Effects of tea or tea extract on metabolic profiles in patients with type 2 diabetes mellitus: a meta-analysis of ten randomized controlled trials

Antioxidants from black and green tea: from dietary modulation of oxidative stress to pharmacological mechanisms

The consumption of tea (Camellia sinensis) has been correlated with a low incidence of chronic pathologies, such as cardiovascular disease and cancer, in which oxidative stress plays a critical role. Tea catechins and theaflavins are, respectively, the bioactive phytochemicals responsible for the antioxidant activity of green tea (GT) and black tea (BT). In addition to their redox properties, tea catechins and theaflavins could have also pharmacological activities, such as the ability to lower glucose, lipid and uric acid (UA) levels. These activities are mediated by pharmacological mechanisms such as enzymatic inhibition and interaction with transporters. Epigallocatechin gallate is the most active compound at inhibiting the enzymes involved in cholesterol and UA metabolism (hydroxy-3-methyl-glutaryl-CoA reductase and xanthine oxidase respectively) and affecting glucose transporters. The structural features of catechins that significantly contribute to their pharmacological effect are the presence/absence of the galloyl moiety and the number and positions of the hydroxyl groups on the rings. Although the inhibitory effects on α-glucosidase, maltase, amylase and lipase, multidrug resistance 1, organic anion transporters and proton-coupled folate transport occur at higher concentrations than those apparent in the circulation, these effects could be relevant in the gut. In conclusion, despite the urgent need for further research in humans, the regular consumption of moderate quantities of GT and BT can effectively modulate their antioxidant capacity, mainly in people subjected to oxidative stress, and could improve the metabolism of glucose, lipid and UA.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Antidiabetic Effects of Tea

Diabetes mellitus (DM) is a chronic endocrine disease resulted from insulin secretory defect or insulin resistance and it is a leading cause of death around the world. The care of DM patients consumes a huge budget due to the high frequency of consultations and long hospitalizations, making DM a serious threat to both human health and global economies. Tea contains abundant polyphenols and caffeine which showed antidiabetic activity, so the development of antidiabetic medications from tea and its extracts is increasingly receiving attention. However, the results claiming an association between tea consumption and reduced DM risk are inconsistent. The advances in the epidemiologic evidence and the underlying antidiabetic mechanisms of tea are reviewed in this paper. The inconsistent results and the possible causes behind them are also discussed.

The role of nutraceuticals in the prevention of cardiovascular disease

Cardiovascular disease (CVD) ranks among the most common health-related and economic issues worldwide. Dietary factors are important contributors to cardiovascular risk, either directly, or through their effects on other cardiovascular risk factors including hypertension, dyslipidemia and diabetes mellitus. Nutraceuticals are natural nutritional compounds, which have been shown to be efficacious in preventative medicine or in the treatment of disease. Several foods and dietary supplements have been shown to protect against the development of CVD. The aim of this review is to present an update on the most recent evidence relating to the use of nutraceuticals in the context of the prevention and treatment of CVD.

Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity: A Comprehensive Review

Suboptimal nutrition is a leading cause of poor health. Nutrition and policy science have advanced rapidly, creating confusion yet also providing powerful opportunities to reduce the adverse health and economic impacts of poor diets. This review considers the history, new evidence, controversies, and corresponding lessons for modern dietary and policy priorities for cardiovascular diseases, obesity, and diabetes mellitus. Major identified themes include the importance of evaluating the full diversity of diet-related risk pathways, not only blood lipids or obesity; focusing on foods and overall diet patterns, rather than single isolated nutrients; recognizing the complex influences of different foods on long-term weight regulation, rather than simply counting calories; and characterizing and implementing evidence-based strategies, including policy approaches, for lifestyle change. Evidence-informed dietary priorities include increased fruits, nonstarchy vegetables, nuts, legumes, fish, vegetable oils, yogurt, and minimally processed whole grains; and fewer red meats, processed (eg, sodium-preserved) meats, and foods rich in refined grains, starch, added sugars, salt, and trans fat. More investigation is needed on the cardiometabolic effects of phenolics, dairy fat, probiotics, fermentation, coffee, tea, cocoa, eggs, specific vegetable and tropical oils, vitamin D, individual fatty acids, and diet-microbiome interactions. Little evidence to date supports the cardiometabolic relevance of other popular priorities: eg, local, organic, grass-fed, farmed/wild, or non-genetically modified. Evidence-based personalized nutrition appears to depend more on nongenetic characteristics (eg, physical activity, abdominal adiposity, gender, socioeconomic status, culture) than genetic factors. Food choices must be strongly supported by clinical behavior change efforts, health systems reforms, novel technologies, and robust policy strategies targeting economic incentives, schools and workplaces, neighborhood environments, and the food system. Scientific advances provide crucial new insights on optimal targets and best practices to reduce the burdens of diet-related cardiometabolic diseases.