"You know, there are men who don’t want to drink soy milk because they have an irrational fear of phytoestrogens—even though soy does not have feminizing effects on men. Yet they’re perfectly willing to drink cow’s milk, which has actual estrogen estrogens in it! Within one hour of the milk hitting their intestines, estrogen levels go significantly up, and testosterone levels go significantly down."
"If you take men on a high-protein diet—”meat, fish, poultry, egg white[s]”—and switch them to a high-carb diet of “bread, vegetables, fruit, and [sugary junk,]” their cortisol levels drop about a quarter within ten days. At the same time, their testosterone levels shoot up by about the same amount. High-protein diets suppress testosterone. That’s why if you take men eating plant-based diets, and have them start eating meat every day, their testosterone levels go down, and actually some estrogens go up.
That’s why bodybuilders can get such low testosterone levels. It’s not the steroids they’re taking. If you look at natural bodybuilders, who don’t use steroids, 75% drop in testosterone levels in the months leading up to a competition. Testosterone levels cut by more than half; enough to drop a guy into an abnormally low range. It’s ironic that they’re eating protein to look manly on the outside, but it makes them less and less manly on the inside. And, from an obesity standpoint, in general, a drop in testosterone levels may increase the risk of gaining weight—gaining body fat."
This was my understanding as well (I'm a big fan of nutrition facts), but I think I misunderstood the parent. I thought they were saying the opposite – that a vegan diet would lead to lower testosterone.
