The medicinal benefits of green tea are renowned. One of the most widely consumed beverages in the world, green tea contains biologically active compounds, known as catechins, that may reduce chronic disease risk and enhance health.
Green tea consumption has been linked to lower cardiovascular risk, higher bone density, and calming effects. More recently, researchers have studied green tea for weight-loss benefits, and it’s emerging as an important ingredient in skin health.
Dozens of in vitro, animal, and epidemiological studies conducted over the last few decades suggest that consumption of green tea may hold benefits for certain types of cancer.
Go Green to Get Lean
The incidence of overweight and obesity is a serious public health crisis in the U.S. and other developed countries. Current estimates show that about 65 percent of U.S. adults are overweight (defined as a body mass index [BMI] between 25 and 29.9) or obese (BMI of 30 or more).
Obesity is a major factor in a number of conditions including heart disease, diabetes, hypertension, stroke, and even certain types of cancer.
Clearly the most successful weight-loss strategy is to reduce overall caloric intake, while increasing caloric expenditure through exercise.
The United States Department of Agriculture (USDA) Dietary Guidelines for Americans put forth strong recommendations on weight loss and physical activity. “Making moderate physical activity a part of an adult’s daily routine for at least 30 minutes per day promotes fitness and reduces the risk of chronic health conditions such as obesity, hypertension, diabetes, and coronary artery disease,” the guidelines state.
They add: “Many adults need to participate in up to 60 minutes of moderate to vigorous physical activity on most days to prevent unhealthy weight gain, while adults who have previously lost weight may need 60 to 90 minutes of moderate physical activity daily to help avoid regain of weight.”
With obesity reaching epidemic proportions in the U.S., it’s not surprising that significant research efforts are targeted toward this health concern, as well as the role that various functional foods or other bioactive compounds may play.
The evidence is growing for green tea in this role. Ingredients that stimulate the activity of the sympathetic nervous system, which, in turn, suppresses hunger, enhances satiety, and stimulates energy expenditure, may contribute to weight loss. Bioactive components in green tea powder suppress fat accumulation in mice. In humans, a green tea extract rich in epigallocatechin gallate (EGCG) increased thermogenesis (production of heat in the body) and 24-hour energy expenditure.
Other researchers have hypothesized that an intervention that reduces the positive energy balance by 100 Kcal/day could offset weight gain in 90 percent of the population. In a recent placebo-controlled, double-blind clinical intervention trial, a combination of capsaicin, green tea extract, tyrosine, and calcium increased 24-hour energy expenditure by about two percent per day, without raising heart rate or having any other adverse effects.
In a second study, 76 overweight and moderately obese subjects followed a very low energy diet for four weeks, followed by three months of weight maintenance. During the weight maintenance period, the low-caffeine consumers who received a daily green tea-caffeine mixture (270 mg EGCG + 150 mg caffeine) experienced reduced body weight, a lower ratio of body fat, and increased resting energy expenditure.
In a third double-blind controlled study in which caffeine intake was minimized, daily consumption of 690 mg of green tea catechins for 12 weeks contributed to a statistically significant reduction in body weight, BMI, waist circumference, and body fat mass in 38 men. Researchers suggest that the catechin-mediated thermogenic effect of tea has therapeutic potential for the management of obesity.
Polyphenols for Photoprotection
Overexposure of the skin to ultraviolet (UV) rays results in a variety of adverse effects, including premature aging, cataracts, and malignant skin cancer.
The incidence of melanoma in certain areas of this country increased by 400 percent between 1960 and 1986, making it the most common type of cancer with one million cases diagnosed annually.
Clearly, the best protections against sunlight-related skin disorders are avoiding sun exposure at times of peak intensity, the use of protective clothing, and conscientious application of broad-spectrum sunscreens with a sun protection factor (SPF) of 15 or higher. In addition, intensive research efforts continue to identify plant extracts that may act as antiaging agents for the human skin, including green tea.
Green tea catechins have been investigated for more than two decades for their chemopreventive, natural healing, and antiaging effects in animal models.
Emerging data suggest that green tea components may benefit human skin, too. In a small study, application of diluted extracts of green tea applied to the back for 30 minutes prior to exposure to solar-simulated UV radiation produced a dose-dependent reduction in erythema, or redness of the skin. A 10 percent solution of green tea polyphenols produced almost complete protection at 48 and 72 hours after sun exposure.
Application of green tea polyphenols also reduced the number of sunburn cells, protected epidermal cells from UV-induced damage, and reduced the DNA damage formed after UV radiation.
More recently, in a placebo-controlled, double-blind study of 60 women aged 25 to 60, application of a gel containing two percent EGCG twice a day for four weeks resulted in marked improvements in texture and appearance of skin in 45 percent of subjects, with no reported side effects.