Acute effects of caffeine ingestion on glycemic indices: A systematic review and meta-analysis of clinical trials

Decoding coffee cardiometabolic potential: Chemical composition, nutritional, and health relationships

Coffee is one of the most consumed beverages worldwide, recognized for its unique taste and aroma and for its social and health impacts. Coffee contains a plethora of nutritional and bioactive components, whose content can vary depending on their origin, processing, and extraction methods. Gathered evidence in literature shows that the regular coffee consumption containing functional compounds (e.g., polysaccharides, phenolic compounds, and melanoidins) can have potential beneficial effects on cardiometabolic risk factors such as abdominal adiposity, hyperglycemia, and lipogenesis. On the other hand, coffee compounds, such as caffeine, diterpenes, and advanced glycation end products, may be considered a risk for cardiometabolic health. The present comprehensive review provides up-to-date knowledge on the structure-function relationships between different chemical compounds present in coffee, one of the most prevalent beverages present in human diet, and cardiometabolic health.

Association between maternal exposure to arsenic by drinking water during pregnancy and risk of preterm birth: a systematic review and meta-analysis

The relation of exposure to arsenic in drinking water during pregnancy to the risk of preterm birth (PTB) was contradictory. This meta-analysis aimed to examine the association between drinking water arsenic and PTB. A systematic search in PubMed and Scopus was performed to achieve all relevant studies. Odds ratios (OR) and 95% confidence intervals (CI) were used to pool data using the random-effect models. Overall, 11 studies with a total sample size of 3,404,189 participants were included in the meta-analysis. Arsenic exposure through drinking water during pregnancy was related to an increased risk of PTB (OR = 1.06; 95%CI = 1.01-1.10 for highest versus lowest category of arsenic), with significant heterogeneity across the studies (I2 = 84.8%, P = 0.001). This finding was supported by cohort studies (OR = 1.05; 95%CI = 1.01-1.10). This meta-analysis proposes that higher arsenic exposure in drinking water may be a risk factor for PTB.

Bitter yet beneficial: The dual role of dietary alkaloids in managing diabetes and enhancing cognitive function

With the rising prevalence of diabetes and its association with cognitive impairment, interest in the use of dietary alkaloids and other natural products has grown significantly. Understanding how these compounds manage diabetic cognitive dysfunction (DCD) is crucial. This comprehensive review explores the etiology of DCD and the effects of alkaloids in foods and dietary supplements that have been investigated as DCD therapies. Data on how dietary alkaloids like berberine, trigonelline, caffeine, capsaicin, 1-deoxynojirimycin, nuciferine, neferine, aegeline, tetramethylpyrazine, piperine, and others regulate cognition in diabetic disorders were collected from PubMed, Research Gate, Web of Science, Science Direct, and other relevant databases. Dietary alkaloids could improve memory in behavioral models and modulate the mechanisms underlying the cognitive benefits of these compounds, including their effects on glucose metabolism, gut microbiota, vasculopathy, neuroinflammation, and oxidative stress. Evidence suggests that dietary alkaloids hold promise for improving cognition in diabetic patients and could open exciting avenues for future research in diabetes management.

Metabolic syndrome in relation to dietary acid load: a dose-response meta-analysis of observational studies

Background and aim

Several studies have identified that dietary acid load (DAL) may be associated with the odds of metabolic syndrome (MetS); however, the evidence is inconclusive. This dose-response meta-analysis aimed to examine the relation of DAL to MetS.

Methods

A systematic literature search was carried out in PubMed and Scopus up to April 2023 for pertinent studies evaluating the relation of DAL scores, including potential renal acid load (PRAL) and net endogenous acid production (NEAP), to the odds of MetS. The odds ratios (OR) with 95% confidence intervals (CI) were pooled using a random-effects meta-analysis to test the association.

Results

Eight studies, with an overall sample size of 31,351 participants, were included in this meta-analysis. Higher DAL scores were significantly related to the elevated odds of MetS (NEAP: OR = 1.42, 95%CI = 1.12-1.79; PRAL: OR = 1.76, 95%CI = 1.11-2.78), with significant evidence of heterogeneity across studies. The linear dose-response analysis proposed that a 10 mEq/day elevation in NEAP and PRAL was linked to a 2% (OR = 1.02, 95%CI = 1.001-1.05) and 28% (OR = 1.28, 95%CI = 1.11-1.47) increased odds of MetS, respectively. No non-linear association was observed between MetS and NEAP (P-non-linearity = 0.75) and PRAL (P-non-linearity = 0.92).

Conclusion

This study revealed a significant direct relationship between DAL and MetS. Therefore, lower acidogenic diets are suggested for the prevention of MetS.

Mechanisms of action of coffee bioactive compounds - a key to unveil the coffee paradox

The knowledge of the relationship between the chemical structure of food components with their mechanisms of action is crucial for the understanding of diet health benefits. This review relates the chemical variability present in coffee beverages with the mechanisms involved in key physiological events, supporting coffee as a polyvalent functional food. Coffee intake has been related with several health-promoting properties such as neuroprotective (caffeine, chlorogenic acids and melanoidins), anti-inflammatory (caffeine, chlorogenic acids, melanoidins, diterpenes), microbiota modulation (polysaccharides, melanoidins, chlorogenic acids), immunostimulatory (polysaccharides), antidiabetic (trigonelline, chlorogenic acids), antihypertensive (chlorogenic acids) and hypocholesterolemic (polysaccharides, chlorogenic acids, lipids). Nevertheless, caffeine and diterpenes are coffee components with ambivalent effects on health. Additionally, a large range of potentially harmful compounds, including acrylamide, hydroxymethylfurfural, furan, and advanced glycation end products, are formed during the roasting of coffee and are present in the beverages. However, coffee beverages are part of the daily human dietary healthy habits, configuring a coffee paradox.

Dietary Inflammatory Index in relation to Type 2 Diabetes: A Meta-Analysis

Background and Aims

Epidemiologic studies show a strong association between chronic inflammation and type 2 diabetes (T2D). Diet may also affect the risk of T2D by modulating inflammation. This meta-analysis aimed to assess the relation of dietary inflammatory index (DII) and risk of T2D.

Methods

PubMed and Scopus were systematically searched from their inception to September 2020 to identify relevant studies. Relative risks, hazard ratios, or odds ratios (OR), with their corresponding 95% confidence intervals (95% CI), were calculated and pooled using a random-effects model.

Results

A total of 48 different studies, with a total sample size of 1,687,424 participants, were eligible to be included in this meta-analysis. In the overall analysis, no significant association was observed between DII and risk of T2D (OR = 1.03, 95% CI: 0.91 to 1.15), with significant evidence for heterogeneity (I 2  = 96.5%, P < 0.001); however, higher DII was identified as being significantly related to increased risk of T2D in high quality studies (OR = 1.58, 95% CI: 1.15 to 2.17). In the stratified analysis by the dietary assessment tool, background disease, and sex of participants, DII showed no significant association with T2D.

Conclusions

Higher DII might be associated with an increased risk of T2D. Additional well-designed studies are required to confirm this finding.

The association between psoriasis and psoriatic arthritis with the risk of osteoporosis, osteopenia and bone fractures: A systematic review and meta-analysis

BACKGROUND AND AIMS

The possible association between psoriatic/psoriatic arthritis (PsA) and bone loss has been observed; however, studies have yielded inconclusive results. This meta-analysis aimed to assess whether there is an increase in the risk of osteoporosis, osteopenia and fractures in patients with psoriasis/PsA, compared with healthy individuals.

METHODS

PubMed and Scopus were systematically searched from their inception to September 2020 to identify relevant studies. Relative risk, hazard ratio or odds ratio (OR), with their corresponding 95% confidence intervals (95% CI) were calculated and pooled using a random-effects model.

RESULTS

A total of 12 different studies, with a total of 199 389 296 participants, were included. Overall, no significant relationship was observed between psoriasis/PsA and the risk of osteoporosis (psoriasis: OR = 1.28, 95%CI = 0.86-1.90; PsA: OR = 1.32, 95%CI = 0.79-2.19) and osteopenia (psoriasis: OR = 1.50, 95%CI = 0.75-3.02; PsA: OR = 1.61, 95%CI = 0.67-3.85). However, in the subgroup analysis, psoriasis was significantly associated with an increased risk of osteoporosis in men (OR = 1.27, 95%CI = 1.02-1.59) and studies with cohort design (OR = 1.04, 95%CI = 1.003-1.09). Psoriasis was also related to the risk of osteopenia in studies on a combination of both genders (OR = 2.86, 95%CI = 2.70-3.02). The pooled analysis demonstrated a significantly higher risk of fractures among patients with psoriasis (OR = 1.29, 95%CI = 1.02-1.63) and PsA (OR = 2.88, 95%CI = 1.51-5.48), compared with participants without psoriasis/PsA.

CONCLUSIONS

Patients with psoriasis/PsA have an increased risk of fractures. There is little evidence supporting the relation of psoriasis to osteoporosis/osteopenia.

Recent consumption of a caffeine-containing beverage and serum biomarkers of cardiometabolic function in the UK Biobank

We investigated the impact of recent caffeine drinking on glucose and other biomarkers of cardiometabolic function under free-living conditions while also accounting for lifestyle and genetic factors that alter caffeine metabolism and drinking behaviour. Up to 447 794 UK Biobank participants aged 37-73 years in 2006-2010 provided a non-fasting blood sample, for genetic and biomarker measures, and completed questionnaires regarding sociodemographics, medical history and lifestyle. Caffeine drinking (yes/no) about 1 h before blood collection was also recorded. Multivariable regressions were used to examine the association between recent caffeine drinking and serum levels of glycated Hb, glucose, lipids, apo, lipoprotein(a) and C-reactive protein. Men and women reporting recent caffeine drinking had clinically and significantly higher glucose levels than those not recently drinking caffeine (P < 0·0001). Larger effect sizes were observed among those 55+ years of age and with higher adiposity and longer fasting times (P ≤ 0·02 for interactions). Significant CYP1A2 rs2472297×caffeine and MLXIPL rs7800944 × caffeine interactions on glucose levels were observed among women (P = 0·004), with similar but non-significant interactions in men. Larger effect sizes were observed among women with rs2472297 CC or rs7800944 CC genotypes than among rs2472297 T or rs7800944 T carriers, respectively. In summary, men and women drinking caffeine within about 1 h of blood draw had higher glucose levels than those not drinking caffeine. Findings were modified by age, adiposity, fasting time and genetic factors related to caffeine metabolism and drinking behaviour. Implications for clinical and population studies of caffeine-containing beverages and cardiometabolic health are discussed.

Novel Facet of an Old Dietary Molecule? Direct Influence of Caffeine on Glucose and Biogenic Amine Handling by Human Adipocytes

Caffeine is a plant alkaloid present in food and beverages consumed worldwide. It has high lipid solubility with recognized actions in the central nervous system and in peripheral tissues, notably the adipose depots. However, the literature is scant regarding caffeine's influence on adipocyte functions other than lipolysis, such as glucose incorporation into lipids (lipogenesis) and amine oxidation. The objective of this study was to explore the direct effects of caffeine and of isobutylmethylxanthine (IBMX) on these adipocyte functions. Glucose transport into fat cells freshly isolated from mice, rats, or humans was monitored by determining [³H]-2-deoxyglucose (2-DG) uptake, while the incorporation of radiolabeled glucose into cell lipids was used as an index of lipogenic activity. Oxidation of benzylamine by primary amine oxidase (PrAO) was inhibited by increasing doses of caffeine in human adipose tissue preparations with an inhibition constant (Ki) in the millimolar range. Caffeine inhibited basal and insulin-stimulated glucose transport as well as lipogenesis in rodent adipose cells. The antilipogenic action of caffeine was also observed in adipocytes from mice genetically invalidated for PrAO activity, indicating that PrAO activity was not required for lipogenesis inhibition. These caffeine inhibitory properties were extended to human adipocytes: relative to basal 2-DG uptake, set at 1.0 ± 0.2 for 6 individuals, 0.1 mM caffeine tended to reduce uptake to 0.83 ± 0.08. Insulin increased uptake by 3.86 ± 1.11 fold when tested alone at 100 nM, and by 3.21 ± 0.80 when combined with caffeine. Our results reinforce the recommendation of caffeine's potential in the treatment or prevention of obesity complications.

Coffee and type 2 diabetes risk: Is the association mediated by adiponectin, leptin, c-reactive protein or Interleukin-6? A systematic review and meta-analysis

AIM

Coffee and diabetes risk association has been demonstrated in numerous studies; however, the exact mechanism has not been clarified yet. The present meta-analysis was conducted to cover the current knowledge regarding the effect of coffee on Type 2 Diabetes (T2D), in addition to the evaluation of adiponectin, leptin, C-reactive protein (CRP) and Interleukin-6 (IL-6) levels among coffee consumers as relatively possible mediators of this effect.

METHOD

A comprehensive search of the literature was carried out using search engines up to March 2020. The effect sizes were investigated using the standardised mean difference (SMD) and odds ratios (OR) or relative risk (RR) with its 95% confidence interval (CI). A total of 69 cross-sectional and cohort studies were included and divided as follows: 31 articles for T2D risk, 15 studies for adiponectin, 6 studies for leptin, 12 studies for CRP and 5 studies for IL-6.

RESULTS

Overall, coffee consumption was inversely associated with T2D risk with an estimated pooled RR of 0.73 (95% confidence interval [0.68, 0.80] for the highest vs lowest coffee consumption categories. The combined SMD between the different coffee intake categories, showed that coffee consumption was associated with higher adiponectin levels (P = .002), and lower level of leptin (P = .04) and CRP (P = .2), with apparently no change in IL-6 levels (P = .91).

CONCLUSION

The present meta-analysis showed strong epidemiological evidence that coffee consumption is inversely associated with the risk of T2D. Also, adiponectin, leptin concentrations appeared to be potential mediators of the coffee effect on diabetes, while IL-6 levels did not.

Protection against developing type 2 diabetes by coffee consumption: assessment of the role of chlorogenic acid and metabolites on glycaemic responses

Epidemiological studies show a convincing long-term and dose-dependent protection of coffee and decaffeinated coffee against developing type 2 diabetes. The mechanisms of this effect are still not understood even though several have been proposed, including a potential effect on blood glucose by chlorogenic acids. However, there is minimal effect of decaffeinated coffee on postprandial blood glucose and insulin when consumed with carbohydrates, although there may be effects on incretin hormones, but these have been measured in only a few studies. Although chlorogenic acids do not affect carbohydrate digestion directly, they may affect glucose absorption and subsequent utilisation, the latter through metabolites derived from endogenous pathways or action of the gut microbiota. To advance understanding of the protective effect of coffee chlorogenic acids, more chronic intervention studies are needed on decaffeinated coffee, coupled with mechanistic studies in vitro using more realistic concentrations of the relevant chlorogenic acid metabolites.

Caffeine and Caffeine Metabolites in Relation to Insulin Resistance and Beta Cell Function in U.S. Adults

The relationship between caffeine and insulin resistance (IR) has been assessed only in terms of caffeine intake, and the association between caffeine and beta cell function (BCF) remains unclear. This study examines the association between urinary caffeine and its metabolites, IR, and BCF in nondiabetic, noninstitutionalized US adults in order to account for the inter-individual differences in caffeine metabolism. Data on urinary caffeine and its metabolites, IR and BCF from adults aged 20 years and older who participated in the 2009–2010 and 2011–2012 National Health and Nutrition Examination Surveys were analyzed (n for caffeine = 994). IR and BCF were assessed using homeostatic model assessment (HOMA) and urinary caffeine and its metabolites were measured using high-performance liquid chromatography-electrospray ionization-tandem quadrupole mass spectrometry. After adjusting for all covariates, increases in urinary 1,3-DMU, 1,7-DMU, 1,3,7-TMU, theophylline, paraxanthine, caffeine, and AAMU were significantly associated with increased HOMA-IR and HOMA-β (HOMA of insulin resistance and beta cell function). Compared with individuals in the lowest quartile of urinary 1,3-DMU, 1,7-DMU, 1,3,7-TMU, theophylline, paraxanthine, caffeine, and AAMU, the regression coefficients for HOMA-IR and HOMA-β were significantly higher among those in the highest quartile. After stratification by prediabetes status, HOMA-IR and HOMA-β showed significant positive associations with urinary caffeine and its metabolites among subjects with normal fasting plasma glucose levels. Our cross-sectional study showed that caffeine and its metabolites were positively related to IR and BCF.

Dietary natural methylxanthines and colorectal cancer: a systematic review and meta-analysis

Some evidence suggests that caffeine, theophylline, and theobromine, as natural methylxanthines (MTXs), possess anti-cancer effects.