BOSTON—Diet does not appear to contribute to the development of multiple sclerosis (MS), according to findings presented at the 2014 Joint ACTRIMS–ECTRIMS Meeting.
None of three dietary indices measured at baseline—the Alternative Healthy Eating Index-2010 (AHEI-2010), the Alternate Mediterranean Diet Index (aMED), and the Dietary Approaches to Stop Hypertension Index (DASH)—was significantly associated with the risk of developing MS in two longitudinal cohort studies, Dalia Rotstein, MD, Clinical Fellow in Neurology, Brigham and Women’s Hospital, Cambridge, Massachusetts, reported. Dr. Rotstein’s group prospectively followed more than 185,000 women from the Nurses’ Health Study (NHS) and the NHS II.
After adjustment for known confounders of MS risk—including age, latitude of residence at age 15, BMI at age 18, pack-years of smoking, total energy intake, supplemental vitamin D intake, and ethnicity—the investigators found that the pooled relative risk of MS for the highest versus the lowest quintile of scores for each index was 0.89 for the AHEI-2010, 1.10 for aMED, and 1.30 for DASH.
A principal-components analysis identified two general dietary patterns among the subjects. One was a “Western” dietary pattern with high intake of red and processed meats, refined grains, and sweets, and the other was a “prudent” dietary pattern with high intake of vegetables, fruit, legumes, fish, poultry, and whole grains. Neither was associated with MS risk (relative risk for the highest vs lowest quintile of scores, 0.71 and 1.09, respectively). The results were similar when looking at mean cumulative dietary scores and when looking at the two cohorts separately.
An exception in the analysis using mean cumulative dietary score was for the Western dietary pattern, which was shown to have a significant inverse association with MS risk (relative risk, 0.66). “This just met statistical significance, and we believe that this result is an artifact,” Dr. Rotstein said.
Study participants completed semiquantitative food frequency questionnaires every four years, beginning in 1984 for the NHS and in 1991 for NHS II. The MS cases were documented as of 2004 for NHS (130 cases) and as of 2009 for NHS II (350 cases).
With the exception of studies on vitamin D intake, prior studies have yielded null or inconsistent results with respect to the role of diet in MS development, and most have been limited by a focus on individual dietary elements and by small sample size.
The current study is the first large, prospective, population-based study to investigate the relationship, and it shows no evidence of an association between overall dietary quality and MS, Dr. Rotstein said.
The study is limited by the inherent subjectivity in dietary scores and by a basis in population norms rather than ideal consumption patterns. Also, the study is conceived around recommendations for cardiovascular health, but other dietary patterns may be more relevant for immunologic health, she said, noting that additional study is needed to determine if dietary quality and individual dietary elements in the early years play a role in MS development.