PSU.edu - Health benefits from polyphenol antioxidants - natural phytochemicals found in many fruits and vegetables - may come at a cost to some people. Penn State nutritional scientists found that eating certain polyphenols - especially EGCG (found in green tea) and grape seed extract - 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.”
The researchers, led by Han, studied the effects of eating grape seed extract and epigallocatechin-3-gallate (EGCG) found in green tea and white 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.
Iron is necessary to carry oxygen from the lungs throughout the body and for other cellular functions. People already at risk for iron deficiency increase that risk if they consume high amounts of grape seed extract or EGCG.
“Iron deficiency is the most prevalent nutrient deficiency in the world, especially in developing countries where meats are not plentiful,” said Han. “People at high risk of developing iron deficiency - such as pregnant women and young children - should be aware of what polyphenols they are consuming.”
Han and her colleagues looked at the heme form of iron found in meats, poultry, and fish. Last year, they performed similar research with non-heme iron found in plants. They published the results of their study on grape seed extract and EGCG in the Journal of Nutrition, showing that eating polyphenols decreased iron absorption.
Both grape seed extract and EGCG are sold in supplement extract form. The results of these studies suggest that consumers should be cautious if using these products.
Han and her colleagues recently received a grant from the National Institutes of Health, National Center for Complementary and Alternative Medicine to expand this research. They will conduct animal studies and eventually hope to do human studies as well.
Editorial note - for those consumers taking EGCG, grape seed extract or other high-potency polyphenol supplements, it is likely that simply taking them at a different time of day from iron supplements or iron-rich foods will help prevent most iron absorption problems, as EGCG and grape seed polyphenols are reportedly rapidly absorbed and thus will not stay present for too long in the GI tract. Also, as a reminder, taking regular vitamin C together with conventional iron supplements such as ferrous sulfate helps with the absorption of the iron. Alternatively, for healthy older men who do not need much iron in their diets, and who eat iron-rich red meat, the inhibition of iron absorption by dietary polyphenols could be healthy, as too much absorbed iron has been correlated with increased free radical production - Dr Z.
PSU.edu - Health benefits from polyphenol antioxidants - natural phytochemicals found in many fruits and vegetables - may come at a cost to some people. Penn State nutritional scientists found that eating certain polyphenols - especially EGCG (found in green tea) and grape seed extract - 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.”
The researchers, led by Han, studied the effects of eating grape seed extract and epigallocatechin-3-gallate (EGCG) found in green tea and white 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.
Iron is necessary to carry oxygen from the lungs throughout the body and for other cellular functions. People already at risk for iron deficiency increase that risk if they consume high amounts of grape seed extract or EGCG.
“Iron deficiency is the most prevalent nutrient deficiency in the world, especially in developing countries where meats are not plentiful,” said Han. “People at high risk of developing iron deficiency - such as pregnant women and young children - should be aware of what polyphenols they are consuming.”
Han and her colleagues looked at the heme form of iron found in meats, poultry, and fish. Last year, they performed similar research with non-heme iron found in plants. They published the results of their study on grape seed extract and EGCG in the Journal of Nutrition, showing that eating polyphenols decreased iron absorption.
Both grape seed extract and EGCG are sold in supplement extract form. The results of these studies suggest that consumers should be cautious if using these products.
Han and her colleagues recently received a grant from the National Institutes of Health, National Center for Complementary and Alternative Medicine to expand this research. They will conduct animal studies and eventually hope to do human studies as well.
Editorial note - for those consumers taking EGCG, grape seed extract or other high-potency polyphenol supplements, it is likely that simply taking them at a different time of day from iron supplements or iron-rich foods will help prevent most iron absorption problems, as EGCG and grape seed polyphenols are reportedly rapidly absorbed and thus will not stay present for too long in the GI tract. Also, as a reminder, taking regular vitamin C together with conventional iron supplements such as ferrous sulfate helps with the absorption of the iron. Alternatively, for healthy older men who do not need much iron in their diets, and who eat iron-rich red meat, the inhibition of iron absorption by dietary polyphenols could be healthy, as too much absorbed iron has been correlated with increased free radical production - Dr Z.