I remember we discussed this shortly a while ago, but also read a new study done independently of the soy industry shows some fairly good evidence that high consumption of soy products and products derived from the soy bean by men in quantity can actually have a negative impact on their sperm count. 

The thought is that the isoflavone count in the soy helps to lessen the sperm production because it has a phytoestrogenic type effect on the male body, which in essence counteracts the male hormone in their body which is responsible for higher sperm counts and healthier sperm production (the male hormone is testosterone, or an androgen, which are male hormones).

The study links soy consumption in men to not only less sperm concentration in semen, but also may be linked to lower sperm quality.  The soy industry is saying that this evidence does not however, match with the data they’ve collected on soy’s effect on male sperm count.  I guess this means that men who are vegetarians may want to get other things to replace their protein, such as beans and legumes and other forms of protein that don’t involve animal fat. 

Only if they’re trying to have a child though probably.  If not, they probably don’t have to worry about consumption of soy.  Also, if you consume it in moderation I’m sure it would be minimally harmful.  The study did mention something abotu the fact that the study subjects did ingest a lot of soy, maybe more than usual.  However, if you are a vegetarian it is easy to consume soy in large portions and several times a day, since it is a palatable substitute for meats and many vegetarians really like it.