Low fish consumption is associated with a small increased risk of MS

Objective We aimed to investigate the influence of lean and fatty fish consumption on MS risk and to what extent a potential effect may be mediated by vitamin D. We also studied the interplay between fish consumption, sun exposure,DRB1*15:01, andA*02:01. Methods We used 2 population-based case-control studies (6,914 cases and 6,590 controls). Subjects with different fish consumption habits were compared regarding MS risk by calculating ORs with 95% CIs using logistic regression models. The mediation effect of vitamin D on the relationship between fish consumption and MS risk was assessed. Potential interactions between fish consumption, sun exposure, and MS-associated HLA genes were assessed on the additive scale. Results Irrespective of sun exposure habits, low fish consumption, including both lean and fatty fish, was associated with increased MS risk (OR 1.2, 95% CI 1.1-1.4) and interacted with theDRB1*15:01allele (AP 0.3,p< 0.0001). The mediation analysis did not support vitamin D as a mediator of the association between fish consumption and MS risk. There was no interaction between fish consumption and sun exposure habits with regard to MS risk. Conclusions Low fish consumption and low sun exposure seem to be separate risk factors for MS. Our findings suggest that fish consumption predominantly influences MS risk by other means than by effecting vitamin D status, which is of relevance for prevention, in particular for those with a genetic susceptibility to MS.