Articles about Vitamins

Getting Your Vitamins

Experts recommend a boost in antioxidants, but they say it's not necessary to spend megabucks on megadoses of vitamins.

Put away the pills and keep eating those fruits and veggies. You've heard this before from nutritionists who for years have said that a balanced diet ought to be enough to keep us health). Now, after an exhaustive review of research, the nation's top scientists have come to the same conclusion.

If you eat a healthy diet there is rarely a need for antioxidant supplements, according to a report by the institute of Medicine, a part of the National Academies of Sciences. Researchers found no evidence that large doses of anti-oxidants--vitamins C and E, selenium, and beta-carotene--prevent chronic diseases.

Setting limits

However, the group did revise the Recommended Dietary, Allowances (RDAs) for antioxidants and, for the first time, set an upper intake level--the largest amount that a person can take without risking health problems.

"I'm glad they set a limit. A lot of people assume a little is good, but more is better. That isn't always the case," says Chris Rosenbloom, Ph.D., spokesperson for the American Dietetic Association and acting chair of the nutrition department at Georgia State University.

The report seems to contradict earlier information about antioxidants. There is evidence that free radicals (compounds that cause damage to cells) are linked to a risk of cancer and heart disease, but there is no proof that antioxidants in humans attack free radicals or limit their damage. It's only been proven in laboratories. Therefore, no evidence exists that taking megadoses of antioxidants prevents cancer, heart disease, or Alzheimer's disease.

"The public is very confused because often when these studies get reported all the facts aren't in," says Sandra Schlicker, director of the study at the Institute of Medicine.

Five-a-day way

In revising the RDAs, the panel looked at published studies and focused on trials involving humans--not animals. The take-home message of this report is simple: Eat more fruits and vegetables every, day. While the panel did not say how many to eat, it did endorse the five-a-day eating plan, advising people to eat at least five servings of fruits and vegetables a day. A typical serving is 1/2 cup of berries, cut-up fruit, or cooked vegetables. One 6-ounce glass of orange juice also is considered a serving. The report, Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids, is available online at http://books.nap.edu/catalog/9810.html.

Here are some of the new recommendations.

Vitamin E

Old RDA: Women, 8 milligrams (12 IU). Men, 10 milligrams (15 IU).

New RDA: 15 milligrams (22 IU) of natural vitamin E, also called d-alpha-tocopherol, for men and women.

Upper intake limit: 1,000 milligrams. Anything higher increases your risk of uncontrolled bleeding.

Vitamin E has been associated with reducing heart disease because it blocks oxidation of LDL (bad) cholesterol, making the cholesterol less likely to cling to artery walls. However, only one out of four large-scale trials of megadoses of vitamin E showed a reduced risk of heart attacks.

"The literature is very conflicting," says Maret Traber, Ph.D., associate professor at the Linus Pauling Institute at Oregon State University, and Institute of Medicine panelist. "There is a lot of experimental data on human tissue and in test tubes, but the studies done on humans are not conclusive enough to prove a beneficial effect."

Because vitamin E is found in fat, some people may need to meet the RDA by taking a supplement. "If you're eating 3,000 calories a day, it's easy to get your 15 milligrams, so don't worry about it," Traber says. "If you're eating only 1,500 calories a day, you may have trouble getting there. I'd rather see someone take a vitamin E supplement and eat a low-fat, low-calorie diet rich in fruit and vegetables than for the person to eat more fat just to get the vitamin E," Traber says.

When buying the supplement, look for natural vitamin E, also known as d-alpha-tocopherol. Researchers used to think synthetic vitamin E, known as dl-alpha-tocopherol, was just as effective, but it is not, Traber says. Many multivitamins contain synthetic vitamin E, Traber warns, so check labels carefully.

Best food sources: Vegetable oils, such as sunflower and safflower; nuts; and seeds. Smaller amounts of vitamin E are found in dairy foods, eggs, beef, whole grains, fruits, and vegetables.

Vitamin C

Old RDA: 60 milligrams.

New RDA: Women, 75 milligrams. Men, 90 milligrams. People who smoke should increase the RDA of vitamin C by 35 milligrams.

Upper intake limit: 2,000 milligrams for men and women. Taking more than the recommended upper limit may cause gastrointestinal distress.

Many studies found an association between vitamin C and a reduced risk for cancer and heart disease, but few established a true cause-and-effect relationship.

Robert A. Jacob, Ph.D., a member of the institute's panel and research chemist with the USDA Western Human Nutrition Research Center in Davis, California, says most of the studies on megadoses of vitamin C had mixed results or were neutral, including those that linked vitamin C to staving off the common cold or preventing heart disease and cancer.

"Studies didn't show harmful outcomes. But if they didn't show consistently positive results, you can't use that as a basis for an RDA," Jacob says.

Most of the research on vitamin C has never shown direct cause and effect. Studies have found only an "association" with health benefits. For example, research may show that people with a high vitamin C intake have lower blood pressure. However, there is no scientific proof that the vitamin is responsible because many other components of a healthy diet may lower blood pressure. "There is an association there, but it doesn't prove that vitamin C lowers blood pressure," Jacob says.

It's easy to get enough vitamin C in your diet. One 6-ounce glass of orange juice has enough vitamin C--about 78 milligrams--to meet the RDA for women. Vitamin C-rich fruits and vegetables typically average about 40 milligrams per serving, Jacob says.

Best food sources: Citrus fruits and juices, kiwifruit, broccoli, strawberries, and red or green sweet peppers.

Selenium

Old RDA: Women, 55 micrograms. Men, 70 micrograms.

New RDA: 55 micrograms for men and women.

Upper intake limit: 400 micrograms. Higher amounts can cause brittleness in hair and nails.

Studies suggesting a link between selenium intake and reduced risk of prostate, colon, and lung cancer aren't conclusive enough to warrant adding a supplement. In fact, if you live in the United States, chances are you're getting enough selenium in your diet. The reason: selenium is in the soil. Produce grown in selenium-rich soil will contain the mineral, says Dr. Raymond Burk, director of clinical nutrition research unit at Vanderbilt University.

Burk says the old RDA that distinguished between men and women was based on body weight, but new research shows that's not necessary. An upper limit of 400 micrograms was set because too much selenium causes hair to fall out, and problems with fingernails and toenails. Best food sources: Brazil nuts, seafood, meat, chicken, and whole-grain foods.

Beta-carotene and other carotenoids (lutein, zeaxanthin, and lycopene)

Old RDA: None. There never was one.

New RDA: None.

Upper intake limit: Beta-carotene supplements are not advised other than as a source of vitamin A.

There appears to be a link between carotenoids and a decreased risk of age-related macular degeneration, cataracts, and some cancers. However, no clinical trial has shown that carotenoids--compounds found in red and yellow plants--are responsible for lowering risk.

"There is encouraging research with certain carotenoids in the prevention of some diseases, but not enough to say what the requirement should be," says Susan Taylor Mayne, Ph.D., associate professor of epidemiology and public health at Yale University School of Medicine. There are some promising associations, such as with lutein and macular degeneration, but they are preliminary, she says.

So all the articles written about lycopene's effect on prostate cancer don't mean much?

"It's all interesting data, but at this point, it is far from proven," Mayne says. "And most of the studies have been done on food, not pills." Mayne recommends getting your carotenoids by eating a variety of foods.

Best food sources: Sweet potatoes, carrots, tomatoes, peppers, spinach, kale, collard greens, squash, apricots, mangoes, cantaloupe, and papayas.