Title: Too much antioxidant?

Key words: free radicals, antioxidants, health problems, cancer, mice, tumours

Date: April 2001

Category: Micronutrients

Type: Article

Too much antioxidant?

Easy does it

Go easy on the vitamins if you want to stay healthy, warns a report published last week by the Institute of Medicine, part of the US National Academy of Sciences. The report reviews all the evidence on antioxidants, mainly vitamin C, vitamin E, selenium and carotenoids. Antioxidants mop up highly reactive free radicals in cells before they can damage tissue and DNA. But "very large quantities" can cause health problems such as diarrhoea, internal bleeding and hair loss, says Norman Krinsky, chair of the panel. The panel says that two glasses of orange juice a day supply enough vitamin C, while nuts, seeds, liver, leafy green vegetables and vegetable oils give you adequate vitamin E. Sources of selenium include seafood, liver, meat and grain.

There's a catch

Antioxidants such as vitamins A and E are often touted as cure-alls for disease and ageing, but researchers in the US believe they may reduce the body's ability to fight cancer.

Most anticancer drugs work against tumours by inducing programmed cell death, or apoptosis. This relies on oxidants acting as signalling molecules, so Rudolph Salganik and his colleagues at the University of North Carolina in Chapel Hill wondered how mopping up oxidants would affect cancers.

He took a strain of mice that develops brain tumours and fed one group a normal diet and the other a diet that lacked vitamins A and E. The mice that ate the vitamin-free diet had tumours that were half the normal size. However, Salganik warns against jumping to conclusions. "We have to be careful," he said at a meeting of the American Society for Cell Biology in Washington DC last week

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