Eating high volumes of ultra-processed foods may be linked to fertility issues in men and could cause delays in couples falling pregnant, a new study has found.
Ultra-processed foods – commonly known as UPFs – are products such as mass-produced bread, cereals, crisps and sweets that contain more additives than natural ingredients.
They are linked to at least 32 serious health conditions including type 2 diabetes, heart disease, dementia and cancer.
Some experts have warned that they are responsible for a ‘chronic disease pandemic’ and while others have disputed such suggestions, intrigue around their effects continues to grow.
Now, a study published in the Oxford Academic Human Reproduction journal, has revealed for the first time that there may be a correlation between UPF consumption and fertility.
The Netherlands-led research observed 831 women and 651 male partners from pre-conception to their child’s early years.
It was uncovered that future fathers with a higher UPF consumption were at a greater risk of having lower fertility. They also noted that a foetus’ embryonic growth and yolk size was smaller in women who had a higher UPF consumption.
Dr Gaillard, an epidemiology professor at Erasmus University Rotterdam and study lead 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.’
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
The research followed the cohort between 2017 and 2021, and saw the team ask future parents questions about their diet when the woman was 12 weeks pregnant.
On average, women reported 22 per cent of their diet containing UPFs while men said theirs was 25 per cent.
More than one in 10 of the couples followed in the group had an intake of more than 30 per cent UPFs in the research.
And while the results of the survey affected both parties, UPF consumption appeared to affect men far more.
It was uncovered that the surveyed men on average were associated with a 37 per cent higher risk of subfertility – meaning it will take their partner longer to become pregnant.
Those in the highest UPF group, meanwhile, were at a 69 per cent higher risk of subfertility.
For women – who received transvaginal ultrasounds after seven, nine and 11 weeks – a higher UPF intake was linked to a slightly smaller yolk sac size at seven weeks pregnant.
It also brought smaller embryonic growth, though the study notes that these effects weakened in the following ultrasounds.
Previous studies have suggested that slower embryonic growth during this period can sometimes be linked to premature births, miscarriage and an increased risk of heart and blood problems in childhood.
Celine Lin, a Phd student at Erasmus University Medical Center, and first author of the study said: ‘We observed that UPFs consumption in women was not consistently related to the risk of subfertility and time to pregnancy, but was associated with slightly smaller embryonic growth and yolk sac size by the seventh week of pregnancy.
‘These differences in early human development were small, but are important from a research perspective and at population level, as we showed for the first time that UPF consumption is not only important for health of the mother, but may also be related to development of the offspring.
‘In men, we observed that higher UPF consumption was related to a higher risk of subfertility and a longer duration until pregnancy was achieved, but not with early embryo development. This association may be explained by the sensitivity of sperm to dietary composition, whereas maternal UPF consumption may directly influence the environment in the womb in which the embryo develops from the start of life onwards.’
The authors were keen to point out that further research was required on their findings particularly because their study was observational and cannot prove the direct cause of UPF consumption on the results.
However, Dr Gaillard 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.’
