You may have heard that male fertility is falling across the developed world. Many studies have been made in order to understand why this is happening and how future parents may overcome this issue. An interesting new study published in Cell Metabolismreports that regular consumption of ultra-processed foods may be linked to a decline in key measures of male fertility. Researchers observed that even on a calorie-controlled diet, participants who ate ultra-processed foods experienced adverse health effects. These included elevated cholesterol levels, an increase in body fat, and an average weight gain of more than a kilogram. Crucially, the researchers noted that "sperm quality trended toward impairment" under these dietary conditions.

This highlights a critical point in nutrition science. Dr. Philip Werthman, a urologist and director of the Center for Male Reproductive Medicine and Vasectomy Reversal, emphasized that the study proves the source of calories matters more than the quantity. In other words, it's not the amount, but the quality of the calories. 

How Ultra-Processed Diets Affect Sperm Quality
The study involved 43 healthy males between the ages of 20 and 35. Each participant followed two distinct three-week dietary plans—one centered on ultra-processed foods and the other on unprocessed foods—separated by a three-month "wash-out" period to reset their systems.

During the ultra-processed diet phase, researchers detected an increase in phthalate cxMINP, a chemical commonly found in plastics known to be an endocrine disruptor. Participants also exhibited decreased levels of testosterone and follicle-stimulating hormone (FSH), both of which are essential for healthy sperm production. The study's authors speculate that these endocrine-disrupting molecules may leach into food from the plastic packaging frequently used for ultra-processed products. They also pointed out that the rise of these foods since the 1970s coincides with a 60% worldwide decline in sperm counts.

Kristin Kirkpatrick, a dietitian at the Cleveland Clinic, stated the research delivers a powerful message. "The study found that endocrine disrupters and other components altered hormone levels in men, even if the men were healthy," she explained. "This means, even if you’re healthy based on other parameters, yet consume a diet higher in ultra-processed foods, you still are at risk for increases in chronic conditions."

However, Dr. Michael Eisenberg, a professor of urology at Stanford University, offered a note of caution. While acknowledging a trend toward declining semen quality in the data, he pointed out that the changes did not reach statistical significance. "However, it’s important to note that the intervention was for three weeks, and a cycle of sperm production typically takes between two to three months," he said, suggesting a longer study might be needed to see more definitive effects.

The Widespread Health Impact of Ultra-Processed Foods
According to the Centers for Disease Control and Prevention (CDC), ultra-processed foods constitute approximately 55% of the total calories consumed by people in the United States. These foods are typically described as "hyper-palatable, energy-dense, low in dietary fiber," and high in salt, sweeteners, and unhealthy fats. Common examples include burgers, sweetened beverages, sweet bakery products, and savory snacks.

Beyond reproductive health, numerous studies have linked these foods to severe health problems:

A July 2025 study identified them as a major factor in obesity, heart disease, type 2 diabetes, and sleep apnea.

An April 2025 study connected ultra-processed foods to 124,000 preventable deaths in the U.S. over a two-year period.

A May 2024 study suggested a link to an increased risk of stroke and cognitive decline.

Kirkpatrick explained that these foods cause harm not only because of their ingredients but also because they displace healthier options. "Consuming ultra-processed foods means that other foods, which are found to help in the prevention of heart disease (like fresh fruit and vegetables, healthy fats, and fiber) are not being consumed," she said.

Practical Steps to Improve Male Reproductive Health
Experts agree that lifestyle changes can significantly improve and maintain male reproductive health.
"In general, a good diet (whole grains, fruits, vegetables), exercise, and maintaining a good body weight will help overall and reproductive health,” said Dr. Eisenberg.

Kirkpatrick echoed this, recommending a nutrient-dense approach like the Mediterranean diet, combined with regular exercise, adequate sleep, and stress management. Abstaining from alcohol and tobacco is also crucial.

Dr. Werthman added that a man’s overall health is directly tied to his fertility. "The reproductive system is a function of your overall health," he explained. "The body is an integrated system." He also reminded men trying to conceive to be mindful of external heat sources like saunas and hot tubs, which can temporarily affect sperm production.