Is fish intake linked to juvenile idiopathic arthritis?

Juvenile idiopathic arthritis (JIA) results from a complex interplay of genetic and environmental factors. Past efforts to identify JIA’s environmental risk factors have been restricted due to limited high-quality data and small sample sizes, mirroring the rarity of the disease.

In 2019, a Swedish prospective birth cohort study of over 15,000 children showed that consuming fish at least once a week during pregnancy and during the first year of life was associated with up to a 5-fold increased risk of JIA, compared to those with fish consumption less than once a week. This increased risk was primarily attributed to elevated exposure to heavy metals.

Now, new research shared at the 2024 congress of EULAR—The European Alliance of Associations for Rheumatology—is investigating the association between the risk of JIA and maternal fish consumption or dietary mercury exposure during pregnancy.

This large, population-based prospective cohort used data from the Norwegian Mother, Father, and Child Cohort Study, which recruited pregnant women in 1999–2008. JIA cases were defined via linkage to the national patient registry. Maternal fish consumption was assessed using a food frequency questionnaire that covered the first half of pregnancy.

High fish consumption was defined as exceeding the 90th percentile—or 252 grams per week for lean and semi-oily fish, 157.5 grams per week for oily fish, and 427 grams per week for total fish intake. Dietary mercury exposure was estimated from the fish consumption data. High mercury intake was classed as more than 20 μg per week. Associations were adjusted for maternal factors, including age, education, pre-pregnancy body mass index, parity, daily caloric intake, inflammatory rheumatic disorders, as well as parental smoking in pregnancy.

The sample included 73,819 mother-child pairs and 218 cases of JIA in the children. The median total fish intake was 218 grams per week, and there was a positive association between JIA and high consumption of lean and semi-oily fish versus those with low consumption. No clear associations were observed between JIA and high consumption of oily and total fish. Notably, no association was found between JIA and high mercury intake versus low.

“We found increased odds of JIA when the maternal intake exceeded 252 grams of lean or semi-oily fish per week compared with low intake,” said Vilde Øverlien Dåstøl, “but the magnitude of our effect estimates was substantially smaller than the Swedish study, and we found no association between total fish consumption or estimated dietary mercury exposure and JIA. It is crucial to emphasize that while our data indicates an association, causation cannot be definitively inferred. Therefore, we cannot caution pregnant women against consuming fish solely based on this study in regards to JIA risk, especially considering other research highlighting the positive impacts of a marine diet.”

Further investigation is needed to clarify the role of heavy metals and other dietary contaminants in JIA etiology.

Provided by
European Alliance of Associations for Rheumatology (EULAR)