When I was trying to get pregnant I wasn’t sure how much to focus on what I ate. My diet had devolved over the years, oriented more towards convenience than nutrition. I do not enjoy cooking. When left to make a meal for myself if my husband isn’t around, I typically snack throughout the day on protein bars and cereal and bits of cheese, eventually settling for something like instant ramen when true hunger hits. My husband jokes that I have a secret bachelor lifestyle, with habits that are not obvious from the outside, my diet being one of them. I tried to eat better, bringing an apple or carrots to work. But by the end of the week I would be eating the free packaged snacks, snickers bars and rice chips, consumed over my desk while I typed. I knew it was recommended to eat whole foods and a balanced diet when trying to conceive. But this advice is true for everyone, not just people trying to get pregnant. I wasn’t sure how much to actually focus on eating better. Should I prioritize it over getting more sleep? Over my running habit?

Eventually I got pregnant. But the question of how my diet of protein bars and instant ramen affected my time to conception remained. Had my at-times poor diet caused it to take longer for my husband and me to conceive? In March 2026, a study was published that addresses this question directly1 — specifically how ultra-processed food consumption affects fertility and early embryonic development.

The researchers followed a large group of couples in the Netherlands who were trying to conceive or were in early pregnancy. The participants, both men and women, filled out a detailed food log, which was then assessed to determine what percentage of the diet was ultra-processed by the NOVA definition. Ultra-processed foods by this classification are largely industrially manufactured — think packaged snacks and sugary drinks — rather than whole foods like bananas and lettuce. The median percentage of food that was ultra-processed was 22% for women and 25% for men.

Ultra-processed food intake and male fertility

Ultra-processed food intake was associated with decreased chances of conception for men. For each standard deviation increase in UPF intake, men had a fecundability ratio of 0.90 — meaning roughly 10% lower per-cycle conception probability. A man whose diet consisted of roughly 36% ultra-processed food had approximately 10% lower per-cycle chance of conception than a man whose diet consisted of roughly 25% ultra-processed food. This is a large effect. For comparison, 10% is roughly the per-cycle difference between a 30-year-old woman conceiving and a 40-year-old woman. This result is consistent with other findings that male diet affects fertility — namely that healthier dietary patterns are associated with better sperm quality.2

Ultra-processed food intake and female fertility

For women, ultra-processed food intake was not associated with a change in fertility. Instead, intake of these foods correlated with a modest decrease in yolk sac size in the growing embryo. The yolk sac is a vital feature of the early embryo. Similar to the nutritional head start present in a seed, it provides nourishment until the placenta takes over around weeks 10–12. Even after it is no longer needed, abnormalities in early fetal growth are correlated with longer-term issues — preterm birth, low birth weight, and cardiovascular problems in childhood.34 The finding that maternal diet is linked to fetal growth is supported by previous research.56 However, this study did not follow pregnancies through to birth, so we don’t know whether the smaller yolk sac led to complications for this specific group — only that early growth abnormalities have generally been associated with these outcomes in other research. Whether ultra-processed food-related yolk sac changes specifically translate to these outcomes remains to be studied.

A few important caveats

The Dutch participants in this study consume a smaller percentage of calories as ultra-processed than the typical American — Americans often consume roughly twice as much.7 The results of this study could be understating the effect of UPF consumption on fertility in the US population. On a similar note, only couples who conceived were included. This means that couples whose diet was so poor as to prevent conception entirely were omitted, again potentially understating the problem by discounting the most affected group.

One additional caveat: NOVA’s ultra-processed classification is a single category for foods that vary enormously in nutritional quality. A Twinkie and an industrially-produced whole wheat bread are both classified as ultra-processed, despite one being high in fat and sugar with little nutritional value and the other being high in fiber with a short ingredient list. This study didn’t account for that variation — likely an impossible task given its design — which means some of the fertility signal attributed to “ultra-processed food” might actually reflect diets that are higher in fat and sugar and lower in fiber generally, rather than something intrinsically harmful about industrial processing itself.

The advice I had heard to eat whole foods and a balanced diet was true. But I had largely focused on the wrong person — my husband’s ultra-processed food consumption was more likely to have affected our time to conception than mine. My energy would have been better spent focused on his lunch than judging myself for mine.