A new study published on Mar. 24 in Human Reproduction finds that eating large amounts of ultra-processed food is linked to reduced fertility in men and slower early embryo growth, including smaller yolk sacs, which are important for embryonic development.
The findings highlight potential concerns about the impact of highly processed foods on reproductive health for both parents and their developing children. Researchers suggest that reducing the intake of these foods may benefit couples planning a pregnancy.
Dr Romy Gaillard, a paediatrician and associate professor at Erasmus University Medical Center in Rotterdam, led the research team. "Even though UPFs are so common in our diets, very little is known about their potential relationship with fertility outcomes, and early human development," said Gaillard. The study involved data from 831 women and 651 male partners enrolled between 2017 and 2021 as part of the Generation R Study Next Programme.
Participants' diets were assessed through questionnaires during early pregnancy, with average consumption of ultra-processed foods making up around one-quarter of daily intake for both women (22%) and men (25%). The researchers also collected information on time to pregnancy, probability of conceiving within one month (fecundability), subfertility rates, embryo size measurements by ultrasound at various stages of gestation, and yolk sac volume.
Celine Lin, first author and PhD student at Erasmus University Medical Center said: "We observed that UPFs consumption in women was not consistently related to the risk of subfertility and time to pregnancy, but was associated with slightly smaller embryonic growth and yolk sac size by the seventh week of pregnancy. These differences in early human development were small, but are important from a research perspective and at population level..."
In men, higher intake of ultra-processed foods was linked to an increased risk of subfertility—meaning it took longer for couples to conceive—but not directly tied to changes in early embryo development. Lin added: "This association may be explained by the sensitivity of sperm to dietary composition... whereas maternal UPF consumption may directly influence the environment in the womb..."
Gaillard emphasized: "Our findings suggest that a diet low in UPFs would be best for both partners..." She noted previous studies have shown slower embryonic growth can increase risks such as premature birth or low birth weight. However, she cautioned: "Importantly... our study shows associations but cannot prove direct causal effects." More research is needed across diverse populations to better understand these relationships.
Gaillard concluded: "Finally,... we should move away from the idea that only the health and lifestyle of mothers-to-be is important for pregnancy... Our results highlight the need to pay more attention to male health in the preconception period."
