Other Proposed Uses
- Cataract Prevention
- Enhancing Mental Function
- Exercise-induced Asthma
- Female Infertility
- HIV Support
- Macular Degeneration Prevention
- Male Infertility
- Parkinson's Disease
- Rheumatoid Arthritis
- Sunburn Prevention
Note: All the significant positive evidence for beta-carotene applies to food sources, not supplements.
Beta-carotene belongs to a family of natural chemicals known as carotenoids . Widely found in plants, carotenoids along with another group of chemicals, bioflavonoids, give color to fruits, vegetables, and other plants.
Beta-carotene is a particularly important carotenoid from a nutritional standpoint, because the body easily transforms it to vitamin A . While vitamin A supplements themselves can be toxic when taken to excess, it is believed (although not proven) that the body will make only as much vitamin A out of beta-carotene as it needs. Assuming this is true, this built-in safety feature makes beta-carotene the best way to get your vitamin A.
Although beta-carotene is not a required nutrient, vitamin A is essential for health, and beta-carotene is converted into vitamin A in the body. The exact conversion factor varies with the circumstances; in general, 2 mcg of beta-carotene in supplement form is thought to be equivalent to 1 mcg of vitamin A. See the article on vitamin A for requirements based on age and sex.
Dark green and orange-yellow vegetables are good sources of beta-carotene. These include carrots, sweet potatoes, squash, spinach, romaine lettuce, broccoli, apricots, and green peppers.
We are not sure at the present time whether it is advisable to take dosages of beta-carotene supplements much higher than the recommended allowance for nutritional purposes, which is about 1.5 to 1.8 mg daily in adults. Rather than taking doses higher than this, it is probably more advisable to increase your intake of fresh fruits and vegetables.
There are no well-documented therapeutic uses of beta-carotene, beyond supplying nutritional doses of vitamin A.
Beta-carotene has been proposed as a treatment for alcoholism , asthma , depression , epilepsy , headaches , heartburn , male infertility , female infertility , Parkinson's disease , psoriasis , rheumatoid arthritis , and schizophrenia , but there is little to no evidence that it works.
What Is the Scientific Evidence for Beta-Carotene?
However, observational studies cannot prove cause and effect. It is always possible that individuals who consume a great deal of carotenoids in the diet are different in other ways; for example, they might exercise more or have healthier lifestyles in other regards.
This is not a purely theoretical issue. For example, based primarily on observational studies, hormone replacement therapy was promoted as a heart-protective treatment for postmenopausal women. However, when placebo-controlled studies were performed, hormone replacement therapy was shown to slightly increase the risk of heart disease. One possible explanation for this discrepancy is that the apparent benefits of hormone replacement therapy were due to the fact that women who used it tended to belong to a higher socioeconomic class than those who did not. (For a variety of reasons, some of which are not known, higher income is associated with improved health.)
Something similar appears to be the case with beta-carotene. Although individuals who consume foods high in beta-carotene appear to obtain some protection from heart disease and cancer, when researchers gave beta-carotene supplements to study participants, there was no protective effect.
Most studies enrolled people in high-risk groups, such as smokers, because it is easier to see results when you look at people who are more likely to develop cancer to begin with.
There are several possible explanations for these apparently contradictory findings. As noted above, it is possible that intake of carotenoids as such is unrelated to cancer, and that some unrelated factor common to individuals with a high carotene diet is the cause of the benefits seen in observational trials.
Heart Disease Prevention
Macular Degeneration and Cataracts
At recommended dosages, beta-carotene is believed to be very safe. The only side effects reported from beta-carotene overdose are diarrhea and a yellowish tinge to the hands and feet. These symptoms disappear once you stop taking beta-carotene or reduce your dose.
- Reviewer: EBSCO CAM Review Board
- Review Date: 07/2012 -
- Update Date: 07/25/2012 -