The global rise in inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, has no clear explanation. A contributing factor is thought to be dietary patterns that affect the bacteria in the gut, the gut microbiota, which is particularly sensitive during the first years of life.

Previous research has looked at dietary patterns and IBD in adults, but research on children’s diets and links to IBD are scarce. The aim of the current study, published in the journal Gut, has been to increase knowledge in this area.

The study’s final analysis includes dietary information on 81,280 1-year-olds in Sweden and Norway. The data on the children included come from the two population studies: All Children in Southeastern Sweden, ABIS, and the Norwegian Mother, Father and Child Cohort Study, MoBa.

Less ulcerative colitis in fish eaters

Parents were asked specific questions about their children’s diet at 12-18 and 30-36 months of age. Diet quality was assessed using a child-friendly version of the Healthy Eating Index tool, which looks at the quality of the whole diet. Diet quality was systematically scored and classified as either low, medium or high.

Higher quality equaled a higher intake of vegetables, fruit, dairy products and fish, and a lower intake of meat, sweets, snacks and sweet drinks. Intakes of individual food groups were also studied.

Data on breastfeeding, and the child’s intake of formula and antibiotics exposure were also included. Children’s health was monitored from the age of 1 and for an average of 21 years for ABIS and 15 years for MoBa, until the end of 2020/2021.

During this period, 307 of the participants were diagnosed with IBD, with 131 having Crohn’s disease, 97 having ulcerative colitis and 79 having an unclassified IBD. The incidence of IBD was higher in the Swedish ABIS study than in Norwegian MoBa cohort, probably due to the longer follow-up time in ABIS.

High fish intake at age 1 year, compared to a low intake, was associated with a 54% lower risk of ulcerative colitis. High vegetable intake at 1 year of age was associated with an overall reduced IBD risk. High intake of sugar beverages, compared to a low intake, was accompanied by a 42% increased risk of IBD.

Findings support the hypothesis

There were no obvious associations between IBD and any of the other food groups: meat, dairy, fruit, grains, potatoes and foods high in sugar or fat, or both. At 3 years of age, only a high fish intake was associated with a reduced risk of IBD, in particular ulcerative colitis.

The associations remained after adjusting for the child’s intake of formula and antibiotics at age 1, as well as for breastfeeding and parents’ total household income. As the study was conducted in high-income countries, it is unclear whether the results can be generalized to low- or middle-income countries with different dietary habits, the researchers say. Causality cannot be established either, as this is an observational study.

“Although we cannot rule out other explanations, the new findings are consistent with the hypothesis that diet early in life, possibly mediated by changes in the gut microbiome, can affect the risk of developing IBD,” says Annie Guo, a dietician and post graduate student in pediatrics at Sahlgrenska Academy at the University of Gothenburg, and the study’s first author.