An article in the journal Fertility and Sterility reports on a study that looked at sperm counts and sperm motility in vegetarians: Decreased sperm concentration and motility in a subpopulation of vegetarian males at a designated blue zone geographic region. The “blue zone” referred to is one of the areas in the world in which longevity is generally higher than normal.
Blue Zone regions identify demographic areas of the world where people have long life spans. This study was conducted in a Blue Zone region where vegetarians consume 3.5 servings of meat substitutes per week. There is a paucity of information on the association between vegetarian diet and male fertility. The premise was that semen parameters were affected by diet. The objective was to compare sperm characteristics of male infertility patients on vegetarian and non-vegetarian diets.
The results were not good for male vegetarians: lower sperm counts and motility. The authors attribute the decrease in sperm counts to increased consumption of soy-based meat substitutes, although that seems to me not supported by the data. It may have some basis in reality, but unless the study looked at the amount of soy consumed and compared this to vegetarians who did not consume soy, then there’s no basis for saying this.
For example, vegetarianism leads to high levels of homocysteine in the blood, which is considered causative of cardiovascular disease. In this study, the authors report that “levels of cysteine and glutathione were significantly decreased in the study [vegetarian] group, demonstrating inhibition of the trans-sulfuration pathway”. Low glutathione can be improved with n-acetylcysteine, which improves semen volume and sperm motility. Therefore, it seems completely plausible that vegetarianism in itself, even without soy, could alter sperm parameters for the worse.
Vegetarianism results in suboptimal health in many ways, and this latest study is another demonstration of that. For men in particular, vegetarianism affects fertility and virility both, so beware.