Oolong tea does not improve glucose metabolism in non-diabetic adults

Baer, David J.; Novotny, Janet A.; Harris, Gabriel K.; Stote, Kim S.; Clevidence, Beverly A.; Rumpler, William V.

doi:10.1038/ejcn.2010.192

Cited by 14 publications

(7 citation statements)

References 25 publications

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“…To date, neither epidemiological nor interventional studies provide clear-cut evidence for glucose-lowering effects of EGCG consumption in humans. [25][26][27][28] Also, antiadipogenic effects of EGCG, reported in previous in vitro investigations, 15.29-31 were not observed in this study. In the present study, animals were housed in groups of four with free access to food and water, and thus individual food intake was not assessed.…”

Section: Discussioncontrasting

confidence: 82%

Oral Green Tea Catechins Transiently Lower Plasma Glucose Concentrations in Female db/db Mice

Wein

Schrader²,

Rimbach³

et al. 2013

Journal of Medicinal Food

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Polyphenols, including green tea catechins, are secondary plant compounds often discussed in the context of health-promoting potential. Evidence for such effects is mainly derived from epidemiological and cell culture studies. The aim of the present study was to investigate antidiabetic, antiadipogenic, and anti-inflammatory effects at nonpharmacological doses in an obese diabetic mouse model that exerts early relevant clinical signs of non-insulin-dependent diabetes mellitus. Female db/db mice received a flavonoid-poor diet either without additive, with rosiglitazone (RSG, 0.02 g/kg diet), or with green tea extract (low-dose green tea extract [LGTE] and high-dose green tea extract [HGTE], 0.1 and 1 g/kg diet). Food and water were freely available. The body weight was monitored weekly. Blood was sampled (12-h fasted) from the tail vein on day 28 and analyzed for glucose, cholesterol, triacylglycerol, nonesterified fatty acids, insulin, adiponectin, and soluble intercellular adhesion molecule-1 (sICAM-1). Blood glucose was also analyzed on day 14. Furthermore, sICAM-1 release was investigated in tumor necrosis factor alpha-stimulated EAhy926 cells. After 14 days, fasting glycemia was improved by RSG or HGTE supplementation compared to controls. However, at the end of the study (day 28), only RSG exhibited glucose-lowering effects and induced plasma adiponectin concentrations, paralleled by higher body weight gain and reduced periuterine fat pads compared to controls. However, only GTE treatment reduced sICAM-1 release in vitro and in vivo. Nonpharmacological HGTE supplementation in db/db mice caused (1) no adiponectin-inducing or antiadipogenic effects, (2) reduced sICAM-1 release, thereby potentially exerting anti-inflammatory effects in the progressive diabetic state, and (3) a transient improvement in glycemia.

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Section: Discussioncontrasting

confidence: 82%

Oral Green Tea Catechins Transiently Lower Plasma Glucose Concentrations in Female db/db Mice

Wein

Schrader²,

Rimbach³

et al. 2013

Journal of Medicinal Food

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“…3, 4 ) and anticarcinogen (e.g. 5, 6, repress hepatic glucose production 7, and may enhance insulin action 8, 9. The exact mechanism of action of EGCG with regard to a number of these effects is not entirely clear.…”

Section: Introductionmentioning

confidence: 99%

Green tea polyphenols in drug discovery: a success or failure?

Smith¹

2011

Expert Opinion on Drug Discovery

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Green tea is made from unfermented dried leaves from Camellia sinensis and has been consumed by humans for thousands of years. For nearly as long, it has been used as a folk remedy for a wide array of diseases. More recently, a large number of in-vitro and in-vivo scientific studies have supported this ancient contention that the polyphenols from green tea can provide a number of health benefits. Since these compounds are clearly safe for human consumption and ubiquitous in the food supply, they are highly attractive as lead compounds for drug discovery programs. However, as drugs, they are far from optimum. They are relatively unstable, poorly absorbed, and readily undergo a number of metabolic transformations by intestinal microbiota and human enzymes. Further, since these compounds target a wide array of biological systems, in-vivo testing is rather difficult since effects on alternative pathways need to be carefully eliminated. The purpose of this review is to discuss some of the challenges and benefits of pursuing this family of compounds for drug discovery.

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“…SigmaStat for Windows (Version 3.5; Aspire Software International, Ashburn, VA, USA) was used for sample size estimations. 26 …”

Section: Statistical Analysesmentioning

confidence: 99%

Effect of cocoa and green tea on biomarkers of glucose regulation, oxidative stress, inflammation and hemostasis in obese adults at risk for insulin resistance

et al. 2012

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BACKGROUND/OBJECTIVES: Flavanols may provide protection against insulin resistance, but little is known about the amounts and types of flavanols that may be efficacious. SUBJECTS/METHODS: This study was designed to determine whether cocoa flavanols, over a range of intakes, improve biomarkers of glucose regulation, inflammation and hemostasis in obese adults at risk for insulin resistance. As an adjunct, green tea and cocoa flavanols were compared for their ability to modulate these biomarkers. In a randomized crossover design, 20 adults consumed a controlled diet for 5 days along with four cocoa beverages containing 30-900 mg flavanol per day, or tea matched to a cocoa beverage for monomeric flavanol content. RESULTS: Cocoa beverages produced no significant changes in glucose, insulin, total area under the concentration-time curve (AUC) for glucose or total insulin AUC. As the dose of cocoa flavanols increased, total 8-isoprostane concentrations were lowered (linear contrast, P ¼ 0.02), as were C-reactive protein (CRP) concentrations (linear contrast, P ¼ 0.01). The relationship between cocoa flavanol levels and interleukin-6 (IL-6) concentrations was quadratic, suggesting that a maximum effective dose was achieved (quadratic contrast, P ¼ 0.01). There were no significant effects on measured indices of glucose regulation, nor on those of total 8-isoprostane, CRP and IL-6 concentrations, when cocoa and green tea were compared. However, relative to cocoa, green tea lowered fibrinogen concentrations (P ¼ 0.0003). CONCLUSIONS: Short-term intake of cocoa and green tea flavanols does not appear to improve glucose metabolism; they do affect selected markers of one or more measures of oxidative stress, inflammation or hemostasis in obese adults at risk for insulin resistance.

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Oolong tea does not improve glucose metabolism in non-diabetic adults

Cited by 14 publications

References 25 publications

Oral Green Tea Catechins Transiently Lower Plasma Glucose Concentrations in Female db/db Mice

Oral Green Tea Catechins Transiently Lower Plasma Glucose Concentrations in Female db/db Mice

Green tea polyphenols in drug discovery: a success or failure?

Effect of cocoa and green tea on biomarkers of glucose regulation, oxidative stress, inflammation and hemostasis in obese adults at risk for insulin resistance

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