Long-term consumption of a green/roasted coffee blend positively affects glucose metabolism and insulin resistance in humans

Mechanistic study on the inhibition of α-amylase and α-glucosidase using the extract of ultrasound-treated coffee leaves

BACKGROUND

Our previous studies have shown that ultrasound-treated γ-aminobutyric acid (GABA)-rich coffee leaves have higher angiotensin-I-converting enzyme inhibitory activity than their untreated counterpart. However, whether they have antidiabetic activity remains unknown. In this study, we aimed to investigate the inhibitory activities of coffee leaf extracts (CLEs) prepared with ultrasound (CLE-U) or without ultrasound (CLE-NU) pretreatment on α-amylase and α-glucosidase. Subsequently, we evaluated the binding interaction between CLE-U and both enzymes using multi-spectroscopic and in silico analyses.

RESULTS

Ultrasound pretreatment increased the inhibitory activities of CLE-U against α-amylase and α-glucosidase by 21.78% and 25.13%, respectively. CLE-U reversibly inhibits both enzymes, with competitive inhibition observed for α-amylase and non-competitive inhibition for α-glucosidase. The static quenching of CLE-U against both enzymes was primarily driven by hydrogen bond and van der Waals interactions. The α-helices of α-amylase and α-glucosidase were increased by 1.8% and 21.3%, respectively. Molecular docking results showed that the key differential compounds, including mangiferin, 5-caffeoylquinic acid, rutin, trigonelline, GABA, caffeine, glutamate, and others, present in coffee leaves interacted with specific amino acid residues located at the active site of α-amylase (ASP197, GLU233, and ASP300). The binding of α-glucosidase and these bioactive components involved amino acid residues, such as PHE1289, PRO1329, and GLU1397, located outside the active site.

CONCLUSION

Ultrasound-treated coffee leaves are potential anti-diabetic substances, capable of preventing diabetes by inhibiting the activities of α-amylase and α-glucosidase, thus delaying starch digestion. Our study provides valuable information to elucidate the possible antidiabetic capacity of coffee leaves through the inhibition of α-amylase and α-glucosidase activities. © 2023 Society of Chemical Industry.

Dietary Supplements Containing Oat Beta-Glucan and/or Green Coffee (Poly)phenols Showed Limited Effect in Modulating Cardiometabolic Risk Biomarkers in Overweight/Obese Patients without a Lifestyle Intervention

Obesity has reached pandemic proportions and has become a major health concern worldwide. Therefore, it is necessary to find new strategies against this condition and its associated comorbidities. Green coffee polyphenols (GCP) and oat beta-glucans (BGs) have proven their hypolipidaemic and hypoglycaemic effects. This study aimed to examine the effects of the long-term consumption of supplements containing GCP, BG or the novel GCP/BG combination on lipid and glucose metabolism biomarkers in overweight/obese subjects who maintained their dietary habits and physical activity, hence addressing the difficulty that this population faces in adapting to lifestyle changes. A randomised, crossover, blind trial was carried out in 29 volunteers who consumed either GCP (300 mg), BG (2.5 g) or GCP/BG (300 mg + 2.5 g) twice a day for 8 weeks. Blood samples were collected, and blood pressure and body composition were measured at the beginning and end of each intervention. Total cholesterol, triglycerides, high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), very low-density lipoprotein (VLDL-C) cholesterol, glycated haemoglobin, fasting glucose, insulin, aspartate transaminase, alanine transaminase and different hormones and adipokines were analysed. Only VLDL-C (p = 0.01) and diastolic blood pressure (p = 0.027) decreased after the intervention, especially with the BG supplement. There were no other significant changes in the analysed biomarkers. In conclusion, the regular intake of GCP, BG and GCP/BG without lifestyle changes is not an efficient strategy to improve lipid and glucose homeostasis in overweight/obese subjects.

Habitual coffee consumption and subsequent risk of type 2 diabetes in individuals with a history of gestational diabetes - a prospective study

BACKGROUND

Females with a history of gestational diabetes mellitus (GDM) are at higher risk of developing type 2 diabetes mellitus (T2D) later in life.

OBJECTIVE

This study prospectively examined whether greater habitual coffee consumption was related to a lower risk of T2D among females with a history of GDM.

METHODS

We followed 4522 participants with a history of GDM in the NHS II for incident T2D between 1991 and 2017. Demographic, lifestyle factors including diet, and disease outcomes were updated every 2-4 y. Participants reported consumption of caffeinated and decaffeinated coffee on validated FFQs. Fasting blood samples were collected in 2012-2014 from a subset of participants free of diabetes to measure glucose metabolism biomarkers (HbA1c, insulin, C-peptide; n = 518). We used multivariable Cox regression models to calculate adjusted HRs and 95% CIs for the risk of T2D. We estimated the least squares mean of glucose metabolic biomarkers according to coffee consumption.

RESULTS

A total of 979 participants developed T2D. Caffeinated coffee consumption was inversely associated with the risk of T2D. Adjusted HR (95% CI) for ≤1 (nonzero), 2-3, and 4+ cups/d compared with 0 cup/d (reference) was 0.91 (0.78, 1.06), 0.83 (0.69, 1.01), and 0.46 (0.28, 0.76), respectively (P-trend = 0.004). Replacement of 1 serving/d of sugar-sweetened beverage and artificially sweetened beverage with 1 cup/d of caffeinated coffee was associated with a 17% (risk ratio [RR] = 0.83, 95% CI: 0.75, 0.93) and 9% (RR = 0.91, 95% CI: 0.84, 0.99) lower risk of T2D, respectively. Greater caffeinated coffee consumption was associated with lower fasting insulin and C-peptide concentrations (all P-trend <0.05). Decaffeinated coffee intake was not significantly related to T2D but was inversely associated with C-peptide concentrations (P-trend = 0.003).

CONCLUSIONS

Among predominantly Caucasian females with a history of GDM, greater consumption of caffeinated coffee was associated with a lower risk of T2D and a more favorable metabolic profile.

Effect of Different Coffee Brews on Tryptophan Metabolite-Induced Cytotoxicity in HT-29 Human Colon Cancer Cells

Coffee consumption positively influences colon health. Conversely, high levels of tryptophan metabolites such as skatole released from intestinal putrefactive fermentation in the presence of excessive dietary animal protein intake, and gut microbiota alterations, may have several adverse effects, including the development of colorectal cancer. Therefore, this study aimed to elucidate the potential protective effects of coffee in the presence of different skatole levels. The results showed that skatole exposure induced reduced cell viability and oxidative stress in the HT-29 human colon cancer cell line. However, co-treatment of cells with skatole and coffee samples was able to reduce ROS production (up to 45% for espresso) compared to cells not treated with coffee. Real-time PCR analysis highlighted that treating HT-29 cells with skatole increased the levels of inflammatory cytokines and chemokines TNF-α, IL-1β, IL-8, and IL12, whereas exposure to coffee extracts in cells that were pretreated with skatole showed anti-inflammatory effects with decreased levels of these cytokines. These findings demonstrate that coffee may counteract the adverse effects of putrefactive compounds by modulating oxidative stress and exerting anti-inflammatory activity in colonocytes, thus suggesting that coffee intake could improve health conditions in the presence of altered intestinal microbiota metabolism.

Comparison of Glycemic Response to Carbohydrate Meals without or with a Plant-Based Formula of Kidney Bean Extract, White Mulberry Leaf Extract, and Green Coffee Extract in Individuals with Abdominal Obesity

Due to the rising prevalence of obesity and type 2 diabetes, a strategy that can positively influence diet quality in a simple way is being explored, since a low glycemic index (GI) diet is advised in the dietoprophylaxis and diet therapy of diabetes. Methods: Twenty-three women with abdominal obesity participated in the study. The postprandial glycemic response and glycemic index were determined after three carbohydrate meals (noodle soup, white rice, strawberry sorbet) without or with the addition of a plant-base supplement (extracts of kidney bean, white mulberry leaf, and green coffee) with a potentially hypoglycemic effect. For two products (instant noodle soup and white rice), the addition of the plant supplement resulted in a reduction in glicemic iAUC values (respectively, by: 17.1%, p = 0.005 and 5.3%; p = 0.03; 40.6%, p = 0.004 and 5.3%, p = 0.019). However, this effect was not observed for strawberry sorbet. The blood glucose concentrations 30 min after the consumption of instant noodle soup and white rice with the plant-based formula addition significantly affected the GI value of tested meals (p = 0.0086, r = 0.53; p = 0.0096, r = 0.53), which may indicate the effect of this plant supplement on enterohormone and/or insulin secretion. Conclusion: A formula containing kidney bean, white mulberry leaves, and green coffee extracts may therefore be a notable factor in lowering postprandial glycemia and the GI of carbohydrate foods. However, further research is needed to determine for which food groups and meals its use may be most effective.

The Effect of Green Coffee Bean Extract on Cardiovascular Risk Factors: A Systematic Review and Meta-analysis

BACKGROUND AND AIM

Cardiovascular disease remains the primary cause of noncommunicable disease- related death. The present systematic review and meta-analysis was performed to assess the possible benefit of the green coffee bean extract on cardio-metabolic markers.

METHODS

PubMed, Scopus, Web of Science, and Cochrane Library were systematically searched to identify clinical trials that examined the effect of green coffee bean extract on cardio-metabolic risk factors including serum lipid profiles, glycemic status-related markers, blood pressure, and anthropometric indices. Since the included RCTs were carried out in different settings, random effect models were used to conduct all meta-analyses.

RESULTS

Fifteen studies (19 arms) consisting of 637 participants were included. The results indicated that green coffee bean extract significantly reduced levels of total cholesterol (-5.93 mg/dl; 95% CI: -9.21, -2.65; I²: 0%), fasting plasma glucose (-2.21 mg/dl; 95% CI: -3.94, -0.48; I²: 32%), systolic blood pressure (-3.08 mmHg; 95% CI: -4.41, -1.75; I²: 26%), diastolic blood pressure (-2.27 mmHg; 95% CI: -3.82, -0.72; I²: 61%), body weight (-1.24 kg; 95% CI: -1.82, -0.66; I²: 15%), and BMI (-0.55 kg/m²; 95% CI: -0.88, -0.22; I²: 73%). Although the pooled effect size of LDL-C, fasting insulin, and waist circumstance were significant, the results were significantly influenced by individual studies. No significant effect was detected for triglycerides, HDL-C, HbA1C, and HOMA-IR. However, the nonsignificant pooled effect size for triglyceride levels was influenced by one individual study.

CONCLUSION

The present study suggests that green coffee been extract consumption can improve total cholesterol, triglycerides, body weight, blood pressure, and fasting plasma glucose.

Antioxidant and Anti-Inflammatory Activity of Coffee Brew Evaluated after Simulated Gastrointestinal Digestion

Coffee contains human health-related molecules, namely polyphenols that possess a wide range of pharmacological functions, and their intake is associated with reduced colon cancer risk. This study aimed to assess the changes in the anti-inflammatory and antioxidant activity of coffee after simulated gastrointestinal digestion. The evaluation of intracellular reactive oxygen species (ROS) levels in the HT-29 human colon cancer cell line and three in vitro spectrophotometric assays were performed to determine the antioxidant activity of the samples. Characterization of coffee composition was also assessed through a Q-Orbitrap high-resolution mass spectrometry analysis. The results highlighted that the levels of polyphenols in the digested coffee brews were higher than those of the non-digested ones. All assayed samples decreased the levels of intracellular ROS when compared to untreated cells, while digested coffee samples exhibited higher antioxidant capacity and total phenolic content than not-digested coffee samples. Digested coffee samples showed a higher reduction in interleukin-6 levels than the not-digested samples in lipopolysaccharide-stimulated HT-29 cells treated for 48 h and fewer cytotoxic effects in the MTT assay. Overall, our findings suggest that coffee may exert antioxidant and anti-inflammatory properties, and the digestion process may be able to release compounds with higher bioactivity.

Impact of Brewing Methods on Total Phenolic Content (TPC) in Various Types of Coffee

Coffee is a widely consumed beverage, both in Europe, where its consumption is highest, and on other continents. It provides many compounds, including phenolic compounds. The aim of the study was to assess the effect of various brewing methods on the total phenolic content (TPC) in the infusion. Research material comprised commercially available coffees: Instant Arabica and Robusta, freshly ground Arabica and Robusta (immediately prior to the analysis), ground Arabica and Robusta, decaffeinated Arabica, and green Arabica and Robusta. The following preparation methods were used: Pouring hot water over coffee grounds or instant coffee, preparing coffee in a percolator and using a coffee machine. Additional variables which were employed were water temperature (90 or 100 °C) and its type (filtered or unfiltered). In order to determine the impact of examined factors, 225 infusion were prepared. Total phenolic content was determined by the spectrophotometric method using the Folin-Ciocalteu reagent and the obtained results were expressed in mg gallic acid (GAE) per 100 g of brewed coffee. The highest value was obtained for 100% Arabica ground coffee prepared in a coffee percolator using unfiltered water at a temperature of 100 °C: 657.3 ± 23 mg GAE/100 g of infusion. High values were also observed for infusions prepared in a coffee machine, where the highest TPC value was 363.8 ± 28 mg GAE/100 g for ground Arabica. In turn, the lowest TPC was obtained for Arabica green coffee in opaque packaging, brewed with filtered water at a temperature of 100 °C: 19.5 ± 1 mg GAE/100 g of infusion. No significant effect of temperature and water type on the TPC within one type of coffee was observed. Due to its high content of phenolic compounds, Arabica coffee brewed in a coffee percolator should be the most popular choice for coffee drinkers.

[Effectiveness of hydroxycinamates and beta-glucans as dietary tools against obesity and its associated dysfunctions, and their application as nutraceuticals]

Introduction

Over the last few years the prevalence of overweight and obesity has increased, affecting in certain parts of the world more than half of the adult population. Obesity has been related to disorders such as type-2 diabetes, non-alcoholic fatty liver disease, and cardiovascular diseases, among others, which has made of obesity the second cause of preventable death, only behind smoking. Bearing this in mind, it is necessary to find new strategies to overcome overweight/obesity and its associated pathologies. In this context, nutraceuticals and dietary supplements have become interesting tools thanks to their composition, rich in bioactive compounds beneficial to health. Among bioactive compounds, this study will focus on β-glucans, a type of soluble dietary fiber, and hydroxycinnamic acids, a group of phenols. Both types of compounds show complex and multifactorial effects, acting as hypolipemic, hypoglycemic, antioxidant, prebiotic and satiating agents. They act by modulating different metabolic pathways, affecting the absorption and metabolism of lipids and carbohydrates, reducing oxidative damage, promoting the proliferation of beneficial bacterial species, and reducing dietary intake. It may be concluded that both beta-glucans and hydroxycinnamates have potential as a nutritional tool for the management of obesity and its associated metabolic dysfunctions.

Green/Roasted Coffee May Reduce Cardiovascular Risk in Hypercholesterolemic Subjects by Decreasing Body Weight, Abdominal Adiposity and Blood Pressure

In previous studies, after regularly consuming a green/roasted coffee blend, body weight, body fat%, glucose, plasminogen activator inhibitor-1 (PAI-1), resistin, leptin, ghrelin, diastolic (DBP) and systolic blood pressure (SBP) significantly changed in healthy and hypercholesterolemic subjects. However, glucagon, total-cholesterol (T-C), triglycerides (TG), LDL-cholesterol (LDL-C) and Homeostasis Model Assessment index to estimate insulin resistance (HOMA-IR) only changed in the hypercholesterolemics. This work looks into the antiobesity effects of coffee blend and into the relationship of antiobesity with the aforementioned cardiometabolic modifications in hypercholesterolemics. (1) Methods: Tricipital and subscapular skinfolds, hip, thigh, arm and waist circumference (WC) were measured in normocholesterolemic and hypercholesterolemics. To understand the relationship between cardiometabolic and antiobesity results in hypercholesterolemics, factor analysis was carried out using baseline values of the variables that changed. (2) Results: WC, WC/hip and WC/height showed significant coffee×group interaction, and in hypercholesterolemics tended to decrease. After factor analysis, three factors emerged, accounting for 29.46, 13.13 and 11.79% of variance. Only factor 1 (main loadings: WC, DBP and SBP, body weight, WC/hip and WC/height ratios, TG and ghrelin, inversely) decreased after coffee intake. (3) Conclusion: Regularly consuming green/roasted coffee may help to control body weight, and in hypercholesterolemics, may reduce cardiovascular risk by reducing abdominal adiposity and blood pressure.

The effect of green coffee extract supplementation on cardio metabolic risk factors: a systematic review and meta-analysis of randomized controlled trials

Purpose

Considering the present controversies on the association between green coffee supplementation and cardio metabolic risk factors, this systematic review and meta-analysis was conducted to evaluate the effect of green coffee supplementation on cardio metabolic risk factors.

Method

A systematic literature search was performed throughout the PubMed, Embase, Scopus, and Web of Science databases up to October 2019. As a result, all randomized controlled trials over the effect of green coffee supplementation on fasting blood sugar (FBS), insulin, triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), C - reactive protein (CRP), and homeostatic model assessment for insulin resistance (HOMA-IR) in adults were examined. Data were extracted from the relevant studies and analyzed using the random-effect or pooled model and standardized mean difference (SMD) with 95% confidence interval (CI).

Results

After excluding the irrelevant articles, 27 studies were included in the final analysis. Pooled results revealed that green coffee supplementation significantly reduced FBS (WMD = -2.28, 95% CI: -4.49 to -0.07, P = 0.043), insulin (WMD = -0.53, 95% CI: -0.93 to -0.14, P = 0.008), and triglyceride (WMD = -9.28, 95% CI: -14.93 to - 3.63, P = 0.001). Furthermore, green coffee supplementation increased the HDL levels (WMD = 1.33, 95% CI: 0.08 to 2.58, P = 0.037). However, the changes in HOMA-IR, LDL, and CRP levels were not significant (P > 0.05).

Conclusion

This meta-analysis indicated that green coffee supplementation significantly decreased FBS, insulin, and triglyceride, but improved HDL. No statistically significant improvement was found in HOMA-IR, LDL, and CRP indices following the green coffee supplementation.

Impact of microwave-assisted extraction on roasted coffee carbohydrates, caffeine, chlorogenic acids and coloured compounds

Microwave-assisted extraction (MAE) allows to quickly achieve soluble compounds from solid matrices due to the promotion of temperatures higher than the solvent (atmospheric) boiling point, once a closed-vessel system is used for operating at high pressure. In this study, the feasibility of MAE for producing high yield coffee extracts with properties that allow their commercial application was tested through a quality by design approach. It was studied the influence of time of extraction (1, 5.5, 10 min), temperature (120, 150, 180 °C) and the mass-to-volume (m/V) ratio (2, 4, 6 g/60 mL) in the overall extraction yield (24-47%, w/w), carbohydrates content (18-43%, w/w), sugars composition, caffeine (4-7%, w/w), 5-caffeoylquinic acid (1-2%, w/w), colour and antioxidant activity of the extracts. FTIR analysis was used to study the resemblance of coffee extracts and commercial instant coffee. MAE allowed overall extraction yields considerably higher than the home brewing methods, mainly when performed at 180 °C, with a substantial increase in arabinogalactans (AG) extraction associated to higher temperatures. Temperature exerted a crucial role in coffee extracts differentiation, although time and m/V ratio also lead to different values in the responses. Under a circular economy concept, MAE was able to produce extracts that can be used as defined food/brew ingredients and provides a galactomannan and cellulose rich residue that can also be valued as a source of dietary fibre.

The effect of green-coffee extract supplementation on obesity: A systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND

Given that the most recent systematic review investigating Green-Coffee Extract (GCE) as a weight loss facilitator was nearly a decade ago and that the authors reported there no consensus on the effect of GCE/CGA (Chlorogenic acids) on body composition indices, a comprehensive systematic review and dose-response meta-analysis of all available randomized controlled trial (RCTs) was undertaken to examine the effect of GCE and CGA intervention on body weight (BW), body mass index (BMI) and waist circumference (WC) in adults.

METHODS

We conducted a systematic search of all available randomized controlled trials (RCTs) performed up to June 2019 in the following electronic databases: PubMed, Scopus and Google Scholar. RCTs that investigated the effect GCE/CGA Supplementation on BW, BMI and WC in adults were included for final analysis. The pooled weight mean difference (WMD) of included studies was estimated using a random-effects model.

RESULTS

A total of 13 articles with 16 RCTs were included in the meta-analysis. Results revealed significant reduction in BMI (WMD: -0.403 kg/m², 95% CI: -0.800, -0.005, p = 0.047) and no significant change in BW (WMD: -0.585 kg, 95% CI: -1.498, 0.329, p = 0.210) and WC (WMD: -0.847 cm, 95% CI: -1.764, 0.071, p = 0.070). In the subgroup analysis, studies that were conducted on baseline BMI ≥25 kg/m² revealed a significant greater reduction in body weight and BMI than those performed on baseline BMI <25 kg/m². Moreover, short supplementation periods of less than 4 weeks had no effect.

CONCLUSION

The results of current meta-analysis study support the use of GCE supplementation for the improvement of obesity indices, with sub-group analysis highlighting greater improvements in individuals with a starting BMI ≥25 kg/m².

Impact of Foods and Dietary Supplements Containing Hydroxycinnamic Acids on Cardiometabolic Biomarkers: A Systematic Review to Explore Inter-Individual Variability

Plant-based diets rich in bioactive compounds such as polyphenols have been shown to positively modulate the risk of cardiometabolic (CM) diseases. The inter-individual variability in the response to these bioactives may affect the findings. This systematic review aimed to summarize findings from existing randomized clinical trials (RCTs) evaluating the effect of hydroxycinnamic acids (HCAs) on markers of CM health in humans. Literature searches were performed in PubMed and the Web of Science. RCTs on acute and chronic supplementation of HCA-rich foods/extracts on CM biomarkers were included. Forty-four RCTs (21 acute and 23 chronic) met inclusion criteria. Comparisons were made between RCTs, including assessments based on population health status. Of the 44 RCTs, only seven performed analyses on a factor exploring inter-individual response to HCA consumption. Results demonstrated that health status is a potentially important effect modifier as RCTs with higher baseline cholesterol, blood pressure and glycaemia demonstrated greater overall effectiveness, which was also found in studies where specific subgroup analyses were performed. Thus, the effect of HCAs on CM risk factors may be greater in individuals at higher CM risk, although future studies in these populations are needed, including those on other potential determinants of inter-individual variability. PROSPERO, registration number CRD42016050790.

Chlorogenic and phenolic acids are only very weak inhibitors of human salivary α-amylase and rat intestinal maltase activities

There is increasing evidence that consumption of polyphenol and phenolic-rich foods and beverages have the potential to reduce the risk of developing diabetes type 2, with coffee a dominant example according to epidemiological evidence. One of the proposed mechanisms of action is the inhibition of carbohydrate-digesting enzymes leading to attenuated post-prandial blood glucose concentrations, as exemplified by the anti-diabetic drug, acarbose. We determined if the phenolic, 5-caffeoylquinic acid, present in coffee, apples, potatoes, artichokes and prunes, for example, and also selected free phenolic acids (ferulic acid, caffeic acid and 3,4-dimethoxycinnamic acid), could inhibit human salivary α-amylase and rat intestinal maltase activities, digestive enzymes involved in the degradation of starch and malto-oligosaccharides. Using validated assays, we show that phenolic acids, both free and linked to quinic acid, are poor inhibitors of these enzymes, despite several publications that claim otherwise. 5-CQA inhibited human α-amylase only by <20% at 5 mM, with even less inhibition of rat intestinal maltase. The most effective inhibition was with 3,4-dimethoxycinnamic acid (plateau at maximum 32% inhibition of human α-amylase at 0.6 mM), but this compound is found in coffee in the free form only at very low concentrations. Espresso coffee contains the highest levels of 5-CQA among all commonly consumed foods and beverages with a typical concentration of ~5 mM, and much lower levels of free phenolic acids. We therefore conclude that inhibition of carbohydrate-digesting enzymes by chlorogenic or phenolic acids from any food or beverage is unlikely to be sufficient to modify post-prandial glycaemia, and so is unlikely to be the mechanism by which chlorogenic acid-rich foods and beverages such as coffee can reduce the risk of developing type 2 diabetes.

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Chlorogenic and phenolic acids weakly inhibit human α-amylase activity.

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Chlorogenic acids weakly inhibit rat maltase activity.

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Free phenolic acids exhibit no inhibition of rat maltase activity.

Bioavailability of hydroxycinnamates in an instant green/roasted coffee blend in humans. Identification of novel colonic metabolites

Roasting greatly reduces the phenolic content in green coffee beans. Considering the beneficial effects of coffee polyphenols, blends containing green coffee beans are being consumed as a healthier alternative to roasted coffee. This study was aimed at assessing the absorption and metabolism of hydroxycinnamates in an instant green/roasted (35/65) coffee blend in healthy humans. Twelve fasting men and women consumed a cup of coffee containing 269.5 mg (760.6 μmol) of chlorogenic acids. Blood and urine samples were taken before and after coffee consumption at different times and analyzed by LC-MS-QToF. Up to 25 and 42 metabolites were identified in plasma and urine, respectively, mainly in the form of sulfate and methyl derivatives, and to a lower extent as glucuronides. Un-metabolized hydroxycinnamate esters (caffeoyl-, feruloyl-, and coumaroylquinic acids), hydroxycinnamic acids (caffeic, ferulic and coumaric acids) and their phase II metabolites, in addition to phase II derivatives of lactones, represented a minor group of metabolites (16.3% of the metabolites excreted in urine) with kinetics compatible with small intestine absorption. Dihydrohydroxycinnamic acids and their phase II derivatives, in addition to feruloylglycine, showed delayed kinetics due to their colonic origin and represented the most abundant group of metabolites (75.7% of total urinary metabolites). Dihydrohydroxycinnamate esters (dihydroferuloyl-, dihydrocaffeoyl- and dihydrocoumaroylquinic acids) have been identified for the first time in both plasma and urine, with microbial origin (excreted 8-12 h after coffee intake) amounting to 8% of total urinary metabolites. In conclusion, coffee polyphenols are partially bioavailable and extensively metabolized, mainly by the colonic microbiota.

The effect of acute caffeine intake on insulin sensitivity and glycemic control in people with diabetes

The prevalence of diabetes is growing globally, and with no current cure for the disease, management is focused on optimizing blood glucose control to limit complications. The purpose of this review was to examine the effect of caffeine intake on blood glucose levels in people with diabetes. Electronic searches were completed using Pub Med, CINAHL, and Web of Science using the search terms "coffee and insulin," "caffeine and insulin," "caffeine and diabetes," "caffeine and type 1 diabetes," "caffeine and type 2 diabetes," and "caffeine and glycemia." Seven trials were found to meet the search criteria. Five of the 7 studies suggest caffeine intake increases blood glucose levels, and prolongs the period of high blood glucose levels. Future research should focus on larger clinical trials to confirm the relationship and mechanism of action related to caffeine intake and glycemic control in individuals with diabetes.