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Evidence show how vitamins prevent cancer
Vitamin E protects against at least two common forms of cancer -- prostate and bladder -- but popping supplements is probably not the best way to get the vital nutrient, researchers said on Sunday. Two studies found that people who either ate the most vitamin E containing food or who had the highest levels in the blood were the least likely to have cancer. But the researchers also noted that there are several different forms of vitamin E and the kind you eat -- in this case alpha tocopherol -- is key. And the best-absorbed form of alpha tocopherol is not found in supplements but in foods such as sunflower seeds, spinach, almonds and sweet peppers. In one of the studies presented to the annual meeting of the American Association of Cancer Research in Orlando, Stephanie Weinstein of the U.S. National Cancer Institute and colleagues found men with the most vitamin E in their systems had the lowest risk of prostate cancer. They looked at data from 29,133 Finnish men aged between 50 and 69 taking part in a smoker's study. All gave blood at the beginning of the study and then took vitamins to see whether the supplements might prevent various forms of cancer. This study is best known for showing that smokers who took beta carotene, which the body converts to vitamin A, actually had higher rates of lung cancer. Weinstein looked at vitamin E and prostate cancer, and they looked at how much E the men had in their blood before they ever took a supplement. They looked at 100 men with prostate cancer and 200 men who did not. "We found that the men who had higher serum (blood) levels of vitamin E had a lower chance of getting prostate cancer," Weinstein told a news conference monitored by telephone. NOT ALL E'S ARE EQUAL Then they looked at the two main forms of vitamin E -- alpha tocopherol and gamma tocopherol. Men with the highest natural levels of alpha tocopherol were 53 percent less likely to later develop prostate cancer. Men with the highest levels of gamma tocopherol, which only represents about 20 percent of the vitamin E in blood -- had a 39 percent lower chance. Taking supplements further reduced prostate cancer rates. "Nuts and seeds, whole grain products, vegetable oils, salad dressings, margarine, beans, peas and other vegetables are good dietary sources of vitamin E," Weinstein said. In a similar study, Dr. Xifeng Wu of the University of Texas M.D. Anderson Cancer Center, John Radcliffe of Texas Woman's University in Houston and colleagues studied 468 bladder cancer patients and 534 cancer-free volunteers. They asked their 1,000 volunteers what they ate, and estimated how much alpha-tocopherol and how much gamma tocopherol they got in their everyday diets and from supplements if they took them. Those with the highest intake of alpha tocopherol from food had a 42 percent reduced risk of bladder cancer, and those who had a vitamin E-rich diet and took supplements too had a 44 percent lower risk. But when broken down into types, they found gamma tocopherol offered no protection against bladder cancer.
"It would not be reckless to encourage people to try and meet the dietary allowance of vitamin E, which is about 50 milligrams a day," Radcliffe told the news conference. Current average U.S. intake of E is only 8 mg a day. One of the best sources, said Radcliffe, a dietician, is a handful of sunflower seeds. Almonds, spinach, mustard greens and green and red peppers are also good sources of alpha tocopherol. Many E supplements, he said, contain both active and inactive forms of E and may not be the best source. Plus, he said, sunflower seeds are high in selenium, another key nutrient, while greens are loaded with desirable nutrients. |
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