Uh-oh! Male vegans and those who are lactose intolerant might want to avoid soy if they’re trying to have children:

“What we found was men that consume the highest amounts of soy foods in this study had a lower sperm concentration compared to those who did not consume soy foods,” said Dr. Jorge Chavarro of the Harvard School of Public Health in Boston, whose study appears in the journal Human Reproduction.
“It was a relatively large difference,” Chavarro said in a telephone interview.
[…]
The difference was striking. Men in the highest intake category had 41 million sperm per milliliter less than men who ate no soy foods. A normal sperm count ranges from 80 million and 120 million per milliliter, and a sperm count of 20 million per milliliter or below is considered low.

I guess this can work in reverse, add soy to your diet if you want to avoid being a father 🙂
It just adds another layer of complexity to the whole vegan diet. I know you guys who do it probably don’t have a problem figuring out your protein and calcium intake but I had a hard time figuring it out for Sarah when she was flirting with trying a vegetarian diet. She saw how complicated it was and decided not to do it. It would have been even more complicated if she wanted to do a vegan diet.