Paternal Ultraprocessed Food Intake Linked to Ten Percent Decrease in Monthly Fecundability and Subfertility Risk

New research links high paternal UPF intake to a 10% drop in fecundability and finds maternal diet affects early embryonic growth and yolk sac development.

By: AXL Media

Published: Mar 26, 2026, 8:37 AM EDT

The Correlation Between Processed Diets and Male Reproductive Health

New findings from the Generation R Next Study indicate a significant link between paternal dietary habits and the probability of conception. According to the research data, every standard deviation increase in ultraprocessed food intake among men is associated with a 10% decrease in fecundability, which is the statistical probability of conceiving within a single month. The study further suggests that men with higher consumption levels face an elevated risk of subfertility, defined as taking more than one year to conceive or requiring medical intervention through assisted reproductive technology. This development highlights the importance of paternal health in the preconception window, a period often overshadowed by maternal health focus.

Maternal Nutrition and the Critical Window of Embryonic Development

While paternal diet appears to influence the timeline of conception, maternal intake of ultraprocessed items shows a more direct impact on the physical development of the embryo itself. Ultrasound assessments conducted at seven weeks of gestation revealed that higher maternal consumption was associated with a reduced crown-rump length, the primary measurement of a developing fetus. The data suggests that these dietary choices may interfere with the earliest stages of life, potentially setting a trajectory for pregnancy outcomes. Although the researchers noted that these associations appeared to weaken by the ninth and eleventh weeks, the initial growth lag remains a point of clinical interest.

The Role of the Yolk Sac in Sustaining Early Life

The research explored the health of the yolk sac, which serves as the primary source of nourishment for the embryo before the placenta becomes fully functional. According to Dr. Liji Thomas, women in the highest quartile of ultraprocessed food consumption exhibited smaller yolk sac volumes at the seven week mark compared to those with the lowest intake. Because a poorly functioning or undersized yolk sac is often a precursor to complications such as miscarriage or preterm birth, these findings suggest that nutrient poor diets may undermine the biological infrastructure required for a healthy pregnancy. This specific measurement provides a tangible link between processed ingredients and early developmental markers.