Category: Soy

 

I’ve read several of Dr. Andrew Weil’s books. I don’t agree with everything he has to say, but I like to read his opinions as they seem less biased. Dr. Andrew Weil is a medical doctor (M.D.) and popular health writer with an interest in alternative medicine. Dr. Weil is just as likely to endorse a conventional medical treatment as give a positive ( or negative ) review of an alternative treatment.

Here is what he has to say in an article about eating foods made from soy beans:

I’m aware of Internet paranoia on the subject of soy and the contention that only fermented soy is safe to consume. That is simply not true. Some of the best forms of soy – edamame, tofu and soy nuts – are unfermented and are much more likely to help you than hurt you.

Claims that unfermented soy foods (such as tofu and soy milk) contain toxins that block the action of enzymes needed to digest protein, and that these toxins cause pancreatic enlargement, cancer and stunted growth in animals are misleading. While soy does contain substances (trypsin inhibitors) that may adversely affect the pancreas in animals, there’s no solid evidence that they cause similar problems in humans. Furthermore, trypsin inhibitors are found in all of the vegetables of the cabbage family as well as in beans other than soy.

Other concerns about soy safety focus on the following issues:

• Breast cancer: Here, the idea is that high levels of isoflavones, active ingredients in soy that behave like estrogen in the body, may increase the risk of breast cancer. While high levels of isolated isoflavones may do so, it appears that the total mix of weak plant estrogens in soy protects the body’s estrogen receptors. This protection may reduce the effects of excess estrogen exposure from such external sources as meats and dairy products from hormone-treated cows as well as artificial chemicals and industrial pollutants that act as foreign estrogens. Japanese women whose diets contain a lot of soy foods have only one-fifth the rate of breast cancer that occurs among Western women.
• Thyroid Problems: Excess consumption of soy can affect thyroid function, but only if you have a thyroid disorder to begin with or if you’re not getting enough iodine in your diet (a rare deficiency in the United States). If you take medication for hypothyroidism (low thyroid), and are concerned about the effect of eating two daily servings of soy, have your thyroid levels checked regularly.
• Mineral absorption: The idea that substances in soy called phytates block absorption of essential minerals is also in circulation, but there is no scientific data suggesting that soy consumption leads to mineral deficiency in humans.

All told, based on the evidence to date, I see no reason to worry about eating soy foods, whether fermented or not. I still recommend consuming one to two servings of soy per day, an amount equivalent to one cup of soy milk, or one half cup of tofu, soy protein (tempeh) or soy nuts.

Andrew Weil, M.D.

Many men are wary of using soy due to urban legends about it lowering testosterone.

This study observed subjects using soy protein powders – highly concentrated soy derivatives – over 12 weeks and found this not to be the case. Most soy foods don’t have any where near the concentrations of controversial substances as found in these kinds of derivatives.

Effect of protein source and resistance training on body composition and sex hormones

Methods
For 12 weeks 20 subjects were supplemented with 50 g per day of one of four different protein sources (Soy concentrate; Soy isolate; Soy isolate and whey blend, and Whey blend only) in combination with a resistance-training program. Body composition, testosterone, estradiol and sex hormone binding globulin (SHBG) were measured at baseline and week 12.

Results
Protein supplementation resulted in a significant increase in lean body mass independent of protein source (0.5 ± 1.1 and 0.9 ± 1.4 kg, p = 0.006, p = 0.007). No significant differences were observed between groups for total and free testosterone, SHBG, percentage body fat, BMI or body weight. The Testosterone/Estradiol ratio increased across all groups (+13.4, p = 0.005) and estradiol decreased (p = 0.002). Within group analysis showed significant increases in the Testosterone/Estradiol ratio in soy isolate + whey blend group (+16.3, p = 0.030). Estradiol was significantly lower in the whey blend group (-9.1 ± 8.7 pg/ml, p = 0.033).

Conclusion
This investigation shows that 12 week supplementation with soy protein does not decrease serum testosterone or inhibit lean body mass changes in subjects engaged in a resistance exercise program.