www.t-mag.com/articles/185soy.html
You can pick up the "Food" section of practically any local newspaper and see glowing reviews of the healthy attributes of soy protein, complete with yummy, Testosterone-lowering recipes. Likewise, the other weightlifting and bodybuilding mags still tout its benefits, and a week doesn't go by that we don't get a letter from some irate soy fan who ends up questioning our parentage. Given all that, we think that the topic deserves to be visited again and again until every man, woman, and child knows the truth. Oh, and make sure you read the letter that follows the article. It was written by two of the Food and Drug Administration's soy experts who attempted to stop FDA approval of soy. Turn on the news and its soy, read a diet book and you'll find soy, go to your local gym and a personal trainer will recommend soy. Well for starters it has many health benefits backed up by good science, it's inexpensive, it has a good track record in Asia, and the government has allowed a seal of approval to be stamped on food items that contain 625 grams of soy protein. In this article we'll uncover the darker side of supposedly innocent soy and show you why you might not choose to include it in your otherwise healthy diet. Many papers have exhorted the benefits of soy, but as the saying goes "if it sounds too good to be true, it probably is" fits soy better than anything else you might imagine. Science has shown soy, more importantly its phyto-estrogen components, namely genistein, has the ability to attach to estrogen receptor sites and through transcription, act as female hormones such as estradiol. This, in some cases, can have benefits so it's not strange that soy would receive some well-deserved attention. The problem with this attention is that individuals who have no need of soy, and even some to which soy could be hazardous, have started using it. Science is now beginning to see what this "benign" protein can do, though. This review will cover the negative effects that soy protein may have on fetal development of both males and females, hormonal balance in males of a pre-mature and mature age, and efforts of weight training individuals trying to increase fat-free muscle mass. Studies will be included of human and non-human species, both immature and mature in age. Only abstracts and full-length articles from peer reviewed journals will be referenced in this paper. Literature Both abstracts and journals were found through the PubMed database and in the local university library. Limits were set on searches such as "human only," "male," "female," "abstract only," and others. Key words used included "soy," "soy protein," "genistein," as well as "Testosterone production," "effects on Testosterone," and others. Finally, studies or points in favor of soy were not included, as countless papers have been written on its positive effects. Findings The largest concern scientists have about soy are its effects on sexual development of infants consuming soy-based formula. The data is startling, yet most concerns have fallen on deaf ears. One study showed that when manufacturer-suggested amounts of soy formula are fed to infants, the infants ingest a daily dose of approximately 3 mg of total isoflavones (ie genistein and daidzein) per kg of body weight, which is maintained at a fairly constant level between 0 and 4 months of age. Supplementing the diet of 4-month old infants with a single daily serving of soy-based cereal can increase their isoflavone intake by over 25%, depending on the brand chosen. This rate of isoflavone intake is much greater than that shown to alter reproductive hormones in adult humans. The available evidence suggests that infants can digest and absorb dietary phytoestrogens in active forms and neonates are generally more susceptible than adults to perturbations of the sex-steroid milieu. Another study assessed the effect of administering neonatal animals genistein in the amount of 4 mg per kg per day from days 2-18 of life. Administration of genistein significantly retarded most measures of pubertal spermatogenesis. Plasma FSH levels in the treatment groups changed in parallel to the spermatogenic changes (reduced when pubertal spermatogenesis retarded, increased when pubertal spermatoenesis advanced). In adulthood, the animals that were fed a soy-free diet in infancy and on, had significantly larger testes than controls fed a soy-containing diet. Of the animals that had neonatal treatment with genistein, a minority did not mate or were infertile. In concluding this article, the authors stated "the presence or absence of soy or genistein in the diet has significant short-term (pubertal spermatogenesis) and long-term (body weight, testis size, FSH levels, and possibly mating) effects on males." The developing fetus is uniquely sensitive to perturbation with estrogenic chemicals. The carcinogenic effect of prenatal exposure to diethylstilbestrol (DES) is the classic example. The carcinogenic potential of genistein, a naturally occurring plant estrogen in soy, has been shown in mice treated neonatally. In a study reported in the journal, Cancer Research, the incidence of uterine adenocarcinoma in 18-month-old mice was 35% for genistein and 31% for DES (diethylstilbestrol). This data suggests that genistein is carcinogenic if exposure occurs during critical periods of differentiation. The author admonished: "Thus, the use of soy-based infant formulas in the absence of medical necessity and the marketing of soy products designed to appeal to children should be closely examined." Finally, as far as soy and its effects on infants, hypothyroidism has been shown in infants receiving soy formula. The next major concern is genistein's estrogenic and anti-androgenic effects on adult male animals and humans. This effect was shown clearly in a study on adult male reproductive tracts. In intact adult male mice, genistein (25 mg per kg of body weight per day for only 9 days) reduced testicular and serum Testosterone concentrations and pituitary LH-content. These results suggest that genistein -- in doses comparble to those that would exist in a soy-based diet -- induced typical estrogenic effects. A second study showed plasma Testosterone and androstenedione levels were significantly lower in the animals fed a phytoestrogen-rich diet compared with animals fed a phytoestrogen-free diet. These results indicated that consumption of dietary phytoestrogens over a relatively short period can significantly alter plasma androgen hormone levels. In a study of Japanese men, total and free Testosterone concentrations were inversely correlated with soy product intake. In rats that were fed a diet in which casein was replaced by soy protein isolate/isoflavones, both serum levels of Testosterone and weight of testes were significantly reduced. Finally, in a study that may correlate more strongly with weight-training athletes, diets that consist of inferior protein (soy) may increase protein breakdown in skeletal muscle. Pigs were fed diets based on soybean-protein isolate or casein for 15 weeks. A transient rise in the level of cortisol was shown to occur in the postprandial phase only in the soybean group. The authors of this study concluded: "These data suggest that the inferior quality of dietary soybean protein induces hormonally-mediated upregulation of muscle protein breakdown for recruitment of circulatory amino acids in a postabsorptive state." In other words, soy intake induces the body to break down muscle protein in order for it to get its required amino acids. Conclusions At this time it's recommended that: Infants not be given soy-based formula until more research is done on safety in regard to neonatal sexual development and its effects on thyroid suppression. Men not use soy products until more research is done on its effects on Testosterone and testicular function. Weight-training individuals who hope for increased muscle hypertrophy not use soy protein until more research is done on effects of decreased Testosterone, increased cortisol levels and muscle protein breakdown. Scientists Protest Soy Approval in Unusual Letter Scientists' Letter DEPAR...
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