Soy And Fat And Bugs, Oh My!
Chester J. Zelasko, Ph.D. | July 1, 2005

“Soy Affects Fertility”
“Omega-3 Fatty Acids May Cause Abnormal Heart Rhythms”
“Viruses Kill Cancer”

These recent health news headlines can get your head spinning. It’s enough to remind me of that line from The Wizard of Oz: “Lions and tigers and bears, oh my!”--thus the title of this newsletter. Let’s examine the research on which these headlines were based.

“Soy May Cause Infertility”
Dr. Lynn Fraser presented data to the European Society of Human Reproduction and Embryology, meeting in Copenhagen, Denmark, suggesting that phytoestrogens in soy may negatively affect fertility. Sperm from mice that were exposed to the isoflavone genistein developed too rapidly; the sperm exposed to phytoestrogen might not be active long enough to fertilize an egg. This is a continuation of research that Dr. Fraser reported in 2002 at a meeting of the same Society. Dr. Fraser speculates that it is more problematic if women eat soy products because the phytoestrogen might affect the development of sperm present in women after intercourse but before fertilization takes place.

The problem is that this is an in vitro or test-tube study. What happens to sperm in a test tube may or may not happen in the male or female who consumes soy products. Other researchers have found no such problem: in one study, male rats fed a diet high in phytoestrogens were not affected by chronic exposure (1); in a review article published in 2002, the author reported that there were no negative effects of soy intake on the fertility of women or men (2).

Bottom line: what happens in test tubes when sperm are exposed to phytoestrogens may not mean anything when soy is consumed as part of the diet. A lot more research is necessary before any conclusions can be reached.

“Fish Oil Carries Risk of Abnormal Heart Rhythms”
This study was recently published in the Journal of the American Medical Association (3). Subjects were given either omega-3 fatty acids from fish oil or a placebo, then monitored for specific abnormal heart rhythms called ventricular tachycardia and ventricular fibrillation. The group receiving the fish-oil supplement had a slightly increased risk of a negative event occurring, surprising the researchers.

However, when the data is examined more closely, we see that while 7 out of 10 patients receiving the fish oil had a negative event in two years, 6 out of 10 receiving a placebo had the same type of negative event.

Further, what is being overlooked entirely in the news reports is that these were the sickest of patients. When the time comes that you need a defibrillator permanently implanted in your chest, you have severe heart disease. It’s not a question of IF an abnormal rhythm is going to occur--it’s a question of when.

Bottom line: if you have an implantable defibrillator, discuss with your physician whether you should take a fish-oil supplement. For the rest of us, the overwhelming data indicates that omega-3 fatty acids prevent sudden death from heart disease, along with other benefits. My wife and I will continue taking our omega-3s.

“Virus Kills Cancer”
In a study presented at a meeting of the American Society for Virology (4), researchers examined a commonly occurring virus in humans called Adeno-Associated Virus type 2 or AAV-2 for short. Under the right conditions, AAV-2 killed a variety of cancer cells such as breast and prostate cancers in a test tube. The important finding is that it did not kill normal cells--only cells growing abnormally. The hope is that the conditions can be replicated in humans to provide a treatment for cancer.

This is a very exciting study, although any conclusions would be very premature. What we may find is that we have systems in our body which can eradicate disease under the right conditions. The real test is finding what those conditions include, such as diet, exercise, stress management, and supplementation.

Bottom line: our immune system is a complex system that uses substances that are seemingly bad--such as free-radicals and viruses--to protect us against worse pathogens and diseases. That’s why balance and variety in what we eat and the supplements we take is so important. Focusing on a single nutrient may throw the system out of balance. Variety may be not only the spice, but also the key to life.

  1. Faqi AS, et al. Reproductive toxicity assessment of chronic dietary exposure to soy isoflavones in male rats. Reprod Toxicol. 2004;18(4):605-11.

  2. MS Kurzer. Hormonal Effects of Soy in Premenopausal Women and Men. J. Nutr. 2002; 132: 570S–573S.

  3. Raitt, MH et al. Fish Oil Supplementation and Risk of Ventricular Tachycardia and Ventricular Fibrillation in Patients With Implantable Defibrillators: A Randomized Controlled Trial. JAMA. 2005;293:2884-2891.

  4. Alam S et al. AAV2 downregulates P21WAF1 expression and induces apoptosis in an HPV31 positive cell line but not in normal keratinocyte lines. American Society for Virology Convention 2005. Abstract W30-11.
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