Advertisements with tantalizing promises of improved health, prevention of cancer and heart disease, and greater energy have lured millions of Americans to spend billions of dollars on the purchase of multivitamins.
An article in the February 9 issue of Archives of Internal Medicine reported that multivitamin use did not protect the 161,808 postmenopausal women enrolled in the Women's Health Initiative Study from common forms of cancer, heart attacks, or strokes. And the numbers of deaths during the 8 years of the study were the same in vitamin users as in non-users. Still, it is important to recognize that this was an observational study, not a more meaningful clinical trial. Although these findings apply only to women, other studies have failed to show benefits of multivitamins in older men.
These results are not at all surprising for several reasons. No large study has shown that multivitamins significantly benefit healthy men and women. In addition, for some years physicians prescribed folic acid and vitamins B12 and B6 in the hopes of preventing heart attacks and strokes by lowering blood levels of homocysteine. (High blood levels of homocysteine are associated with an increased risk of coronary and other vascular diseases.) A number of recent studies, however, have shown that, while these vitamins do lower homocysteine levels, they do not prevent heart attacks or strokes.
Many doctors have also prescribed the antioxidants vitamin E and beta-carotene to reduce the risk of cardiovascular diseases and cancer. Alas, studies have now proven that these supplements are not protective--and may even be harmful.
No one denies that an adequate intake of vitamins is essential; however, vitamins can and should be obtained from eating enough healthy foods rather than from swallowing vitamin supplements.
Then what about vitamins being a great source of energy? Some multivitamin ads do indeed claim that their supplements boost energy; and some professional athletes gobble handfuls of vitamin pills to increase their energy and strength. But researchers proved long ago that energy comes from calories, not vitamins. The highly touted cholesterol-lowering effects of substances added to some multivitamin supplements? Still unproven.
All this is not to say that specific vitamins supplements are never desirable. Vitamins can be valuable in certain situations:
- Folic acid supplements in women who are pregnant or plan to become pregnant can help to prevent serious neural-tube defects that affect the baby's brain and spine.
- Supplements that contain more vitamin D and calcium than is present in regular multivitamin pills can help older men, and especially women, avoid osteoporosis and bone fractures.
- Supplements of vitamins C and E, beta-carotene, zinc, and copper may slow the progression of vision loss in people with early macular degeneration.
And multivitamins are beneficial for some entire groups of people:
- those on a very-low-calorie weight-loss diet
- strict vegetarians
- heavy alcohol drinkers
- individuals who are not getting an adequate diet because they are too sick or too poor--or live by themselves and are unable to prepare proper meals for themselves
I also agree with a comment made by one of the coauthors of the Archives of Internal Medicine article about postmenopausal women mentioned above. An 8-year follow-up period may not be long enough to show that multivitamins protect against cancers that take many years to develop.
All the same, the results of the studies on vitamins so far point to one conclusion: Healthy people who eat enough calories from a varied diet do not benefit from multivitamin supplements.
No comments:
Post a Comment