Eating large amounts of ultra-processed foods (UPF) could cause reduced fertility in men and pregnancy issues such as slow growth of embryos in women, a new study suggests.
More than half of calories consumed across the UK are from UPFs, which include foods such as crisps, chocolate, some cereals and instant noodles, but the impact of eating too much convenience food on embryonic development has not been studied before.
Not only may eating too much processed food lead to reduced fertility in men, but also to slower growth in early embryos, and smaller yolk sacs, which are essential for early embryonic development, researchers from the Netherlands found.
Researchers have said their findings suggest that reducing the consumption of UPFs, especially around the time of conception and pregnancy, is better for both parents and embryos.
“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,” said Dr Romy Gaillard, a paediatrician and associate professor of developmental epidemiology at Erasmus University Medical Center, Rotterdam, The Netherlands, who led the study.
But experts remain skeptical on whether ultra-processed foods are to blame for these fertility issues, and stress that weight gain and weight loss show more significant results.
“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,” Channa Jayasena, Professor of Reproductive Endocrinology at Imperial College London, who was not involved in the study, said.
“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 UPFs are causing reproductive problems, their impact on individuals appears very small indeed.”
For the study, published in the journal Human Reproduction, findings from 831 women and 651 male partners who were during the pre-conception period or during pregnancy between 2017 and 2021, were analysed.
The parents’ diet was assessed using a questionnaire during early pregnancy around 12 weeks and found an average of 22 per cent of women’s diets and 25 per cent of men’s were UPFs.
A questionnaire also provided information about the pregnancy and the size of the embryo.
Embryos of the mothers who ate the most UPFs tended to be smaller throughout the first trimester of pregnancy, in comparison to mothers who ate the least amount of UPFs, the study found.
Other studies have shown that slower embryonic growth in the first trimester is associated with an increased risk of adverse birth outcomes, including premature birth (birth before 37 weeks), low birth weight, and an increased risk of heart and blood vessel problems in childhood. Impaired yolk sac development is associated with an increased risk of miscarriage and premature birth.
The first author of the study, Celine Lin, a Phd student at Erasmus University Medical Center, said: “We observed that UPFs consumption in women was not consistently related to the risk of subfertility (reduced fertility) 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 the health of the mother, but may also be related to the development of the offspring.”
