Dietary fiber and amyotrophic lateral sclerosis: results from 5 large cohort studies

Amyotrophic lateral sclerosis (ALS) is a fast-progressing neurodegenerative disease with a median survival time from diagnosis of 1.5-3 years. The cause of ALS is unknown, but inflammation may play a role. Fiber has been shown to lower inflammatory markers, and a high fiber intake was associated with a lower risk of ALS in a case-control study; however, prospective studies are lacking. We explored the relation between dietary intake of fiber and the risk of ALS in 5 large prospective cohort studies comprising over 1,050,000 US citizens who contributed 1,133 ALS cases during a mean of 15 years of follow-up (1980-2008). Cox proportional hazards models were used within each cohort, and cohort-specific estimates were subsequently pooled using a random-effects model. We found that intakes of total fiber, cereal fiber, vegetable fiber, and fruit fiber were not associated with ALS risk when comparing the highest quintile of intake with the lowest (for total fiber, pooled multivariable relative risk (RR) = 0.99, 95% confidence interval (CI): 0.80, 1.24; for cereal fiber, RR = 1.13, 95% CI: 0.94, 1.37; for vegetable fiber, RR = 0.97, 95% CI: 0.77, 1.23; and for fruit fiber, RR = 1.05, 95% CI: 0.86, 1.29). These findings do not support the hypothesis that fiber intake is a major determinant of ALS risk.