UPFs linked to fertility issues in men, study suggests

Men who eat more ultra-processed food may be more likely to face fertility issues, a study suggests.

Ultra-processed foods, or UPFs, include bread, cakes, pastries, fried foods and salty snacks.

They contain artificial ingredients and high levels of fat, sugar and salt. Previous studies have linked UPFs to at least 32 serious health conditions, including heart disease, cancer and dementia.

Romy Gaillard, an epidemiologist at Erasmus University Rotterdam and lead researcher of the study, said: “Our findings suggest that a diet low in UPFs would be best for both partners, not only for their own health, but also for their chances of pregnancy and the health of their unborn child.

“We should move away from the idea that only the health and lifestyle of mothers-to-be is important for pregnancy and offspring outcomes, and recognise that the health and lifestyle of both the mother- and father-to-be play an important role.

“Our results highlight the need to pay more attention to male health in the preconception period, which has traditionally been overlooked.”

The Dutch study tracked health data from 831 women and 651 men who were trying for a baby.

On average, women said about a fifth of their diet consisted of UPFs, while men said roughly a quarter did. More than one in ten couples said more than a third of their diet was made up of UPFs.

Researchers at Erasmus University Rotterdam found that men with the highest UPF intake were at a 75 per cent greater risk of subfertility, where it takes longer for a partner to become pregnant, than those with an average diet.

Just under 40 per cent of the men surveyed experienced subfertility overall, but among those consuming the most UPFs this rose to nearly 70 per cent.

The study also found that the unborn children of women with UPF-heavy diets were slightly more likely to experience developmental issues.

These unborn children had slightly smaller yolk sacs, one of the earliest structures to form in pregnancy during the first six weeks.

They also took marginally longer to develop from a fertilised egg into an embryo, a process known as embryonic growth that generally happens in the first two months of pregnancy.

Previous studies have suggested slower embryonic growth can sometimes be linked to premature birth, miscarriage and an increased risk of heart and blood problems in childhood.

The authors said further research was needed, particularly because the study was observational, meaning it cannot prove that UPF consumption directly led to these fertility issues.

However, the researchers said the findings suggest couples, but particularly men, trying for a baby should avoid UPFs where possible.

Experts welcomed the findings but urged caution over the study’s limitations on such a sensitive subject.

Channa Jayasena, a professor of reproductive endocrinology at Imperial College London, said the results were ‘interesting, but there are several reasons to be cautious interpreting them’.

He said: “First, we have no way of knowing whether it is UPF itself, or some other behaviour that is linked with the things they observed.

“Secondly, the differences observed are tiny, and hardly significant compared with measures such as weight loss.

“This means that even if UPF are causing reproductive problems, their impact on individuals appears very small indeed.

“We know from previous research that in general all couples should prioritise a healthy diet, exercise, and smoking cessation when trying to get pregnant.

“Whether avoiding UPF will offer additional benefits remains unresolved.”

Gunter Kuhnle, a professor of nutrition and food science at the University of Reading, said ‘fertility is an important but very sensitive topic and should therefore be handled accordingly’.

He raised concerns about the questionnaire used in the study, which he said ‘does not appear to have been developed or validated for ultra-processed food’.

Kuhnle added: ‘Given that the assessment of ultra-processed food intake has severe limitations, the conclusions of the study, and the recommendations, need to be interpreted carefully.”