Eating certain polyphenols, substances found in many fruits and vegetables, decreases the amount of iron the body absorbs, which can increase the risk of developing an iron deficiency, Penn State nutritional scientists have found.
"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. 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.
The result has been published in the Journal of Nutrition.