Ultra-processed foods may impact men’s fertility and developing embryos, study finds

Both men and women should probably avoid  ultra-processed foods when trying to have a baby, according to a new study of 651 couples from Rotterdam in the Netherlands.

The findings, published March 24 in the journal Human Reproduction, found lower fertility in men who ate more ultra-processed foods in their diets, while women with such diets had slower-growing embryos during pregnancy and smaller yolk sacs to nourish the embryos during early development. The study is the first to assess how ultra-processed foods in both the mother’s and father’s diet affect early pregnancy and a couple’s ability to conceive, according to the authors.

Ultra-processed foods, such as lunch meats, chips, candy, frozen meals, some breads and cereals, include a broad range of products that may contain chemical preservatives and sweeteners and undergo processing techniques to heavily alter their ingredients. These foods make up about 70% of the US food supply, according to the US Food and Drug Administration (FDA), with some ultra-processed foods linked to heart disease, obesity and certain cancers.

“Paternal diet quality may be an important yet underrecognized target for preconception care and fertility interventions,” the study authors wrote. “These associations were observed even at relatively low levels of [ultra-processed food] intake, which may suggest that modest dietary improvements in men could have meaningful benefits for reproductive outcomes.”

The study did not find a link between ultra-processed food consumption and fertility in women, although the authors suggested that their findings, along with previous research, indicate specific types of these foods may impact women’s reproductive health more than the total amount of ultra-processed foods they consume. For example, artificially sweetened beverages and processed meats have been linked to an increased risk of experiencing multiple health problems at once, while ultraprocessed breads and cereals have not. 

The authors also note that the study participants ate relatively healthy diets, which may have limited their ability to find associations between ultra-processed food intake and fertility in women. People that eat more ultra-processed foods than the couples in the study may have more pronounced impacts to their fertility and early pregnancies, they wrote.

“This study adds important biological insight, particularly around early embryonic development,” said Anthea Christoforou, an assistant professor at McMaster University, who was not involved in the new study.

In research published last week, Christoforou and colleagues analyzed data from the US National Health and Nutrition Examination Survey for over 2,500 women, finding that those who consumed less ultra-processed foods were more likely to conceive even after adjusting for obesity and other lifestyle factors. While the Human Reproduction study used data from couples who ultimately became pregnant, Christoforou’s research included women who were unable to conceive, “providing a more complete picture of infertility,” she said.

“Differences in study design-particularly the use of time to pregnancy among couples who ultimately conceived-as well as a relatively healthier population with lower ultra-processed food intake, may help explain why findings with respect to fertility differ across studies,” said Christoforou.

While there is currently no single US definition of ultra-processed foods, the FDA and the US Department of Agriculture (USDA) in July submitted a request for information they said they would use to establish a uniform definition.

“A uniform UPF definition, developed as part of a joint effort by federal agencies, would allow for consistency in research and policy to pave the way for addressing health concerns associated with the consumption of UPFs,” said the agencies in a statement. 

Food advocates, farmers, chefs and scientists have been urging the FDA to account for new health risks and what’s added or taken away from foods during processing in its definition. In a recent podcast interview, US Health Secretary Robert F. Kennedy Jr. said the definition may be announced as soon as April.

Featured image: Kelly Sikkema/ Unsplash