Men who eat too much junk food are significantly more likely to struggle with fertility issues, a new study has found.
Researchers found that men with diets high in ultra-processed foods – such as bread, cakes, pastries, fried foods and salty snacks – were at a 75 per cent greater risk of a condition called subfertility, where it takes longer for their partner to become pregnant, than those with an average diet.
The Dutch study also found that the unborn children of women who regularly eat ultra-processed foods are slightly more likely to experience developmental issues.
Ultra-processed foods, also known as UPFs, 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.
The scientists behind the new study are now calling on couples trying for a child to stick to a low-UPF diet in order to boost the chances of conception and limit the risk of dangerous birth complications.
Researchers at the Erasmus University Rotterdam, in The Netherlands, tracked the health data of 831 women and 651 men who were trying for a baby.
The participants were quizzed on how often they consumed UPFs. On average, the women reported that about a fifth of their diet consisted of UPFs. Meanwhile the men said that, on average, a quarter of their diet was UPFs.
Additive-laden foods such as crisps and sweets have been vilified for decades over their supposed risks, with dozens of studies linking them to type 2 diabetes, heart disease and cancer
More than one in ten of the couples admitted that more than a third of their diet was made up of UPFs.
The researchers found that these participants were significantly more likely to struggle with pregnancy issues. On average, just under 40 per cent of the men surveyed experienced subfertility.
But, for those who consumed the highest amount of UPFs, this risk rose to nearly 70 per cent.
Meanwhile, the children of women who had UPF-heavy diets were more to suffer abnormalities during pregnancy. These unborn children had slightly smaller yolk sacs – one of the earliest stages of pregnancy that forms in 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 that slower embryonic growth can sometimes be linked to premature births, miscarriage and an increased risk of heart and blood problems in childhood.
The authors were keen to point out that further research on the topic was required, particularly because their study was observational, meaning it cannot prove that UPF consumption directly led to these fertility issues.
Other experts have argued that the changes recorded in this study were marginal and could have been triggered by other factors beyond UPFs.
However, the researchers argue that their study shows that couples – but particularly men – trying for a baby should avoid UPFs where possible.
Prof 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.’
She added: ‘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.’
Experts welcomed the findings but urged caution around the limitations of the study around such a sensitive subject.
Channa Jayasena, a professor of reproductive endocrinology at Imperial College London, said the results are ‘interesting, but there are several reasons to be cautious interpreting them’.
Prof Jayasena continued: ‘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 first raised concerns with the ‘several limitations’ of the questionnaire, which he says ‘does not appear to have been developed or validated for ultra-processed food’.
Prof 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. The authors point out that their study is observational so cannot prove causality, but then they also suggest that ‘a diet low in UPFs would be best for both partners’, which could be interpreted as them suggesting they do assume causality.
‘A concern is that such result my cause distress and self-blame in people who have unsuccessfully tried to conceive – and that it is used to give advice to people trying to conceive.’
