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- Cocoa (Theobroma cacao)
- Green Tea (Camellia sinensis)
- Insulin Resistance
- Obesity
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Date:
01-31-2013 | HC# 101232-465
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Re: Green Tea and Cocoa Flavanols Provide Some Health Benefits in Obese Adults at Risk for Insulin Resistance
Stote
KS, Clevidence BA, Novotny JA, Henderson T, Radecki SV, Baer DJ. Effect of
cocoa and green tea on biomarkers of glucose regulation, oxidative stress,
inflammation and hemostasis in obese adults at risk for insulin resistance. Eur J Clin Nutr. October
2012;66(10):1153-1159.
Insulin
resistance increases an individual's chance of developing type 2 diabetes
mellitus and cardiovascular diseases. Lifestyle changes, including dietary
modification, may improve insulin resistance. Among the plant flavonoids
associated with beneficial health effects are those found in cocoa (Theobroma
cacao)
and green tea (Camellia
sinensis). The exploratory study
reported in this article was designed to evaluate the ability of dietary cocoa
flavanols to improve health indices in a group of obese adults at risk for
insulin resistance. The outcome variables were those related to glucose
metabolism and to biomarkers of oxidative stress, inflammation, and hemostasis,
which play a prominent role in diabetes and cardiovascular diseases. Cocoa
flavanols were compared with green tea flavanols for their ability to modulate
those biomarkers.
The
authors recruited men and women, aged 25 to 55 years, through advertisements in
the Washington, D.C. metropolitan area. Risk for insulin resistance was
determined by routine clinical measurements: body mass index (BMI), waist
circumference (WC), fasting blood glucose concentration, blood insulin
concentration, blood lipids, blood pressure, and family history of diabetes
mellitus. The crossover study included five 5-day treatment periods separated
by 10-day washout periods. Twenty subjects (10 men and 10 women) were randomly
assigned to the treatments and completed all the treatment periods. One subject
was excluded from the final analysis.
The
subjects consumed 2 servings of the treatment beverage per day: 1 at breakfast
and 1 at the evening meal, as part of a controlled diet. The cocoa beverage
(Mars Incorporated; Hackettstown, New Jersey) provided flavanols at ~30 mg
daily (control), 180 mg daily (low-flavanol), 400 mg daily (medium-flavanol),
and 900 mg daily (high-flavanol). The tea used was Lipton Green Tea To Go (Unilever;
Englewood Cliffs, New Jersey). The beverages were prepared from dry powders in
individual packets.
During
the treatment periods, subjects consumed a controlled diet: a 5-day menu cycle
of typical American foods low in polyphenols. Foods in the 5-day menu cycle
were analyzed for macronutrients, fatty acids, cholesterol, and dietary fiber.
The subjects were weighed before breakfast Monday through Friday. The subjects
completed a daily questionnaire about their general health, any prescription or
over-the-counter medications used, dietary compliance, exercise performed, and
questions or problems with the diet. The experimental diets provided, on
average, 54% of calories from carbohydrates, 32% from fat, and 14% from
protein. The diet provided 297 mg of cholesterol and 24 g of dietary fiber
daily.
Blood
pressure, anthropometric variables, and body composition were measured at
baseline. Oral glucose tolerance tests (OGTTs) were performed on the mornings
following the 5-day treatment periods.
Of
the 19 subjects included in the final analysis, the OGTT results were normal in
13, and 6 were classified as having impaired glucose tolerance. Body weight did
not change significantly throughout the study.
The
authors report that the cocoa treatments did not significantly change the glucose,
insulin, or triglyceride levels, whether measured after an overnight fast or in
response to the OGTT. Values for areas under the curve (AUCs) for glucose and
insulin and surrogate markers of insulin resistance (homeostasis model
assessment of insulin resistance) and insulin sensitivity (quantitative insulin
sensitivity check index) were not significantly affected by the cocoa
treatments. When comparing the high-flavanol cocoa and green tea treatments,
the authors saw no significant effects on concentrations of glucose, insulin,
and triglycerides; values for AUCs for glucose and insulin; or the surrogate
markers of insulin resistance and insulin sensitivity.
The
authors did report that the cocoa flavanols significantly affected the
biomarkers for oxidative stress and inflammation. As the cocoa flavanol dose
increased, the total 8-isoprostane concentrations (P=0.02) and C-reactive
protein (CRP) concentrations decreased (P=0.01). The authors noted a quadratic
relationship between cocoa flavanol levels and interleukin-6 (IL-6)
concentrations, "suggesting that a maximum effective dose was achieved."
No significant differences were observed among the cocoa treatments on intercellular
adhesion molecule-1 (ICAM-1) and fibrinogen concentrations.
Although
no significant effects on total 8-isoprostane, CRP, IL-6, and ICAM-1
concentrations were reported when comparing the high-flavanol cocoa and green
tea treatments, the authors did find that the green tea lowered fibrinogen
concentrations by 7% (P=0.0003), compared with the high-flavanol cocoa.
In
this study, the short-term consumption of flavanols from cocoa and green tea did
not improve glucose metabolism in obese adults at risk for insulin resistance.
However, certain markers of oxidative stress, inflammation, and hemostasis were
improved. "Given that these processes likely promote diabetes,
cardiovascular disease and other chronic diseases, long-term studies of
flavanols are warranted particularly in at-risk populations," say the
authors.
—Shari Henson
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