Mike, I like PJW's views....on politics and current affairs....but this vegan attack thing by conservatives and libertarians is unwise. The science is way too nuanced for such videos.
The situation regarding soy's effect on testosterone levels is not settled.
Below are several highly regarded papers on the matter, all finding soy in even moderately high quantities has not been shown to reduce testosterone.
this paper regarded as very strong evidencehttps://www.ncbi.nlm.nih.gov/pubmed/19524224
Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis.
Hamilton-Reeves JM1, Vazquez G, Duval SJ, Phipps WR, Kurzer MS, Messina MJ.
Fertil Steril. 2010 Aug;94(3):997-1007.
RESULT(S): No significant effects of soy protein or isoflavone intake on T, SHBG, free T, or FAI were detected regardless of statistical model.
CONCLUSIONS: The results of this meta-analysis suggest that neither soy foods nor isoflavone supplements alter measures of bioavailable T concentrations in men
__________________________________________________https://www.ncbi.nlm.nih.gov/pmc/articl ... 91152a.pdf
Hormones and diet: low insulin-like growth factor-I but
normal bioavailable androgens in vegan men
NE Allen, PN Appleby, GK Davey and TJ Key
British Journal of Cancer, (2000) 83(1), 95–97
Mean serum insulin-like growth factor-I was 9% lower in 233 vegan men than in 226 meat-eaters and 237 vegetarians (P= 0.002). Vegans had higher testosterone levels than vegetarians and meat-eaters, but this was offset by higher sex hormone binding globulin, and there were no differences between diet groups in free testosterone, androstanediol glucuronide or luteinizing hormone.
13%> meat eaters, 8% >vegetarians
6%>meat eaters, 7%>vegetarians
The vegan advantage is accounted for by higher levels of SHBG (sex hormone binding globulin).There's no difference in free testosterone between groups.
vegan men IGF-1 9%<meat eaters
Fertil Steril. 2010 May 1;93(7):2095-104
Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence.
OBJECTIVE: To critically evaluate the clinical evidence, and when not available, the animal data, most relevant to concerns that isoflavone exposure in the form of supplements or soy foods has feminizing effects on men.
DESIGN: Medline literature review and cross-reference of published data.
RESULT(S): In contrast to the results of some rodent studies, findings from a recently published metaanalysis and subsequently published studies show that neither isoflavone supplements nor isoflavone-rich soy affect total or free testosterone (T) levels. Similarly, there is essentially no evidence from the nine identified clinical studies that isoflavone exposure affects circulating estrogen levels in men. Clinical evidence also indicates that isoflavones have no effect on sperm or semen parameters, although only three intervention studies were identified and none were longer than 3 months in duration. Finally, findings from animal studies suggesting that isoflavones increase the risk of erectile dysfunction are not applicable to men, because of differences in isoflavone metabolism between rodents and humans and the excessively high amount of isoflavones to which the animals were exposed.
CONCLUSION(S): The intervention data indicate that isoflavones do not exert feminizing effects on men at intake levels equal to and even considerably higher than are typical for Asian males
The Science of Soy: What Do We Really Know?
Julia R. Barrett
Environ Health Perspect. 2006 Jun; 114(6): A352–A358
In advising caution in feeding infants soy formula, several groups cite a study led by Richard Sharpe at the Centre for Reproductive Biology in Edinburgh, Scotland. The study, published in Human Reproduction in July 2002, compared infant marmosets fed cow’s milk–based formula with others that were fed soy-based formula. The soy-fed marmosets had comparatively lower testosterone levels and higher numbers of Leydig cells per testis. However, a follow-up study published in April 2006, also in Human Reproduction, indicated no obvious effects on reproduction.