BARCELONA—Overall intake of polyunsaturated fatty acids (PUFAs) is associated with a lower risk of multiple sclerosis (MS), according to a prospective study described at the 31st Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS). The association mainly results from the effect of plant-derived PUFAs, especially alpha-linolenic acid. Fish-derived fatty acids appear to have no significant association with MS risk.
“While confirmation from other studies is needed, low PUFA intake may be another modifiable risk factor for MS,” said Kjetil Bjørnevik, MD, a research fellow in the neuroepidemiology group at Harvard T.H. Chan School of Public Health in Boston.
Kjetil Bjørnevik, MD
For more than 50 years, investigators have been studying the role that fat intake may play in the development of MS. In a 1952 New England Journal of Medicine article, researchers proposed that differences in the incidence of MS in distinct regions of Norway resulted from differences in diet. Subsequent animal studies suggested that omega-6 PUFAs have disease-modifying effects. A recent Cochrane review of randomized controlled trials concluded that PUFAs play no major role on the clinical outcomes of MS. A recent study, however, found an inverse association between overall omega-3 PUFA intake and MS risk.
Dr. Bjørnevik and colleagues prospectively followed more than 175,000 participants in the Nurses’ Health Studies I and II. Participants received questionnaires every second year, and their diet was assessed every fourth year. Dr. Bjørnevik’s team used food-frequency questionnaires to assess the nurses’ intake of alpha-linolenic acid, linoleic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) at baseline (ie, in 1984 and 1991) and during follow-up. The questionnaires had been specifically validated for the intake of PUFAs. The study’s follow-up time spanned several decades. During follow-up, 479 participants developed MS. Each diagnosis of MS was confirmed by a treating neurologist or by medical records. The researchers used a Cox proportional h<hl name="5"/>azard model to calculate acid ratios in each cohort and adjusted all analyses for age, ethnicity, BMI at age 18, smoking, vitamin D intake from supplements, and total caloric intake.
The investigators found no significant association between overall fat intake and MS risk. Neither saturated fat intake nor monounsaturated fat intake was associated with MS. “This [result] is interesting, as it has been suggested that a diet rich in saturated fat could increase MS risk,” said Dr. Bjørnevik. PUFA intake, however, was significantly associated with lower MS risk. The hazard ratio of MS among participants in the top quintile of PUFA intake was 0.66. The researchers also observed a trend toward lower risk of MS in the other quintiles of PUFA intake. No such association obtained for any other fat studied.
When the group examined the specific types of PUFAs, they found no association between dietary intake of fatty-fish-derived PUFAs, including EPA and DHA, and MS risk. “It is mostly these fatty acids that have been suggested to be beneficial for MS risk,” said Dr. Bjørnevik. Both plant-derived PUFAs (ie, alpha-linolenic acid and linoleic acid), however, were associated with lower MS risk. The hazard ratio of MS for the top quintile of alpha-linolenic acid intake was 0.64.
Finally, Dr. Bjørnevik and colleagues compared the effect estimates for PUFA in the baseline analysis and in the cumulative analysis. The results of both analyses were similar. The overall intake of PUFAs was consistently associated with lower MS risk in both analyses. The fish-derived PUFAs were not significantly associated with MS risk in either analysis, but plant-derived PUFAs were associated with a lower MS risk in both analyses.
—Erik Greb