Polyphenols And Green Tea

Many of the high potassium foods are also high in other food components necessary to good health. Antioxidants, for example, are found in abundance in the fruits and vegetables that are high in potassium. Because the populations that live the longest, healthiest lives have a heavy proportion of their diets composed of these fruits and vegetables, scientists have been trying to study what components of the fruits and vegetables contribute the most to health.

There is strong evidence that a high potassium and low sodium content to the daily diet contribute to lower blood pressure, less cardiovascular disease, less osteoporosis and fewer kidney stones. The contribution of antioxidant molecules has not been as easy to study. Multiple population studies of people supplementing their diet with direct antioxidants have not shown the expected advantages. We discussed the problems with those studies in the last post.

While there are ongoing studies of the direct antioxidants, such as Vitamins A, C and E, there are increasing numbers of studies of the other components of fruits and vegetables. Indirect antioxidants have been getting a lot of attention the past several years. Because most of their benefit does not come from direct action on free radicals, the test tube antioxidant assays cannot reveal their true antioxidant value. It is still too early to know how valuable the current intracellular antioxidant assays will be.

Without a specific intracellular assay, multiple approaches are being used to determine how the indirect antioxidants work. Most seem to work by up-regulating enzymes in the cell that counter the free radicals. In a recent report (1) related to the benefits of green tea, researchers studied how one of the polyphenols (EGCG) in green tea protects cells from free radicals. They measured various molecules, such as enzymes, precursor molecules and intermediate molecules involved in producing free radicals. Additionally, they microscopically examined cells' appearances and measured damaged proteins in cell membranes. They found both direct and indirect antioxidant actions of the polyphenol.

This was just one step in better understanding of how the polyphenols work. But with similar studies of the other polyphenols and green tea antioxidants, better epidemiological studies of green tea can be designed. And with similar studies of the antioxidants in other foods, such as the over 60 polyphenols of red wine, eventually enough will be known to make solid recommendations concerning antioxidant supplements. A nice review article (2) of the polyphenols in red wine and beer can be found here.

In the meantime, do not use antioxidant supplements as a substitute for a healthy diet. They may complement a diet consisting of foods high in antioxidants. But there are probably as yet undiscovered components of these foods that contribute to health that will not be present in the supplements alone. At present, we know that diets of the healthiest populations are high in potassium, low in sodium, and consist mostly of vegetables (especially cruciferous) and fruits with some dairy and eggs or fish, and some intact grain and nuts. Using an antioxidant supplement will not make up for a diet high in saturated fat, sugar and processed flour products.
1. Green Tea Polyphenols for the Protection against Renal Damage Caused by Oxidative Stress.
Yokozawa T, Noh JS, Park CH. http://www.hindawi.com/journals/ecam/2012/845917/
Evid Based Complement Alternat Med. 2012;2012:845917. Epub 2012 Jul 10.

2. Wine, beer, alcohol and polyphenols on cardiovascular disease and cancer.
Arranz S, Chiva-Blanch G, Valderas-Martínez P, Medina-Remón A, Lamuela-Raventós RM, Estruch R.
http://www.mdpi.com/2072-6643/4/7/759 Nutrients. 2012 Jul;4(7):759-81. Epub 2012 Jul 10.