Green Tea Extracts vs. Green Tea Beverages
Mainstream doctors often advocate obtaining nutrients from foods rather than supplements. A problemwith certain nutrients, however, is that they are bound so tightly to food that less-than-optimal amounts of the active constituents are absorbed into the bloodstream.
Examples of nutrients that are better absorbed from supplements than from food include vitamin K, folic acid, and chlorophyll.3-5 Lycopene, on the other hand, may be better absorbed from cooked tomato products6 than from supplements.
In a recent study published in the American Journal of Clinical Nutrition, scientists sought to determine whether the active ingredients in green tea were better absorbed from green tea extract capsules or by drinking green tea. Thirty healthy test subjects were recruited and given either a specially prepared green tea beverage standardized for green tea’s most active constituents (such as EGCG and ECG) or equally standardized green tea extract capsules.7
The results showed that subjects who received the green tea extract caps had a 60% greater increase in EGCG (epigallocatechin gallate) and a 90% greater increase in ECG (epicatechin gallate) compared to those who drank the identical amounts of these green tea constituents in standardized beverage form. The antioxidant effects in those who swallowed the green tea caps were also greater than in the green tea drinkers.7
The scientists concluded that when administered in the form of a green tea supplement, the active constituents (polyphenols) showed enhanced bioavailability compared to when identical amounts of polyphenols were provided in a green tea beverage.7
One reason for conducting this study was previous findings that green tea polyphenols might be effective in preventing and treating cancer. By documenting that green tea extract supplements are superior to drinking green tea beverages, scientists now have a solid basis to test green tea extract capsules in human clinical studies.
Not All Green Tea Beverages Are the Same
The amount of polyphenols contained in green tea beverages varies considerably, depending on where the tea is harvested and how it is processed. One study examined 19 commercial brands of green tea and found significant variation in the content of the polyphenols EGCG and ECG. The scientists who conducted this study recommended that the labels of green tea bags state the amount of the polyphenols (EGCG and ECG) contained in each cup so that consumers know how many milligrams of these active ingredients they are consuming each day.8
References:
1. Wu F, O’Connell M, Roberts S, et al. Do the effects of testosterone on muscle strength, physical function, body composition and quality of life persist six months post-treatment in intermediate-frail and frail elderly men. J Endocrinol. 2011 Feb. [Accepted for publication]
2. Available at: http://www.webmd.com/breast-cancer/news/20101027/green-tea-doesnt-prevent-breast-cancer-study-finds. Accessed October 27, 2010.
3. Garber AK, Binkley NC, Krueger DC, Suttie JW. Comparison of phylloquinone bioavailability from food sources or a supplement in human subjects. J Nutr. 1999 Jun;129(6):1201-3.
4. Berg MJ. The importance of folic acid. J Gend Specif Med. 1999 May-Jun;2(3):24-8.
5. Ferruzzi MG, Schwartz SJ. Thermal degradation of commercial grade sodium copper chlorophyllin. J Agric Food Chem. 2005 Sep 7;53(18):7098-102.
6. van het Hof KH, de Boer BC, Tijburg LB, et al. Carotenoid bioavailability in humans from tomatoes processed in different ways determined from the carotenoid response in the triglyceride-rich lipoprotein fraction of plasma after a single consumption and in plasma after four days of consumption. J Nutr. 2000 May;130(5):1189-96.
7. Henning SM, Niu Y, Lee NH, et al. Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement. Am J Clin Nutr. 2004 Dec;80(6):1558-64.
8. Seeram NP, Henning SM, Niu Y, et al. Catechin and caffeine content of green tea dietary supplements and correlation with antioxidant capacity. J Agric Food Chem. 2006 Mar 8;54(5):1599-603.
Article from LEF magazine.