Exploring the sense and nonsense of food and health

The Case Against Antioxidant Supplements?

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Dietary supplements, such as the vitamin B sup...

Dietary supplements, such as the vitamin B supplement show above, are typically sold in pill form. (Photo credit: Wikipedia)

By Sally J. Feltner, Ph.D, RDN

A 2014 survey from the Council for Responsible Nutrition reports that 68% of U.S. adults take dietary supplements. Eighty-three percent of these adults express confidence in the safety, quality and effectiveness.  Retail sales in the U.S.of dietary supplements are projected to be $35 billion dollars in 2016. Antioxidant supplements are popular especially among elderly consumers. Antioxidant products are prime examples of the hype and claims that promise so much – in this case, blocking potentially harmful free radicals with the result that heart disease, cancer and aging can be prevented.

The free radical theory of disease was for many years and still is the darling of the nutrition field. Simply, free radicals are atoms with at least one unpaired electron. When this occurs, they seek to pair up that one electron with another electron and in doing so, make them extremely reactive often-causing damage to DNA or cell membranes. Free radicals are not always damaging: for example, they are used by the body’s immune cells to destroy foreign invaders.

Antioxidants simply are the antithesis of free radicals, so the theory goes. They are supposed to squelch the damaging radicals. Antioxidants are found primarily in plant foods as phytochemicals with the most famous being the vitamins, beta carotene, E, and C. A plethora of clinical trials followed to test  how well these performed fighting diseases they were claimed to prevent.

Without going into details, so far, the results of these trials have been mostly unsuccessful. The most dramatic results involved beta carotene and vitamin E. The results shocked the nutrition antioxidant world. When beta carotene was given to smokers, they experienced 18% more lung cancers and found no benefits from vitamin E.   In addition, the overall death rate from beta carotene supplementation was 8% higher than controls. To make matters worse, the vitamin E group also had a higher rate of hemorrhagic stroke.

The same conclusions were reached when beta carotene, vitamin E or a placebo were given to 1,862 men who had had a previous heart attack. There were  significantly more deaths from heart disease in the beta-carotene group and a similar trend in the vitamin E group, although it was not significant.

Study after study using either beta carotene, vitamin E, or vitamin C followed with similar negative results. In most of the studies, relatively high doses of antioxidant vitamins were given to the subjects – a great deal higher than what would be consumed in a diet even high in fruits and vegetables.

By 2007, the Cochrane Collaboration team, after review of 68 randomized controlled trials with 232,606 patients given various combinations of antioxidant vitamins or minerals (beta carotene, vitamin A, vitamin C, vitamin E and/or selenium) compared to no intervention or using a placebo concluded:

  • “There was no convincing evidence that antioxidant supplements have beneficial effects on overall death rate.
  • In 47 trials with 180,938 participants, the antioxidant supplements significantly increased the death rate.
  • Beta carotene, vitamin A, and vitamin E given singly or combined with other antioxidant supplements significantly increase mortality.”

Source: JAMA 297:842-857, 2007

In spite of this extensive research, supplement makers continue to market these supplements as vigorously as if they were beneficial.




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