As a guy, I don’t want hear that anything is bad for the boys, but new research by the Harvard School of Public Health
insists that even eating half a serving of soy food a day lowers sperm concentrations.
The study appears in the journal of Human Reproduction
. Here’s the abstract via PubMed
BACKGROUND: High isoflavone intake has been related to decreased fertility in animal studies, but data in humans are scarce. Thus, we examined the association of soy foods and isoflavones intake with semen quality parameters.
METHODS: The intake of 15 soy-based foods in the previous 3 months was assessed for 99 male partners of subfertile couples who presented for semen analyses to the Massachusetts General Hospital Fertility Center. Linear and quantile regression were used to determine the association of soy foods and isoflavones intake with semen quality parameters while adjusting for personal characteristics.
RESULTS: There was an inverse association between soy food intake and sperm concentration that remained significant after accounting for age, abstinence time, body mass index, caffeine and alcohol intake and smoking. In the multivariate-adjusted analyses, men in the highest category of soy food intake had 41 million sperm/ml less than men who did not consume soy foods (95% confidence interval = -74, -8; P, trend = 0.02). Results for individual soy isoflavones were similar to the results for soy foods and were strongest for glycitein, but did not reach statistical significance. The inverse relation between soy food intake and sperm concentration was more pronounced in the high end of the distribution (90th and 75th percentile) and among overweight or obese men. Soy food and soy isoflavone intake were unrelated to sperm motility, sperm morphology or ejaculate volume.
CONCLUSIONS: These data suggest that higher intake of soy foods and soy isoflavones is associated with lower sperm concentration.
Relax, don’t freak out just yet. “It's way too early to say stop eating soy foods. It's not time to worry about whether you're eating too much soy. There's not enough information to conclusively say that,” lead researcher Dr. Jorge Chavarro, M.D.
, a research fellow at the Harvard School of Public Health
, told Steven Reinberg of HealthDay News
And just to be sure, I asked Dr. Fuhrman for his thoughts on this study. Here’s what he had to say:
This study showed that high levels of processed soy foods, not edamame or unprocessed soy beans, may lower sperm counts in obese men.
The higher intake of soy foods, lowered sperm counts, but the counts were still in the normal range. Obesity increases the body’s estrogen production, and the extra pro-estrogenic effects of soy apparently was enough to reduce sperm levels, in these overweight men whose estrogen levels were already somewhat elevated due to their heightened body weight.
When most people think soy, they think soy ice cream or soy “meat” products. They forget about edamame beans. Edamame beans are nutritional rock stars! From Wikipedia
, check this out:
Fiber-rich carbohydrates such as edamame help prevent mood fluctuations by keeping blood-sugar levels steady. Edamame also contains protein, which further helps stabilize blood sugar, and omega-3 fatty acids.
Edamame beans contain higher levels of abscissic acid, sucrose, protein than other types of soybean. They also contain a high source of vitamin A, vitamin B and calcium.
And besides, we already know that processed soy foods are NOT something you want to base your diet around. Dr. Fuhrman explains:
Studies have shown soy's beneficial effects on cholesterol and other cardiovascular risk factors. However, there is no reason not to expect the same results from beans of any type--it's merely that more studies have been done on soy than on any other beans. There are numerous studies indicating that soybeans are rich in various anti-cancer compounds such as isoflavones. Most beans are rich in these beneficial anti-cancer compounds, and many different flavonoids with anti-cancer effects are found in beans of various color. I always recommended the consumption of a broad variety of phytochemical-rich foods to maximize one's health. Beans are no exception--try to eat different types of beans, not just soy.
You should be aware that soy nuts, soymilk, and other processed soy products do not retain many of the beneficial compounds and omega-3 fats that are in the natural bean. The more the food is processed, the more the beneficial compounds are destroyed. Remember, though, tofu and frozen or canned soybeans are a good source of omega-3 fat and calcium.
Most of the processed soy products can be tasty additions to a plant-based diet, but they are generally high in salt and are not nutrient-dense foods, so use them sparingly. In conclusion, the soybean is a superior food, containing the difficult-to-find omega-3 fats. Beans in general are superior foods that fight against cancer and heart disease, which is why you will benefit from using a variety of beans in your diet.
So I think the real point to take away from this study is processed soy foods are not health-promoting and being overweight or obese lowers male fertility. For more on that, read: Obese men have less semen, more sperm abnormalities, and should lose weight before trying for a baby