| Vitamin A is vital for a variety of bodily functions. | | | | were high. |
| These include: | | | | Two separate clinical trials raised concerns about the |
| - Maintaining healthy teeth. | | | | association between beta-carotene supplements and |
| - Building strong bones. | | | | a greater incidence of lung cancer and death in |
| - Strengthening the optical system. | | | | smokers. However, other conflicting studies show |
| - Growth and maintenance of healthy skin and tissue. | | | | opposite results. Differences in these studies, as well |
| - Protection from cardiovascular disease and cancer. | | | | as their methods, make this information difficult to |
| - Promoting good vision, particularly in low light. | | | | interpret. |
| - Reproduction and breastfeeding. | | | | In the Alpha-Tocopherol Beta-Carotene (ATBC) |
| - Cell division and cell differentiation (a process in | | | | Cancer Prevention Study, more than 29,000 male |
| which a cell becomes part of the brain, muscle, lungs, | | | | smokers were randomized to receive 20 mg of |
| blood, etc.). | | | | beta-carotene alone, 50 mg of alpha-tocopherol |
| - Regulation of the immune system. | | | | (vitamin E) alone, supplements of both, or a placebo |
| Vitamin A occurs in 2 forms: preformed Vitamin A, | | | | for 5 to 8 years. The incidence of lung cancer was 18 |
| also known as active Vitamin A, and proVitamin A. | | | | percent higher among the men taking the |
| Preformed Vitamin A is better known as retinol. This | | | | beta-carotene supplement. Eight percent more men in |
| is considered the active form because it most | | | | this group died, as compared to those receiving other |
| immediately usable form. Retinol is fat-soluble, | | | | treatments or placebo. |
| meaning it is stored in the liver and requires dietary | | | | Similar results were seen in the Carotene and Retinol |
| fats for absorption. Large amounts of this form can | | | | Efficacy Trial (CARET). This lung cancer chemo |
| be toxic, as the body does not rid itself of the | | | | prevention study provided subjects with supplements |
| excess. | | | | of 30 mg of beta-carotene and 25,000 IU of retinyl |
| Retinol is found only in animal foods. Sources that are | | | | palmitate (a form of Vitamin A), or a placebo. |
| especially rich in retinol are fish liver oils from cod, | | | | Researchers stopped this study once they that the |
| halibut, salmon, and shark. Other good sources include | | | | subjects receiving beta-carotene had a 46 percent |
| eggs and dairy products. | | | | higher risk of dying from lung cancer. |
| ProVitamin A is actually a group of carotenoids. | | | | On the opposite side of the spectrum, in a study of |
| Carotenoids are dark colored dyes found in plant | | | | more than 22,000 male physicians, the Physicians |
| foods that the body turns into Vitamin A as needed. | | | | Health Study compared the effects of taking 50 mg |
| Scientists have identified 563 carotenoids. Few of | | | | of beta-carotene every other day to taking a |
| these can be used by the body to produce Vitamin | | | | placebo. No adverse health effects were discovered. |
| A. The best known and researched carotenoid as a | | | | A clinical trial in China tested the ability of four |
| Vitamin A precursor is beta-carotene. | | | | different nutrient combinations to help prevent the |
| Beta-carotene is an antioxidant, which functions to | | | | development of esophageal and gastric cancers in |
| protect cells from damage caused by free radicals. | | | | 30,000 men and women. This study showed that |
| Free radicals are unstable by-products of oxygen | | | | after five years those who had taken a combination |
| metabolism that contribute to illness and the | | | | of beta-carotene, selenium, and vitamin E had a 13 |
| degenerative process of aging. | | | | percent reduction in cancer deaths. |
| Beta-carotene is considered non-toxic. The body will | | | | Swiss researchers studied the association of Vitamin |
| only convert this to Vitamin A when needed. | | | | A and beta-carotene with lung cancer in an "at-risk" |
| Excessive beta-carotene intake can result in a yellow | | | | population of smokers and workers exposed to |
| orange cast to the skin, which is sometimes seen in | | | | asbestos. Researchers reported a more than 50 |
| those who drink extreme amounts of carrot juice. | | | | percent reduction in the development of lung cancer |
| This condition is harmless and will correct itself as | | | | in the supplemented group when compared to the |
| soon as the beta-carotene intake is lowered. | | | | control group. |
| Beta-carotene is only found in plant-based foods. | | | | One lung cancer research trial may help explain the |
| Sources include carrots, pumpkin, sweet potatoes, | | | | discrepancy between these studies. This research |
| winter squash, cantaloupe, broccoli, kale, and spinach. | | | | found that men who consumed more than 11 grams |
| As a general rule, the more intense the color of the | | | | per day of alcohol (approximately one drink per day) |
| fruit of vegetable, the higher the beta-carotene | | | | were more likely to show an adverse response to |
| content will be. | | | | beta-carotene supplements. These results suggest a |
| Many healthcare practitioners find that beta-carotene | | | | potential negative relationship between alcohol and |
| works remarkably well in the treatment of acne, as | | | | beta-carotene. |
| well as eczema and psoriasis. Beta-carotene is | | | | Studies are currently being run on the relationship |
| completely nontoxic, allowing high doses to be used | | | | between Vitamin A and osteoporosis. In Sweden, a |
| safely. | | | | small study of nine healthy people found that the |
| Human studies have shown that Vitamin A, | | | | amount of Vitamin A in one serving of liver may |
| particularly in the form of beta-carotene, aids in the | | | | impair the ability of vitamin D to promote calcium |
| protection and treatment of cardiovascular disease. | | | | absorption. |
| Harvard researchers followed a total of 22,000 male | | | | In the U.S., the Nurses Health Study looked at the |
| physicians in the Physician's Health Study. Ten years | | | | association between Vitamin A intake and hip |
| into the study, researchers evaluated a subgroup of | | | | fractures in over 72,000 postmenopausal women. |
| 333 men with histories of cardiovascular disease. The | | | | Those women who consumed the most Vitamin A in |
| physicians in the subgroup who were taking | | | | foods and supplements (3,000 mcg or more per day |
| approximately 85,000 IUs of beta-carotene every | | | | as retinol equivalents, which is over three times the |
| other day experienced half the heart attacks, | | | | recommended intake) had a marked increase in their |
| strokes, and deaths due to heart disease as did | | | | risk of hip fracture as compared to those consuming |
| those not taking the supplement. | | | | the least amount (less than 1,250 mcg/day) of the |
| One study of women with breast cancer who were | | | | same form of Vitamin A. |
| being treated with chemotherapy found that those | | | | No association has been found between |
| with higher blood levels of Vitamin A responded | | | | beta-carotene intake and increased risk of |
| twice as well to their treatment as did those with | | | | osteoporosis. Research shows only the possible link |
| lower levels of Vitamin A. In a separate study, | | | | between osteoporosis and excess retinol intake. |
| Scottish researchers found that patients with breast | | | | As with all supplements and medications, for |
| cancer, bowel cancer, and melanoma all responded | | | | information on specific use be sure to discuss your |
| better to chemotherapy when their Vitamin A levels | | | | particular situation with your doctor. |