Diet and male fertility: What helps, what hurts

Papers examining the effects of diet and substance use on male fertility presented at the recently concluded American Society for Reproductive Medicine annual meeting in Honolulu may appear to provide conflicting findings, but an expert in andrology says the observational studies don’t tell the complete story.

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One study found that, while consumption of fruits and vegetables with high levels of pesticide residue can affect sperm quality, in vitro fertilization (IVF) rates are better for those men consuming more fruits and vegetables overall. A second study showed that vegetarians have significantly poorer sperm concentration and motility than non-vegetarians. In a third study, authors reported that infertile men who smoke tobacco are more likely to experience sexual or erectile dysfunction, but those who drink alcohol are less likely to report sexual or erectile problems.

A fourth paper suggests high male caffeine consumption lowers couples’ chances of achieving a clinical pregnancy, while male alcohol consumption appears to enhance their chances.

“While the results of some studies presented at the meeting seem to be contradictory, it is important to remember that observational studies often can't tell the whole truth,” said Craig S. Niederberger, MD, of the University of Illinois, Chicago. “A more rigorous scientific approach would include randomly assigning people to diets-what scientists call prospective randomization-and seeing what happens.”

Ethical considerations would preclude conducting such a study involving toxic substances such as tobacco and pesticides, he pointed out.

“So we're left with a basic rule of thumb: if it's healthy for other parts of the body, it's probably good for reproduction, too,” said Dr. Niederberger, a member of the Urology Times Editorial Council.

Next: High-residue fruit/vegetable consumption examined

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In the first study, a prospective cohort study from the Massachusetts General Hospital in Boston, 155 men seen at a fertility center between April 2007 and June 2012 completed a food frequency questionnaire. The different fruits and vegetables reported in their diets were noted for having high or low pesticide residue based on USDA reports. Each participant’s intake of pesticide residues was calculated and the range of intake was divided into quartiles.

The men’s total intake of fruits and vegetables and of low-residue fruits and vegetables was found to be unrelated to semen quality, but men in the top quartile of high-residue fruit/vegetable consumption had a 70% lower motile sperm count and 64% lower number of normally shaped sperm than men in the lowest quartile of high-residue fruit/vegetable consumption.

When 105 of the participants and their partners were treated with IVF, the researchers found that those with a greater total fruit and vegetable intake, which included more low-residue fruits and vegetables, had better fertilization rates with conventional insemination, but not with intracytoplasmic sperm injection.

In a retrospective study from Loma Linda University School of Medicine in Loma Linda, CA, results from semen analyses conducted between 2009 and 2013 on 26 vegetarians, five vegans, and 443 non-vegetarians were compared. Vegetarians had significantly lower average sperm concentrations (51 million/mL vs. 70 million/mL) than non-vegetarians and lower average sperm motility (33% vs. 58%), although their results were not classified in the infertile range. Vegans’ results were similar to vegetarians.

There was no difference in sperm progression or the results of sperm function and DNA integrity tests between the groups. All the groups’ sperm morphology fell into the normal range. While more research is needed, study authors postulate that estrogenic compounds and/or chemical residues in the vegetarians’ diets could be a cause for poorer sperm parameters.

In the third paper, researchers from the University of Rochester Medical Center in Rochester, NY examined survey results in 753 male infertility clinic patients who were asked about their drinking and smoking habits and their sexual health and satisfaction. Their average age was 35 years, 16% used tobacco, and 73% used alcohol.

Based on their scores on the International Index of Erectile Dysfunction, 8.4% of smokers had moderate to severe erectile dysfunction. Smokers were more likely to be unsatisfied with sex and had much less confidence than non-smokers in their ability to get and keep an erection and complete sexual intercourse.

Conversely, drinkers reported better sexual function than teetotalers. Men who did not consume alcohol were more likely to report deficiencies in their erections and ability to complete intercourse. However, there was no difference in sexual satisfaction reported by drinkers and non-drinkers.

In a related study, Massachusetts General Hospital researchers analyzed data from men who underwent IVF between 2007 and 2013 and provided information on their pre-treatment diet, including alcohol and caffeine. Data were analyzed, adjusting for male and female age and BMI, infertility diagnosis, male smoking, male nutrient intake, and female caffeine and alcohol intake. Couples with male partners whose caffeine intake was in the study’s highest range (>265 mg daily) were only half as likely to have a clinical pregnancy as couples where the male consumed less than 88 mg of caffeine a day.

For couples whose male partner consumed alcohol, the chances of clinical pregnancy increased with consumption levels. 

“The human organism is complex and substances we inhale and imbibe have systemic effects beyond the stimulation the user is seeking,” ASRM President Rebecca Z. Sokol, MD, MPH said. “These studies provide new information that can help men make healthy choices for themselves, their partners, and their future children.”

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