Antioxidant supplements bring billions of dollars in revenue each year in the U.S. Americans spend
about $2 billion on Vitamin E, C, and beta carotene alone hoping to stave off heart disease, cancer, and memory loss.
But research in the past few years has been somewhat disappointing and a little scary.
What exactly are antioxidants? A textbook definition says they are substances that neutralize harmful-oxygen-containing free radicals that can cause cell damage. Antioxidants block the process of oxidation by neutralizing
free radicals. In doing so, the antioxidants themselves become oxidized. That
is why we need a constant supply since antioxidants “sacrifice” themselves in
the process. In certain circumstances, an antioxidant may even act as a “pro-oxidant“that generates toxic oxygen species that may harm the cell and its DNA by reactions that they’re supposed to prevent.
The free radicals come from internal and external sources. They are generated by normal metabolic reactions in the body or areproduced by pollutants, cigarette smoke, radiation and environmental chemicals. The immune system relies on them to fight against toxins, foreign substancessuch as bacteria, and even cancer cells. However, they can damage proteins, fats and carbohydrates that reside in
our cell membranes and blood vessels allowing substances such as tumor cells to
enter the blood and metastasize.
Along came the supplement makers and the idea of anantioxidant in a bottle was dreams come true, at least for a while. In 2008, the Cochrane Collaboration, an
international body of scientists who examine medical research looked at 67
studies that included almost 400,000 participants. They concluded that there
was no evidence to support the claim that antioxidant supplements would
decrease mortality from cardiovascular disease, Alzheimer’s disease, lung
cancer or other diseases thought to be caused in part by free radical
production. And even more disturbing was the finding that vitamins C, E and beta carotene actually increased mortality in some cases. It remains to be understood why this occurred.
There have been some alarming studies in several intervention trials as well as some with mixed or slightly beneficialresults. Beta carotene appears to be the most troublesome.
In the Carotenoid and Retinol Efficacy Trial (CARET), 18,314 smokers or asbestos workers were randomized to receive 30 mg of synthetic beta carotene and 25,000 IU of retinol (pre-formed vitamin A) or a placebo. The study was terminated 21 months early due to the result that there was a 28% increase in lung cancer rates and 17% more deaths in the beta-carotene group compared to the placebo group. These results were highly consistent with the results from the Alpha Tocopherol Beta Carotene Prevention Study with Finnish male smokers.
In 1997, a study from the Journal of the American Medical Association revealed that 60 mg of vitamin E a day strengthened the immune system in a group of healthy participants at least 65 years old and 200 mg generated a four-to-six fold
improvement after four months while, 800 mg of vitamin E resulted in worse
immunity than those receiving no vitamin E at all. So more was not beneficial. Vitamin E is sold as supplements declaring the vitamin content as International Units (IU) rather than micrograms stated in the RDA.·
The RDA for vitamin E is 15 mg/d or 22.4 IU for people over 14 years old. Many vitamin E supplements are sold in doses well above this amount.
In the Journal of the Medical Association (Feb, 2007), researchers analyzed the results of 68 clinical trials with a total population of 190,938 subjects. The trials included supplements containing beta-carotene, vitamin A, vitamin C, vitamin E and selenium. It was reported that beta-carotene, vitamin A and vitamin E either taken together or alone increased mortality significantly. Vitamin C and selenium did not appear to influence mortality.
It’s important to realize that these results do not refer to vitamins from foods that contain antioxidants, only supplements. Supplements often contain high doses while the amounts in most foods are quite low. The phytochemicals in foods not only provide some antioxidant protection, but also have beneficial hormonal and enzyme effects. Others interfere with DNA replication thus preventing cancer cell multiplication. There are also antibacterial effects from some foods like allicin in garlic. See my previous post, Antiseptics in the Kitchen.
Just another reason to stick with real foods. And in this case, more is better!