The powerful antioxidant beta-carotene has been found to help prevent cancer and aging (however, beta-carotene supplements may increase the risk of lung cancer in smokers). In animal and human studies, betakaroten and other carotenoids increased the number and activity of immune cells, an effect that did not appear to be related to their role as vitamin A precursors. At 25,000-100,000 IU per day, increases the number of certain white blood cells and improves immune function against cancer in healthy people. Beta-carotene supplements are being studied for their ability to reduce the risk of certain types of cancer and possibly heart disease.
Vitamin A can be toxic in high doses, and studies also show that beta-carotene from a concentrated supplement can be harmful for some people (but beta-carotene from food sources is considered safe). Vitamin A toxicity can occur when consuming too much preformed vitamin A from foods and/or supplements.
It is best to choose a multivitamin supplement that contains all or most of the vitamin A in the form of beta-carotene; many multivitamin manufacturers have already reduced the amount of preformed vitamin A in their products. While beta-carotene can help treat vitamin A deficiency, depending on the severity of your condition, vitamin A supplements may be more effective and work faster than supplemental beta-carotene alone.
Evidence suggests that eating a variety of vitamin A-rich foods, especially fruits and vegetables, protects against some diseases. Supplements have been proven to help prevent heart problems, in addition to antioxidant foods. Some doctors recommend antioxidant supplements to reduce the risk of macular degeneration; Reasonable levels for adults include 200 micrograms of selenium, 1,000 mg of vitamin C, 400 IU of vitamin E, and 25,000 IU of natural beta-carotene per day.
A study on age-related eye disease found that a combined supplement of beta-carotene, vitamin C, vitamin E, zinc, and copper reduced the risk of disease progression and vision loss in people with advanced macular degeneration. In a small double-blind study that included patients with acute and chronic relapsing pancreatitis, patients with acute and chronic relapsing pancreatitis were supplemented to provide daily doses of 600 mcg selenium, 9000 IU beta-carotene, 540 mg vitamin C, 270 IU vitamin E and 2000 mg of methionine significantly reduced pain, normalized several blood parameters for antioxidant levels and free radical activity, and prevented acute recurrence of pancreatitis.
In a second double-blind study, supplementation with natural mixed carotenoids equivalent to 120,000 IU of beta-carotene per day significantly increased survival time in adults with advanced AIDS who were also receiving conventional therapy and a multivitamin. Studies of smokers and/or people exposed to asbestos initially found that people who received supplemental beta-carotene (at least 20 mg per day) had an increased risk of developing lung cancer, especially those who also consumed a lot of alcohol.
Task Force members said research shows that beta-carotene supplements may increase the chances of getting lung cancer in people who are already at higher risk (for example, people who smoke or have been exposed to asbestos at work). It appears that carotenoids may promote health when eaten, but may have adverse effects when taken in high doses by people who smoke or have been exposed to asbestos. This can be avoided because research has linked high doses of these nutrient supplements to an increased risk of lung cancer in people who smoke.
A 2002 Yale University School of Medicine study found that a high intake of fruits and vegetables, especially a diet rich in carotenoids, reduced the risk of lung cancer. However, it should be noted that the Alpha-Tocopherol CARET study found a similar increase in lung cancer risk among smokers who received b-carotene supplements; this study was conducted in the United States and included males and females, as well as some non-white participants, and used a different dose and preparation of beta-carotene. This consistency suggests that lack of generalization may not be a significant issue.
Early observational studies have identified a protective association between β-carotene-rich vegetable consumption and lung cancer risk, sparking interest in β-carotene supplementation as a potential chemoprevention strategy. chemoprophylactic studies of beta-carotene supplementation, including the alpha-tocopherol, beta-carotene, and retinol efficacy study (CARET). In fact, the historic 1996 Carotene and Retinol Efficacy Study, or CARET, designed to test the effectiveness of supplements in cancer prevention, found that current and former smokers who took beta-carotene supplements actually showed a higher risk of contracting the disease.
To learn more about beta carotene supplements, please click here.