The independent experts, working for the Scientific Advisory Committee on Nutrition (SACN), were asked to examine the safety of vitamin A consumption after a report commissioned by the Food Standards Agency (FSA) during 2003 warned that high intakes of vitamin A may increase the risk of bone fractures in the long term.
As a result of evidence of this risk to bone health, the FSA's expert group on vitamins and minerals, charged with defining maximum safe levels of the nutrients, recommended that consumption of vitamin A should not exceed 1.5mg per day.
However they said that evidence of the bone fracture risk was not robust enough to set a Safe Upper Level but should only inform a 'guidance level' - an approximate indication that would not be expected to cause adverse effects but has been derived from limited data and is less secure than a SUL.
SACN's draft report published yesterday failed to offer any more conclusive findings on this link between the vitamin and bone health.
It said that some epidemiological data suggest that retinol intakes of 1.5mg per day and above are associated with an increased risk of bone fracture, but only one intervention study has examined this relationship.
This study showed no effect of short-term supplementation using a very high dose of retinol (7.5mg) on healthy men. The long-term effects of supplementation are however unknown.
Comments received by the committee over the next three months will be considered before it publishes the final report this summer, after which the FSA will review its advice to consumers.
The agency currently advises: "You should be able to get all the vitamin A you need by eating a varied and balanced diet. But if you do decide to take a supplement that contains vitamin A, it's a good idea not to take too much because this could be harmful."
"Having a total of 1.5mg or less of vitamin A on average a day from diet and supplements combined is unlikely to cause any harm."
The report recommends that people who eat liver once a week or more should avoid taking supplements containing vitamin A. It also concludes that it may be advisable for people at risk of bone fractures, such as post-menopausal women and older people, not to have more than 1.5mg of vitamin A per day, and reinforces current advice for women who are pregnant or thinking of having a baby to avoid taking supplements containing vitamin A.
Copies of the draft report, published on the SACN website, have been distributed to over 250 interested parties for comment including Government departments, the food and drink and supplements sectors, the feeding stuffs industry, universities and research centres.
Comments can be emailed to SACN.