Science - June 17, 2004

Human body absorbs little goodness from apples

Most of the health-promoting substance quercetin in our food is not absorbed by the body. It does not make it through the wall of the small intestine. An article on the research done by Wageningen scientists was published recently in the British Journal of Nutrition.

Quercetin is found in tea and fruit and clears up aggressive substances, and may therefore reduce the risk of cancer. In the Dutch diet the main sources of quercetin are tea and apples, but most of the quercetin found in food is attached to sugars like galactose, rhamnose and arabinose.

Dr Ilja Arts of the Sub-department of Human Nutrition who works at Rikilt Institute for Food Safety: “The small intestine cannot absorb quercetin in these forms. It can only deal with quercetin that is attached to glucose.” Apples only contain ten percent of the form that can be absorbed by the human body.

The researchers discovered that it is the enzyme LPH in the small intestine that helps the absorption process, by splitting the glucose from the quercetin, thereby enabling the latter to pass through the gut wall. “We are doing a lot of research on quercetin, as we regard it as a model for a larger group of similar substances,” adds Arts. “So far we know little about how the body absorbs quercetin and what it does with it.”

Willem Koert

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