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Ralph Teller

Soy Lowers Men's Testosterone Levels and Increases Estrogen

by Ralph Teller

Soy Increases Estrogen Levels causing a Decrease in Testosterone Levels in Men

Testosterone is a hormone that is predominant in men. Testosterone plays an important role in men's health. Testosterone is responsible for (i) muscular development, (ii) libido, and (iii) bone development. Testosterone also plays a role in red blood cell production. There are a number of natural things men can do to help maintain and increase testosterone levels. See How to Increase Testosterone Naturally.

Soy contains compounds with estrogen like properties that increase estrogen levels in men causing a decrease in testosterone levels. Phytoestrogen compounds found in soy can interfere with both hormone levels and normal hormone function.

Doctors at the University of Medicine and Dentistry of New Jersey/Robert Wood Johnson Medical School examined the impact of soy protein powder on testosterone levels in male participants. The male participants consumed two scoops of soy protein powder, which contained 56 g of soy, daily for 28 days. Researchers reported in the April 2007 issue of Cancer Epidemiology, Biomarkers & Prevention that subjects experienced decreases in testosterone levels. Testosterone levels increased within two weeks after discontinuing soy protein powder use.

Soy not only can lower a man's testosterone levels, but has soy has also been found to lower men's sperm count. US researchers have found that Eating a half serving a day of soy-based foods could be enough to significantly lower a man's sperm count.

The study was the largest in humans to look at the relationship between semen quality and a plant form of the female sex hormone estrogen known as phytoestrogen, which is plentiful in soy-rich foods. "What we found was men that consume the highest amounts of soy foods in this study had a lower sperm concentration compared to those who did not consume soy foods," said Dr. Jorge Chavarro of the Harvard School of Public Health in Boston, whose study appears in the journal Human Reproduction.

Soy has become a Filler in many Foods

Warning! Soy has become a filler for many products, including many so called 'health' or 'protein' bars, drinks and shakes.

Read food content labels before you buy and have your mom, wife or girlfriend read them before they buy for you. Products that contain soy should be avoided by men.

Guys, the indications are that soy reduces testosterone. Why take that risk?!

Soy, because it encourages the production of estrogen, also can inhibit production of the Growth Hormone. See What Stimulates and Inhibits the Growth Hormone

Male Athletes Should Avoid Soy as a Protein Source

Soy Lowers Iron IntakeMale Athletes should also note that soy protein is a rich in phytic acid which reduces mineral and trace element absorption. Studies assessing markers of Iron status show that supplementing isoflavone rich soy protein isolate reduces Iron status by more than 7%. In contrast, the same study also showed that a whey protein supplement actuall increased iron status by more than 9%.

Iron is essential to red blood cell production essential for oxygen transport and to maintain muscle performance, yet many athletes suffer with low iron stores. Symptoms of low Iron include shortness of breath, poor exercise performance and slow recovery after exercise. It is clear that supplements containing soy proteins could bring about iron deficiency and impair exercise performance. For natural sources of Iron see Natural Food Sources of Iron.

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Articles on Increasing Testosterone

PublicationSoy Products & Testosterone Levels, Brandon Dotson, Livestrong

PublicationDoes Soy Affect Your Hormones?, Stephanie Chandler, Livestrong

PublicationMen With High Testosterone May Live Longer, Metaba.Net

Low Testosterone Linked to Increase Risk of Death, Professor Kay-Tee Khaw, University of Cambridge School of Clinical Medicine

Soy Based Foods May Lower Sperm Count, Julie Steenhuysen, Reuters

PublicationSoy Formula Can Reduce Testosterone Levels, Dr. Richard Sharpe, Senior scientist at the Medical Research Council Human Reproductive Sciences Unit in Edinburgh

PublicationEffect of Exercise on Serum Sex Hormones in Men: A 12-Month Randomized Clinical Trial , Vivian N. Hawkins; Karen Foster-Schubert, Medicine and Science in Sports and Exercise

PublicationHighest Testosterone Levels Equal Lowest Risk for CV Events, Lisa Nainggolan, Medscape, Heartwire

PublicationEffects of Vitamin D Supplementation on Testosterone Levels in Men, S. Pilz, Medical University of Graz, Austria, National Institute of Health

PublicationSoy Linked to Low Sperm Count, HealthDay News: Eating half a serving of soy food a day lowers sperm concentrations and may play a role in male infertility, particularly in obese men, Harvard University researchers report. The reason for this relationship between soy and sperm count isn't clear. However, researchers speculate that soy increases estrogen activity, which may have a negative affect on sperm production and also interfere with other hormonal signals.

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