Wetenschap - 7 maart 2002

Cancer cell reveals the downside of protective nutrient

Cancer cell reveals the downside of protective nutrient

A nutrient which food manufacturers claim can help prevent cancer, may also increase the risk of cancer, according to research done by a Wageningen PhD student. Although scientists were already aware of the potential negative effects of the substance, the research carried out by Hanem Mohamed Awad is the first which has shown the effects in living cells.

Awad did research on quercetin, an antioxidant found in fruit and vegetables that makes harmful molecules in the body harmless. Makers of supplements use quercetin in preparations which are geared to delaying ageing or diseases in which aggressive substances are released. Some supplements already contain up to a few hundred milligrams of quercetin and breeders are working on producing fruit and vegetable sorts that contain higher quantities of the protective substance.

"Every antioxidant changes after it has cleared up an aggressive molecule," explains Awad's supervisor Professor Ivonne Rietjens. Awad examined the effect of quercetin on skin cancer cells. These are known to manufacture aggressive molecules readily.

"We discovered quercetin that had already done its clearing up job then went on to combine with glutathione, a small protein," tells Rietjens. Cells use glutathione to remove dangerous substances more quickly. But these compounds we discovered are a source of concern. "Substances that combine with glutathione can also do the same with genetic material. If that is the case then quercetin can harm DNA instead of protecting it."

Rietjens' Toxicology group will carry out further research on quercetin within an NWO (Netherlands Organization for Scientific Research) project. Five research assistants will work together with researchers from TNO Nutrition, the University of Maastricht and Rikilt (State Institute for Quality Control of Agricultural Products) to examine when quercetin protects, and when this function ceases. "We are not saying that quercetin is bad," continues Rietjens. "It is one of the best antioxidants we know of. We just don't know enough about it yet."

Willem Koert

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