Depending on who you ask, soy products are either a great boon to mankind or the worst crap on Earth. Those who advocate the use of soy in its various forms, including soy protein, tofu and soy flour, point to many studies that show protective effects. A study of Seventh Day Adventist (a religious movement) men, for example, associated drinking soy milk with a 70 percent reduction in prostate cancer.
In vitro, or isolated-cell, studies show that the primary active ingredients in soy, isoflavones, can block the growth of prostate cancer cells. Soy also appears to offer protective effects against estrogen-related cancers in women, such as breast and uterine cancers. Incidence of these types of cancer is lower in Asian countries, where soy intake is higher.
Those who shun soy in any form point out that soy isoflavones are phytoestrogens, or plant estrogens. Although the naturally occurring estrogen like compounds have only about 1/10,000 the potency of direct estrogen, they can still interact with hormones in the body. In fact, that’s the main controversy about soy: It may exert estrogen-like effects in men and could interfere with androgen, or testosterone, activity.
Although considered a complete protein, soy is naturally low in the essential amino acid methionine. Companies that make soy products circumvent that problem by adding methionine, which makes soy protein compare favorably to milk and egg proteins. Like whey protein, it’s also rich in the beneficial branched chain amino acids.
Those pesky soy isoflavones, though, may still interfere. Studies examining the effects of soy protein on testosterone are equivocal, with some indicating an interference and others showing no effect.
In the latest study to examine the issue, 35 men, aged 20 to 40, got either a milk protein isolate or one of two different types of soy protein, one having a high isoflavone content and the other having a low isoflavone content. After 57 days, those getting the soy protein showed lower levels of DHT than those in the milk group.
DHT is testosterone’s evil twin. It has little or no anabolic effect in muscle but promotes prostate enlargement and cancer, acne and male-pattern baldness. Soy lowered DHT without influencing 5-alpha reductase, the enzyme that converts testosterone into DHT.
Only the low-isoflavone soy lowered total testosterone, and that occurred at the 29th day of the study. Free, or active, testosterone was also lowered but not to a significant degree. The low-isoflavone soy also increased DHEA-S, the circulating form of the adrenal androgen DHEA in the body. That may have affected the increased estrogen level seen in the low-isoflavone group at day 5, since DHEA is usually converted into estrogen in younger men.
Collectively, these results don’t paint a pretty picture of the effects on young men who use soy. The mysterious aspect of the study, which the authors didn’t explain, was why only the low-isoflavone soy produced those hormonal effects. Since the isoflavones are considered the active components of soy that affect hormonal activity, the higher-isoflavone soy should have produced the greatest effects, but that wasn’t the case. There may be something else in soy that affects hormones.
Source: Ironman
Ed. Note: Soy, once only found in cheap protein products, has now become a key ingredient in many big name sports nutrition shakes, meal replacements and bars, as it is stable over many months, has good mouth texture and is very cheap. But is there any real scientific evidence to support the use of soy in these products? Or is it just a cheap trick to make high protein claims and 'tasty' bars, whilst not giving a damn about their customers? I recommend you start checking the ingredients of your protein drink, shakes and bars and look for those that only contain milk proteins and whey. For the whole story, read the article we were asked NOT to publish.
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