As discussed in the Vitamin A Supplements Review
, beta-carotene is actually a "pre-vitamin A" -- it is converted in the body to vitamin A based on the body's need for vitamin A — an essential nutrient. This should make it a "safer" form of vitamin A, since too much vitamin A can be toxic, and, unlike vitamin A, for which there is an upper tolerable intake level, no such limit has been established for beta-carotene.
However, as noted in the Concerns and Cautions
section of the Review, an analysis of many studies found a slight (5%) but statistically significant increase in mortality (i.e., more people died during studies) associated with the use of supplements containing beta-carotene, leading to the conclusion that the current evidence does not support the use of beta-carotene supplements in the general population. In particular, smokers and people who have been exposed to asbestos should avoid beta-carotene from supplements. Although it is still sometimes added to supplements for vision health, beta-carotene does not appear to reduce the risk of macular degeneration
Eating foods rich in beta-carotene has not been found to have the negative effects associated with beta-carotene supplements -- although it may cause yellowing of the skin.
For more about the pros and cons of taking beta-carotene, see the What It Does
and the Concerns and Cautions
sections of the Vitamin A Supplements Review