Male fertility has declined in recent decades, with male factors contributing to an estimated 40%-50% of infertility cases among couples. Although environmental exposures and lifestyle factors have long been implicated, growing evidence suggests that ultraprocessed foods (UPFs) may also contribute. Recent studies have linked diets high in UPFs to hormonal alterations and poor semen quality, raising concerns regarding their potential effects on reproductive health.

Declines in sperm concentration, motility, and morphology have been well documented. Nearly a decade ago, a meta-analysis reported a substantial decline in sperm counts across Western countries. Since then, researchers have increasingly focused on potentially modifiable contributors, with growing attention directed toward dietary patterns.

UPFs and Semen Quality

Most studies examining diet and fertility have relied on the NOVA classification system developed by Brazilian epidemiologist Carlos A Monteiro. Under this framework, UPFs are industrial formulations primarily composed of refined ingredients and additives. Examples include sugar-sweetened beverages, packaged snacks, processed meats, ready meals, and refined grain products containing added sugars.

The concern extends beyond nutritional quality alone. These products undergo extensive industrial processing to improve their shelf life, safety, appearance, and palatability, characteristics that distinguish them from minimally processed foods.

Several studies have examined the relationship between consumption of UPF and semen quality. Among the most notable is a study published in Cell Metabolism in 2025, which reported that consumption of UPFs is detrimental for cardiometabolic and reproductive outcomes, regardless of excessive caloric intake. The findings suggested that the observed effects may be related not only to the quantity of food consumed but also to the industrial processing itself.

The researchers compared the effects of a UPF diet with those of a minimally processed diet in 43 men aged 20-35 years. Participants followed each dietary pattern for 3 weeks, separated by a 3-month washout period. Both diets contained similar amounts of calories, proteins, carbohydrates, and fats, with the degree of food processing being the principal difference between the two dietary patterns.

After only 3 weeks, participants consuming the UPF diet showed increased body fat, less favorable lipid profiles, including changes in high-density lipoprotein and low-density lipoprotein cholesterol levels, and hormonal alterations associated with spermatogenesis.

Similar findings emerged from a study published in Human Reproduction Open in 2024, in which the researchers analyzed the effect of diet on the fertility of 200 healthy men and found that higher consumption of “unhealthy foods” was associated with lower sperm concentration, lower total sperm counts, and poorer sperm motility.

Another study published in Nutrients in 2025 also reported a trend toward poorer sperm morphology among men with unhealthy dietary patterns. The authors concluded that diet should be considered a potentially modifiable factor in efforts to improve male fertility.

Hormonal Effects

Although these studies did not establish causality, the available evidence suggests that diets high in UPFs may contribute to impaired male reproductive function.

Male fertility is linked to hormonal regulation, which is associated with dietary habits. Several studies have reported associations between the consumption of high UPF and lower testosterone levels, as well as reduced levels of follicle-stimulating hormone, a key regulator of spermatogenesis.

These findings raise the possibility that industrially processed foods may affect the hypothalamic-pituitary-gonadal axis, extending the effects of diet beyond semen parameters to include endocrine pathways that regulate reproduction.

Potential Mechanisms

Researchers have proposed several biologic mechanisms that may explain these associations. One leading hypothesis involves low-grade chronic inflammation. Diets high in UPFs can promote a proinflammatory environment and increase oxidative stress, factors that may damage sperm DNA and impair sperm function.

Metabolic dysfunction may also contribute to impaired sperm function. Associations among obesity, insulin resistance, and male infertility are well established, and the consumption of UPF is a risk factor for developing these conditions.

A large meta-analysis published in the BMJ in 2024 reported associations between the consumption of UPF and obesity, type 2 diabetes, cardiovascular disease, and increased mortality. Therefore, reproductive decline may be another manifestation of broader metabolic dysfunction.

Exposure to endocrine-disrupting chemicals is another possible explanation. Contact with compounds such as phthalates and bisphenols, which may migrate from food packaging or materials used during industrial processing, could interfere with hormonal signaling, even at relatively low levels of exposure.

Changes in the gut microbiome have attracted considerable attention. Dietary patterns high in UPFs can alter microbial composition, potentially affecting reproductive function through metabolic and immune pathways.

Clinical Implications

These theories suggest that dietary assessment may warrant greater attention during the evaluation and management of male infertility. Nutritional counseling aimed at reducing the consumption of UPF could become a key component of prevention and management strategies.

Research is also expanding into areas such as sperm epigenetics, transgenerational effects, and the influence of paternal diet on early embryonic development. These emerging fields are examining whether dietary exposure affects not only an individual’s reproductive health but also the health of future generations.

Further research is needed to determine the extent and clinical significance of these factors.

This article was translated from El Médico Interactivo.