The Nutrition Source
The Institute of Medicine's current recommended intake of vitamin A is 900 micrograms of retinol for men (equivalent to 3,000 IU) and 700 micrograms of retinol for women (equivalent to 2,333 IU). The upper limit for vitamin A intake from retinol is 3,000 micrograms, but intakes this high may increase the risk of hip fracture or interfere with the beneficial actions of vitamin D.
Food sources: Many breakfast cereals, juices, dairy products, and other foods are fortified with retinol (also known as preformed vitamin A). Many fruits and vegetables, and some supplements, also contain beta-carotene and other vitamin A precursors, which the body can turn into vitamin A. It's best to choose a multivitamin supplement that has all or the vast majority of its vitamin A in the form of beta-carotene.
Although it's possible to get too little vitamin A, it's easy to get too much preformed vitamin A (retinol) from supplements. Intake of up to 3,000 micrograms of preformed vitamin A, more than three times the current recommended daily level, is thought to be safe. However, there is some evidence that this much preformed vitamin A might increase the risk of hip fracture (1-3) or some birth defects. (4) Another reason to avoid too much preformed vitamin A is that it may interfere with the beneficial actions of vitamin D.
In contrast to preformed vitamin A, beta-carotene is not toxic even at high levels of intake. The body can form vitamin A from beta-carotene as needed, and there is no need to monitor intake levels, as there is with preformed vitamin A. Therefore, it is preferable to choose a multivitamin supplement that has all or the vast majority of its vitamin A in the form of beta-carotene; many multivitamin manufacturers have already reduced the amount of preformed vitamin A in their products.
(But of course, everything in reason)
Reprinted from the Harvard School of Public Health