Acute caffeine ingestion reduces insulin sensitivity in healthy subjects: a systematic review and meta-analysis

Maternal caffeine, coffee and cola drink intake and the risk of gestational diabetes - Kuopio Birth Cohort

AIMS

Coffee intake is associated with a decreased risk of type 2 diabetes among non-pregnant people. We aimed to investigate the association between caffeine, coffee and cola drink intake in early pregnancy and the risk of gestational diabetes (GDM).

METHODS

Kuopio Birth Cohort (KuBiCo) is a prospective cohort study including pregnant women who were followed at the prenatal clinics in outpatient healthcare centers and gave birth in Kuopio University Hospital, Finland (n=2214). Maternal diet during the first trimester of pregnancy was assessed using a 160-item food frequency questionnaire. GDM was diagnosed by oral glucose tolerance test according to the Finnish national guidelines mainly between 24 and 28 gestational weeks.

RESULTS

Women with moderate coffee intake in the first trimester were less likely diagnosed with GDM than women without coffee intake in an age-adjusted model (OR 0.87; 95% CI 0.76-0.99; p = 0.03), but the association was attenuated in multi-adjusted models (p = 0.11). No association was found between caffeine intake and GDM. One third (32.4%) of pregnant women consumed caffeine over the recommendation (> 200 mg/d). Women who consumed cola drinks more than the median (33.3 mL/d) had an increased risk of GDM (OR 1.29; 95% CI 1.02-1.63, p = 0.037) in multi-adjusted model compared to those who consumed less.

CONCLUSIONS

Caffeine intake during the first trimester of pregnancy was not associated with the risk of GDM but a minor non-significant decrease was seen with moderate coffee intake. Although the average consumption of cola drinks was low in the KuBiCo cohort, higher consumption was associated with an increased risk of GDM. Further studies are needed to evaluate the safe amount of coffee during pregnancy, since the recommended caffeine intake was exceeded in almost half of the coffee drinkers.

Estimate the prevalence of daily caffeine consumption, caffeine use disorder, caffeine withdrawal and perceived harm in Iran: a cross-sectional study

One of the informal diagnoses in DSM-5 is Caffeine Use Disorder (CUD). CUD and high levels of caffeine consumption could impact mental health conditions. This study aimed to estimate the prevalence of CUD, caffeine consumption, caffeine-related harms, and related psychiatric symptoms in Iran. A cross-sectional survey with a convenience sample of 1228 adults were conducted in Iran. Caffeine consumption was assessed across 20 products in Iran. Caffeine Use Disorder Questionnaire (CUDQ), Caffeine Withdrawal Symptoms Questionnaire (CWSQ), 14-item Caffeine-related Harm Screening (CHS), and Symptom Checklist-25 (SCL-25) were used in the present study. We used SPSS (desktop version 26.0) to analyze the data using descriptive statistics, chi-square, and the least significant difference (LSD) post hoc test. The daily average caffeine consumption was 146.67 mg. The prevalence of CUD and caffeine withdrawal (C.W.) were estimated at 19.5% and 46.62%, respectively. Also, 12.9% of responders received CUD and C.W.s simultaneously. The prevalence of CUD was higher in men than females (25.08% vs. 13.93%). 95% of participants (n = 1166) reported using at least one caffeine product yesterday. Moreover, the most reported caffeine-related harms were the desire for sugar (42.9%), insomnia (39.3%), and caffeine dependence (38.3%). Age significantly correlates with CUD (- 0.07) and daily caffeine intake (0.08). Moreover, all SCL-90 subscales had a significant correlation with daily caffeine intake. Finally, responders at younger ages reported higher levels of CUD and caffeine consumption than older adults(P < 0.05). High rates of C.W. and CUD in the Iranian population suggest that it is necessary to develop evidence-based treatments.

The impact of taxing sugar-sweetened beverages on diabetes: a critical review

The global burden of type 2 diabetes is increasing at an alarming rate, fuelled by the obesity epidemic, with significant associated health and economic consequences and apparent inequalities. Sugar-sweetened beverages (SSBs) are a major source of added sugars in diets worldwide and have been linked to an increased risk of type 2 diabetes through a variety of mechanisms, including excess weight. Taxing SSBs has become a promising public health strategy to reduce consumption and mitigate the burden of type 2 diabetes. A substantial body of evidence suggests that SSB taxes lead to increased prices and subsequent reduced consumption, with a potentially greater effect among lower socioeconomic groups. This highlights the potential for tax policies to have an impact on type 2 diabetes and address health inequalities. Evidence from several ongoing SSB tax schemes, including sales and excise taxes, indicates positive effects on improving consumption patterns, and modelling studies point to health gains by averting type 2 diabetes and other cardiometabolic diseases. In contrast, evidence from empirical evaluation of the impact of SSB tax is scarce. Continued monitoring and the strengthening of evaluation research to develop context-tailored policies are required. In addition, there is a need to implement complementary efforts to amplify the impact of SSB taxation and effectively address the global burden of type 2 diabetes.

Associations between artificial sweetener intake from cereals, coffee, and tea and the risk of type 2 diabetes mellitus: A genetic correlation, mediation, and mendelian randomization analysis

BACKGROUND

Previous studies have emphasized the association between the intake of artificial sweeteners (AS) and type 2 diabetes mellitus (T2DM), but the causative relationship remains ambiguous.

METHODS

This study employed univariate Mendelian randomization (MR) analysis to assess the causal link between AS intake from various sources and T2DM. Linkage disequilibrium score (LDSC) regression was used to evaluate the correlation between phenotypes. Multivariate and mediation MR were applied to investigate confounding factors and mediating effects. Data on AS intake from different sources (N = 64,949) were sourced from the UK Biobank, while T2DM data were derived from the DIAbetes Genetics Replication And Meta-analysis.The primary method adopted was inverse variance weighted (IVW), complemented by three validation techniques. Additionally, a series of sensitivity analyses were performed to evaluate pleiotropy and heterogeneity.

RESULTS

LDSC analysis unveiled a significant genetic correlation between AS intake from different sources and T2DM (rg range: -0.006 to 0.15, all P < 0.05). After correction by the false discovery rate (FDR), the primary IVW method indicated that AS intake in coffee was a risk factor for T2DM (OR = 1.265, 95% CI: 1.035-1.545, P = 0.021, PFDR = 0.042). Further multivariable and mediation MR analyses pinpointed high density lipoprotein-cholesterol (HDL-C) as mediating a portion of this causal relationship. In reverse MR analysis, significant evidence suggested a positive correlation between T2DM and AS intake in coffee (β = 0.013, 95% CI: 0.004-0.022, P = 0.004, PFDR = 0.012), cereal (β = 0.007, 95% CI: 0.002-0.012, P = 0.004, PFDR = 0.012), and tea (β = 0.009, 95% CI: 0.001-0.017, P = 0.036, PFDR = 0.049). No other causal associations were identified (P > 0.05, PFDR > 0.05).

CONCLUSION

The MR analysis has established a causal relationship between AS intake in coffee and T2DM. The mediation by HDL-C emphasizes potential metabolic pathways underpinning these relationships.

Coffee intake and risk of diabetic nephropathy: a Mendelian randomization study

Rationale and objective

A causal relationship concerning coffee intake and diabetic nephropathy (DN) is controversial. We conducted a Mendelian randomization study to assess the causal nature of these associations.

Methods

40 independent single nucleotide polymorphisms (SNPs) associated with coffee intake were selected from the UK Biobank study. Summary-level data for diabetic nephropathy were obtained from publicly available genome-wide association studies (GWAS) and the FinnGen consortium. Inverse variance weighted (IVW), MR-Egger, and weighted median (WM) methods were used to examine a causal association. Sensitivity analyses included Cochran's Q test, the intercept of MR-Egger, MR-PRESSO, and the Outlier method. Leave-One-Out sensitivity analyses were also conducted to reduce the heterogeneity.

Results

Our current study demonstrated positive associations of genetically predicted coffee intake with diabetic nephropathy (OR=1.939; P = 0.045 and type 2 diabetes with renal complications (OR = 2.787, P= 0.047). These findings were robust across several sensitivity analyses.

Conclusions

This study found a positive correlation between coffee consumption and the risk of diabetic nephropathy using genetic data. For a more accurate and trustworthy conclusion, subgroup analysis on coffee intake, including preparing method, variety of coffee, and quantity, is required.

Dual A1 and A2A adenosine receptor antagonists, methoxy substituted 2-benzylidene-1-indanone, suppresses intestinal postprandial glucose and attenuates hyperglycaemia in fructose-streptozotocin diabetic rats

BACKGROUND/AIM

Recent research suggests that adenosine receptors (ARs) influence many of the metabolic abnormalities associated with diabetes. A non-xanthine benzylidene indanone derivative 2-(3,4-dihydroxybenzylidene)-4-methoxy-2,3-dihydro-1 H-inden-1-one (2-BI), has shown to exhibit higher affinity at A₁/A_2A ARs compared to caffeine. Due to its structural similarity to caffeine, and the established antidiabetic effects of caffeine, the current study was initiated to explore the possible antidiabetic effect of 2-BI.

METHODS

The study was designed to assess the antidiabetic effects of several A₁ and/or A_2A AR antagonists, via intestinal glucose absorption and glucose-lowering effects in fructose-streptozotocin (STZ) induced diabetic rats. Six-week-old male Sprague-Dawley rats were induced with diabetes via fructose and streptozotocin. Rats were treated for 4 weeks with AR antagonists, metformin and pioglitazone, respectively. Non-fasting blood glucose (NFBG) was determined weekly and the oral glucose tolerance test (OGTT) was conducted at the end of the intervention period.

RESULTS

Dual A₁/A_2A AR antagonists (caffeine and 2-BI) decreased glucose absorption in the intestinal membrane significantly (p < 0.01), while the selective A_2A AR antagonist (Istradefylline), showed the highest significant (p < 0.001) reduction in intestinal glucose absorption. The selective A₁ antagonist (DPCPX) had the least significant (p < 0.05) reduction in glucose absorption. Similarly, dual A₁/A_2A AR antagonists and selective A_2A AR antagonists significantly reduced non-fast blood glucose and improved glucose tolerance in diabetic rats from the first week of the treatment. Conversely, the selective A₁ AR antagonist did not reduce non-fast blood glucose significantly until the 4th week of treatment. 2-BI, caffeine and istradefylline compared well with standard antidiabetic treatments, metformin and pioglitazone, and in some cases performed even better.

CONCLUSION

2-BI exhibited good antidiabetic activity by reducing intestinal postprandial glucose absorption and improving glucose tolerance in a diabetic animal model. The dual antagonism of A₁/A_2A ARs presents a positive synergism that could provide a new possibility for the treatment of diabetes.

The impact of genetic variability on the relationship between caffeine and cardiometabolic outcomes: A systematic review

The relationship between caffeine consumption and cardiometabolic health has been reported, however with heterogenous results. Discrepancies in study results may be due to inter-individual variability between study participants. This systematic review aimed to identify the impact of genetics on the relationship between caffeine consumption and cardiometabolic outcomes. Electronic databases (PubMed and EMBASE) were searched for studies published until July 2021. Selected studies were of both intervention and observational design and included (1) analysis of at least one of the selected cardiometabolic outcome (type 2 diabetes, glucose/insulin levels, cardiovascular disease [CVD], blood pressure [BP] or hypertension, and blood lipid and catecholamine levels), (2) adults aged 18-65 years, and (3) genetic analysis of individuals consuming caffeine. Seventeen studies were included: four randomised controlled trials and an interventional and quasi-experimental study, six population-based prospective cohort studies, three cross-sectional studies, and three case-control studies. CYP1A2 rs762551 and ADORA rs5751876 were associated with glucose response when caffeine was consumed with carbohydrates. CYP1A2 rs762551 moderated the association between coffee intake and hypertension. Moreover, ADORA2A rs5751876 and the ADRA2B I variants moderated the associations between caffeine and BP. Studies that investigated the effects of genetic variations on CVD and caffeine consumption reported equivocal findings (CYP1A2) or warrant replication (COMT, ADORA and TRIB1). Elucidating the extent to which these genes moderate the association between caffeine and cardiometabolic outcomes will enable caffeine consumption advice to be tailored to specific individuals to optimise health.

Sugar-Sweetened Coffee Intake and Blood Glucose Management in Korean Patients with Diabetes Mellitus

One of the most frequently consumed beverages by Korean adults is 3-in-1 coffee (mixed coffee) with sugar and creamer. Hence, understanding the effect of sugar-sweetened coffee (SSC) consumption on blood sugar levels in patients with diabetes mellitus (DM) is important. This study was conducted using the Korea National Health and Nutrition Examination Survey data from 2008 to 2020. In total, 5671 patients with DM were included in the analysis. Coffee consumption patterns were assessed using a 24 h recall. Fasting blood glucose (FBG) and hemoglobin A1c (HbA1c) levels were used to evaluate whether patients reached the glycemic control targets defined by the Korean Diabetes Association. In total, 46.57% of patients with DM included in this analysis consumed SSC. Patients who frequently consumed SSC had significantly higher FBG and HbA1c levels than those who did not (both p for trend <0.01). In a multivariate logistic regression model, the odds ratios of not achieving the target FBG and HbA1c levels were 1.24 (95% confidence interval [CI]: 1.03−1.48, p for trend = 0.01) and 1.29 (95% CI: 1.05−1.58, p for trend = 0.009), respectively. Frequent consumption of SSC can cause difficulty in FBG and HbA1c management in patients with DM.

Can coffee silverskin be a useful tool to fight metabolic syndrome?

Coffee is one of the most consumed products in the world, and its by-products are mainly discarded as waste. In order to solve this problem and in the context of a sustainable industrial attitude, coffee by-products have been studied concerning their chemical and nutritional features for a potential application in foodstuffs or dietary supplements. Under this perspective, coffee silverskin, the main by-product of coffee roasting, stands out as a noteworthy source of nutrients and remarkable bioactive compounds, such as chlorogenic acids, caffeine, and melanoidins, among others. Such compounds have been demonstrating beneficial health properties in the context of metabolic disorders. This mini-review compiles and discusses the potential health benefits of coffee silverskin and its main bioactive components on metabolic syndrome, highlighting the main biochemical mechanisms involved, namely their effects upon intestinal sugar uptake, glucose and lipids metabolism, oxidative stress, and gut microbiota. Even though additional research on this coffee by-product is needed, silverskin can be highlighted as an interesting source of compounds that could be used in the prevention or co-treatment of metabolic syndrome. Simultaneously, the valorization of this by-product also responds to the sustainability and circular economy needs of the coffee chain.

Dietary Supplements for Weight Management: A Narrative Review of Safety and Metabolic Health Benefits

Dietary supplements for weight management include myriad ingredients with thermogenic, lipotropic, satiety, and other metabolic effects. Recently, the safety of this product category has been questioned. In this review, we summarize the safety evidence as well as relevant clinical findings on weight management and metabolic effects of six representative dietary supplement ingredients: caffeine, green tea extract (GTE), green coffee bean extract (GCBE), choline, glucomannan, and capsaicinoids and capsinoids. Of these, caffeine, GTE (specifically epigallocatechin gallate [EGCG]), and choline have recommended intake limits, which appear not to be exceeded when used according to manufacturers’ instructions. Serious adverse events from supplements with these ingredients are rare and typically involve unusually high intakes. As with any dietary component, the potential for gastrointestinal intolerance, as well as possible interactions with concomitant medications/supplements exist, and the health status of the consumer should be considered when consuming these components. Most of the ingredients reviewed also improved markers of metabolic health, such as glucose, lipids, and blood pressure, although the data are limited for some. In summary, weight management supplements containing caffeine, GTE, GCBE, choline, glucomannan, and capsaicinoids and capsinoids are generally safe when taken as directed and demonstrate metabolic health benefits for overweight and obese people.

Methods paper: Performance characteristics of novel assays for circulating levels of proglucagon-derived peptides and validation in a placebo controlled cross-over randomized clinical trial

BACKGROUND

The measurement of proglucagon-derived peptides (PGDPs) is a challenging task mainly due to major overlaps in their molecular sequence in addition to their low circulating levels. Here, we present the technical characteristics of novel ELISA assays measuring C-peptide and all six PGDPs including, for the first time, major proglucagon fragment (MPGF), and we validate them by performing a pilot in vivo cross-over randomized clinical trial on whether coffee consumption may affect levels of circulating PGDPs.

METHODS

The performance and technical characteristics of novel ELISA assays from Ansh measuring GLP-1, GLP-2, oxyntomodulin, glicentin, glucagon, MPGF and C-peptide were first evaluated in vitro in procured samples from a commercial vendor as well as in deidentified human samples from three previously performed clinical studies. Their performance was further evaluated in vivo in the context of a cross-over randomized controlled trial, in which 33 subjects consumed in random order and together with a standardized meal, 200 ml of either (a) instant coffee with 3 mg/kg caffeine, or (b) instant coffee with 6 mg/kg caffeine, (c) or water.

RESULTS

All assays demonstrated high accuracy (spike and recovery and average linearity recovery ±15%), precision (inter-assay CV ≤ 6.4%), specificity (no significant cross-reactivities) and they were sensitive in low concentrations. Measurements of glicentin in archived random human samples using the Ansh assay correlated strongly with the glicentin measurements of Mercodia assay (r = 0.968) and of GLP-1 modestly with Millipore GLP-1 assay (r = 0.440). Oxyntomodulin, glicentin and glucagon concentrations were 2-5 fold higher in plasma compared to serum and serum concentrations correlated modestly (for oxyntomodulin and glicentin) or poorly (for glucagon) with the plasma concentrations. The evaluated assays detected a postprandial increase of gut-secreted PGDPs (GLP-1, GLP-2, oxyntomodulin and glicentin) and a postprandial decrease of pancreas-secreted PGDPs (glucagon, MPGF) in response to consuming coffee in comparison to consuming water with breakfast (enter here composition of breakfast). Only coffee consumption at the high dose alter levels of gut-secreted PGDPs and both at low and high dose to lower levels of pancreas-secreted PGDPs compared to water consumption during breakfast.

CONCLUSION

Accurate, precise and specific measurement of six PGDPs is possible with novel assays. A randomized controlled trial demonstrated in vivo utility of those assays and supports the notion that coffee may exert part of its beneficial effects on glucose homeostasis in the short term through the regulation of PGDPs.

Data driven patterns of nutrient intake and coronary artery disease risk in adults with type 1 diabetes

AIMS

Dietary intake provides a potential intervention target to reduce the high risk for coronary artery disease (CAD) in type 1 diabetes. This effort aimed to identify patterns of nutrient intake in young/middle-aged adults with type 1 diabetes and to examine associations between those patterns and development of CAD.

METHODS

Principal component analysis was used to derive nutrient intake patterns among 514 individuals with childhood-onset (<17 years old) type 1 diabetes aged 18+ years and free of CAD (defined as CAD death, myocardial infarction, revascularization, ischemia, or study physician diagnosed angina). Cox models were used to assess the association between nutrient patterns and CAD incidence over 30-years of follow-up.

RESULTS

Three nutrient principal components (PC) were identified: PC1 (high caffeine and saccharin intake), PC2 (high alcohol and caffeine, lower intake of essential nutrients) and PC3 (higher fiber/micronutrients, low alcohol). In unadjusted Cox models, only PC1 (negatively) and PC2 (positively) were associated with CAD risk. These associations were no longer significant after adjusting for diabetes duration.

CONCLUSIONS

Important dietary components underlying the three patterns identified may have been influenced by diabetes duration or age. Future research can continue to explore patterns of nutrient intake over time and CAD development in type 1 diabetes.

Coffee Increases Post-Exercise Muscle Glycogen Recovery in Endurance Athletes: A Randomized Clinical Trial

Coffee is one of the most widely consumed beverages worldwide and caffeine is known to improve performance in physical exercise. Some substances in coffee have a positive effect on glucose metabolism and are promising for post-exercise muscle glycogen recovery. We investigated the effect of a coffee beverage after exhaustive exercise on muscle glycogen resynthesis, glycogen synthase activity and glycemic and insulinemic response in a double-blind, crossover, randomized clinical trial. Fourteen endurance-trained men performed an exhaustive cycle ergometer exercise to deplete muscle glycogen. The following morning, participants completed a second cycling protocol followed by a 4-h recovery, during which they received either test beverage (coffee + milk) or control (milk) and a breakfast meal, with a simple randomization. Blood samples and muscle biopsies were collected at the beginning and by the end of recovery. Eleven participants were included in data analysis (age: 39.0 ± 6.0 years; BMI: 24.0 ± 2.3 kg/m²; VO_2max: 59.9 ± 8.3 mL·kg⁻¹·min⁻¹; PPO: 346 ± 39 W). The consumption of coffee + milk resulted in greater muscle glycogen recovery (102.56 ± 18.75 vs. 40.54 ± 18.74 mmol·kg dw⁻¹; p = 0.01; d = 0.94) and greater glucose (p = 0.02; d = 0.83) and insulin (p = 0.03; d = 0.76) total area under the curve compared with control. The addition of coffee to a beverage with adequate amounts of carbohydrates increased muscle glycogen resynthesis and the glycemic and insulinemic response during the 4-h recovery after exhaustive cycling exercise.

Interaction of Energy Drinks with Prescription Medication and Drugs of Abuse

In recent years, the consumption of energy drinks (EDs) has become increasingly popular, especially among adolescents. Caffeine, a psychostimulant, is the main compound of EDs which also contain other substances with pharmacological effects. This review aims to compile current evidence concerning the potential interactions between EDs, medicines, and drugs of abuse as they are frequently consumed in combination. The substances involved are mainly substrates, inductors or inhibitors of CYP1A2, psychostimulants, alcohol and other depressant drugs. Furthermore, intoxications reported with EDs and other substances have also been screened to describe acute toxicity. The results of our review show that the consumption of both EDs alone and in combination is not as safe as previously thought. Health professionals and consumers need to be aware of the potential interactions of these drinks as well as the absence of long-term safety data.

Beverage Intake and the Risk of Gestational Diabetes Mellitus: The SECOST

The contribution and impact of beverage intake to total nutrient and energy intake may be substantial. Given the link between lifestyle, diet, and the risk of pregnancy complications, this study investigated the association between the quantity and types of beverages with gestational diabetes mellitus (GDM) risk. The study included 452 women from the Seremban Cohort Study (SECOST). The mean energy by beverage intake was 273 ± 23.83 kcal/day (pre-pregnancy), 349 ± 69.46 kcal/day (first trimester) and 361 ± 64.24 kcal/day (second trimester). Women significantly increased intake of maternal milks and malted drinks, but significantly reduced the intake of carbonated drinks and other drinks from before until the second trimester of pregnancy. For chocolate drinks, carbonated drinks, and soy milk, women increased intake from pre-conception to the first trimester, but reduced their intake from the first to the second trimester. While higher intake of cultured-milk drinks was associated with an increased risk of GDM, higher fruit juice intake was associated with a lower risk of GDM. However, these associations were only observed for intake prior to pregnancy and during the first trimester. Further research is needed to corroborate these findings and investigate the contributions of different beverages to overall diet quality as well as adverse health outcomes during pregnancy.

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.

Effects of supplementation with main coffee components including caffeine and/or chlorogenic acid on hepatic, metabolic, and inflammatory indices in patients with non-alcoholic fatty liver disease and type 2 diabetes: a randomized, double-blind, placebo-controlled, clinical trial

Background

Non-alcoholic fatty liver disease (NAFLD) is much more frequent and more severe, including cirrhosis, hepatocellular carcinoma in patients with type 2 diabetes. Coffee is a complex beverage with hundreds of compounds whereas caffeine and chlorogenic acid are the most abundant bioactive compounds. The published epidemiological data demonstrating beneficial associations between all categories of coffee exposure and ranges of liver outcomes are rapidly growing; however, the main contributors and cause-effect relationships have not yet been elucidated. To address existing knowledge gaps, we sought to determine the efficacy and safety of 6 months chlorogenic acid and/or caffeine supplementation in patients with type 2 diabetes affected by NAFLD.

Methods

This trial was carried out at two Diabetes Centers to assess the effects of supplementation with daily doses of 200 mg chlorogenic acid, 200 mg caffeine, 200 mg chlorogenic acid plus 200 mg caffeine or placebo (starch) in patients with type 2 diabetes and NAFLD. The primary endpoint was reduction of hepatic fat and stiffness measured by FibroScan, and changes in serum hepatic enzymes and cytokeratin − 18 (CK-18) levels. Secondary endpoints were improvements in metabolic (including fasting glucose, homeostasis model assessment-estimated insulin resistance (HOMA-IR), hemoglobin A1c (HBA1C), C-peptide, insulin and lipid profiles) and inflammatory (including nuclear factor k-B (NF-KB), tumor necrosis factor (TNF-α), high sensitive- C reactive protein(hs-CRP)) parameters from baseline to the end of treatment.

Results

Neither chlorogenic acid nor caffeine was superior to placebo in attenuation of the hepatic fat and stiffness and other hepatic outcomes in patients with diabetes and NAFLD. Except for the lower level of total cholesterol in caffeine group (p = 0.04), and higher level of insulin in chlorogenic acid plus caffeine group (p = 0.01) compared with placebo, there were no significant differences among the treatment groups.

Conclusion

These findings do not recommend caffeine and/or chlorogenic acid to treat NAFLD in type 2 diabetes patients.

Trial registration

IRCT201707024010N21. Registered 14 September 2017.

Coffee and Lower Risk of Type 2 Diabetes: Arguments for a Causal Relationship

Prospective epidemiological studies concur in an association between habitual coffee consumption and a lower risk of type 2 diabetes. Several aspects of these studies support a cause–effect relationship. There is a dependency on daily coffee dose. Study outcomes are similar in different regions of the world, show no differences between sexes, between obese versus lean, young versus old, smokers versus nonsmokers, regardless of the number of confounders adjusted for. Randomized controlled intervention trials did not find a consistent impact of drinking coffee on acute metabolic control, except for effects of caffeine. Therefore, lowering of diabetes risk by coffee consumption does not involve an acute effect on the post-meal course of blood glucose, insulin or insulin resistance. Several studies in animals and humans find that the ingestion of coffee phytochemicals induces an adaptive cellular response characterized by upregulation and de novo synthesis of enzymes involved in cell defense and repair. A key regulator is the nuclear factor erythroid 2-related factor 2 (Nrf2) in association with the aryl hydrocarbon receptor, AMP-activated kinase and sirtuins. One major site of coffee actions appears to be the liver, causing improved fat oxidation and lower risk of steatosis. Another major effect of coffee intake is preservation of functional beta cell mass via enhanced mitochondrial function, lower endoplasmic reticulum stress and prevention or clearance of aggregates of misfolded proinsulin or amylin. Long-term preservation of proper liver and beta cell function may account for the association of habitual coffee drinking with a lower risk of type 2 diabetes, rather than acute improvement of metabolic control.

Caffeine and high energy drink use and knowledge by nurses in three countries

AIM

The purpose of this study was to examine nurses' use and knowledge of caffeine and high energy drinks (HED) in three countries.

METHODS

Nurses in each country completed a survey on caffeine and HED use and knowledge.

RESULTS

In a sample of 182 nurses, caffeine use was high with 92% of nurses in Korea, 90.8% in Italy and 88.1% in the United States (US) having at least one cup of coffee a day while 64% of Koreans and 11.9% of those in the US had at least one HED per day. In Korea 68% of nurses (Italy 63.1% and 35.8% US) had at least one cup of caffeinated tea per day. Most agreed there is a need to educate nurses about HED, which contain high amounts of caffeine. Over half of nurses in Korea (58%) and the US (56.7%) said their colleagues consume HED at work.

CONCLUSION

Findings of this study indicate many nurses are consuming caffeine at work and there is a need for education. It is unclear how caffeine affects nurses' clinical performance, which raises the issue of patient safety. Further research is needed regarding safe amounts of caffeine while nurses are on the job as well as an understanding of how HED additives may affect the well-being and clinical care of nurses.

Caffeine Optimizes HIIT Benefits on Obesity-associated Metabolic Adversity in Women

PURPOSE

We investigated whether obesity adversities such as excessive body fat, compensatory hyperinsulinemia, metabolic endotoxemia, irregular androgenicity, and reduced cardiorespiratory and anaerobic fitness are ameliorated by high-intensity interval training (HIIT) with or without caffeine supplementation in women with obesity.

METHODS

Twenty-four women with obesity (Asian cutoff point body mass index ≥ 27 kg·m, body fat = 40%) were evenly randomized to caffeine (CAF) and placebo (PLA) trials for an 8-wk HIIT program (10 × 1-min sprints, interspersed by 1-min rest). CAF (3 mg·kg·bw) and PLA were supplemented before each training session. Body fat was assessed by dual-energy x-ray absorptiometry before and after training together with assessments of glucose tolerance (oral glucose tolerance test, or OGTT), lipopolysaccharide endotoxins, testosterone, cardiorespiratory, and anaerobic fitness.

RESULTS

Significant interaction between HIIT and CAF was found for OGTT glucose and OGTT insulin levels (P = 0.001 and P = 0.049 respectively). HIIT-alone increased glucose at 90 min (P = 0.049) and OGTT insulin at 60 min (P = 0.038). Conversely, HIIT with CAF decreased OGTT glucose at 120 min (P = 0.024) without affecting OGTT insulin. HIIT-alone induced 28.3% higher OGTT insulin (effect size d = 0.59 for area under the curve) and 14.5% higher OGTT glucose (d = 0.28). Conversely, HIIT with CAF decreased OGTT glucose by 19.1% (d = 0.51 for area under the curve) without changing OGTT insulin. HIIT-alone effects on glycemia and insulinemia were concurrent with a 31% increase in lipopolysaccharide endotoxins (P = 0.07; d = 0.78; confidence interval, 5.7-8.7) in the PLA but not in CAF treatment (P = 0.99; d = 0.003; confidence interval, 6.5-10.6), although endotoxin level remained within the recommended healthy thresholds. Furthermore, either HIIT alone or with CAF reduced body fat percentage (P < 0.001, ANOVA main training effects), increased muscle mass (P = 0.002), reduced testosterone (P = 0.005), and increased cardiorespiratory and anaerobic capacity (P < 0.001).

CONCLUSIONS

HIIT induces fat loss and decreases androgenicity in women with obesity. However, its side effects such as endotoxemia and hyperinsulinemia are ameliorated by caffeine supplementation.

Purinergic signaling in diabetes and metabolism

Purinergic signaling, a concept originally formulated by the late Geoffrey Burnstock (1929-2020), was found to modulate pathways in every physiological system. In metabolic disorders there is a role for both adenosine receptors and P2 (nucleotide) receptors, of which there are two classes, i.e. P2Y metabotropic and P2X ionotropic receptors. The individual roles of the 19 receptors encompassed by this family have been dissected - and in many cases the effects associated with specific cell types, including adipocytes, skeletal muscle, liver cells and immune cells. It is suggested that ligands selective for each of the four adenosine receptors (A₁, A_2A, A_2B and A₃), and several of the P2 subtypes (e.g. P2Y₆ or P2X7 antagonists) might have therapeutic potential for treating diabetes and obesity. This is a developing story with some conflicting conclusions relevant to drug discovery, which we summarize here.

Caffeine-Containing Energy Shots Cause Acute Impaired Glucoregulation in Adolescents

Caffeine-containing, nutritionally fortified energy shots are consumed at high rates by adolescents, yet little is known about their metabolic impact. The purpose of this study was to examine the consequences of small format, caffeinated energy shots on glucose metabolism and gastrointestinal hormone secretion in adolescents. Twenty participants aged 13-19 years participated in a double-blind, randomized cross-over study consisting of two trials separated by 1-4 weeks. Participants consumed a volume-matched caffeinated energy shot (CAF, 5 mg/kg) or a decaffeinated energy shot (DECAF) followed by a 2 h oral glucose tolerance test. Blood samples were collected and area under the curve (AUC) calculated for glucose, insulin and gut and metabolic hormones. Consumption of CAF resulted in a 25% increase in glucose and a 26% increase in insulin area under the curve (AUC, p = 0.037; p < 0.0001) compared to DECAF. No impact on gut hormones was observed. To further characterize responses, individuals were classified as either slow or fast caffeine metabolizers based on an allele score. Glucose intolerance was greater in genetically fast vs. slow caffeine metabolizers and differences between groups were supported by distinct serum metabolomics separation. Consumption of caffeine-containing energy shots results in acute impaired glucoregulation in healthy adolescents as characterized by hyperinsulinemia following an oral glucose challenge.

Association of Coffee Intake With Survival in Patients With Advanced or Metastatic Colorectal Cancer

Importance

Several compounds found in coffee possess antioxidant, anti-inflammatory, and insulin-sensitizing effects, which may contribute to anticancer activity. Epidemiological studies have identified associations between increased coffee consumption and decreased recurrence and mortality of colorectal cancer. The association between coffee consumption and survival in patients with advanced or metastatic colorectal cancer is unknown.

Objective

To evaluate the association of coffee consumption with disease progression and death in patients with advanced or metastatic colorectal cancer.

Design, Setting, and Participants

This prospective observational cohort study included 1171 patients with previously untreated locally advanced or metastatic colorectal cancer who were enrolled in Cancer and Leukemia Group B (Alliance)/SWOG 80405, a completed phase 3 clinical trial comparing the addition of cetuximab and/or bevacizumab to standard chemotherapy. Patients reported dietary intake using a semiquantitative food frequency questionnaire at the time of enrollment. Data were collected from October 27, 2005, to January 18, 2018, and analyzed from May 1 to August 31, 2018.

Exposures

Consumption of total, decaffeinated, and caffeinated coffee measured in cups per day.

Main Outcomes and Measures

Overall survival (OS) and progression-free survival (PFS).

Results

Among the 1171 patients included in the analysis (694 men [59%]; median age, 59 [interquartile range, 51-67] years). The median follow-up time among living patients was 5.4 years (10th percentile, 1.3 years; IQR, 3.2-6.3 years). A total of 1092 patients (93%) had died or had disease progression. Increased consumption of coffee was associated with decreased risk of cancer progression (hazard ratio [HR] for 1-cup/d increment, 0.95; 95% CI, 0.91-1.00; P = .04 for trend) and death (HR for 1-cup/d increment, 0.93; 95% CI, 0.89-0.98; P = .004 for trend). Participants who consumed 2 to 3 cups of coffee per day had a multivariable HR for OS of 0.82 (95% CI, 0.67-1.00) and for PFS of 0.82 (95% CI, 0.68-0.99), compared with those who did not drink coffee. Participants who consumed at least 4 cups of coffee per day had a multivariable HR for OS of 0.64 (95% CI, 0.46-0.87) and for PFS of 0.78 (95% CI, 0.59-1.05). Significant associations were noted for both caffeinated and decaffeinated coffee.

Conclusions and Relevance

Coffee consumption may be associated with reduced risk of disease progression and death in patients with advanced or metastatic colorectal cancer. Further research is warranted to elucidate underlying biological mechanisms.

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.

Beneficial Impact of Semicarbazide-Sensitive Amine Oxidase Inhibition on the Potential Cytotoxicity of Creatine Supplementation in Type 2 Diabetes Mellitus

Creatine supplementation of the population with type 2 diabetes mellitus (T2DM) combined with an exercise program is known to be a possible therapy adjuvant with hypoglycemic effects. However, excessive administration of creatine leads to the production of methylamine which is deaminated by the enzyme semicarbazide-sensitive amine oxidase (SSAO) and as a result, cytotoxic compounds are produced. SSAO activity and reaction products are increased in the serum of T2DM patients. Creatine supplementation by diabetics will further augment the activity of SSAO. The current review aims to find a feasible way to ameliorate T2DM for patients who exercise and desire to consume creatine. Several natural agents present in food which are involved in the regulation of SSAO activity directly or indirectly are reviewed. Particularly, zinc-α2-glycoprotein (ZAG), zinc (Zn), copper (Cu), histamine/histidine, caffeine, iron (Fe), and vitamin D are discussed. Inhibiting SSAO activity by natural agents might reduce the potential adverse effects of creatine metabolism in population of T2DM.

Plasma metabolite biomarkers of boiled and filtered coffee intake and their association with type 2 diabetes risk

BACKGROUND

Habitual coffee intake has been associated with a lower risk of developing type 2 diabetes (T2D), but few studies used biomarkers to reflect intake and investigated different coffee brews, that is boiled and filtered, separately.

OBJECTIVES

To identify plasma metabolites associated with boiled or filtered coffee intake and to examine their association with T2D risk in Swedish adults.

METHODS

In a case-control study nested within the Västerbotten Intervention Programme, baseline plasma samples from 421 case-control pairs and samples from a subset of 149 pairs at a 10-year follow-up were analysed using untargeted LC-MS metabolomics. We identified metabolites associated with food frequency questionnaires (FFQ)-estimated coffee intake and assessed odds ratios of T2D.

RESULTS

In total, 24 and 32 metabolites were associated with boiled or filtered coffee intake. We determined robust metabolite panels for highly specific prediction of boiled or filtered coffee. We observed an inverse association between the metabolite panel of filtered coffee and T2D risk. No association with T2D was observed for the panel of boiled coffee intake. Similar results were observed for FFQ-estimated coffee intake.

CONCLUSIONS

We identified plasma metabolites specifically associated with boiled or filtered coffee intake, which might be used as selective biomarkers. Our study supports a protective role of habitual intake of filtered coffee on T2D development. The lack of association for boiled coffee intake might be due to the lack of a protective effect of boiled coffee or due to the limited number of boiled coffee consumers in this population, but it warrants further investigation.

Hypoglycemia After Upper Gastrointestinal Surgery: Clinical Approach to Assessment, Diagnosis, and Treatment

CONTEXT

Post-bariatric hypoglycemia (PBH) is an increasingly encountered complication of upper gastrointestinal surgery; the prevalence of this condition is anticipated to rise given yearly increases in bariatric surgical procedures. While PBH is incompletely understood, there is a growing body of research describing the associated factors, mechanisms, and treatment approaches for this condition.

EVIDENCE ACQUISITION

Data are integrated and summarized from studies of individuals affected by PBH and hypoglycemia following upper gastrointestinal surgery obtained from PubMed searches (1990-2020).

EVIDENCE SYNTHESIS

Information addressing etiology, incidence/prevalence, clinical characteristics, assessment, and treatment were reviewed and synthesized for the practicing physician. Literature reports were supplemented by clinical experience as indicated, when published data were not available.

CONCLUSION

PBH can be life-altering and severe for a subset of individuals. Given the chronic nature of this condition, and sequelae of both acute and recurrent episodes, increasing provider awareness of both the condition and associated risk factors is critical for assessment, prompt diagnosis, treatment, and preoperative identification of individuals at risk.

Effects of coffee consumption on glucose metabolism: A systematic review of clinical trials

Epidemiological studies indicate an inverse association of coffee consumption with risk of type 2 diabetes mellitus. However, studies to determine the clinical effects of coffee consumption on the glucose metabolism biomarkers remain uncertain. The aim of this systematic review was to evaluate the effects of coffee consumption on glucose metabolism. A search of electronic databases (PubMed and Web of Science) was performed identifying studies published until September 2017. Eight clinical trials (n = 247 subjects) were identified for analyses. Participants and studies characteristics, main findings, and study quality (Jadad Score) were reported. Short-term (1-3 h) and long-term (2-16 weeks) studies were summarized separately. Short-term studies showed that consumption of caffeinated coffee may increase the area under the curve for glucose response, while for long-term studies, caffeinated coffee may improve the glycaemic metabolism by reducing the glucose curve and increasing the insulin response. The findings suggest that consumption of caffeinated coffee may lead to unfavourable acute effects; however, an improvement on glucose metabolism was found on long-term follow-up.

Caffeine Consumption through Coffee: Content in the Beverage, Metabolism, Health Benefits and Risks

Caffeine (1,3,7-trimethylxanthine) is the most consumed psychoactive substance in the world, acting by means of antagonism to adenosine receptors, mainly A1 and A2A. Coffee is the main natural source of the alkaloid which is quite soluble and well extracted during the brew’s preparation. After consumption, caffeine is almost completely absorbed and extensively metabolized in the liver by phase I (cytochrome P450) enzymes, mainly CYP1A2, which appears to be polymorphically distributed in human populations. Paraxanthine is the major caffeine metabolite in plasma, while methylated xanthines and methyluric acids are the main metabolites excreted in urine. In addition to stimulating the central nervous system, caffeine exerts positive effects in the body, often in association with other substances, contributing to prevention of several chronic diseases. The potential adverse effects of caffeine have also been extensively studied in animal species and in humans. These aspects will be approached in the present review.

Tea, coffee, caffeine intake and the risk of cardio-metabolic outcomes: findings from a population with low coffee and high tea consumption

Background

This study aimed to assess the potential effects of long-term intake of caffeine and habitual consumption of coffee and tea on the occurrence of cardio-renal events among an Iranian population with low coffee and high tea consumption.

Methods

Adult participants of the Tehran Lipid and Glucose Study (2006-2008 to 2012-2014) who met the study inclusion criteria, were recruited. Habitual dietary intakes were assessed using a validated food frequency questionnaire. Demographics, anthropometrics, blood pressure, and biochemical variables were evaluated at baseline and during follow-up examinations. Multivariate Cox proportional hazard and logistic regression models adjusted for potential confounders were used to estimate the risk of cardiovascular disease (CVD), hypertension (HTN) and chronic kidney disease (CKD).

Results

During median 6 years of follow-up, the incidence rate of CVD outcomes, HTN, and CKD were 3.3%, 15.5%, and 17.9%, respectively. The risk of CVD was increased more than two-fold in the highest tertile of tea consumption (HR = 2.44, 95% confidence interval, CI = 1.40-4.27; P for trend = 0.001), and caffeine intakes (HR = 2.22, 95% CI = 1.23-4.01; P for trend = 0.005). A 42% lower incidence of CVD was observed in coffee drinkers, compared to non-drinkers (HR = 0.58, 95% CI = 0.36-0.93; P for trend = 0.023). No significant association was observed between tea, coffee or caffeine intakes and the risk of HTN or CKD.

Conclusions

Findings of our study support previous data regarding the protective effects of coffee on CVD. Contrary to the previous studies, we found that higher intakes of tea and caffeine, mainly originated from tea in our population, may increase risk of CVD events. It may be related to the type of tea and its preparation methods, additives or artificial colors in tea consumed in Iran, and sweets or sugar that mostly consumed accompanied by tea. Also, genetic variants of the liver enzymes may modify the association of dietary caffeine sources and incidence of CVD. Further prospective studies with incorporation of different population with different dietary habits and genetic backgrounds are needed to clarify the contradictions.

The acute effects of the non-nutritive sweeteners aspartame and acesulfame-K in UK diet cola on glycaemic response

Substituting sugar-sweetened for artificially sweetened beverages may reduce energy intakes. This study aims to ascertain the acute glycaemic effects of the NNS aspartame and acesulfame-K in UK diet-cola (DC). Ten healthy participants attended the laboratory fasted on three occasions. Individuals drank (1) 25 g glucose in 125 mL water + 236 mL water, (2) 25 g glucose in 125 mL water with 236 mL DC and (3) 236 mL sucrose-sweetened cola with 125 mL water. Blood (glucose) was measured pre-test and every 15 minutes over a 120-minute period using portable glucometers. The glucose-control and glucose + DC elicited similar blood glucose rises above pre-prandial levels. Sucrose-sweetened cola showed a non-significant lower rise in postprandial glycaemia, exhibiting the lowest glycaemic index (GI) (77.0 ± 9.1). GI of glucose (100.0 ± 15.2) and glucose + DC (104.3 ± 8.5) was similar and a one-way repeated-measures ANOVA showed no significant differences in glycaemic response between test drinks (F(2,29) = 1.68, p > .05). Results demonstrate the glycaemic inactivity of non-nutritive sweeteners.

Citrus Aurantium and caffeine complex versus placebo on biomarkers of metabolism: a double blind crossover design

BACKGROUOND

The purpose of this study was to examine resting the metabolic response to the ingestion of a complex containing Citrus Aurantium + Caffeine (CA + C) and if its consumption influences metabolic recovery following a high-intensity anaerobic exercise bout in habitual caffeine users.

METHODS

Ten physically active males (25.1 ± 3.9 years; weight 78.71 ± 9.53 kg; height 177.2 ± 4.6 cm; body fat 15.5 ± 3.13%) participated in this study. This study was performed in a double-blind, randomized crossover fashion consisting of two exhaustive exercise protocols. On each visit the participants consumed either a CA + C (100 mg of CA and 100 mg of C) or placebo (dextrose) capsule. After consumption, participants were monitored throughout a 45-min ingestion period, then completed a repeated Wingate protocol, and were then monitored throughout a 45-min recovery period. Metabolic function was measured through blood glucose, plasma insulin, plasma triglycerides, and plasma catecholamines: epinephrine (E) and norepinephrine (NE). Biomarkers were taken at four different time points; Ingestion period: baseline (I1), post-ingestion period (I2); Recovery period: immediately post-exercise (R1), post-recovery period (R2).

RESULTS

A repeated measures ANOVA revealed significant time-dependent increases in plasma E and NE at I2 only in the CA + C trial (p < 0.05), and a significant decrease in blood glucose at I2 in the PLA trial (p < 0.05); however, no meaningful changes in glucose was observed following CA + C ingestion. No changes in insulin or triglycerides were observed during the ingestion period. No trial-dependent differences were observed in the Recovery period. All biomarkers of metabolic recovery were equivalent when evaluating R1 v R2. Participants recovered in a similar time-dependent manner in all markers of metabolism following the PLA and CA + C trials.

CONCLUSION

The findings of this study suggested that normal recommended dosages of 100 mg CA + 100 mg C is sufficient to promote glucose sparing at rest, with modest increases in SNS activity; however, the individual role of CA or C in this response cannot be determined.

Effects of Coffee and Tea Consumption on Glucose Metabolism: A Systematic Review and Network Meta-Analysis

Prospective cohort studies have described an association between coffee or tea consumption and the risk of developing diabetes. However, whether coffee or tea improves glucose metabolism remains uncertain. We investigated the effect of coffee and tea on glucose metabolism by conducting a systematic review and meta-analysis of randomized controlled trials. Electronic databases were searched for articles published up 19 February 2017. The primary endpoint was the mean difference in post-intervention fasting blood glucose (FBG) levels between the groups. Of 892 citations screened, 27 studies (1898 participants) were included in our meta-analysis. A network meta-analysis suggested that green tea, but not caffeinated/decaffeinated coffee or black tea, may reduce FBG levels, compared with placebo/water (−2.10 mg/dL; 95% confidence interval (CI), −3.96 to −0.24 mg/dL; p = 0.03; moderate quality of evidence). In a subgroup analysis, the effect of green tea on FBG levels was statistically significant only in studies with a mean age of < 55-years-old or Asian-based studies. The oolong tea group also showed a significant decrease in FBG, but the quality of evidence was very low. In conclusion, green tea consumption might decrease FBG levels, especially in < 55-year-olds or Asian-based populations.

Lack of acute or chronic effects of epicatechin-rich and procyanidin-rich apple extracts on blood pressure and cardiometabolic biomarkers in adults with moderately elevated blood pressure: a randomized, placebo-controlled crossover trial

Background

The reported effects of flavanol-rich foods such as cocoa, dark chocolate, and apples on blood pressure and endothelial function may be due to the monomeric flavanols [mainly (-)-epicatechin (EC)], the oligomeric flavanols [procyanidins (PCs)], or other components. Reports of well-controlled intervention studies that test the effects of isolated oligomeric flavanols on biomarkers of cardiovascular health are lacking.

Objective

We studied the acute and chronic effects of an EC-rich apple flavanol extract and isolated apple PCs on systolic blood pressure (BP) and other cardiometabolic biomarkers.

Design

Forty-two healthy men and women with moderately elevated BP completed this randomized, double-blind, placebo-controlled, 4-arm crossover trial. Participants ingested a single dose of an apple flavanol extract (70 mg monomeric flavanols, 65 mg PCs), a double dose of this extract (140 mg monomeric flavanols, 130 mg PCs), an apple PC extract (130 mg PCs, 6.5 mg monomeric flavanols), or placebo capsules once daily for 4 wk, in random order. Biomarkers of cardiovascular disease risk and vascular function were measured before and 2 h after ingestion of the first dose and after the 4-wk intervention.

Results

Compared with placebo, none of the isolated flavanol treatments significantly (P < 0.05) changed systolic or diastolic BP (peripheral and aortic), plasma nitric oxide (NO) reaction products, or measures of arterial stiffness (carotid femoral pulse-wave velocity, brachial-ankle pulse-wave velocity, or Augmentation Index) after 2 h or 4 wk of the intervention. There were no changes in plasma endogenous metabolite profiles or circulating NO; endothelin 1; total, HDL, or LDL cholesterol; triglycerides; fasting glucose; fructosamine; or insulin after 4 wk of the intervention.

Conclusions

Our data suggest that, in isolation, neither monomeric flavanols nor PCs affect BP, blood lipid profiles, endothelial function, or glucose control in individuals with moderately elevated BP. The reported benefits of consuming flavanol-rich cocoa, chocolate, and apple products appear to be dependent on other components, which may work in combination with monomeric flavanols and PCs. This trial was registered at www.clinicaltrials.gov as NCT02013856.

Effects of Unfiltered Coffee and Bioactive Coffee Compounds on the Development of Metabolic Syndrome Components in a High-Fat-/High-Fructose-Fed Rat Model

The literature is inconsistent as to how coffee affects metabolic syndrome (MetS), and which bioactive compounds are responsible for its metabolic effects. This study aimed to evaluate the effects of unfiltered coffee on diet-induced MetS and investigate whether or not phenolic acids and trigonelline are the main bioactive compounds in coffee. Twenty-four male Sprague‒Dawley rats were fed a high-fat (35% W/W) diet plus 20% W/W fructose in drinking water for 14 weeks, and were randomized into three groups: control, coffee, or nutraceuticals (5-O-caffeoylquinic acid, caffeic acid, and trigonelline). Coffee or nutraceuticals were provided in drinking water at a dosage equal to 4 cups/day in a human. Compared to the controls, total food intake (p = 0.023) and mean body weight at endpoint (p = 0.016) and estimated average plasma glucose (p = 0.041) were lower only in the coffee group. Surrogate measures of insulin resistance including the overall fasting insulin (p = 0.010), endpoint HOMA-IR (p = 0.022), and oral glucose tolerance (p = 0.029) were improved in the coffee group. Circulating triglyceride levels were lower (p = 0.010), and histopathological and quantitative (p = 0.010) measurements indicated lower grades of liver steatosis compared to controls after long-term coffee consumption. In conclusion, a combination of phenolic acids and trigonelline was not as effective as coffee per se in improving the components of the MetS. This points to the role of other coffee chemicals and a potential synergism between compounds.

Polyphenol-rich foods and risk of gestational diabetes: a systematic review and meta-analysis

Animal studies have demonstrated anti-diabetic properties of several food-derived polyphenols, but data in humans remains unclear. This study aimed to review and meta-analyse evidence concerning the effect of the intake of several polyphenol-rich foods on gestational diabetes (GDM) risk. A systematic literature search was conducted in PubMed, Web of Science and Embase databases for observational studies on the association between dietary intake of foods/diets rich in polyphenols and GDM risk. Inclusion criteria were original research articles with full texts published in peer-reviewed English language journals, which investigated foods within the top 100 richest dietary sources of polyphenols and reported odds ratio/relative risk with their corresponding 95% confidence intervals. The quality of included studies was assessed using the Newcastle-Ottawa Scale. The intake of polyphenol-rich foods and dietary patterns in relation to GDM were pooled with fixed- and random-effects models. In total, 12 (10 cohort, 1 cross-sectional and 1 case-control) studies were included for the final systematic review, comprising 124,959 participants and including 5,786 women with GDM. Five studies found a significant, inverse association between the intake of polyphenol-rich foods or Mediterranean diet and GDM, whereas five studies reported no association and two exhibited a positive association. Meta-analyses further showed that the risk of GDM was about halved amongst women with the highest score of Mediterranean diet compared to those with the lowest score. The results suggest that dietary patterns rich in polyphenols may reduce the risk of GDM despite inconclusive evidence for polyphenol-rich food groups.

Association between habitual coffee consumption and metabolic syndrome in type 1 diabetes

BACKGROUND AND AIMS

In the general population, habitual coffee consumption is inversely associated with the metabolic syndrome, a syndrome that is rather common also in patients with type 1 diabetes. However, whether coffee intake is beneficially related to the metabolic syndrome also in type 1 diabetes, is not known. We, therefore, studied the potential association between coffee consumption and the metabolic syndrome in a large population of individuals with type 1 diabetes. Furthermore, we investigated whether coffee consumption is associated with insulin resistance (estimated glucose disposal rate, eGDR), kidney function (estimated glomerular filtration rate, eGFR), and low-grade chronic inflammation (high-sensitivity C-reactive protein, hsCRP).

METHODS AND RESULTS

Data from 1040 participants in the Finnish Diabetic Nephropathy Study were included in these cross-sectional analyses. Metabolic syndrome was assumed if at least 3 of the following cardiovascular risk factors were present: central obesity, high blood pressure, low HDL-cholesterol concentration, high triglyceride concentration, and hyperglycaemia. Subjects were categorized based on self-reported daily coffee intake: non-consumers (<1 cup/d), low (≥1 cups/d < 3), moderate (≥3 cups/d < 5), and high coffee consumption (≥5 cups/d). In multivariable logistic regression analysis, moderate and high coffee consumption was associated with increased odds of the metabolic syndrome. Moreover, any level of coffee consumption was associated with increased risk of the blood pressure-component. An increasing trend was observed in the eGFR with increasing coffee consumption.

CONCLUSIONS

In type 1 diabetes, high coffee intake is associated with the metabolic syndrome, and especially its blood pressure-component.

Antioxidant and Antimicrobial Activities of (-)-Epigallocatechin-3-gallate (EGCG) and its Potential to Preserve the Quality and Safety of Foods

Quality deterioration of fresh or processed foods is a major challenge for the food industry not only due to economic losses but also due to the risks associated with spoiled foods resulting, for example, from toxic compounds. On the other hand, there are increasing limitations on the application of synthetic preservatives such as antioxidants in foods because of their potential links to human health risks. With the new concept of functional ingredients and the development of the functional foods market, and the desire for a "clean" label, recent research has focused on finding safe additives with multifunctional effects to ensure food safety and quality. (-)-Epigallocatechin-3-gallate (EGCG), a biologically active compound in green tea, has received considerable attention in recent years and is considered a potential alternative to synthetic food additives. EGCG has been shown to prevent the growth of different Gram-positive and Gram-negative bacteria responsible for food spoilage while showing antioxidant activity in food systems. This review focuses on recent findings related to EGCG separation techniques, modification of its structure, mechanisms of antioxidant and antimicrobial activities, and applications in preserving the quality and safety of foods.

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 at a Moderate Dose Did Not Affect the Skeletal System of Rats with Streptozotocin-Induced Diabetes

Diabetes may lead to the development of osteoporosis. Coffee drinking, apart from its health benefits, is taken into consideration as an osteoporosis risk factor. Data from human and animal studies on coffee and caffeine bone effects are inconsistent. The aim of the study was to investigate effects of caffeine at a moderate dose on the skeletal system of rats in two models of experimental diabetes induced by streptozotocin. Effects of caffeine administered orally (20 mg/kg aily for four weeks) were investigated in three-month-old female Wistar rats, which, two weeks before the start of caffeine administration, received streptozotocin (60 mg/kg, intraperitoneally) alone or streptozotocin after nicotinamide (230 mg/kg, intraperitoneally). Bone turnover markers, mass, mineral density, histomorphometric parameters, and mechanical properties were examined. Streptozotocin induced diabetes, with profound changes in the skeletal system due to increased bone resorption and decreased bone formation. Although streptozotocin administered after nicotinamide induced slight increases in glucose levels at the beginning of the experiment only, slight, but significant unfavorable changes in the skeletal system were demonstrated. Administration of caffeine did not affect the investigated skeletal parameters of rats with streptozotocin-induced disorders. In conclusion, caffeine at a moderate dose did not exert a damaging effect on the skeletal system of diabetic rats.