The food authority surveyed 200 supplements and said that most had levels of metals within safety guidelines. But eight products were found to have levels of metals above those amounts recommended by an expert group on vitamins and minerals in 2003.
There is currently no legislation in place controlling the maximum levels of nutrients in food supplements. But following the expert group's report, member companies of the trade association HFMA agreed to label any supplements containing higher doses of nutrients with an advisory statement about potential side effects.
The Food Standards Agency said sampling for the survey was undertaken soon after advisory statements were agreed in 2004 and therefore not all products carried these labels. However it warned that it will do a further survey in early 2005 to check the extent to which these statements are being used.
In the future, the EU food supplements directive will set maximum levels for nutrients. But the UK food authorities have told the government to push for national exceptions to permitted levels of vitamins and minerals under the new European law.
The results released yesterday came from a survey done last summer that measured levels of aluminium, arsenic, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, selenium, thallium and zinc in supplements bought from supermarkets, pharmacies and health stores across the UK, as well as from mail order and internet companies overseas.
Brands including Galens Choice, Health Aid, Solgar and Vitabiotics had iron levels about the recommended daily amounts of 20mg. Asda's Glucosamine & Chondroitin, Musahi ZMA+ and Nature's Life manganese had higher levels of manganese than the RDA, and Nature's Plus Ultra Mins had levels of both metals as well as zinc well above the RDA.
The FSA also said it has tested a similar-sized sample for PAHs (polycyclic aromatic hydrocarbons), a group of chemicals present in the environment as a result of burning fuel and other pollution, which can find their way into foods.
Scientific experts have warned that they can be carcinogenic.
The FSA said there was no threat to consumers from PAHs in supplements, based on its survey. The highest levels of PAHs were found in plant-derived products, such as ginseng, but were found less often in multivitamin or single vitamin products.
Low levels were generally found in fish oils and plant oils.
The companies whose products contained the highest levels were advised to investigate ways to reduce them.
"The Agency does not recommend that consumers change their current food supplement choices on the basis of this survey," said the Food Standards Agency.