You are right to be concerned about vitamin A toxicity. But first, please note that vitamin A comes in many forms. It is the animal form that is toxic, not plant-derived beta-carotene, which is the form I recommend in the Vitamin Advisor.
The Upper Limit of vitamin A set by the Food and Nutrition Board of the National Academy of Sciences is 10,000 IU per day. Vitamin A can be found in such dietary supplements as palmitate, acetate or fish liver oil, all of which are derived from animal sources. Although vitamin A is an essential nutrient, an excessive chronic intake of these forms of vitamin A can be toxic, leading to hair loss, confusion, liver damage, and - more recently discovered - bone loss.
The form of vitamin A I recommend in our Vitamin Advisor is beta-carotene in addition to other mixed carotenoids. The body can make all the vitamin A it needs from beta-carotene, which is not toxic, unlike the animal forms of vitamin A. Carotenoids are plant pigments found in orange and yellow fruits and vegetables and dark leafy greens. Unlike vitamin A, beta-carotene is water-soluble and does not accumulate in the body (although very high intakes - 100,000 IU or more a day - can cause an orange tint to your skin). Aside from being unsightly, this side effect is innocuous.
Carotenoid-containing fruits and vegetables have great cancer-protective value. In addition to beta-carotene, the antioxidant formulation I recommend contains lycopene, alpha-carotene, astaxanthin, lutein, and zeaxanthin. Lycopene is the red pigment in tomatoes that helps prevent prostate cancer, and lutein has been found to protect against cataracts and macular degeneration.
Taking a mixed carotenoid supplement does not excuse you from eating tomatoes, carrots, fruits, and greens, but it is useful insurance against failing to supply your body with all the antioxidant protection it needs. Read labels carefully to make sure the product you're using includes lycopene AND lutein and provides at least 20,000 IU of beta-carotene.
Andrew Weil, M.D.
Dosage Update, October, 2004
In order to provide the most up-to-date health information, I may change my recommendations from time to time. Due to compelling new research on carotene, I now suggest that you take 15,000 IU of mixed carotenes. (My previous recommendation was 25,000 IU; please adjust your dosage accordingly.)