The Food Standards Agency is warning people not to take very high doses of many popular vitamins.
How will this affect the average vitamin-user?
What are vitamins?
Vitamins are chemicals which are obtained by the body from a healthy, balanced diet.
Many appear to perform important roles in key body functions - a lack of some key vitamins has been linked to certain illnesses.
For example, a diet with no vitamin C can cause scurvy.
People take vitamin supplements both to make sure they get enough of certain vitamins, and because there is some limited evidence that supplementation intake of certain vitamins may be beneficial.
Some scientists say that while some groups of people - for example pregnant women, infants and the elderly - may benefit from supplements, the evidence supporting supplement use by young, healthy adults is patchy at best.
However, this doesn't stop people - an estimated 10 million people in the UK take supplements every day, and the industry is worth almost £350 million a year.
What is the problem highlighted by the report?
As with anything that may produce a health benefit, some consumers are prepared to go to extremes in an effort to maximise this effect.
Particularly popular in recent years is the taking of very large doses of certain vitamins.
Many celebrities swear by huge doses of, for example, vitamin C, saying it protects them from picking up colds and flu.
The evidence to support these claims is patchy.
However, the Food Standards Agency is warning that there is some evidence suggesting health problems among people who take very large amounts of certain vitamins.
I take a multivitamin supplement once a day - does this affect me?
No. The amounts being discussed as potentially harmful by the Food Standards Agency are much larger than the doses found in multivitamin tablets.
Taking vitamin C as an example, most multivitamins contain approximately 40mg - the maximum recommended by the group is 1,000mg a day.
Should some supplements be banned?
Initially, the Food Standards Agency called for the supplement chromium picolinate to be banned.
There was concern that it could increase the risk of cancer.
However, after a review of the evidence the FSA decided that a ban was not necessary, as there was no evidence that the supplement could damage DNA.
But it will be keeping its advice about chromium supplements under review and looking at evidence that emerges in the future.
Are any other particular vitamins causing concerns?
The recommended limits set by the FSA may fall outside the amounts found in multivitamins, but consumers buying some of these vitamins individually may find themselves taking more than the recommended daily dose.
For example, the "safe" level of beta-carotene recommended by the FSA is 7mg a day - most tablets contain as much as 20mg.
Can the FSA bring in a ban?
No. It would require government intervention to take these vitamins off the shelves.
The FSA has consulted manufacturers about removing chromium picolinate from sale, and is hopeful that doses of some other vitamins on sale can be reduced.