Article Abstract:
Beta-carotene, a yellow pigment present in dark green and yellow vegetables and fruits, is a precursor of vitamin A and is stored and converted to vitamin A (retinol) in the liver. Various studies suggest that oral beta-carotene may be effective against certain types of cancer, and high doses of retinol were shown to be effective against certain tumors. However, the toxicity of these substances may limit their use in preventing cancer. Retinoids have been shown to increase blood levels of triglycerides, or fats, which may increase risk for some cardiovascular diseases. Only a portion of beta-carotene is converted to retinol, and daily oral doses of 50 milligrams (mg) of beta-carotene do not produce increases in blood retinol levels. However, it is unclear whether beta-carotene can increase blood levels of triglycerides. The effects of oral beta-carotene on blood lipid levels were assessed in 61 patients with skin cancer over six months. Thirty-one patients were treated with 50 mg per day of oral beta-carotene, while the remaining 30 received a placebo, or substance with no therapeutic effect. Blood samples were obtained at the start and end of the study and analyzed for triglyceride, total cholesterol, high-density-lipoprotein (HDL) cholesterol, retinol, and beta-carotene levels. Retinol levels were unchanged while beta-carotene levels increased substantially in treated patients. The changes in triglycerides, total cholesterol, and HDL cholesterol were similar for the two groups. These findings suggest that daily doses of 50 mg oral beta-carotene do not affect blood lipids. (Consumer Summary produced by Reliance Medical Information, Inc.)
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Article Abstract:
It has been estimated that diet may play a role in approximately 35 percent of deaths due to cancer, but much still needs to be learned about which substances may have adverse or protective effects. Studies show that long-term consumption of carotenoids, such as beta-carotene, is associated with a decreased incidence of cancer. Beta-carotene is a precursor of vitamin A which is stored and then converted to vitamin A in the liver. Carotenoids may protect against cancer by inactivating highly reactive and potentially damaging elements called free radicals. In addition, carotenoids may enhance the production of certain immune cells. Beta-carotene is transported in the blood by low-density lipoproteins (LDLs), very-low-density lipoproteins (VLDLs), and high-density lipoproteins (HDLs). The blood levels of beta-carotene have been correlated with those of blood cholesterol, LDLs, and HDLs. Blood levels of beta-carotene and effects on various immune factors were assessed in 50 healthy subjects, who in groups of 10 received 0, 15, 45, 180, or 300 milligrams (mg) of beta-carotene each day for one month. The results show that the blood levels of beta-carotene increased within two weeks. The extent of increase was related to the dose. The levels reached a peak, or maximum, between two and four weeks, and then did not change in all groups with the exception of those receiving 300 mg beta-carotene. Beta-carotene did not appear to affect immune factors but caused modest increases in HDL levels for all groups given beta-carotene. (Consumer Summary produced by Reliance Medical Information, Inc.)
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Article Abstract:
Beta-carotene is the form of vitamin A found in fruits and vegetables. In the last few years there has been increased interest in beta-carotene for its possible therapeutic effects. This vitamin may ultimately play a role in treating certain skin diseases by preventing photosensitivity (sensitivity to light), and may also be an effective anticancer agent. Research is needed into the absorption of beta-carotene when it is taken as a supplement. This study investigated blood beta-carotene levels after ingestion of 180 milligrams (mg) beta-carotene per day for 10 or 11 weeks. The subjects were 38 healthy men, aged 22 to 49, who were participating in research on the effects of beta-carotene on skin response to sun exposure. The 180 mg dose of beta-carotene is considered high, and is equal to the dose being investigated for treating light-sensitive skin diseases. The subjects' blood levels reached a plateau after 1.5 to 4 weeks, but maximum blood levels varied considerably among individuals. Most of the men developed carotenodermia, a slight yellowing of the skin that was most noticeable on the palms and soles of the feet. One subject liked the change in color of his face and arms, and wanted to keep taking the beta-carotene indefinitely to maintain this appearance, which looked like a suntan. In agreement with the findings of other researchers, there was no indication that the dose of beta-carotene was toxic to the body. (Consumer Summary produced by Reliance Medical Information, Inc.)
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