Science - March 22, 2007

Vitamins knocked off their pedestal

Vitamins are healthy, so we believe. That’s why we take vitamin pills or eat food products that have been fortified with vitamins. But according to a big Danish study published recently in the medical journal Jama, added vitamins can increase your chance of dying.

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Dr Christian Gluud, who works at the University of Copenhagen, is against functional foods and vitamin supplements. In February 2007, his research group published a meta-analysis in the Journal of the American Medical Association (Jama) on the safety of a number of anti-oxidant vitamins. The researchers gathered the results from nearly 50 trials on a total of 180,000 test subjects and re-analysed them. These include two studies done in Wageningen. Most of the studies involved tests in which doctors prescribed high doses of vitamins.
Gluud’s conclusions are devastating. The vitamins A, C and E and beta-carotene do not have a positive effect. In fact, beta-carotene and vitamin A and E increase the chance of dying by five percent compared with people who do not take these nutrients. This amount is not much compared with the effect of smoking, which increases the chance of dying by a few hundred percent. ‘But nobody buys vitamin pills or enriched food products to die earlier,’ says Gluud. ‘People buy vitamins because they think that they will make them healthier.’

Cancer
Vitamin A comes out the worst in Gluud’s analysis. But beta-carotene, a substance found in vegetables that the body converts into vitamin A, does not come out much better. Dr Jaap Keijer of Rikilt Institute of Food Safety is not surprised. He has devoted years to studying how beta-carotene behaves in the body.
‘We are trying to unravel the mechanisms involved,’ says Keijer. ‘When bioactive components suddenly became the rage in the 1990s we knew little about them. They remove free radicals, said the food manufacturers and the researchers, and they neutralise aggressive components in the body. Substances like beta-carotene were thought to protect cells and reduce the chance of cancer, heart and circulatory disease and other chronic illnesses. Now we know that the way in which these substances work is much more complex.’
Jaap Keijer is not against added vitamins. ‘But I think the additives should only be allowed on the market once we know how they work, once we have understood the mechanism,’ he says. ‘And of course, manufacturers must be able to show that they are effective and safe.’
If it had been a matter of pharmacological compounds created in a laboratory, Keijer would have had the law on his side as well. But when it comes to vitamins that occur naturally in our food, legislators have a blind spot. As a result, the range of foods with added vitamins is growing in supermarkets. You find them in desserts, dairy drinks, candy, fruit juice and even chewing gum. It’s not that you’ll find products in the shops with dangerously high levels of vitamins but, because there are so many enriched products, it is possible that the total intake of a vitamin reaches high levels among some groups.

Folic acid
Until now, food manufacturers have mainly used anti-oxidant vitamins, but there is a new star on the additives horizon. The Dutch government is seriously considering making compulsory the addition of B vitamin folic acid to flour. ‘If this happens we will all take in extra folic acid through bread, cookies and other products containing flour,’ says Dr Ellen Kampman of the Division of Human Nutrition. ‘The US government introduced the measure in 1996 in the hope that this will lead to fewer children born with spina bifida.’
Recent studies have shown that extra folic acid reduces the chance of circulatory diseases and mental ageing. These studies have received much publicity. Less well known are the studies that Kampman and Jaap Keijer have been involved in as supervisors. These studies suggest that a big increase in folic acid intake leads to a higher risk of bowel cancer.
Kampman is trying to get funding to do a trial that will show more clearly what the risks of a fortification programme are. ‘It’s difficult to get such an expensive project off the ground,’ says Kampman. ‘But it needs to be done. And preferably before we start adding folic acid to bread.’
‘Really manufacturers should only add substances to foods which make them more healthy,’ says Gluud. ‘Otherwise not.’ And it’s not enough to just think that the additives are healthy. They must be able to prove that the addition is a hundred percent safe. If they don’t have that proof, the manufacturers are pulling the wool over the consumers’ eyes. Maybe even killing them.’

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