It seems that both vitamin A and its chemical "cousin," beta-carotene, have been receiving quite a beating in the media lately.
First, a Finnish study concluded last year that beta-carotene not only doesn't prevent cancer but might even play a role in making
the disease worse. A subsequent study indicated that pregnant women who take as little as 25,000 IU of vitamin A may increase their
risk of bearing a child with birth defects.
A subsequent study conducted in the United States found that beta-carotene had no effect on the prevention of heart disease. Like its Finnish counterpart, this new study also found that beta- carotene might actually increase the spread of cancer during advanced stages of the disease. The combination of these adverse reports have left many bodybuilders wondering if they should dump beta-carotene supplements, which had heretofore been viewed favorably as antioxidants.
Before you do anything rash, you might consider a few of the lesser-publicized aspects of the aforementioned studies. Both studies involved long-time smokers already afflicted with cancer. For example, in the Finnish study, which included 29,133 male subjects aged 50 to 69; a criterion for participation was having smoked an average of 20 cigarettes a day for 36 years. There is no reason to believe that beta-carotene would have salutary effects on individuals whose health was literally past the point of no return.
What is known about beta-carotene is that it's an effect-metabolic by-products called free radicals, which tend to attack structures in the body such as cell membranes. By reacting with the fat naturally residing in cell membranes, free radicals lipid peroxide - which in turn lowers cell permeability and imperils vital nucleic acids (RNA and DNA). In short, compromising the structural integrity and ability of the cell leaves the door open for carcinogens. The interaction of these carcinogens with DNA in the cell nucleus results in cancer.
Previous studies have shown that foods known to be rich in beta-carotene, such as yellow fruits and vegetables and dark-green vegetables, protect against free radicals. However, these foods also contain other constituents that might have been responsible for the protective benefits. In addition, over 500 other carotenoids occur naturally in food. This doesn't mean, though, that beta-carotene wasn't also involved.
A recent study, for example, found that a high consumption of red vegetables, such as tomatoes, produced a 45% reduction in the incidence of prostate cancer. Once again, the press jumped on the story, reporting the news under sensational headlines such as "Pizza Prevents Cancer." In actuality, the active agent was a carotenoid similar to beta-carotene called lycopene found in red vegetables.
In fact, a study published in the journal Nutrition and Cancer (24:257-266, 1995) found that researchers may have been focusing on the wrong carotenoid as far as cancer prevention is concerned. While beta-carotene has been considered the star of the show, other studies have shown that lycopene may help prevent cancers of the bladder as well as the deadliest cancer of all, cancer of the pancreas. Other studies show that lycopene is over twice as effective against free radicals as beta-carotene is.
A particularly interesting finding of this study is that lycopene appears to completely inhibit the cancer-promoting effects of insulinlike growth factor-i. IGF-1 has acquired near-legendary status among many athletes of late, but few realize that IGF-l is produced not only in the liver under the aegis of growth hormone but also in other tissues, including muscle.
The little-discussed dark side of IGF-1 is its ability to stimulate accelerated cell division, a hallmark of all cancers. The bottom line is that bodybuilders, who because of intense exercise regimens produce more IGF-1 than normal individuals do, should be especially careful to include red vegetables in their diets to help prevent cancer.
Various measures of toxicity have failed to indicate negative health consequences from beta carotene consumption. These include tests that measure possible carcinogenic activity in test tubes (i.e., in vitro tests) and animal tests. Giving large doses of beta- carotene to dogs for over two years, for example, produced no increased incidence of cancer in the subjects. For a while, some studies suggested that beta-carotene might lower vitamin E levels in the body, but this too proved to be a false alarm, disproved by follow-up studies.
About the worst thing that will happen if you megadose on beta-carotene is that your skin may take on a yellow-orange hue. Look on the positive side: You'll get a head start on your tan.