There is evidence that doing "manly stuff" for men, like hunting, increases testosterone production. Also a lot of food like red meat, eggs etc increases testosterone production. Something vegans don't eat.
It is important for all aspects of mens health and well being, especially when you get older.
“Vegans had 13% higher T [testosterone] concentration than meat-eaters and 8% higher than vegetarians.” Not only did vegan men have as much testosterone as meat eaters, they actually have 13% MORE of this manly hormone. On the flip side, too much testosterone can be a bad thing because it leads to higher levels of IGF-I – a risk factor for certain cancers. Surprisingly, the report also found this: “Vegan men had on average 9% lower IGF-I levels than meat-eaters.”