This Common Habit Is Ruining Your Sperm

A surprising new study suggests that a everyday dietary choice many of us make without thinking could be quietly undermining male fertility. The habit? Relying too heavily on ultra-processed foods (UPFs) — the packaged snacks, sugary drinks, instant noodles, processed meats, and ready-made meals that have become staples in modern diets.

Published on March 24, 2026, in the journal Human Reproduction, the research from Erasmus University Medical Center in Rotterdam examined data from the Generation R Next Study. It involved 831 women and 651 of their male partners, tracking diet around the time of conception and early pregnancy outcomes.

Key Findings on Men’s Fertility

Researchers found that higher consumption of ultra-processed foods in men was linked to reduced fecundability — the probability of conceiving in any given menstrual cycle — and a higher risk of subfertility (taking longer than a year to conceive).

• For every standard deviation increase in UPF intake (as a percentage of total diet), the odds of subfertility rose by about 36%.
• Men with higher UPF consumption took longer, on average, to achieve pregnancy.
• The median UPF intake among men in the study was roughly 25% of their total food consumption, a level common in many Western-style diets.

Importantly, these associations held even after adjusting for factors like age, socio-economic status, lifestyle habits, and the woman’s own diet. The study did not find a strong link between paternal UPF intake and early embryo development once pregnancy occurred.

Effects in Women

The research also revealed sex-specific patterns. While women’s UPF consumption was not tied to overall fertility rates in the same way, higher intake was associated with slightly smaller embryonic growth (measured by crown-rump length) and smaller yolk sac volume at around 7 weeks of gestation. These differences tended to lessen by 9–11 weeks. The yolk sac plays a critical early role in nourishing the embryo.

Why Ultra-Processed Foods Might Harm Sperm and Fertility

Ultra-processed foods are typically:

• Low in essential nutrients, antioxidants, and healthy fats that support sperm production and protect against oxidative damage.
• High in added sugars, unhealthy fats, additives, and potential contaminants (such as those leaching from packaging).

Poor nutrition can increase oxidative stress, disrupt hormone levels, and impair sperm quality, including count, motility, and DNA integrity. A separate controlled trial from 2025 also linked UPF-heavy diets to reduced sperm motility and changes in reproductive hormones like follicle-stimulating hormone.

Experts note that sperm are particularly sensitive to dietary quality, while maternal diet may more directly influence the early uterine environment.

Broader Context on Declining Sperm Health

This study adds to growing evidence about lifestyle factors contributing to falling sperm counts observed globally over recent decades. Other well-established habits with stronger or comparable impacts include:

• Smoking or tobacco use, which damages sperm DNA and reduces motility.
• Excessive alcohol consumption.
• Obesity and a sedentary lifestyle, which alter hormone balance.
• Chronic scrotal overheating (from tight clothing, hot tubs, or prolonged laptop use on the lap).
• High stress levels.

The researchers emphasize that the associations appeared even at moderate UPF levels, suggesting that modest dietary shifts could make a meaningful difference for couples trying to conceive.

Practical Steps to Protect Sperm Health

Sperm production takes about 2–3 months, so positive changes can show results relatively quickly. Recommendations include:

• Reduce ultra-processed foods and aim to keep them well below 20–25% of your daily intake.
• Focus on whole, nutrient-dense foods: leafy greens, berries, nuts (especially walnuts), fatty fish, fruits, and vegetables rich in antioxidants.
• Maintain a healthy weight through balanced eating and regular moderate exercise.
• Quit smoking, limit alcohol, manage stress, and prioritize good sleep.
• Avoid prolonged heat exposure to the testes.

If you’re planning to start a family and have concerns, consult a doctor for a semen analysis. While lifestyle plays a major role, medical factors like hormonal issues or varicocele may also need attention.

Fertility is influenced by many variables, and this observational study shows association rather than definitive causation. Still, the findings highlight diet as an underappreciated factor in preconception health — for both men and women. Cutting back on ultra-processed foods isn’t just good for fertility; it’s beneficial for overall well-being. Small, consistent improvements in what you eat could support your chances of conceiving and contribute to healthier early development.

For couples hoping to grow their family, paying closer attention to food quality around the periconception period may offer real benefits.

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