Around the world, men are facing an “infertility crisis," an event marked by plunging sperm counts over the past four decades. It's unclear what exactly is driving the crisis, but a recent study, including 2,935 young Danish men unaware of their fertility status, suggests adjusting one's diet may be a tactic worth taking to reverse this trend, boost sperm count, and improve semen quality.

In the study, researchers explored the link between food choices and testicular function. Men who ate a Western diet had the lowest total sperm count (109 to 138 million) compared to three other popular diets.

Men who ate “prudently” came out on top, averaging 146 to 183 million sperm in a single semen sample. A “prudent” diet is one that is “generally healthy,” the researchers say, including lots of fruit, vegetables, fish, and chicken. Meanwhile, a Western diet is full of red meat, fried food, and sugar-sweetened drinks and desserts. A "vegetarian-like" approach to eating (little meat and a high intake of vegetables, eggs, and milk) came in second to a prudent diet.

"Dietary factors are necessary for the production of healthy functioning sperm with high fertility potential," co-author Feiby Nassan, a researcher at the Harvard T.H. Chan School of Public Health, tells Inverse.

Antioxidant supplements, seafood, poultry, nuts, whole grains, fruits, and vegetables are important because they provide antioxidation and omega 3 fatty acids — which are essential for good sperm production, Nassan says.

These findings were published Friday in the journal JAMA Network Open.

"I believe that it is not only, 'You are what you eat,' but it is also 'Your sperm is what you eat,'" Nassan says.

The diet-sperm connection

For this study, the researchers rounded up a large group of young, healthy men in Denmark. At 18, all Danish men are required to undergo physical evaluations to determine if they are fit for military service. During these routine exams, the research team invited the young men to participate in their study exploring male fertility and reproductive potential.

"Your sperm is what you eat."

Once they opted in, the group was surveyed on their demographic characteristics, eating and lifestyle habits, and medical history. They reported how many foods they ate over the past three months leading up to the study from a list of 136 different food items. The researchers split the group into four different dietary patterns: vegetarian-like, Western, prudent, and open-sandwich — that's a traditional Danish eating approach composed of whole grains, cold cuts, and dairy.

Next, they gave semen and blood samples, as well as underwent a physical exam measuring their weight, height, and BMI. The men were instructed to abstain from ejaculation for the two days prior to giving their semen samples (although, if they didn’t follow those instructions, they weren’t excluded from the study).

The researchers took the semen samples and assessed semen volume, sperm concentration or count, sperm motility or movement, and sperm morphology or shape. They also analyzed the blood samples, measuring reproductive hormone levels including testosterone, FSH, inhibin B, and estradiol.

Downstream effects

Ultimately, the team realized that adherence to certain diets correlated with huge differences in key metrics for fertility.

Men who ate a Western diet had the lowest semen quality. They also showed lower serum inhibin B concentrations and ratios of inhibin B to FSH — metrics that suggest lower sperm production. In contrast, eating “prudently” was associated with the best semen quality.

People who ate the “open-sandwich” diet had the fastest sperm, while vegetarians had the most "normally-shaped" sperm.

Study results: Adjusted median differences in semen quality parameters according to quintiles of adherence to dietary patterns JAMA Network Open

These findings jibe with previous research: Diets where the bulk of energy comes from vegetables, fish, fruit, and lean meats like the Mediterranean diet have been linked with better semen quality. This study is the largest to date exploring the links between testicular function and diet, the researchers say.

"Because following a generally-healthy diet pattern is a modifiable behavior, our results suggest the possibility of using dietary intervention as a possible approach to improve sperm quality of men in reproductive age," Nassan says.

Nassan recommends that men looking to improve their sperm follow a generally healthy diet and up their intake of fish, chicken, vegetables, fruit, and water. This also means that this group should reduce their intake of pizza, French fries, processed and red meats, snacks, refined grains, high-energy drinks, and sweets.

Importantly, this study, however large, was conducted on a homogenous population. Before any diet recommendations become standard approaches to improving male fertility, the experiment needs to be conducted in other places and with different ethnicities. There's also controversy in the scientific field over using single semen samples as reliable metrics for male fertility.

How food choices influence men's fertility isn't totally clear. Diet may impact mood or psychological states, which can have downstream effects on sexual health.

Diet could be just one piece amongst a complicated web of factors shaping male fertility. But this study suggests a prudent diet is a potentially cheap, modifiable factor to fight infertility, an issue that can often feel out of control for many people.

Besides, there are lots of reasons to eat "prudently," beyond sexual health: Eating lots of water, vegetables, fish, and fruit is a tried and tested way to stay healthy in the long-term.

ABSTRACT:

IMPORTANCE: Diet may play a role in testicular function, but data on how adherence to different diet patterns influences human testicular function are scarce.

OBJECTIVE: To determine whether adherence to specific dietary patterns is associated with testicular function in young men.

DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study included 2935 young Danish men unselected regarding fertility status who were enrolled from April 1, 2008, through May 31, 2017. Data were analyzed from July 1, 2017, to January 30, 2019.

EXPOSURES: Dietary patterns identified with principal component analysis based on responses to a validated food frequency questionnaire.

MAIN OUTCOMES AND MEASURES: Standard semen quality assessment; serum concentrations of testosterone, free testosterone, estradiol, inhibin B, follicle-stimulating hormone, luteinizing hormone, and sex hormone–binding globulin; and testicular volume measured with ultrasonography.

RESULTS: Among the 2935 participants included in the analysis, median age was 19 (interquartile range, 19-20) years and 2290 (78.0%) had normal body mass index. The 4 dietary patterns identified included Western, prudent, open-sandwich (a traditional Danish eating pattern), and vegetarian like. The greatest adherence to the prudent pattern was associated with the highest total sperm count (median, 167 [95% CI, 146-183] million), followed by adherence to vegetarian like (median, 151 [95% CI, 134-168] million) and open-sandwich (median, 146 [95% CI, 131-163] million) patterns. Adherence to the Western pattern was associated with the lowest total sperm count (median, 122 [95% CI, 109-138] million), which was significantly lower than sperm count in the other 3 diet patterns. After adjusting for confounders, the median total sperm count for men in the highest quintile of adherence to the Western pattern was 26 million lower (95% CI, –42 to –9 million) than for men in the lowest quintile of adherence to this pattern. Conversely, the median total sperm count of men in the highest quintile of adherence to the prudent pattern was 43 million (95% CI, 23-63 million) higher than that of men in the lowest quintile. Men with the highest adherence to the Western pattern had a lower median ratio of inhibin B to follicle-stimulating hormone (–12 [95% CI, –20 to –3]) and higher median ratio of free testosterone to luteinizing hormone (10 [95% CI, 2-19]) compared with men with lowest adherence to this pattern.

CONCLUSIONS AND RELEVANCE: In this cross-sectional study, adherence to generally healthy diet patterns was associated with better semen quality, with potentially more favorable fertility potential mong adult men.