Tea consumption and risk of type 2 diabetes mellitus: a systematic review and meta-analysis update

Yang, Jian; Mao, Qunxia; Xu, Hongxia; Ma, Xu; Zeng, Chunyu

doi:10.1136/bmjopen-2014-005632

Cited by 81 publications

(59 citation statements)

References 50 publications

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“…A cohort study of oolong tea consumption also suggested that consuming either one or two cups of oolong tea per day had a significant linear and inverse correlation incident rate of type 2 diabetes (Hayashino, Fukuhara, Okamura, Tanaka, & Ueshima, 2011). A study suggested that a daily tea consumption (≥3 or ≥4 cups/day) is associated with a lower T2DM risk, but some clinical trials show that the risk of T2DM has no significant relationship with tea consumption (Jing et al, 2009;Yang, Mao, Xu, Ma, & Zeng, 2014). More clinical trials should be conducted to assess the effects of tea consumption on T2DM.…”

Section: Antidiabetes Effectmentioning

confidence: 99%

Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

Liang

Zhou

et al. 2019

Comp Rev Food Sci Food Safe

361

237

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Tea is a typical processed beverage from the fresh leaves of Camellia sinensis [Camellia sinensis (L.) O. Kuntze] or Camellia assamica [Camellia sinensis var. assamica (Mast.) Kitamura] through different manufacturing techniques. The secondary metabolites of fresh tea leaves are mainly flavan‐3‐ols, phenolic acids, purine alkaloids, condensed tannins, hydrolysable tannins, saponins, flavonols, and their glycoside forms. During the processing, tea leaves go through several steps, such as withering, rolling, fermentation, postfermentation, and roasting (drying) to produce different types of tea. After processing, theaflavins, thearubigins, and flavan‐3‐ols derivatives emerge as the newly formed compounds with a corresponding decrease in concentrations of catechins. Each type of tea has its own critical process and presents unique chemical composition and flavor. The components among different teas also cause significant changes in their biological activities both in vitro and in vivo. In the present review, the progress of tea chemistry and the effects of individual unit operation on components were comprehensively described. The health benefits of tea were also reviewed based on the human epidemiological and clinical studies. Although there have been multiple studies about the tea chemistry and biological activities, most of existing results are related to tea polyphenols, especially (‐)‐epigallocatechin gallate. Other compounds, including the novel compounds, as well as isomers of amino acids and catechins, have not been explored in depth.

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Section: Antidiabetes Effectmentioning

confidence: 99%

Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

Liang

Zhou

et al. 2019

Comp Rev Food Sci Food Safe

361

237

View full text Add to dashboard Cite

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“…Regular consumption of tea is also associated with reduced risk of developing type 2 diabetes in meta‐analyses (Yang et al . , ; Fig. ).…”

Section: Human Intervention Studies On Flavanols and Flavanol‐rich Fomentioning

confidence: 94%

“…Data on tea are supported by the meta‐analysis reported by Yang et al . (). [Colour figure can be viewed at wileyonlinelibrary.com]…”

Section: Human Intervention Studies On Flavanols and Flavanol‐rich Fomentioning

confidence: 97%

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The role of polyphenols in modern nutrition

2017

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Polyphenols are found in plant‐based foods and beverages, notably apples, berries, citrus fruit, plums, broccoli, cocoa, tea and coffee and many others. There is substantial epidemiological evidence that a diet high in polyphenol‐rich fruit, vegetables, cocoa and beverages protects against developing cardiovascular disease and type 2 diabetes. The absorption and metabolism of these compounds have been well described and, for many, the gut microbiota play a critical role in absorption; taking into consideration the parent compound and the metabolites from colon bacteria catabolism, more than 80% of a dose can be absorbed and ultimately excreted in the urine. Common polyphenols in the diet are flavanols (cocoa, tea, apples, broad beans), flavanones (hesperidin in citrus fruit), hydroxycinnamates (coffee, many fruits), flavonols (quercetin in onions, apples and tea) and anthocyanins (berries). Many intervention studies, mechanistic in vitro data and epidemiological studies support a role for polyphenols against the development of chronic diseases. For example, flavanols decrease endothelial dysfunction, lower blood pressure and cholesterol, and modulate energy metabolism. Coffee and tea both reduce the risk of developing type 2 diabetes, through action of their constituent polyphenols. Despite extensive research, the exact mechanisms of action of polyphenols in the human body have not been decisively proven, but there is strong evidence that some targets such as nitric oxide metabolism, carbohydrate digestion and oxidative enzymes are important for health benefits. Consumption of polyphenols as healthy dietary components is consistent with the advice to eat five or more portions of fruit and vegetables per day, but it is currently difficult to recommend what ‘doses’ of specific polyphenols should be consumed to derive maximum benefit.

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“…Regarding tea intake, several meta-analyses also reported potential beneficial effects, although it is not clear whether they are in a dose-response manner [47,48,49,50]. These beneficious effects on T2DM include an association with decreased IR [50,51], but not with increased insulin secretion and postprandial effects rather than in fasting glucose metabolism [52,53].…”

Section: Effects Of Nutrients On Gene Expression In the Pathogenesmentioning

confidence: 99%

Gene-Diet Interactions in Type 2 Diabetes: The Chicken and Egg Debate

Ortega

Berná

Rojas

et al. 2017

IJMS

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Consistent evidence from both experimental and human studies indicates that Type 2 diabetes mellitus (T2DM) is a complex disease resulting from the interaction of genetic, epigenetic, environmental, and lifestyle factors. Nutrients and dietary patterns are important environmental factors to consider in the prevention, development and treatment of this disease. Nutritional genomics focuses on the interaction between bioactive food components and the genome and includes studies of nutrigenetics, nutrigenomics and epigenetic modifications caused by nutrients. There is evidence supporting the existence of nutrient-gene and T2DM interactions coming from animal studies and family-based intervention studies. Moreover, many case-control, cohort, cross-sectional cohort studies and clinical trials have identified relationships between individual genetic load, diet and T2DM. Some of these studies were on a large scale. In addition, studies with animal models and human observational studies, in different countries over periods of time, support a causative relationship between adverse nutritional conditions during in utero development, persistent epigenetic changes and T2DM. This review provides comprehensive information on the current state of nutrient-gene interactions and their role in T2DM pathogenesis, the relationship between individual genetic load and diet, and the importance of epigenetic factors in influencing gene expression and defining the individual risk of T2DM.

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Tea consumption and risk of type 2 diabetes mellitus: a systematic review and meta-analysis update

Cited by 81 publications

References 50 publications

Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

The role of polyphenols in modern nutrition

Gene-Diet Interactions in Type 2 Diabetes: The Chicken and Egg Debate

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