Soy, dairy, and male fertility

This study looked at how diet relates to sperm quality. It found that men who eat soy are less likely to have low sperm count, and that men who include milk in their diets have better sperm quality.

In roughly half of the heterosexual couples experiencing infertility, the male partner has low sperm count or quality. Furthermore, several review studies have found that sperm count has declined since the 1940s in Europe, America, and other Western areas. Diet may play a role in low sperm count and quality.

Phytoestrogens are compounds found in plants that act like reproductive hormones in the human body. Soy is a particularly rich source of phytoestrogens, but they are also found in other plant sources such as flax seeds and sesame seeds. It is not clear whether eating soy influences sperm quality.

This study included 1907 men of couples with infertility. All men gave sperm samples and completed questionnaires of diet.

How often men ate fish, poultry, and fruit was not related to sperm count or quality. Men who ate at least 3.7 servings of vegetables per day had a trend toward less low sperm count (22% lower odds). Men who ate red meat at least three times a week tended to have low sperm count (13% higher odds) but were significantly less likely to have abnormally shaped sperm (33% lower odds).

Men who did not drink milk were more likely to have low sperm count (71% higher odds) and abnormally shaped sperm (85% higher odds) than men who used full-fat milk. Men who ate more soy than average had a lower risk of low sperm count (25% reduced odds).

This study found that dairy and soy consumption may influence sperm quality.

Because people have many dietary habits, it is difficult to tease out the effect of a single habit. Most of the correlations in this paper were not significant. Larger studies are needed.