Vitamin sales boom sparks fears over risk of excess doses

One in three women and one in four men take dietary supplements to boost their health. Swallowing a vitamin C tablet for breakfast has become de rigueur among the health conscious. But as the market for supplements has boomed, so have the risks.

The biggest safety review yet of vitamins and minerals, published today, has concluded that people who take dietary supplements to improve their health may be doing the opposite. Cancer, liver damage, loss of feeling in the arms and legs, and weakened bones are among the side-effects of taking excessive doses.

The review by the Food Standards Agency (FSA), a government watchdog, has concluded that six supplements can cause irreversible harm if taken in high doses, and three have temporary side-effects.

The six are beta carotene, which has been linked with increased rates of lung cancer in smokers, nicotinic acid, zinc, manganese, phosphorus and vitamin B6, which can lead to loss of feeling in the arms and legs. It is also warning that too much vitamin C, which can cause abdominal pain and diarrhoea in high doses, as well as calcium or iron in supplement form may be damaging although consumers are unlikely to suffer any long-term effect if they stop taking them.

One supplement, chromium piccolinate, which is used as a slimming aid, should be banned because it is a potential cause of cancer, the FSA says. But 10mg a day of other forms of chromium are said to be safe.

Most people eating a normal, balanced diet do not need supplements, the FSA says, but their huge popularity has raised concerns that some people could be doing themselves harm by taking too many.

The FSA set up a committee in 1998 to review the safety of 34 of the better-known vitamin and mineral supplements. The 12-member group has taken four years to produce a report of 350 pages, based on reviews of each nutrient. A total of 10,000 references were considered, or 300 per substance. "That shows the scale of the work," said Professor Michael Langman, its chairman.

Despite this, the review was blighted by a lack of good evidence. "The database supporting the safety-in-use of vitamins and supplements is generally poor," it says. There is a shortage of good studies looking at people taking supplements at different levels for different lengths of time and little information on vulnerable groups such as children and older people. For some nutrients, the expert group had to rely on animal studies, and it warns that many of its recommendations are based on "very limited data".

The review considered the risks of the supplements and looked at their long-term effects. It says for some, "it is possible ... larger amounts could be consumed for shorter periods without risk to health" but the evidence was too limited to make such recommendations. The review will be sent to the European Food Safety Authority and will be used to determine safe levels to be set throughout the EU by 2005.

Safe upper limits are suggested for eight supplements (vitamin B6, beta carotene, vitamin E, boron, copper, selenium, zinc and silicon). "Guidance" is suggested for 23 where the evidence is not strong enough to recommend a safe upper level – biotin, folic acid, niacin, pantothenic acid, riboflavin, thiamin, vitamin B12, vitamin C, vitamin A, vitamin D, vitamin K, chromium, cobalt, iodine, manganese, molybdenum, nickel, tin, calcium, iron, magnesium, phosphorus and potassium. For three substances – germanium, vanadium and sodium chloride (common salt) – the data was inadequate even to offer guidance on safe doses.

Dr Diane Benford, of the FSA's chemical safety and toxicological division, said: "Most people don't need to take supplements but we recognise many people do. The agency considered that maximum limits should be set to protect public health but without unnecessarily restricting consumer choice."

A spokeswoman for the agency said most people taking a multivitamin supplement would not exceed the daily maximum for any one substance. "But if they are taking another high-dose specific vitamin or mineral they might be building up levels that could cause harm in the future."

Gerald Eva, the managing director of Solgar Vitamins, said the agency had once been very supportive of the industry but had turned 180 degrees against it. "On the one hand the FSA says we should take less supplements but on the other it says we should eat more fruit and vegetables because they contain vitamins and minerals. Its messages are very mixed and unscientific."

Sue Croft, of Consumers for Health Choice, saidthe 10mgs limit for vitamin B6 recommended by the FSA contrasted with the 25mg limit set by the Scientific Committee for Food in Brussels. "How can one group of scientists in the UK come up with a different level from another group of scientists in the EU? If they can't get it right on B6 then I don't trust them on anything else."