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Fertility rates are falling worldwide, with two thirds of countries below the replacement level. “Fertility is a public health issue, with 1 in 6 individuals experiencing infertility,” said Rachel Lévy, professor of developmental and reproductive biology and medicine at the Faculty of Medicine, Sorbonne University, and head of the Laboratory of Reproductive Biology-CECOS, Tenon Hospital, both in Paris, France.

Sperm concentration has reportedly halved over the past 50 years, with environmental and lifestyle factors, including obesity and poor nutrition, playing significant roles.

During Institut Benjamin Delessert’s annual event on January 31, 2025, in Paris, Lévy presented the current level of evidence on how modifiable factors contribute to infertility and examined the potential impact of targeted nutritional interventions on improving fertility outcomes.

The relationship between body mass index, diet, and sperm quality is significant. The global rise in body mass index closely parallels the decline in fertility rates. Among men undergoing medically assisted procreation, overweight and obesity increase the risk for oligozoospermia and azoospermia, reducing fertilisation, pregnancy, and live birth rates.

Diet directly affects spermatogenesis. Studies have confirmed that adherence to the Mediterranean diet improved sperm quality and fertility. Additionally, the paternal diet before conception influences DNA methylation in human sperm, potentially affecting fertility and embryonic development.

Hormonal imbalances, oxidative stress, inflammation, and epigenetic factors create both risks and “a window of opportunity to improve fertility,” Lévy noted.

Clinical studies suggest that some of these effects may be reversible. For instance, a study reported that physical activity and a balanced diet before conception helped normalise metabolic, hormonal, and body measurements while improving sperm quality, including reduced DNA damage, lower oxidative stress, and stronger antioxidant defence mechanisms in semen.

Artificial intelligence (AI) has also contributed to understanding unexplained infertility. Lévy and colleagues have developed an AI-based tool to identify nutritional factors in infertile couples undergoing medically assisted procreation.

“By analysing plasma levels of 13 antioxidant micronutrients, we established a ‘nutrifertility score’ that can differentiate between fertile and infertile individuals with more than 80% accuracy,” she reported. These 13 micronutrients represent key intervention points to potentially enhance the chances of success in assisted reproduction.

It is important to note that targeting these parameters can improve sperm DNA fragmentation rates without necessarily affecting conventional semen parameters such as concentration and morphology.

This raises the question of whether traditional semen analysis alone is sufficient to assess the benefits of nutritional interventions. Numerous interventional studies have been published on this topic, and a Cochrane review suggested that antioxidant supplementation may improve live birth rates in men with subfertility undergoing assisted reproductive techniques. However, most studies in this area have methodological biases, and no consensus exists regarding systematic supplementation.

Nonetheless, comprehensive interventions combining dietary changes, personalised coaching, and supplementation over a 15-week period have been effective in reducing sperm DNA fragmentation rates when compared with control groups. Additionally, certain genetic polymorphisms affecting key enzymes can increase oxidative stress and impair sperm quality. These findings highlight the potential of targeted nutrition to correct these imbalances and improve fertility outcomes.

Nutritional balancing with targeted supplementation, including vitamin C, vitamin E, selenium, zinc, coenzyme Q10, and omega-3 fatty acids, may be beneficial when deficiencies are found or redox balance is disrupted. However, these treatments should be supervised by healthcare professionals until more conclusive studies are available.

This story was translated and adapted from Univadis France using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.