Too Many Vitamin Pills Can Be Bad for You: Study
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LONDON (Reuters) - Some vitamin and mineral supplements can be bad for you if you take too many for too long, Britain's food watchdog cautioned Thursday.

Most supplements are safe, the Food Standards (news - web sites) Agency (FSA) said. But in new advice for the public, the agency said high levels of the supplement chromium picolinate may cause cancer, and identified other common vitamins and minerals whose long-term use could be dangerous.

Three other common supplements -- vitamin C, calcium and iron -- may have harmful effects in large doses even over short periods, although the symptoms from these disappear if the supplements are no longer taken.

'While in most cases you can get all the nutrients you need from a balanced diet, many people choose to take supplements. But taking some high-dose supplements over a long period of time could be harmful,' Sir John Krebs, the chairman of the agency, said in a statement.

The FSA said more than 1,000 milligrams (mg) per day of vitamin C, 1,500 mg per day of calcium or 17 mg of iron can cause abdominal pain and diarrhea in some people, although the symptoms disappear after the supplements are no longer taken.

The agency advised against taking more than 10 mg of vitamin B6 daily unless under medical care.

Beta-carotene, an antioxidant found in orange and yellow fruits and vegetables, could cause irreversible harmful effects in smokers if taken long-term and in high doses, it said.

Manganese could be dangerous for older people over an extended period of time, the agency said, while nicotinic acid, zinc and phosphorous could also be harmful in high doses over the long term.

The advice, which is listed on the FSA's Web site (www.food.gov.uk), is based on an independent expert review of the scientific evidence on the safety of vitamins and minerals. It is designed to help consumers make informed choices.

'In addition, the Board of the Food Standards Agency will be considering what further action we would wish the supplements industry to take,' Krebs added.

The FSA reviewed 34 vitamins and minerals with particular emphasis on long-term use.

It suggests that 10 mg a day or less of chromium in forms other than chromium picolinate is safe. The agency said it is also consulting on a proposal to ban chromium picolinate, which is sometimes promoted as being helpful in evening out blood sugar levels, in the manufacture of food supplements.