Green tea and Obesity?

Does green tea catechin consumption enhance fat loss?

A recent study published in the Journal of Nutrition (Maki et al, 2009) found that moderately obese subjects who consumed a beverage containing 625 mg of green tea catechins lost more abdominal fat mass than subjects who consumed a caffeine-only control drink over a 12-week time period.  In addition to consuming the beverages, the test subjects and control groups both engaged in a moderate exercise program.

Though both groups lost similar amounts of body fat, the catechin group lost more abdominal fat than the control group.

In yet another study on a catechin containing beverage (582.8 mg of catechins) which was published in the journal, Obesity, the study authors found that it reduced waste circumference and hemoglobin A (1c) levels after 12 weeks (Nago et al, 2009).  Adiponectin which is negatively correlated with visceral obesity was significantly higher in the catechin group.  All of the subjects in this study had type 2 diabetes but were not receiving insulin therapy.

Green tea and cardiovascular risk?

Cholesterol
Researchers at the University of Florida, Gainesville, published a recent study which study the effects of a decaffeinated green tea capsule on blood pressure, serum lipids, and oxidative stress (Nantz et al, 2009).  Results of the study were as follows:

Hypertension
A similar study published in the British Journal of Nutrition (Brown et al, 2009) also found that green tea (400 mg EGCG) lowered blood pressure in test subjects while also having a positive effect on their mood.

Green tea in preventing influenza?
Researchers in Japan conducted a randomized controlled trial comparing the efficacy of a green tea supplement (containing 378 mg/d catechins and 210 mg/d of theanine on preventing infection with influenza virus in healthcare workers (Matsumoto K et al, 2011).

The main outcome measure of their study included the incidence of clinically defined influenza infection.  Indeed, they found that incidence was lower in the intervention group–4 (4.1%) participants compared to 13 (13.1%) (adjusted OR, 0.25; 95% CI, 0.07 to 0.76, P = 0.022).

However, this preliminary study had a number of limitations including the fact that 93% of the people enrolled in the study were vaccinated for influenza.  A slightly higher percentage of those randomized to the catechin group were vaccinated (93.8% vs. 91.9%).

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References:

  Khan N, Mukhtar H.  Tea polyphenols for health promotion.  Life Sci. 2007 Jul 26;81(7):519-33. Epub 2007 Jun 28.
  Sueoka N, Suganuma M, Sueoka E, Okabe S, Matsuyama S, Imai K, Nakachi K, Fujiki H. A new function of green tea: prevention of lifestyle-related diseases. Annals of New York Academy of Sciences. 2001;928:274–280.
  Zheng J, Yang B, Huang T, Yu Y, Yang J, Li D. Green tea and black tea consumption and prostate cancer risk: an exploratory meta-analysis of observational studies. Nutr Cancer. 2011;63(5):663-72. Epub 2011 Jun 11. PubMed.  PMID: 21667398.
  Jian L, Xie LP, Lee AH, Binns CW. Protective effect of green tea against prostate cancer: a case-control study in southeast China. International Journal of Cancer 2004. 2004;108(1):130–135.
  Josic J, Olsson AT, Wickeberg J, Lindstedt S, Hlebowicz J. Does green tea affect postprandial glucose, insulin and satiety in healthy subjects: a randomized controlled trial. Nutr J. 2010 Nov 30;9:63. PubMed PMID: 21118565;
  PubMed Central PMCID: PMC3002911.
  Dean S, Braakhuis A, Paton C.  The effects of EGCG on fat oxidation and endurance performance in male cyclists.  Int J Sport Nutr Exerc Metab. 2009 Dec;19(6):624-44.
  Maki KC, Reeves MS, Farmer M, Yasunaga K, Matsuo N, Katsuragi Y, Komikado M, Tokimitsu I, Wilder D, Jones F, Blumberg JB, Cartwright Y.  Green tea catechin consumption enhances exercise-induced abdominal fat loss in overweight and obese adults.  J Nutr. 2009 Feb;139(2):264-70. Epub 2008 Dec 11.

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Jarret Morrow, M.D.