplemented with free iron ions, known to lead to increased lipid peroxidation. The concentration of antioxidative vitamins (ascorbic acid, tocopherol, and retinoic acid) in the cells and supernatant was determined using reversed-phase high-performance liquid chromatography. Apoptosis was assessed by quantification of caspase-3-like activity, using annexin-V/propidium iodide stains for flow cytometry. Lipid peroxidation was assessed using the malondialdehyde method. Supplementation of antioxidative vitamins was tested in the setting of apoptosis.

RESULTS

Increasing levels of free iron led to a rapid loss of antioxidative vitamins in the supernatant and corneal endothelial cells. This was correlated with rising levels of malondialdehyde and increased apoptosis. Supplementation with ascorbic acid or alpha-tocopherol alone was not sufficient to prevent lipid peroxidation in the cells, whereas a combination of vitamins C and E was able to do so. In contrast, supplementation with vitamin A alone significantly reduced oxidative stress and apoptosis.

CONCLUSIONS

We present an in vitro model to test the direct influence of vitamin supplementation on corneal endothelial cells with regard to lipid peroxidation and apoptosis. We show that supplementation with antioxidative vitamins of corneal endothelial cells significantly prevents the generation of free-radical injury, lipid peroxidation, and consequent apoptosis.

Micronutrient requirements in older women

The nutritional requirements of older women is an area of great interest because the extended life expectancy leads to an increase in women living into their 80s, 90s, and longer. The recommended dietary allowances (RDAs) and dietary reference intakes (DRIs) are not specific for women living to advanced ages, and little research has been conducted specifically on the micronutrient needs of elderly women. Older adults are at greater risk for nutritional deficiencies than are younger adults due to physiologic changes associated with aging, acute and chronic illnesses, prescription and over-the-counter medications, financial and social status, and functional decline. Among the significant age-associated changes in nutrient requirements, the need for energy decreases and the requirements for protein increase with age. Among the micronutrients, the significant ones that may be associated with deficiencies in elderly women include vitamin B-12, vitamin A, vitamin C, vitamin D, calcium, iron, zinc, and other trace minerals. In old and very old women, these are micronutrients of interest but there is a great need for research to determine appropriate recommendations. The importance of these selected nutrients and the reasons for the likelihood of deficiency are discussed briefly. However, there is little specific information regarding micronutrient requirements for elderly women. One reason for this is the difficulty in conducting reliable and valid studies due to the heterogeneity of older adults and their unique rate of aging associated with their health status, limited income, disability, and living situation.

The release of vitamin C from chewing gum and its effects on supragingival calculus formation

The aims of this study were to evaluate (i): whether vitamin C in chewing gum, alone or in combination with carbamide, influences calculus formation, and (ii) whether carbamide affects the release, stability and uptake of vitamin C in a chewing gum. In two test series (Series I and II), 30 subjects, all calculus formers, participated. They were instructed to chew on five (Series I) or 10 (Series II) pieces of gum per day for a period of 3 months. The chewing gums were: vitamin C (60 mg, Series I), non-vitamin C (Series I) and vitamin C + carbamide (30 mg + 30 mg, Series II). In both series, no gum was used as a negative control. Calculus formation was scored on three lingual sites on the six anterior mandibular teeth according to the Volpe-Manhold index. The effect on plaque and gingivitis was also determined. A significant reduction in the total calculus score was observed after the use of vitamin C (33%) and vitamin C + carbamide (12%) gums compared with no gum use; this reduction was most pronounced in the heavy calculus formers. A reduced amount of visible plaque was also observed after use of vitamin C and non-vitamin C gum, but only the vitamin C gum reduced the number of bleeding sites (37%). In a separate study, the release, stability and uptake of vitamin C were evaluated using the iodine titration method in both saliva and urine after exposure to the following gums: vitamin C + carbamide (30 mg + 30 mg) and vitamin C (30 mg). There was no indication that carbamide affected the release, stability or uptake of vitamin C when used in a chewing gum.

Vitamin C protects HL60 and U266 cells from arsenic toxicity

Although there is no compelling evidence that vitamin C has antitumor activity in humans, clinical trials are testing the hypothesis that ascorbic acid (AA) will enhance the efficacy of arsenic trioxide (As2O3) in myeloma. In vitro, AA cytotoxicity depends on its interaction with free transition metal ions in culture media leading to the generation of H2O2 and other reactive oxygen species (ROSs). Therefore, to circumvent the extracellular in vitro pro-oxidant effects of AA, we loaded HL60, U266, and RPMI-8226 cells with vitamin C by incubation with dehydroascorbic acid (DHA). Loading cells in this manner resulted in prominent, dose-dependent protection of As2O3-treated cells as measured by viability, colony formation, and apoptosis assays. Glutathione depletion enhanced cell sensitivity to the cytotoxic effects of As2O3 and vitamin C loading provided protection. AA was found to generate cytotoxic concentrations of H2O2 in culture medium without cells and copper/iron chelators inhibited this reaction. However, AA did not generate H2O2 in simple buffer or human plasma. Direct incubation with AA resulted in increased intracellular ROSs, whereas DHA incubation decreased it. These results clarify an apparent paradox and indicate that vitamin C loading in HL60, U266, and RPMI-8226 cells ameliorates As2O3 cytotoxicity.

Carences en vitamine C

BACKGROUND

Hypovitaminosis C is frequent in populations at risk (men who live alone, old people, homelessness, patients with psychiatric diseases, foodfaddists,...) and is underestimated in the general population.

STRONG POINTS

Scurvy occurs after 3 months without consumption of ascorbic acid, and is due to lack of consumption fresh fruits and vegetables. Clinical manifestations are weakness, myalgia and arthralgia, vascular purpura and hemorrhagic syndrome, and later the stomatologic manifestations: gingivorragia and loss of teeth. Biological signs are nonspecific: anemia, hypocholesterolemia, hypoalbuminemia. Clinical suspicion must be confirmed by a low level of ascorbic acid (<2.5 mg/l), but this value needs to be interpretated according to the presence of an acute phase response. Leucocyte ascorbic acid level reflects total body store and is more reliable, but not available in practice. Treatment consists in administration of 1 g vitamin C per day during 15 days.

PERSPECTIVES

Vitamin C depletion (serum ascorbic acid level between 2 and 5 mg/l) may occur long-term complications such as increase cardiovascular and neoplasic risks or cataract. The new recommended dietary allowance of vitamin C (110 mg per day for an adult) takes into account of these risks.

Six-year effect of combined vitamin C and E supplementation on atherosclerotic progression: the Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) Study

BACKGROUND

Self-selected supplementation of vitamin E has been associated with reduced coronary events and atherosclerotic progression, but the evidence from clinical trials is controversial. In the first 3 years of the ASAP trial, the supplementation with 136 IU of vitamin E plus 250 mg of slow-release vitamin C twice daily slowed down the progression of carotid atherosclerosis in men but not women. This article examines the 6-year effect of supplementation on common carotid artery (CCA) intima-media thickness (IMT).

METHODS AND RESULTS

The subjects were 520 smoking and nonsmoking men and postmenopausal women aged 45 to 69 years with serum cholesterol > or =5.0 mmol/L (193 mg/dL), 440 (84.6%) of whom completed the study. Atherosclerotic progression was assessed ultrasonographically. In covariance analysis in both sexes, supplementation reduced the main study outcome, the slope of mean CCA-IMT, by 26% (95% CI, 5 to 46, P=0.014), in men by 33% (95% CI, 4 to 62, P=0.024) and in women by 14% (not significant). In both sexes combined, the average annual increase of the mean CCA-IMT was 0.014 mm in the unsupplemented and 0.010 mm in the supplemented group (25% treatment effect, 95% CI, 2 to 49, P=0.034). In men, this treatment effect was 37% (95 CI, 4 to 69, P=0.028). The effect was larger in subjects with either low baseline plasma vitamin C levels or CCA plaques. Vitamin E had no effect on HDL cholesterol.

CONCLUSIONS

These data replicate our 3-year findings confirming that the supplementation with combination of vitamin E and slow-release vitamin C slows down atherosclerotic progression in hypercholesterolemic persons.

Morbidity risk in HFE associated hereditary hemochromatosis C282Y heterozygotes

Hereditary hemochromatosis (HHC) is a late-onset, autosomal recessive disorder leading to a chronic iron overload syndrome, finally causing diabetes, cardiomyopathy and liver disease. HHC is the most common single gene disorder in northern Europeans that occurs with a frequency of approximately 0.5%, and most of these patients carry the C282Y and H63D mutation in the HFE gene on chromosome 6p21.3. The vast majority of HHC patients are homozygous for the C282Y mutation, but HHC phenotypes are observed in other genotypes. Expression of the disease, in those homozygous for the C282Y mutation, is highly variable depending on the various features of the population studied. C282Y heterozygotes have slightly increased iron stores and in absence of other genetic and/or environmental factors do usually not develop the HHC phenotype. It is currently a matter of debate whether C282Y heterozygotes may have an increased risk for morbidity. Different studies investigating the association of C282Y heterozygocity with morbidity have given conflicting results, as is exemplified by extrahepatic cancers, cardiovascular diseases, alcoholic liver disease, and diabetes. However, there are examples of clear and unambiguous disease associations, such as with sporadic pophyria cutanea tarda. It remains to be seen whether a strong correlation between the C282Y heterozygous state and distinct pathological conditions will exist and large-scale genotyping studies will help to identify such potential risk groups in the future.

Ascorbic acid supplement during luteal phase in IVF

PURPOSE

To evaluate the impact of ascorbic acid of different doses as additional support during luteal phase in infertility treatment by means of a prospective, randomized, placebo-controlled, group comparative, double-blind study.

METHODS

Voluntary daily oral intake of either ascorbic acid (1, 5, or 10 g/day) or Placebo for 14 days after follicle aspiration for IVF-ET procedure. Data was obtained on 620 cases of women, age <40 years, undergoing first IVF-embryo transfer cycles in two private outpatient infertility clinics. All women were stimulated by the same protocol. The mean age was 31.73 (+/- 4.4 SD) years.

RESULTS

No differences in clinical pregnancy rate and implantation rate were noted in statistical logistic regression analysis between the four intake groups.

CONCLUSIONS

There was no clinical evidence of any beneficial effect, as defined by main outcome measures, of ascorbic acid on IVF-ET. Our data suggest there is no obvious value of high dosed intake of vitamin C during luteal phase in infertility treatment.

Vitamins C and E improve rat embryonic antioxidant defense mechanism in diabetic culture medium

BACKGROUND

Diabetes teratogenicity seems to be related to embryonic oxidative stress and the extent of the embryonic damage can apparently be reduced by antioxidants. We have studied the mechanism by which antioxidants, such as vitamins C and E, reduce diabetes-induced embryonic damage. We therefore compared the antioxidant capacity of 10.5-day-old rat embryos and their yolk sacs cultured for 28h in diabetic culture medium with or without vitamins C and E.

METHODS

The embryos were cultured in 90% rat serum to which 2mg/ml glucose, 2mg/ml beta hydroxy butyrate (BHOB) and 10 microg/ml of acetoacetate were added. Rat embryos were also cultured in a diabetic medium with 25 microg/ml of vitamin E and 50 microg/ml of vitamin C. Control embryos were cultured in normal rat serum with or without vitamins C and E.

RESULTS

Decreased activity of Cu/Zn superoxide dismutase (SOD) and of catalase (CAT) in the "diabetic" embryos and their yolk sacs, and reduced concentrations of low molecular weight antioxidant (LMWA) were found. Under these conditions we also found a decrease in vitamin C and vitamin E concentrations in the embryos, as measured by HPLC. In situ hybridization for SOD mRNA showed a marked reduction of SOD mRNA in the brain, spinal cord, heart and liver of embryos cultured in diabetic medium in comparison to controls. Following the addition of vitamins C and E to the diabetic culture medium, SOD and CAT activity, the concentrations of LMWA, the levels of vitamin C and E and the expression of SOD mRNA in the embryos and yolk sacs returned to normal.

CONCLUSIONS

Diabetic metabolic factors seem to have a direct effect on embryonic SOD gene and perhaps genes of other antioxidant enzymes, reducing embryonic endogenous antioxidant defense mechanism. This in turn may cause a depletion of the LMWA, such as vitamins C and E. The addition of these vitamins normalizes the embryonic antioxidant defense mechanism, reducing the damage caused by the diabetic environment.

Vitamin C inhibits NF-kappa B activation by TNF via the activation of p38 mitogen-activated protein kinase

The transcription factor NF-kappaB is a central mediator of altered gene expression during inflammation, and is implicated in a number of pathologies, including cancer, atherosclerosis, and viral infection. We report in this study that vitamin C inhibits the activation of NF-kappaB by multiple stimuli, including IL-1 and TNF in the endothelial cell line ECV304 and in primary HUVECs. The induction of a NF-kappaB-dependent gene, IL-8, by TNF was also inhibited. The effect requires millimolar concentrations of vitamin C, which occur intracellularly in vivo, particularly during inflammation. Vitamin C was not toxic to cells, did not inhibit another inducible transcription factor, STAT1, and had no effect on the DNA binding of NF-kappaB. Inhibition by vitamin C was not simply an antioxidant effect, because redox-insensitive pathways to NF-kappaB were also blocked. Vitamin C was shown to block IL-1- and TNF-mediated degradation and phosphorylation of I-kappaBalpha (inhibitory protein that dissociates from NF-kappaB), due to inhibition of I-kappaB kinase (IKK) activation. Inhibition of TNF-driven IKK activation was mediated by p38 mitogen-activated protein kinase, because treatment of cells with vitamin C led to a rapid and sustained activation of p38, and the specific p38 inhibitor SB203580 reversed the inhibitory effect of vitamin C on IKK activity, I-kappaBalpha phosphorylation, and NF-kappaB activation. The results identify p38 as an intracellular target for high dose vitamin C.

Natural vitamins may be superior to synthetic ones

There appears to be a tendency to label those who profess that natural vitamins are better than synthetic ones as quacks. This broad brush label may be stifling legitimate nutrition research. This paper describes physiochemical differences between certain natural and synthetic vitamins, proven clinical advantages of natural vitamins, and some of the effects this labeling may lead to. It concludes that lessons of history as well as modern science support the view that natural vitamins are nutritionally superior to synthetic ones.

Ascorbic acid supplementation does not lower plasma lipoprotein(a) concentrations

Elevated plasma concentrations of lipoprotein(a) (Lp[a]) are associated with premature coronary heart disease (CHD). Lp(a) is a lipoprotein particle consisting of low-density lipoprotein (LDL) with apolipoprotein (apo) (a) attached to the apo B-100 component of LDL. It has been hypothesized that ascorbic acid supplementation may reduce plasma levels of Lp(a). The purpose of this study was to determine whether ascorbic acid supplementation at a dose of 1 g/day would lower plasma concentrations of Lp(a) when studied in a randomized, placebo-controlled, blinded fashion. One hundred and one healthy men and women ranging in age from 20 to 69 years were studied for 8 months. Lp(a) values at baseline for the placebo group (n = 52) and the ascorbic acid supplemented group (n = 49) were 0.026 and 0.033 g/l, respectively. The 8-month concentrations were 0.027 g/l (placebo) and 0.038 g/l (supplemented group). None of these values were significantly different from each other. In addition, no difference in plasma Lp(a) concentration was seen between the placebo and supplemented groups when only subjects with an initial Lp(a) value of > or = 0.050 g/l were analyzed. Our data indicate that plasma Lp(a) concentrations are not significantly affected by ascorbic acid supplementation in healthy human subjects.

Natural electrophoresis of norepinephrine and ascorbic acid

The electric field produced by cell membranes, extending only a few nanometers, is 1000 times stronger than the electric fields required to produce dissociation of molecular complexes. Using the complex formed by norepinephrine (NE) and ascorbic acid (AA), we have demonstrated the quantitative binding of AA to NE, the use of capillary electrophoresis to measure quantitative binding of nonelectrolyte complexes, the determination of a dissociation constant (Kd) from electric field-dissociation constants (Ke), and a model for natural dissociation of the NE-AA complex due to the electric field generated by a cell membrane. NE-AA dissociation constants show little effect of NE concentration or pH changes. NE-related compounds also bind AA: epinephrine > norepinephrine > tyrosine > histamine > phenylalanine. Serotonin does not bind AA. Phosphorylated AA and glucose also bind NE at 0.05 and 0.08 of the AA binding, respectively. Natural electrophoresis of molecular complexes allows compounds to travel through the body in a protected state and still be available for physiological activity upon reaching a membrane.

Vitamins and minerals

Increasing attention has been given in recent years to the importance of diet in promoting health and preventing illness. The benefits of specific food components that expand the role of diet in health promotion have been identified. With a variety of compounds readily available to consumers, more people are taking self-prescribed supplemental nutrients to maintain or improve health. Vitamins and minerals are essential to the health of women across the lifespan, but deficiencies may occur because of inadequate diet; life-style choices and habits; increased requirements during growth, menstruation, pregnancy, and lactation; menopause; and illness. Critical knowledge for women's health care practitioners includes the recommended daily allowances of vitamins and minerals, sources, factors affecting dietary intake and use, and considerations for nutritional assessment and intervention.

Vitamin C reduces ischaemia-reperfusion-induced acute lung injury

OBJECTIVES

to evaluate vitamin C supplementation in the prevention of ischaemia-reperfusion (I-R) induced acute lung injury.

DESIGN

Sprague-Dawley rats (n =6/group) were randomised into Control, I-R and I-R pretreated with vitamin C (3.3 g over 5 days). Ischaemia-reperfusion injury was induced by 30 minutes infrarenal aortic cross-clamping and 120 minutes reperfusion.

METHODS

pulmonary microvascular injury was measured by broncho-alveolar lavage protein concentration, pulmonary neutrophil infiltration by tissue myeloperoxidase activity and bronchoalveolar lavage neutrophil counts. In a second experiment (n =5/group) neutrophil respiratory burst activity was measured in Control and vitamin C groups.

RESULTS

ischaemia-reperfusion resulted in a significant increase in both microvascular leakage and pulmonary neutrophil infiltration as measured by bronchoalveolar lavage protein concentration and pulmonary myeloperoxidase activity respectively. Pretreatment with vitamin C significantly attenuated both microvascular leakage and neutrophil infiltration. Neutrophil respiratory burst activity was significantly reduced in the vitamin C group (13.02 m.c.f.+/-0.3) compared with Control (19.04 m.c.f.+/-1. 9),p <0.02.

CONCLUSION

these data suggest that oral vitamin C therapy protects against ischaemia-reperfusion-induced acute lung injury, possibly by attenuating neutrophil respiratory burst activity.

Vitamin C: prospective functional markers for defining optimal nutritional status

Most species of plants and animals synthesize ascorbic acid, but human subjects cannot, making vitamin C an essential component of our diet. Relationships between vitamin C intake and status, and between status and health are not yet clear. There is evidence, however, that higher intake of vitamin C is associated with lower risk of disease, supporting the concept that optimal intake is needed for optimal vitamin C status, and that both factors are required for optimal health. Vitamin C has low toxicity in healthy subjects, but a clear definition of optimal status and the dietary intake required to meet and maintain this status is needed before a change in the current recommended intake can be considered. Available evidence suggests that intake of 200 mg vitamin C/d saturates tissues and maintains fasting plasma levels above the proposed threshold (50 mumol/l) for minimum risk of CHD. However, the issue of whether or not these levels produce 'optimal vitamin C status' awaits the clear and accepted definition of the term. This definition in turn awaits the development of reliable functional markers capable of assessing the effects of varying levels of vitamin C nutriture. In the present paper the relationship between intake and body stores of vitamin C and the role of vitamin C in human health are reviewed briefly. The requirements of a reliable functional marker of human vitamin C status are defined, three classes of functional markers (molecular, biochemical and physiological) are described, and possible candidate markers are examined.

Establishing the significance and optimal intake of dietary antioxidants: the biomarker concept

Diets rich in fruits and vegetables are associated with decreased risk of cardiovascular disease and cancer. Biomarkers of oxidative DNA damage and lipid peroxidation can be used to establish the role of antioxidants in this protection and the optimal intake of those antioxidants. This concept is based on the presumptions that oxidative DNA damage is a significant contributor to the age-related development of some cancers and that lipid peroxidation plays a key role in the development of cardiovascular disease. Mass spectrometric measurements of various families of isoprostanes (F2-, F3-, and F4-isoprostanes) and of multiple DNA base oxidation products are probably the most promising biomarkers for use in human nutritional intervention studies. Biomarker studies should precede, as well as accompany, major intervention trials that measure disease incidence. The use of biomarkers provides a logical scientific basis for major intervention trials of antioxidants; such trials will, in turn, eventually validate or disprove the biomarker concept.

Can oxidative DNA damage be used as a biomarker of cancer risk in humans? Problems, resolutions and preliminary results from nutritional supplementation studies

Damage to DNA by oxygen radicals and other reactive oxygen/nitrogen/chlorine species occurs in vivo despite the presence of multiple antioxidant defence and repair systems. Such damage is thought to make a significant contribution to the age-related development of cancer. Modulation of oxidative DNA damage by diet thus constitutes a "biomarker" putatively predictive of the effect of diet on cancer incidence, provided that DNA damage can be accurately quantitated by validated methods. Current issues addressed in this article include the problems of artifactual DNA oxidation during isolation and analysis, the relative merits of different analytical methods, the advantages and disadvantages of relying on measurement of 8-hydroxydeoxyguanosine (8OHdG, 8-oxodG) as an index of oxidative DNA damage, and the limited data that are so far available on how diet can affect "steady-state" levels of oxidative DNA damage in humans. It appears that such damage can be modulated by vegetable intake, although the effects of vegetables may be mediated by components different from the "classical" antioxidants vitamin C, alpha-tocopherol and beta-carotene.