One of the most common questions that a couple attempting to conceive will ask is, “What can I do to enhance my fertility/chance of conception?” Exposure of testes to excessive heat, whether recreational (hot tubs, saunas/Jacuzzis) or occupational (welders, bakers, sedentary jobs with extensive seating [drivers, office workers]) should be limited because heating of the testes decreases sperm production.
Patients are also often interested in the relationship between exercise and male fertility. Although a sedentary lifestyle may impair sperm production, it’s not clear how much exercise is helpful. It is evident that men who have excessive physical activity, where exercise extends more than 90 minutes per day (studied in runners training for marathons) may actually have lower sperm production than men with more moderate activity.
The nutritional choices of a man are worth considering. Fortunately, this is an area where some research has been done at least a few rationale recommendations can be made. We know that there are clear effects of male obesity on sperm production and fertility. An overweight male has several things going against him from a fertility standpoint. First of all, the extra fat on the thighs and genital region of an obese male cause the testes to be closer to body temperature, heating the testes (that need to be at least 4 degrees cooler than the rest of the body) and decreasing sperm production. In addition to the local heat effects of obesity, the extra fat affects hormone balance in a male. Testosterone (the major male hormone) is excessively converted to estrogens (female hormones) in obese males, causing lower circulating testosterone levels. This excess conversion of hormones in fat can be treated by medications (called aromatase inhibitors) that block this conversion of the testosterone to estrogens by the aromatase enzyme. Weight loss will eventually change some of the effects of obesity, but acute, sudden weight loss may produce a “starvation mode” whereby the body responds to the apparent lack of nutrients by decreasing stimulation of the testis, reducing sperm production. So, although weight loss will benefit a man’s fertility (not to mention overall health!) in the long term, patients should avoid excessively aggressive attempts at weight loss.
What nutritional changes can the “non-obese” male make to enhance sperm production? The answer is not completely clear. Some anti-oxidant materials (selenium, lycopenes, etc.) are known to protect sperm from oxidative damage, but there is little or no fertility benefit that has been demonstrated to occur from dietary supplementation with these agents. One of the problems with studies that involve dietary manipulation is that most of the patients “treated” with a dietary change have not been compared to “control” patients, i.e., men who receive no specific intervention. This “control arm” is critically important because the most commonly analyzed measure of a change in fertility (semen analysis) is highly variable regardless of any intervention. So, unless a “control arm” is analyzed in a study, the “benefit” of an intervention may be due to random chance rather than a specific improvement in fertility from the treatment provided.
So, what is the ideal diet for a man interested in optimizing his fertility? Unfortunately, we don’t really know. Cross-sectional studies have shown that men who have a diet richer in fruits and vegetables than meats and fats tend to have higher sperm production. So, judicious enhancement of fruits & vegetables in diet is worthwhile. The type of vegetables may be important to consider as well. Soy-based diets that are often recommended for overall health may be bad for sperm production. Soy is a very weak estrogen, and estrogens given to men tend to decrease testosterone production and stimulation of the testes to produce sperm, so it is not surprising that dietary soy can decrease a man’s fertility. The extensive intake of meats may also have some of its adverse effects through hormones. In the United States, antibiotics and hormonally based agents are often given to animals to boost meat development (and milk production.) Therefore, diets rich in meats may result in exposure of men to some antibiotics that adversely affect sperm production, as well as weak or potent (e.g., zearalone) estrogens that impair sperm production.
In summary, diet and lifestyle can have an effect on sperm production. Men interested in fertility should consider enhancing the fruit and vegetable content of their diets, avoiding excess heat and having moderate but not excessive physical activity.