Coffee consumption, type 2 diabetes and impaired glucose tolerance in Swedish men and women

The association of coffee consumption with prediabetes, diabetes, and markers of glucose metabolism in rural Vietnam: a cross-sectional study

BACKGROUND

Coffee consumption has been shown to be protective against diabetes, but the effects of coffee with additives, such as condensed milk in Vietnam, remain underexplored. This cross-sectional study aimed to examine the associations of coffee consumption with prediabetes, diabetes, and markers of glucose metabolism among 3,000 middle-aged rural residents in Vietnam.

METHODS

Multinomial logistic regression was used to examine the associations of coffee consumption (0, 0.1-0.9, 1-1.9, or ≥ 2 cups/day) with prediabetes and diabetes, adjusting for demographics, lifestyle factors, dietary intake, comorbidities, and use of additives. Associations with insulin resistance and insulin secretion (as assessed by homeostatic model assessment of insulin resistance (HOMA-IR) and homeostatic model assessment of β-cell function (HOMA-β)) were examined using linear regression.

RESULTS

Adjusted odds ratios (95% confidence interval) for prediabetes were 1.02 (0.78-1.32), 1.18 (0.91-1.52), 0.60 (0.35-1.03) for 0.1-0.9, 1-1.9, or ≥ 2 cups/day, respectively, compared to non-coffee drinkers (p for trend = 0.84). For diabetes, the corresponding figures were 1.74 (1.14-2.67), 1.43 (0.92-2.20), 0.59 (0.22-1.59) (p for trend = 0.50). No significant associations were observed for HOMA-IR (p for trend = 0.41) or HOMA-β (p for trend = 0.44).

CONCLUSION

The present study among rural residents in Vietnam did not find clear associations of coffee consumption with prediabetes, diabetes, or markers of glucose metabolism, including the effects of coffee with additives, underscoring the complexity of these associations and the need for further research to confirm the findings in rural Vietnam.

Association of caffeine intake with all-cause and cardiovascular mortality in diabetes and prediabetes

BACKGROUD

The association between caffeine intake and mortality in prediabetes and diabetes is not well defined. This study was designed to investigate the association between caffeine intake and all-cause mortality and cardiovascular disease (CVD) mortality in adults with prediabetes and diabetes in the United States.

METHODS

This analysis included 18,914 adult patients with diabetes and prediabetes from the National Health and Nutrition Examination Survey (NHANES) 2003-2018. Follow-up extended to December 31, 2019. Weighted Cox proportional hazards regression models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) for all-cause mortality and CVD mortality.

RESULTS

During 142,460 person-years of follow-up, there were 3,166 cases of all-cause mortality and 1,031 cases of CVD mortality recorded. In the fully adjusted models, caffeine intake showed a significant dose-response association with the risk of all-cause mortality and CVD mortality in individuals with diabetes and prediabetes. When comparing extreme quartiles of caffeine intake, the multivariable-adjusted hazard ratio for all-cause mortality was 0.78 (0.67-0.91) (P for trend = 0.007); however, there was no significant association with the risk of CVD mortality. Results remained consistent in stratified analyses by sex, age, race/ethnicity, education level, family income-poverty ratio, BMI, hypertension, smoking status, alcohol intake, and HEI-2015.

CONCLUSIONS

This study suggests that caffeine intake is significantly inversely associated with the risk of all-cause mortality in individuals with diabetes and prediabetes. In individuals with prediabetes, there is also a significant inverse association between caffeine intake and CVD events, but this association is not present in those with diabetes.

Association between tea consumption and glucose metabolism and insulin secretion in the Shanghai High-risk Diabetic Screen (SHiDS) study

INTRODUCTION

The relationship between tea consumption and glucose metabolism remains controversial. This study investigated the associations of tea consumption with impaired glucose regulation, insulin secretion and sensitivity in Shanghai High-risk Diabetic Screen project.

RESEARCH DESIGN AND METHODS

A total of 2337 Chinese subjects were enrolled in the study from 2014 to 2019. Each participant conducted a 75 g oral glucose tolerance test (OGTT) with five-point glucose and insulin level examined. They also completed a nurse-administered standard questionnaire including tea, coffee, and alcohol consumption, smoking habit, physical activity, education, sleep quality, etc. RESULTS: The result showed that tea consumption was positively associated with plasma glucose levels during OGTT after adjusting for confounder (Ps <0.05) and was associated with worsening glucose tolerance (OR 1.21, 95% CI 1.01-1.44; p=0.034). Strong tea consumption or long-term tea intake (>10 years) had an increased risk of glucose intolerance (all p<0.05). These associations did not vary in participants drinking green tea. In addition, insulin secretion indexes were decreased 7.0%-13.0% in tea consumption group. Logistic regression analysis showed that tea consumption was independently associated with lower insulin secretion (homeostasis model assessment of β-cell function (HOMA-β) (OR 0.81, 95% CI 0.68-0.97; p=0.021); Stumvoll first-phase index (OR 0.81, 95% CI 0.68-0.97; p=0.020)) in a fully adjusted model. Green tea consumption showed a negative association with insulin secretion (HOMA-β (OR 0.77, 95% CI 0.62-0.96; p=0.019)).

CONCLUSIONS

Tea intake is associated with an increased risk of glucose intolerance in a large high-risk diabetic Chinese population. Habitual tea consumption subjects might have lower pancreatic β-cell function.

Sociodemographic, anthropometric, and lifestyle correlates of prediabetes and type 2 diabetes in europe: The Feel4Diabetes study

BACKGROUND AND AIMS

The current work aimed to identify the predominant correlates of prediabetes and T2DM among a variety of socio-demographic, anthropometric and lifestyle indices, in a large sample of adults from families at high risk for T2DM.

METHODS AND RESULTS

In this cross-sectional study, 2816 adults were recruited from low-socioeconomic areas in high-income countries (HICs) (Belgium-Finland), HICs under austerity measures (Greece-Spain), and low/middle-income countries (LMICs) (Bulgaria-Hungary). A positive association between the male sex (OR, 95% C.I.2.77 (1.69-4.54)) and prediabetes was revealed compared to females, while there was a negative association between younger age (<45 years) (OR, 95% C.I. 0.58 (0.37-0.92)), and low/medium levels of waist circumference (OR, 95% C.I. 0.44 (0.22-0.89)) with prediabetes compared to older age and high levels of waist circumference, respectively. Concerning T2DM, 0-0.5 cups/day of fruits and berries (OR, 95% C.I.2. 13 (1.16-3.91)) and 150-300 g fish/week (OR, 95% C.I. 2.55 (1.01-6.41)) have a positive association compared to higher consumptions, respectively. Conversely, <1 cup/week legumes (OR, 95% C.I. 0.55 (0.31-0.99) as well as 0-0.5 servings (OR, 95% C.I. 0.34 (0.12-0.95) and 0.5-1 servings (OR, 95% C.I. 0.37 (0.19-0.71) of full-fat dairy/day have a negative association compared to higher consumptions, respectively.

CONCLUSION

These findings indicate the need for diabetes prevention measures targeting young adults and especially men, above 45 years of age, with central obesity and poor dietary habits and prioritize vulnerable groups and populations living in LMICs.

NATIONAL CLINICAL TRIAL NUMBER

NCT02393872.

Coffee Chlorogenic Acids Incorporation for Bioactivity Enhancement of Foods: A Review

The demand of foods with high antioxidant capacity have increased and research on these foods continues to grow. This review is focused on chlorogenic acids (CGAs) from green coffee, which is the most abundant source. The main CGA in coffee is 5-O-caffeoylquinic acid (5-CQA). Coffee extracts are currently the most widely used source to enhance the antioxidant activity of foods. Due to the solubility of CGAs, their extraction is mainly performed with organic solvents. CGAs have been associated with health benefits, such as antioxidant, antiviral, antibacterial, anticancer, and anti-inflammatory activity, and others that reduce the risk of cardiovascular diseases, type 2 diabetes, and Alzheimer's disease. However, the biological activities depend on the stability of CGAs, which are sensitive to pH, temperature, and light. The anti-inflammatory activity of 5-CQA is attributed to reducing the proinflammatory activity of cytokines. 5-CQA can negatively affect colon microbiota. An increase in anthocyanins and antioxidant activity was observed when CGAs extracts were added to different food matrices such as dairy products, coffee drinks, chocolate, and bakery products. The fortification of foods with coffee CGAs has the potential to improve the functionality of foods.

Caffeine and rheumatoid arthritis: A complicated relationship

The current ideal goal of rheumatoid arthritis (RA) management is to resolve joint and systemic inflammation by using pharmacological interventions, assuming this will correspondingly lead to overall well-being. Nonetheless, it has emerged that a substantial number of RA patients do not reach optimal disease control. Thus suggesting the holistic management of subjective symptoms might be overlooked. This poses significant medical challenges; hence the proposal of incorporating lifestyle interventions as part of a multidimensional approach. Among these aspects, both patients and physicians perceive the important role of nutrition. This review shall examine how caffeine, one of the most studied bioactive components of the most widely consumed beverages, may potentially interfere with RA management. In particular, the mechanism by which caffeine affects RA pathogenesis, as a trigger for RA onset or flare, including its influence on rheumatic drug metabolism and the most common RA comorbidities and constitutional symptoms are outlined, highlighting important knowledge gaps and unmet research needs.

Longitudinal study of the relationship between coffee consumption and type 2 diabetes in Chinese adult residents: Data from China Health and Nutrition Survey

BACKGROUND

Increasing coffee intake was inversely associated with risk of type 2 diabetes in Western countries. However, in China where coffee consumption and diabetes population has been growing fast in recent years, studies on the impact of coffee intakes on the onset of type 2 diabetes are lacking. This study attempts to determine the associations between coffee consumption and type 2 diabetes in Chinese adults.

METHODS

This longitudinal study analyzed 10447 adults who had participated in at least two rounds of the China Health and Nutrition Survey (CHNS), which is a survey database of multistage, random cluster process during 1993-2011. Coffee consumption and type 2 diabetes incidence were measured in the survey. Body mass index (BMI), age, sex, place of residence, waves, education level, smoking, drinking alcohol and tea drinking frequency were adjusted as covariate. We used longitudinal fixed effects regression models to assess changes within person.

RESULTS

After adjusting confounding factors, lower risk of diabetes is observed among Chinese adults who drink coffee occasionally (Adjusted Odds Ratio (AOR)  = 0.13, 95% CI = 0.05, 0.34) and drink almost every day (AOR = 0.61, 95% CI = 0.45, 0.83), compared with those who do not or hardly drink. In the subgroup analysis, among women aged 45-59 who drink coffee one to three times a week (AOR = 0.21, 95% CI = 0.08, 0.52) and men over 60 who drink coffee almost every day (AOR = 0.19, 95% CI = 0.07, 0.53), protective effects were found. For young men aged 19-29, drinking coffee almost every day showed a risk effect (AOR = 20.21, 95% CI = 5.96-68.57).

CONCLUSIONS

Coffee drinking habit is an independent protective factor for adult on type 2 diabetes in China. And it varies among people with different ages and genders. The rapid growth of coffee consumption in China in recent years may help reduce the risk of type 2 diabetes, but at the same time, the risk of type 2 diabetes in adolescents needs attention.

Non-Alcoholic Beverages, Old and Novel, and Their Potential Effects on Human Health, with a Focus on Hydration and Cardiometabolic Health

The Beverage Guidance System has established dietary recommendations for daily intake of commonly consumed beverages including water, tea, coffee, milk, non-calorically sweetened beverages, and calorically sweetened beverages. As obesity in America continues to be a growing problem, this guidance becomes of increasing importance due to many beverages' potential links to Type 2 Diabetes Mellitus (T2DM), Cardiovascular disease (CVD), and numerous other harmful health effects. However, the growing popularity of "better for you" beverages is causing a shift in the market, with consumers pushing for healthier beverage alternatives. Beverages simultaneously present advantages while posing concerns that need to be evaluated and considered. In this review, health effects of nonalcoholic beverages are discussed including various aspects of consumption and current trends of the beverage market such as the novel Soft Seltzer category as an alternative to Hard Seltzer and various mashups. A variety of advisory boards and agencies responsible for dietary guidelines in various countries suggest drinking water as the preferred practice for hydration.

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.

The influence of green coffee bean extract supplementation on blood glucose levels: A systematic review and dose-response meta-analysis of randomized controlled trials

Studies regarding the influence of green coffee extract (GCE) on blood glucose levels are conflicting. Thus, we sought to conduct a meta-analysis and systematic review of all available randomized controlled trials (RCTs) to quantify the effects of GCE and CGA intervention on blood glucose and insulin levels. We performed systematic online searches in Scopus, Web of science, and PubMed databases, from inception to July 2019. Data were combined analyzed using a random effects model (Der Simonian-Laird method) and reported as weighted mean differences (WMD). Ten trials reported the influences of GCE on FBS and insulin and were subsequently entered into the meta-analysis. Combined results highlighted that FBS was significantly altered after GCE consumption (WMD: -1.791 mg/dl, 95% CI -3.404, -0.177), with no significant heterogeneity among the studies (I² = 35.0%, p = .128). However, overall results demonstrated that GCE administration did not result in any significant alteration in insulin levels (WMD: -0.925 μU/ml, 95% CI:-1.915, 0.064), with significant heterogeneity found across studies (I² = 87.9%). In sub-group analysis, insulin levels were significantly reduced when GCE was supplemented in dosages of ≥400 mg/day (WMD:-1.942 mg/dl, 95% CI:-1.184, -0.975; I² = 0.0%). The results of present study support the use of GCE for the enhancement of blood glucose, while subgroup analysis highlighted significant improvements in insulin levels when GCE is supplemented in doses ≥400 mg/day.

Impact of female daily coffee consumption on successful fertility treatment: a Danish cohort study

OBJECTIVE

To investigate whether female coffee consumption affects the chance of achieving a clinical pregnancy and a live birth among women and couples receiving medically assisted reproduction (MAR) treatment.

DESIGN

Cohort study with prospectively collected exposure data.

SETTING

Public fertility clinic.

PATIENT(S)

A total of 1,708 women and potential partners undergoing fertility treatment, contributing with 1,511 intrauterine insemination (IUI) cycles, 2,870 in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles, and 1,355 frozen embryo transfer cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy and live birth in consecutive treatment cycles in the Danish national health registries, enabling complete follow-up, and estimation of the cumulative chance of live birth for three consecutive treatment cycles.

RESULT(S)

Among women receiving IVF or ICSI treatment, coffee consumption did not seem to affect the chance of achieving a clinical pregnancy and a live birth. Women treated with IUI who had a daily coffee consumption of 1-5 cups were more likely to achieve a clinical pregnancy (adjusted relative risk 1.49; 95% confidence interval, 1.05-2.11) and live birth (adjusted relative risk 1.53; 95% confidence interval, 1.06-2.21) compared with the reference group of coffee abstainers.

CONCLUSION(S)

Women consuming 1-5 cups versus none had a 1.5-fold higher probability of achieving a pregnancy or a live birth when receiving IUI. No associations were found, however, between women's daily coffee consumption and achieving a pregnancy or a live birth from IVF/ICSI.

Potential nutraceutical and food additive properties and risks of coffee: a comprehensive overview

Coffee is a composite mixture of more than a thousand diverse phytochemicals like alkaloids, phenolic compounds, vitamins, carbohydrates, lipids, minerals and nitrogenous compounds. Coffee has multifunctional properties as a food additive and nutraceutical. As a nutraceutical, coffee has anti-inflammatory, anti-oxidant, antidyslipidemic, anti-obesity, type-2 diabetes mellitus (DM), and cardiovascular diseases (CVD), which can serve for the treatment and prevention of metabolic syndrome and associated disorders. On the other hand, as a food additive, coffee has antimicrobial activity against a wide range of microorganisms, inhibits lipid peroxidation (LPO), and can function as a prebiotic. The outcomes of different studies also revealed that coffee intake may reduce the incidence of numerous chronic diseases, like liver disease, mental health, and it also overcomes the all-cause mortality, and suicidal risks. In some studies, high intake of coffee is linked to increase CVD risk factors, like cholesterol, plasma homocysteine and blood pressure (BP). There is also a little evidence that associated the coffee consumption with increased risk of lung tumors in smokers. Among adults who consume the moderate amount of coffee, there is slight indication of health hazards with strong indicators of health benefits. Moreover, existing literature suggests that it may be cautious for pregnant women to eliminate the chances of miscarriages and impaired fetal growth. The primary purpose of this narrative review is to provide an overview of the findings of the positive impacts and risks of coffee consumption on human health. In conclusion, to date, the best available evidence from research indicates that drinking coffee up to 3-4 cups/day provides health benefits for most people.

Coffee consumption is positively related to insulin secretion in the Shanghai High-Risk Diabetic Screen (SHiDS) Study

Background

It has been proved that coffee consumption was associated with a lower risk of type 2 diabetes mellitus. But the benefit effect of coffee on hyperglycemia in Chinese population was largely unknown. Besides, the relationship of coffee intake and diabetic pathogenesis was still unclear.

Methods

The study population was selected from the Shanghai High-Risk Diabetic Screen (SHiDS) project. A total of 1328 individuals over 18 years of age who have the information of coffee intake were enrolled in the study from 2012 to 2016. Each participant finished a five-point 75 g oral glucose tolerance test and finished a standard questionnaire. Insulin resistance was evaluated by HOMA-IR and insulin secretion was evaluated by HOMA-β, Stumvoll first phase and second phase indexes.

Results

Coffee consumption group had lower plasma glucose levels at 2-h and 3-h and higher insulin levels at fasting, 30-min and 1-h during OGTT after adjustment with age, fat%, BMI, waist, tea intake, smoking habit, alcohol intake, diabetes family history and educational status (P for PG2h = 0.002; P for PG3h = 0.010; P for FIN = 0.010; P for IN30min = 0.001; P for IN1h = 0.002). Both HOMA-β and Stumvoll formula indexes were positively related to coffee consumption (P for HOMA-β = 0.033; P for Stumvoll first phase = 0.003; P for Stumvoll second phase = 0.001). Logistic regression analysis further confirmed that coffee intake was independently associated with higher levels of HOMA-β and Stumvoll insulin secretion indexes [OR (95% CI) for HOMA-β = 2.270 (1.456–3.538); OR (95% CI) for Stumvoll first phase = 2.071 (1.352–3.173); OR (95% CI) for Stumvoll second phase = 1.914 (1.260–2.906)].

Conclusions

Coffee intake is independently and positively related to pancreatic beta cell function in a large high-risk diabetic Chinese population.

Coffee, tea and caffeine consumption and risk of primary infertility in women: a Danish cohort study

INTRODUCTION

The aim of this study was to investigate whether consumption of coffee, tea and caffeine affects the risk of primary infertility in women.

MATERIAL AND METHODS

We selected nulliparous Danish women aged 20-29 years from a prospective cohort and retrieved information on coffee and tea consumption from a questionnaire and an interview at enrollment. We assessed the women's fertility by linkage to the Danish Infertility Cohort and retrieved information on children and vital status from the Civil Registration System. All 7574 women included for analysis were followed for primary infertility from the date of enrollment (1991-1993) until 31 December 2010. Analyses were performed with Cox proportional hazard models.

RESULTS

During follow up, primary infertility was diagnosed in 822 women. Compared with never consumers, the risk of primary infertility among women who drank coffee or tea was not affected. The risk of primary infertility was neither associated with an increasing number of daily servings of coffee (hazard ratio 1.00; 95% confidence interval (CI), 0.97-1.03) or tea (hazard ratio 1.01; 95% CI, 0.99-1.03) in consumers only. Concerning total caffeine consumption (from coffee and tea), the risk of infertility was similar among consumers compared with never consumers. Finally, none of the additional daily 100 mg of caffeine affected the risk among consumers only (hazard ratio 1.00; 95% CI 0.98-1.02).

CONCLUSIONS

In this population-based cohort study, not restricted to women seeking pregnancy, we found no association between coffee, tea or total caffeine consumption and the risk of primary infertility in women.

The Potential Effects of Caffeinated Beverages on Insulin Sensitivity

Caffeinated beverages, most commonly tea and coffee, may have important effects on insulin regulation that may give their consumption an important role among nutritional factors in the development of diseases of glucose and insulin metabolism, such as diabetes and atherosclerotic vascular diseases. These beverages include compounds that may have contradictory effects on insulin and glucose: Caffeine impairs insulin sensitivity, but polyphenolic molecules within tea, coffee, and cocoa augment the effects of insulin. In addition, epidemiologic associations exist between greater consumption of such beverages and lower risk of diabetes. The beneficial effects of such beverages might be enhanced by changing the process of their preparation and substitution of other substances commonly added to caffeinated beverages that impair the effect of insulin, such as sugar or milk.

Genetic variation of habitual coffee consumption and glycemic changes in response to weight-loss diet intervention: the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial

Background: Coffee consumption has been associated with glucose metabolism and risk of type 2 diabetes.Objective: We examined whether the genetic variation determining habitual coffee consumption affected glycemic changes in response to weight-loss dietary intervention.Design: A genetic risk score (GRS) was calculated based on 8 habitual coffee consumption-associated single nucleotide polymorphisms. We used general linear models to test changes in glycemic traits in groups randomly assigned to high- and low-fat diets according to tertiles of the GRS.Results: We observed significant interactions between the GRS and low compared with high dietary fat intake on 6-mo changes in fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR) (P-interaction = 0.023 and 0.022, respectively), adjusting for age, sex, race, physical activity, smoking, alcohol, seasonal variation, and baseline values of the respective outcomes. Participants with a higher GRS of habitual coffee consumption showed a greater reduction in fasting insulin and a marginally greater decrease in HOMA-IR in the low-fat diet intervention group.Conclusions: Our data suggest that participants with genetically determined high coffee consumption may benefit more by eating a low-fat diet in improving fasting insulin and HOMA-IR in a short term. This trial was registered at clinicaltrials.gov as NCT00072995 and NCT03258203.

Caffeine and cardiovascular diseases: critical review of current research

Caffeine is a most widely consumed physiological stimulant worldwide, which is consumed via natural sources, such as coffee and tea, and now marketed sources such as energy drinks and other dietary supplements. This wide use has led to concerns regarding the safety of caffeine and its proposed beneficial role in alertness, performance and energy expenditure and side effects in the cardiovascular system. The question remains "Which dose is safe?", as the population does not appear to adhere to the strict guidelines listed on caffeine consumption. Studies in humans and animal models yield controversial results, which can be explained by population, type and dose of caffeine and low statistical power. This review will focus on comprehensive and critical review of the current literature and provide an avenue for further study.

Polyphenols and Glycemic Control

Growing evidence from animal studies supports the anti-diabetic properties of some dietary polyphenols, suggesting that dietary polyphenols could be one dietary therapy for the prevention and management of Type 2 diabetes. This review aims to address the potential mechanisms of action of dietary polyphenols in the regulation of glucose homeostasis and insulin sensitivity based on in vitro and in vivo studies, and to provide a comprehensive overview of the anti-diabetic effects of commonly consumed dietary polyphenols including polyphenol-rich mixed diets, tea and coffee, chocolate and cocoa, cinnamon, grape, pomegranate, red wine, berries and olive oil, with a focus on human clinical trials. Dietary polyphenols may inhibit α-amylase and α-glucosidase, inhibit glucose absorption in the intestine by sodium-dependent glucose transporter 1 (SGLT1), stimulate insulin secretion and reduce hepatic glucose output. Polyphenols may also enhance insulin-dependent glucose uptake, activate 5' adenosine monophosphate-activated protein kinase (AMPK), modify the microbiome and have anti-inflammatory effects. However, human epidemiological and intervention studies have shown inconsistent results. Further intervention studies are essential to clarify the conflicting findings and confirm or refute the anti-diabetic effects of dietary polyphenols.

Enrichment and separation of chlorogenic acid from the extract of Eupatorium adenophorum Spreng by macroporous resin

A simple and efficient chromatographic method for separation of chlorogenic acid from Eupatorium adenophorum Spreng extract was developed. The adsorption properties of nine macroporous resins were evaluated. NKA-II resin showed much better adsorption/desorption properties. The adsorption of chlorogenic acid on NKA-II resin at 25°C was well fitted to Langmuir isotherm model and pseudo-second-order kinetic model. The dynamic adsorption and desorption experiments were carried out on columns packed with NKA-II resin to optimize the separation process. The content of chlorogenic acid in the product increased to 22.17%, with a recovery yield of 82.41%.

Nonpharmacological Management of Gout and Hyperuricemia: Hints for Better Lifestyle

We reviewed lifestyle factors that influence serum uric acid levels and risk of gout flare, and how to improve their deleterious effects. Since obesity increases uric acid and weight gain increases gout risk, weight reduction by daily exercise and limiting intake of excess calories is recommended. However, strenuous exercise, which causes adenine nucleotide degradation; starvation, which decreases uric acid excretion; and dehydration may raise the level of uric acid in serum and trigger gout. Increased intake of purine-rich foods, such as meat and seafood, raise the level of uric acid in serum and is associated with increased risk of gout, whereas dairy products, especially low-fat types, are associated with a lower risk of gout. Also, heavy alcohol drinking raises the uric acid level and increases the risk of gout through adenine nucleotide degradation and lactate production. Sweet fruits and soft drinks containing fructose should be moderated, since fructose may raise uric acid and increase gout risk through uric acid production and/or decreased excretion. On the other hand, the Mediterranean diet is recommended for gout patients, since it may also help prevent hyperuricemia. Furthermore, coffee and vitamin C supplementation could be considered as preventive measures, as those can lower serum uric acid levels as well as the risk of gout.

Coffee Consumption, Newly Diagnosed Diabetes, and Other Alterations in Glucose Homeostasis: A Cross-Sectional Analysis of the Longitudinal Study of Adult Health (ELSA-Brasil)

Introduction

Observational studies have reported fairly consistent inverse associations between coffee consumption and risk of type 2 diabetes, but this association has been little investigated with regard to lesser degrees of hyperglycemia and other alterations in glucose homeostasis. Additionally, the association between coffee consumption and diabetes has been rarely investigated in South American populations. We examined the cross-sectional relationships of coffee intake with newly diagnosed diabetes and measures of glucose homeostasis, insulin sensitivity, and insulin secretion, in a large Brazilian cohort of middle-aged and elderly individuals.

Methods

We used baseline data from 12,586 participants of the Longitudinal Study of Adult Health (ELSA-Brasil). Logistic regression analyses were performed to examine associations between coffee consumption and newly diagnosed diabetes. Analysis of covariance was used to assess coffee intake in relation to two-hour glucose from an oral glucose tolerance test, fasting glucose, glycated hemoglobin, fasting and –2-hour postload insulin and measures of insulin sensitivity.

Results

We found an inverse association between coffee consumption and newly diagnosed diabetes, after adjusting for multiple covariates [23% and 26% lower odds of diabetes for those consuming coffee 2–3 and >3 times per day, respectively, compared to those reporting never or almost never consuming coffee, (p = .02)]. An inverse association was also found for 2-hour postload glucose [Never/almost never: 7.57 mmol/L, ≤1 time/day: 7.48 mmol/L, 2-3 times/day: 7.22 mmol/L, >3 times/day: 7.12 mol/L, p<0.0001] but not with fasting glucose concentrations (p = 0.07). Coffee was additionally associated with 2-hour postload insulin [Never/almost never: 287.2 pmol/L, ≤1 time/day: 280.1 pmol/L, 2–3 times/day: 275.3 pmol/L, >3 times/day: 262.2 pmol/L, p = 0.0005) but not with fasting insulin concentrations (p = .58).

Conclusion

Our present study provides further evidence of a protective effect of coffee on risk of adult-onset diabetes. This effect appears to act primarily, if not exclusively, through postprandial, as opposed to fasting, glucose homeostasis.

Usual coffee intake in Brazil: results from the National Dietary Survey 2008-9

Coffee is central to the economy of many developing countries, as well as to the world economy. However, despite the widespread consumption of coffee, there are very few available data showing the usual intake of this beverage. Surveying usual coffee intake is a way of monitoring one aspect of a population's usual dietary intake. Thus, the present study aimed to characterise the usual daily coffee intake in the Brazilian population. We used data from the National Dietary Survey collected in 2008-9 from a probabilistic sample of 34,003 Brazilians aged 10 years and older. The National Cancer Institute method was applied to obtain the usual intake based on two nonconsecutive food diaries, and descriptive statistical analyses were performed by age and sex for Brazil and its regions. The estimated average usual daily coffee intake of the Brazilian population was 163 (SE 2.8) ml. The comparison by sex showed that males had a 12% greater usual coffee intake than females. In addition, the highest intake was recorded among older males. Among the five regions surveyed, the North-East had the highest usual coffee intake (175 ml). The most common method of brewing coffee was filtered/instant coffee (71%), and the main method of sweetening beverages was with sugar (87%). In Brazil, the mean usual coffee intake corresponds to 163 ml, or 1.5 cups/d. Differences in usual coffee intake according to sex and age differed among the five Brazilian regions.

Relationship of Caffeine with Adiponectin and Blood Sugar Levels in Subjects with and without Diabetes

INTRODUCTION

Coffee though not usually thought of as healthy food but can be treated as one of the beneficial drink. Many researchers have found strong evidence that coffee reduces the risk of several serious ailments, including diabetes, heart disease, cirrhosis of the liver, etc. The long term beneficial effect of coffee on diabetes is now understood to be more influential and obliging.

MATERIALS AND METHODS

This study comprised 220 healthy subjects of which 143 consumed coffee and 77 did not. These were matched with 90 diabetic subjects. Among the 90 diabetics, 48 consumed coffee and 42 did not consume coffee.

RESULTS

The mean adiponectin value was significantly higher in coffee consumed normal and diabetic subjects than the subjects who did not consume coffee. The decrease in fasting blood sugar and HbA1c values were also observed in normal and diabetic subjects who consumed coffee than the other groups who did not consume coffee. Significant difference (p<0.05) in mean FBG, PPBS, HbA1c and adiponectin were observed between coffee consumed and no coffee consumed groups.

CONCLUSION

The long term use of caffeine is more efficient on blood sugar and adiponectin levels, which needed in the prevention of complications in diabetic subjects.

Modifiable Risk Factors and Infertility: What are the Connections?

Infertility is a relatively common condition, greatly affecting couples medically and psychologically. Although infertility treatment is safe, it can be time-intensive, expensive and increase the risk of multiple gestations. Thus, to reduce costs and risks, couples may initially consider lifestyle change to increase their fertility and chances of pregnancy. For many of the diet factors studied (for example: caffeine, soy, protein, iron), there are conflicting data. However, there are some items men and women consume that are detrimental to fertility, such as alcohol and tobacco. The data on exercise are varied but may have an effect on ovulation and fertility - positive or negative. Body mass index appears to impact fertility also, with obesity in both men and women negatively affecting pregnancy rates. In addition, there remains concern and a growing body of research on environmental toxin exposures and reproductive health. Finally, supporting patients through infertility diagnosis and treatment is critical, as psychological stress may impact conception. It is imperative that the relationship between lifestyle factors and fertility continue to be explored as to lessen the morbidity associated with infertility.

Coffee consumption and the risk of latent autoimmune diabetes in adults--results from a Swedish case-control study

AIMS

Coffee consumption is associated with a reduced risk of Type 2 diabetes. Our aim was to investigate if coffee intake may also reduce the risk of latent autoimmune diabetes in adults, an autoimmune form of diabetes with features of Type 2 diabetes.

METHODS

We used data from a population-based case-control study with incident cases of adult onset (≥ 35 years) diabetes, including 245 cases of latent autoimmune diabetes in adults (glutamic acid decarboxylase antibody positive), 759 cases of Type 2 diabetes (glutamic acid decarboxylase antibody negative), together with 990 control subjects without diabetes, randomly selected from the population. Using questionnaire information on coffee consumption, we estimated the odds ratio of latent autoimmune diabetes in adults and Type 2 diabetes adjusted for age, sex, BMI, smoking, physical activity, alcohol, education and family history of diabetes.

RESULTS

Coffee intake was inversely associated with Type 2 diabetes (odds ratio 0.92, 95% CI 0.87-0.98 per cup/day). With regard to latent autoimmune diabetes in adults, the general trend was weak (odds ratio 1.04, 95% CI 0.96-1.13), but stratification by degree of autoimmunity (median glutamic acid decarboxylase antibody levels) suggested that coffee intake may be associated with an increased risk of high glutamic acid decarboxylase antibody latent autoimmune diabetes in adults (odds ratio 1.11, 95% CI 1.00-1.23 per cup/day). Furthermore, for every additional cup of coffee consumed per day, there was a 15.2% (P = 0.0268) increase in glutamic acid decarboxylase antibody levels.

CONCLUSIONS

Our findings confirm that coffee consumption is associated with a reduced risk of Type 2 diabetes. Interestingly, the findings suggest that coffee may be associated with development of autoimmunity and possibly an increased risk of more Type 1-like latent autoimmune diabetes in adults.

Characterization of diterpenoid glucosides in roasted puer coffee beans

Five new diterpenoid glucosides, named mascaroside I (1), mascaroside II (2), paniculoside VI (3), cofaryloside I (4), and villanovane I (5), along with seven known ent-kaurane diterpenoid glucosides (6-12) were isolated from acetone extracts of the roasted coffee beans of Coffea arabica var. yunnanensis. Their structures were established by extensive spectroscopic analysis including 1D and 2D NMR (HSQC, HMBC, COSY, and ROESY) and by comparison with published data. Cytotoxicities evaluation of the isolates showed that they were inactive against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cells.

Coffee and green tea consumption is associated with insulin resistance in Japanese adults

OBJECTIVE

Higher coffee and green tea consumption has been suggested to decrease risk of type 2 diabetes, but their roles in insulin resistance (IR) and insulin secretion remain unclear. This study examined the association between habitual consumption of these beverages and markers of glucose metabolism in a Japanese working population.

MATERIALS/METHODS

Participants were 1440 Japanese employees (1151 men and 289 women) aged 18-69years. Consumption of coffee and green tea was ascertained via a validated brief diet history questionnaire. Multilevel linear regression was used to estimate means (95% confidence intervals) of fasting insulin, fasting plasma glucose, homeostatic model assessment of IR (HOMA-IR), homeostatic model assessment of β-cell function (HOMA-β) and glycated hemoglobin (HbA1c) with adjustment for potential confounding variables.

RESULTS

Coffee consumption was significantly, inversely associated with HOMA-IR (P for trend=0.03), and the association appeared to be confined to overweight subjects (BMI≥25kg/m(2)) (P for trend=0.01, P for interaction=0.08). Unexpectedly, green tea consumption was positively associated with HOMA-IR (P for trend=0.02), though there was no dose-response relationship among daily consumers of green tea. Neither coffee nor green tea consumption was associated with HOMA-β and HbA1c.

CONCLUSIONS

Our findings indicate that coffee consumption may be associated with decreased IR, but not with insulin secretion. The positive association between green tea consumption and IR warrants further investigation.

Roles of chlorogenic Acid on regulating glucose and lipids metabolism: a review

Intracellular glucose and lipid metabolic homeostasis is vital for maintaining basic life activities of a cell or an organism. Glucose and lipid metabolic disorders are closely related with the occurrence and progression of diabetes, obesity, hepatic steatosis, cardiovascular disease, and cancer. Chlorogenic acid (CGA), one of the most abundant polyphenol compounds in the human diet, is a group of phenolic secondary metabolites produced by certain plant species and is an important component of coffee. Accumulating evidence has demonstrated that CGA exerts many biological properties, including antibacterial, antioxidant, and anticarcinogenic activities. Recently, the roles and applications of CGA, particularly in relation to glucose and lipid metabolism, have been highlighted. This review addresses current studies investigating the roles of CGA in glucose and lipid metabolism.

Caffeine and glucose homeostasis during rest and exercise in diabetes mellitus

Caffeine is a substance that has been used in our society for generations, primarily for its effects on the central nervous system that causes wakefulness. Caffeine supplementation has become increasingly more popular as an ergogenic aid for athletes and considerable scientific evidence supports its effectiveness. Because of their potential to alter energy metabolism, the effects of coffee and caffeine on glucose metabolism in diabetes have also been studied both epidemiologically and experimentally. Predominantly targeting the adenosine receptors, caffeine causes alterations in glucose homeostasis by decreasing glucose uptake into skeletal muscle, thereby causing elevations in blood glucose concentration. Caffeine intake has also been proposed to increase symptomatic warning signs of hypoglycemia in patients with type 1 diabetes and elevate blood glucose levels in patients with type 2 diabetes. Other effects include potential increases in glucose counterregulatory hormones such as epinephrine, which can also decrease peripheral glucose disposal. Despite these established physiological effects, increased coffee intake has been associated with reduced risk of developing type 2 diabetes in large-scale epidemiological studies. This review paper highlights the known effects of caffeine on glucose homeostasis and diabetes metabolism during rest and exercise.

The Emerging Health Benefits of Coffee with an Emphasis on Type 2 Diabetes and Cardiovascular Disease

Debate persists whether coffee is beneficial or problematic for human health. Coffee consumption has been associated with a decrease in risk of developing type 2 diabetes, and numerous epidemiological studies have demonstrated that healthy, habitual coffee drinkers are more protected from the risk of contracting diabetes than individuals who do not drink coffee. Coffee consumption has been associated with a reduced incidence of impaired glucose tolerance, hyperglycaemia and insulin sensitivity. Data suggest that several coffee components, such as chlorogenic acids, are involved in the health benefits of coffee. Various mechanisms for this protective effect have been proposed, including effects on incretin release, liver glucose metabolism and insulin sensitivity. Epidemiological data support numerous other health benefits for coffee, including reduced cardiovascular disease (CVD), a protective effect against some neurodegenerative conditions, a favourable effect on liver function and a protective effect against certain cancers These associations are based mainly on observational studies and are currently insufficient to recommend coffee consumption as an interventional strategy for risk reduction in type 2 diabetes and other metabolic diseases While excessive consumption can have adverse effects on some conditions, particularly in terms of sleep quality, these effects vary among individuals and most people do not have any symptoms from coffee drinking. Moderate coffee consumption is associated with no or little risk of severe diseases and may offer substantial health benefits. Thus, coffee is a safe, low-energy beverage and suitable for most adult people.

The association of coffee intake with liver cancer incidence and chronic liver disease mortality in male smokers

Background:

Coffee intake is associated with reduced risk of liver cancer and chronic liver disease as reported in previous studies, including prospective ones conducted in Asian populations where hepatitis B viruses (HBVs) and hepatitis C viruses (HCVs) are the dominant risk factors. Yet, prospective studies in Western populations with lower HBV and HCV prevalence are sparse. Also, although preparation methods affect coffee constituents, it is unknown whether different methods affect disease associations.

Methods:

We evaluated the association of coffee intake with incident liver cancer and chronic liver disease mortality in 27 037 Finnish male smokers, aged 50–69, in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, who recorded their coffee consumption and were followed up to 24 years for incident liver cancer or chronic liver disease mortality. Multivariate relative risks (RRs) and 95% confidence intervals (CIs) were estimated by Cox proportional hazard models.

Results:

Coffee intake was inversely associated with incident liver cancer (RR per cup per day=0.82, 95% CI: 0.73–0.93; P-trend across categories=0.0007) and mortality from chronic liver disease (RR=0.55, 95% CI: 0.48–0.63; P-trend<0.0001). Inverse associations persisted in those without diabetes, HBV- and HCV-negative cases, and in analyses stratified by age, body mass index, alcohol and smoking dose. We observed similar associations for those drinking boiled or filtered coffee.

Conclusion:

These findings suggest that drinking coffee may have benefits for the liver, irrespective of whether coffee was boiled or filtered.

Dose- and gender-dependent interactions between coffee consumption and serum GGT activity in alcohol consumers

AIMS

Coffee consumption has been recently linked with decreased blood gamma-glutamyltransferase (GGT) activities and protection from alcoholic liver disease. To explore the relationship and dose response, we assessed the impacts of coffee and alcohol intake on serum GGT activity in apparently healthy men and women with varying levels of coffee and alcohol consumption.

METHODS

Data on coffee, alcohol consumption and serum GGT activities were collected from 18,899 individuals (8807 men and 10,092 women), mean age 48 years, range 25-74 years, who participated in a large national cross-sectional health survey. Body mass index, smoking index and age were used as covariates in all analyses.

RESULTS

Among the study population, 89.8% reported varying levels of coffee consumption; 6.9% were abstainers from alcohol, 86.1% moderate drinkers, 3.7% heavy drinkers and 3.3% former drinkers. In men, the elevation of GGT induced by heavy drinking (>280 g/week) was found to be significantly reduced by coffee consumption exceeding 4 cups per day. A similar trend was also observed among women, which however, did not reach statistical significance.

CONCLUSION

Coffee modulates the effect of ethanol on serum GGT activities in a dose- and gender-dependent manner. These observations should be implicated in studies on the possible hepatoprotective effects of coffee in alcohol consumers.

Coffee consumption, serum γ-glutamyltransferase, and glucose tolerance status in middle-aged Japanese men

Recently, coffee consumption has been related to decreased risk of type 2 diabetes mellitus (DM) among those with high levels of serum γ-glutamyltransferase (GGT). We examined the association between coffee and glucose tolerance, determined by a 75 g oral glucose tolerance test, and the effect modification of serum GGT on the association.

The study subjects were 5320 men aged 46–60 years who received a health examination at two Self-Defense Forces hospitals from January 1997 to March 2004. Those medicated for DM were excluded. Coffee consumption was classified into <1, 1–2, 3–4, and ≥5 cups/day. Statistical adjustment was made for age, body mass index, smoking, alcohol use, leisure-time physical activity, green tea consumption, parental diabetes, hospital, and rank in the Self-Defense Forces.

Men with normal glucose tolerance, isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT), combined IFG/IGT, and type 2 DM numbered 3384, 398, 790, 348, and 400, respectively. The prevalence odds of isolated IGT, combined IFG/IGT, and type 2 DM, but not of isolated IFG, decreased with increasing consumption of coffee. An inverse association with coffee was observed for isolated IGT in both low (≤40 IU/L) and high (>40 IU/L) GGT groups, and for combined IFG/IGT and type 2 DM in the latter group.

Coffee drinking is protective against glucose intolerance. A possible effect modification of GGT on the coffee-DM association warrants further studies.

Caffeine ingestion impairs insulin sensitivity in a dose-dependent manner in both men and women

The effects of alkaloid caffeine on insulin sensitivity have been investigated primarily in men, and with a single caffeine dose most commonly of 5-6 mg·kg(-1) of body weight (BW). It is unknown if the effects of caffeine on glucose homeostasis are sex-specific and (or) dose-dependent. This study examined whether caffeine ingestion would disrupt glucose homeostasis in a dose-dependent or threshold manner. It also examined whether sex-specific responses to caffeine exist. It was hypothesized that women would have an exaggerated response to caffeine, and that caffeine would only impair glucose metabolism once a threshold was reached. Twenty-four healthy volunteers (12 males, 12 females) participated in 4 trials, in a crossover, randomized, and double-blind fashion. They ingested caffeine (1, 3, or 5 mg·kg(-1) of BW) or placebo followed, 1 h later, by a 2-h oral glucose tolerance test. Glucose, insulin, C-peptide area under the curve (AUC), and insulin sensitivity index data were fitted to a segmented linear model to determine dose-responses. There were no differences between sexes for any endpoints. Regression slopes were significantly different from zero (p < 0.05) for glucose, insulin, and C-peptide AUCs, with thresholds being no different from zero. Increasing caffeine consumption by 1 mg·kg(-1) of BW increased insulin and C-peptide AUCs by 5.8% and 8.7%, respectively. Despite this exaggerated insulin response, glucose AUC increased by 11.2 mmol per 120 min·L(-1) for each mg·kg(-1) BW consumed. These results showed that caffeine ingestion disrupted insulin sensitivity in a dose-dependent fashion beginning at very low doses (0-1 mg·kg(-1) BW) in both healthy men and women.

Role of coffee in modulation of diabetes risk

Coffee consumption has been associated with a lower risk of type 2 diabetes. This association does not depend on race, gender, geographic distribution of the study populations, or the type of coffee consumed (i.e., caffeinated or decaffeinated). This review discusses the strength of this relationship, examines the possibility that the pattern of coffee consumption could influence the association, and evaluates the possible relationship between coffee consumption and other risk factors associated with diabetes. Particular attention is paid to the identification, on the basis of the scientific evidence, of the possible mechanisms by which coffee components might affect diabetes development, especially in light of the paradoxical effect of caffeine on glucose metabolism. In addition to the role of coffee in reducing the risk of developing type 2 diabetes, the possible role of coffee in the course of the illness is explored. Finally, the possibility that coffee can also affect the risk of other forms of diabetes (e.g., type 1 diabetes and gestational diabetes) is examined.

Chlorogenic acid stimulates glucose transport in skeletal muscle via AMPK activation: a contributor to the beneficial effects of coffee on diabetes

Chlorogenic acid (CGA) has been shown to delay intestinal glucose absorption and inhibit gluconeogenesis. Our aim was to investigate the role of CGA in the regulation of glucose transport in skeletal muscle isolated from db/db mice and L6 skeletal muscle cells. Oral glucose tolerance test was performed on db/db mice treated with CGA and soleus muscle was isolated for 2-deoxyglucose transport study. 2DG transport was also examined in L6 myotubes with or without inhibitors such as wortmannin or compound c. AMPK was knocked down with AMPKα1/2 siRNA to study its effect on CGA-stimulated glucose transport. GLUT 4 translocation, phosphorylation of AMPK and Akt, AMPK activity, and association of IRS-1 and PI3K were investigated in the presence of CGA. In db/db mice, a significant decrease in fasting blood sugar was observed 10 minutes after the intraperitoneal administration of 250 mg/kg CGA and the effect persisted for another 30 minutes after the glucose challenge. Besides, CGA stimulated and enhanced both basal and insulin-mediated 2DG transports in soleus muscle. In L6 myotubes, CGA caused a dose- and time-dependent increase in glucose transport. Compound c and AMPKα1/2 siRNA abrogated the CGA-stimulated glucose transport. Consistent with these results, CGA was found to phosphorylate AMPK and ACC, consistent with the result of increased AMPK activities. CGA did not appear to enhance association of IRS-1 with p85. However, we observed activation of Akt by CGA. These parallel activations in turn increased translocation of GLUT 4 to plasma membrane. At 2 mmol/l, CGA did not cause any significant changes in viability or proliferation of L6 myotubes. Our data demonstrated for the first time that CGA stimulates glucose transport in skeletal muscle via the activation of AMPK. It appears that CGA may contribute to the beneficial effects of coffee on Type 2 diabetes mellitus.

Association of moderate coffee intake with self-reported diabetes among urban Brazilians

Coffee has been associated with reductions in the risk of non-communicable chronic diseases (NCCD), including diabetes mellitus. Because differences in food habits are recognizable modifying factors in the epidemiology of diabetes, we studied the association of coffee consumption with type-2 diabetes in a sample of the adult population of the Federal District, Brazil. This cross-sectional study was conducted by telephone interview (n = 1,440). A multivariate analysis was run controlling for socio-behavioural variables, obesity and family antecedents of NCCD. A hierarchical linear regression model and a Poisson regression were used to verify association of type-2 diabetes and coffee intake. The independent variables which remained in the final model, following the hierarchical inclusion levels, were: first level—age and marital status; second level—diabetes and dyslipidaemias in antecedents; third level—cigarette smoking, supplement intake, body mass index; and fourth level—coffee intake (≤100 mL/d, 101 to 400 mL/day, and >400 mL/day). After adjusting hierarchically for the confounding variables, consumers of 100 to 400 mL of coffee/day had a 2.7% higher (p = 0.04) prevalence of not having diabetes than those who drank less than 100 mL of coffee/day. Compared to coffee intake of ≤100 mL/day, adults consuming >400 mL of coffee/day showed no statistically significant difference in the prevalence of diabetes. Thus, moderate coffee intake is favourably associated with self-reported type-2 diabetes in the studied population. This is the first study to show a relationship between coffee drinking and diabetes in a Brazilian population.

An oral lipid challenge and acute intake of caffeinated coffee additively decrease glucose tolerance in healthy men

Lipid-induced insulin resistance has been investigated primarily with i.v. infusions, and caffeine-induced insulin resistance, with alkaloid caffeine. The effects of orally consumed lipids and coffee have not been established and to our knowledge have never been simultaneously investigated. The goals of this study were to determine whether an oral lipid challenge and caffeinated coffee would disrupt glucose homeostasis and to characterize their respective incretin responses. It was hypothesized that oral ingestion of saturated lipids would impair glucose tolerance and that caffeinated coffee would further hinder glucose management. Ten young, healthy males participated in 5 trials in a randomized, cross-over design. At time 0 h, they underwent an oral fat tolerance test (OFTT: 1 g lipid/kg body weight) or consumed water, followed 5 h later by caffeinated (5 mg/kg) coffee, decaffeinated coffee, or water. At 6 h, volunteers underwent an oral glucose tolerance test (OGTT). Consumption of the OFTT increased glucose concentrations (P < 0.05) after a subsequent OGTT. At 7 h, caffeinated coffee produced the highest glucose concentrations (P < 0.05). Glucagon-like peptide-1 active (GLP-1a) and glucose-dependent insulinotropic polypeptide (GIP) were both increased for up to 6 h in all OFTT trials (P < 0.05). Compared to all other treatments, caffeinated and decaffeinated coffee produced higher GLP-1a response at 6.25 h (P < 0.05), whereas only caffeinated coffee increased GIP secretion (P < 0.05). These results show that oral consumption of lipids and caffeinated coffee can independently and additively decrease glucose tolerance. Incretin hormones could explain at least in part this impaired glucose homeostasis.

Associations between the intake of caffeinated and decaffeinated coffee and measures of insulin sensitivity and beta cell function

AIMS/HYPOTHESIS

Although protective relationships between coffee consumption and type 2 diabetes mellitus have consistently been observed, few studies have examined the relationships between coffee consumption and underlying pathophysiological defects that characterise diabetes aetiology. The aim of this study was to explore the associations between caffeinated and decaffeinated coffee consumption and measures of insulin sensitivity and secretion.

METHODS

The study population included 954 multi-ethnic non-diabetic adults from the Insulin Resistance Atherosclerosis Study (IRAS). Multiple regression analyses were performed to examine the cross-sectional relationships between caffeinated and decaffeinated coffee intake and insulin sensitivity and acute insulin response, measured by a frequently sampled intravenous glucose tolerance test, 2 h postload glucose measured by OGTT, fasting insulin, and proinsulin to C-peptide ratios.

RESULTS

Caffeinated coffee intake was positively associated with insulin sensitivity (β = 0.054; SE = 0.026; p = 0.04) and inversely related to 2 h postload glucose (β = -0.37; SE = 0.10; p = 0.0003) in fully adjusted models. Caffeinated coffee intake was not associated with acute insulin response or proinsulin ratios. Decaffeinated coffee intake was inversely related to 2 h postload glucose (β = -0.47; SE = 0.18; p = 0.0096) and positively related to acute insulin response (β = 0.191; SE = 0.077; p = 0.0132). Decaffeinated coffee intake was inversely related to the ratios of both intact and split proinsulin to C-peptide (β = -0.150; SE = 0.061; p = 0.0148; β = -0.254; SE = 0.068; p = 0.0002, respectively).

CONCLUSIONS/INTERPRETATION

In this cross-sectional study, caffeinated coffee was positively related to insulin sensitivity and decaffeinated coffee was favourably related to measures of beta cell function. These results provide pathophysiological insight as to how coffee could impact the risk of type 2 diabetes mellitus.

Methylxanthines and human health: epidemiological and experimental evidence

When considering methylxanthines and human health, it must be recognized that in many countries most caffeine is consumed as coffee. This is further confounded by the fact that coffee contains many bioactive substances in addition to caffeine; it is rich in phenols (quinides, chlorogenic acid, and lactones) and also has diterpenes (fatty acid esters), potassium, niacin, magnesium, and the vitamin B(3) precursor trigonelline. There is a paradox as consumption of either caffeine or caffeinated coffee results in a marked insulin resistance and yet habitual coffee consumption has repeatedly been reported to markedly reduce the risk for type 2 diabetes. There is strong evidence that caffeine reduces insulin sensitivity in skeletal muscle and this may be due to a combination of direct antagonism of A(1) receptors and indirectly β-adrenergic stimulation as a result of increased sympathetic activity. Caffeine may also induce reduced hepatic glucose output. With the exception of bone mineral, there is little evidence that caffeine impacts negatively on other health issues. Coffee does not increase the risk of cardiovascular diseases or cancers and there is some evidence suggesting a positive relationship for the former and for some cancers, particularly hepatic cancer.