June 28, 2019
A Western junk food diet — high in processed and red meats, refined grains, chips, and sweets — is associated with lower sperm count and overall impaired testicular function, according to a talk given at the annual conference of the European Society for Human Reproduction and Embryology that is being held in Vienna this week.
The talk is based on an unpublished study conducted by American, Dutch, and Danish researchers, who also found that a diet high in fish, chicken, vegetables, fruit, and water is associated with improved testicular function.
The findings add to a growing body of research examining the decline in sperm counts over the past 50 years and identifying lifestyle and diet as possible determinants of sperm quality.
"Sperm count has been declining in the Western countries over the past few decades, and determining the risk factors for this is crucial," the authors write in the study abstract. "Coinciding with the decline in sperm count has been a decline in diet quality."
The authors analyzed data collected over a span of 9 years from nearly 3000 Danish men. The men's diet, semen quality, hormone levels, and lifestyles were recorded during a medical examination conducted before compulsory military service.
The potential recruits' eating habits were then categorized into four different groups: the "Western" pattern, consisting mainly of junk food and snacks; the "Prudent" pattern, consisting of fish, chicken, and fresh produce; the "Smørrebrød" or Scandinavian pattern, characterized by cold processed meats, whole grains, and dairy; and the "Vegetarian" pattern. Of these four groups, men who adhered to the "Prudent" pattern consistently had higher sperm counts, lower estradiol levels (P trend = .001), and higher SHBG (sex hormone binding globulin) concentrations (P trend = .04). Men whose diets followed the "Western" pattern had lower inhibin-B levels (P trend = .006) and higher free testosterone concentrations (P trend < .0001).
The authors noted that nothing beyond correlation can be inferred from the results because of the nature of the study: "This was a cross-sectional study, which limits our ability to determine causality," they write.
"This is an important talk because we know that male reproductive health is declining year by year," said Albert Salas-Huetos, PhD, a postdoctoral fellow in urology and andrology at the University of Utah, in Salt Lake City. "The most recent meta-analyses say that in the last 50 years, this decline has been of about 40% in sperm count and sperm concentration."
The study is the first of its kind to include such a large cohort of healthy men, according to Salas-Huetos, who was part of a team that conducted the first systematic review of observational studies of diet and sperm health in 2017. The review found that diets rich in certain nutrients and antioxidants and low in saturated and trans-fatty acids were positively associated with high semen quality parameters. The same is true for diets rich in fish, shellfish, seafood, poultry, cereals, vegetables, fruits, and low-fat dairy. Diets rich in processed meat, soy, alcohol, and sugar were positively associated with low semen quality parameters. They also found that a high intake of alcohol, caffeine, and red and processed meat negatively influenced fertilization rates.
Another review from 2017, which included 23 observational studies on the relationship between dietary habits and semen quality, arrived at similar conclusions.
A possible explanation for these findings is the strong correlation between high levels of reactive oxygen species and increased levels of sperm DNA damage as well as decreased sperm motility. Antioxidants and some nutrients contained in healthy food can regulate these levels of reactive oxygen species, according to Salas-Huetos. Additionally, he said, fiber consumption can reduce plasma estrogen levels: "High estrogen levels can disrupt endocrine homeostasis, which is essential for normal spermatogenesis."
"The data are becoming more convincing that [overall lifestyle] has an impact on male reproductive function," said Natan Bar Chama, MD, director of male reproductive medicine and surgery at Mount Sinai in New York City. This study is "a significant contribution to bolster the concept that diet and health and lifestyle are affecting our reproductive health," he added.
Bar Chama noted that, in addition to affecting testicular function, lifestyle also has an impact on epigenetics and can have long-term effects on sperm DNA.
"The implication is not just that it may be more difficult to conceive, but we're putting at risk our children," he said. "Reproductive health is a barometer of overall health and should be taken seriously, not only for your health and your ability to conceive but potentially the health of your children."