Population-based case-control study of amyotrophic lateral sclerosis in western Washington State. II. Diet

The association of nutrient intake with the risk of amyotrophic lateral sclerosis (ALS) was investigated in a population-based case-control study conducted in three counties of western Washington State from 1990 to 1994. Incident ALS cases (n = 161) were identified and individually matched on age and gender to population controls (n = 321). A self-administered food frequency questionnaire was used to assess nutrient intake. Conditional logistic regression analysis was used to compute odds ratios adjusted for education, smoking, and total energy intake. The authors found that dietary fat intake was associated with an increased risk of ALS (highest vs. lowest quartile, fiber-adjusted odds ratio (OR) = 2.7, 95% confidence interval (CI): 0.9, 8.0; p for trend = 0.06), while dietary fiber intake was associated with a decreased risk of ALS (highest vs. lowest quartile, fat-adjusted OR = 0.3, 95% CI: 0.1, 0.7; p for trend = 0.02). Glutamate intake was associated with an increased risk of ALS (adjusted OR for highest vs. lowest quartile = 3.2, 95% CI: 1.2, 8.0; p for trend < 0.02). Consumption of antioxidant vitamins from diet or supplement sources did not alter the risk. The positive association with glutamate intake is consistent with the etiologic theory that implicates glutamate excitotoxicity in the pathogenesis of ALS, whereas the associations with fat and fiber intake warrant further study and biologic explanation.