University Park, Pa. — Health benefits from polyphenol antioxidants — substances found in many fruits and vegetables — may come at a cost to some people. Penn State nutritional scientists found that eating certain polyphenols decreased the amount of iron the body absorbs, which can increase the risk of developing an iron deficiency.
"Polyphenols have been known to have many beneficial effects for human health, such as preventing or delaying certain types of cancer, enhancing bone metabolism and improving bone mineral density, and decreasing risk of heart disease," said Okhee Han, assistant professor of nutritional sciences. "But so far, not many people have thought about whether or not polyphenols affect nutrient absorption."
Let me offer a contrarian spin: the people who absorb and retain too much iron (probably because of genetic variants selected for by iron-poor environments of their ancestors) might be living longer due to high-polyphenol fruits and vegetables. The polyphenols are reducing the damage done by reducing the incidence of (not always diagnosed) iron toxicity.
The researchers, led by Han, studied the effects of eating grape seed extract and epigallocatechin-3-gallate (EGCG) found in green tea. They used cells from the intestine — where iron absorption takes place — to assess the polyphenols' effect and found that polyphenols bind to iron in the intestinal cells, forming a non-transportable complex. This iron-polyphenol complex cannot enter the blood stream. Instead, it is excreted in the feces when cells are sloughed off and replaced.
Of course, if you do drink a lot of tea, eat lots of apples and grapes, and consume other high polyphenol foods you can always supplement your diet with copious quantities of steaks and hamburgers. So can't control your craving for grapes and cranberries? Got a really strong tea addiction? Treat it with red meat.
Now, maybe the whole polyphenol-iron connection is overblown. Even if so, you can still go on a high-meat Paleo Diet and think of yourself as guided by the latest wisdom in evolutionary biological thinking.
|Share |||Randall Parker, 2010 August 24 09:40 PM Nutrition Antioxidant Sources|