Ultra-processed foods (UPFs) have been linked to health problems such as heart disease and diabetes, and a new study suggests they might also be contributing to chronic insomnia in some people.

These UPFs can be any foodstuffs that are heavily modified to improve their taste, or produce them on a mass scale, or help them to last longer. They contrast with foods like fruit or vegetables, that come mostly as they are.

Researchers led by a team from Sorbonne Paris Nord University in France looked at data collected on 38,570 adults as part of the NutriNet-Santé research project, mapping diet information against sleep variables.

"At a time when more and more foods are highly processed and sleep disturbances are rampant, it is important to evaluate whether diet could contribute to adverse or good quality sleep," says Marie-Pierre St-Onge, a nutrition and sleep scientist at Columbia University in the US.

St-Onge and her colleagues found a statistically significant association between higher UPF consumption and increased chronic insomnia risk, after allowances were made for sociodemographic, lifestyle, diet quality, and mental health factors.

Overall, the study participants got 16 percent of their daily energy from UPFs, while 19.4 percent of the cohort reported symptoms of chronic insomnia – and this group tended to have more UPFs in their dietary intake.

The data also showed a slightly stronger association in men. The study only assessed single points in time, and relied on self reporting, but the large number of people involved suggests this is a link that's worthy of future investigation.

"It is important to note that our analyses were cross-sectional and observational in nature, and we did not evaluate longitudinal association," says epidemiologist Pauline Duquenne from Sorbonne Paris Nord University.

"While data do not establish causality, our study is [the] first of its kind and contributes to the existing body of knowledge on UPF."

Considering the previous research we've seen, and the well-established links between diet and sleep, it's perhaps not surprising that UPFs might be having an impact on our bodies in terms of chronic insomnia risk.

Some of the same researchers have previously found an association between the Mediterranean diet and a lower risk of insomnia, so this new study seems to present the other side of that relationship.

It's not yet clear why this relationship might exist. Matching UPFs with weight gain is easier, because of their high calorie content, but further research will be needed to understand how these foods might be keeping us up at night.

"In the future, prospective epidemiological as well as clinical and experimental research could advance knowledge about causality and mediation pathways," write the researchers in their published paper.

The research has been published in the Journal of the Academy of Nutrition and Dietetics.