A diet heavy in junk food could cause irreversible reproductive harm to men, according to new research from Danish and Icelandic scientists in conjunction with the Harvard T.H. Chan School of Public Health.
Recent comprehensive scientific reviews revealed that sperm counts in the West have plummeted by nearly 60 percent in the past 40 years, and scientists are clamoring to figure out what the root causes may be. Some argue that it's stemming from damage caused by modern life, and the new research about diet's effect on male fertility backs that theory up.
Men who adhere to high-fat Western dietary patterns (diets high in processed, fatty and sugary foods) were found to have significantly lower sperm counts than those who eat more well-rounded diets, the study found.
Researchers assessed the diet, sperm count, semen quality, reproductive hormones and lifestyle factors of 2,395 healthy young Danish men between the ages of 18 and 22 by studying data collected as part of the routine physical examination process that determines fitness for military service. The assessments were performed from 2008 to 2017.
Study subjects were divided into four categories based off of eating habits. The "Western" pattern refers to a diet saturated with high-fat junk foods, like pizza, chips, processed and red meats, snacks, refined grains, high-energy drinks and sweets.
The "Prudent" pattern is more lean and consists of an intake high in fish, chicken, vegetables, fruit, and water.
The "Smørrebrød" pattern is traditionally Scandinavian, consisting of cold processed meats, whole grains, mayonnaise, cold fish, condiments and dairy. The last dietary pattern was "Vegetarian," consisting mostly of vegetables and soymilk, but also making exception for eggs.
Testicular function was then determined by measuring the semen volume, sperm concentration, total sperm count and motility, as well by analyzing serum concentrations of the reproductive hormones LH, FSH, testosterone, Estradiol, SHBG and inhibin-B.
The men who adhered most closely to the "Western" dietary pattern were found to have the lowest sperm counts, averaging 25.6 million less sperm per ejaculation than those with the healthiest eating habits. According to the Mayo Clinic, a healthy average sperm count is 39 million per ejaculation.
Those men adhering to the "Prudent" dietary pattern were found to have the highest sperm counts, followed by men who adhere to the "Vegetarian" and then ""Smørrebrød" patterns.
Researchers also conducted hormonal tests to determine the health of Sertoli cells, the somatic cells of the testis that are essential in the creation of sperm, and found that they were depleted in young men who adhered to the "Western" dietary pattern, The Telegraph reported.
While improving dietary patterns and lifestyles can improve sperm health over time, it is believed that Sertoli cells lost to oxidative stress cannot ever be replaced.
This means that men who eat junk food-heavy diets have likely already done irreparable damage by the age of 20.
The research is set to be presented at the European Society for Human Reporduction and Embryology (ESHRE) annual conference in Vienna.
"Most men think they're invincible until their first big health event occurs, which is often either miscarriage or infertility," Dr. Roy Farquharson, an NHS consultant and president of ESHRE, told the Telegraph. "Then their partner will quite rightly ask them, 'what are you doing?' Because the sperm is just as important as the egg."
Farquharson says that sperm health can improve in just two to three months, however, with dedicated positive lifestyle changes.