Dietary fiber and progression of atherosclerosis: the Los Angeles atherosclerosis study

Background: Several epidemiologic studies found weak protective relations between dietary fiber intake and the risk of cardiovascular disease events. However, few of the studies addressed possible mechanisms of the effect. Objective: In the present study, we estimated relations between the progression of atherosclerosis and the intake of selective dietary fiber fractions. Mediation of the relations by serum lipids was also investigated. Design: Participants who were free of heart disease and aged 40-60 y were recruited into the cohort (n = 573; 47% women). The intima-media thickness (IMT) of the common carotid arteries was measured ultrasonographically at the baseline examination and at 2 follow-up examinations (n = 500), dietary intakes were assessed with six 24-h recalls (3 at baseline and 3 at the first follow-up examination), and blood samples were analyzed at baseline and at both follow-up examinations. Results: A significant inverse association was observed between IMT progression and the intakes of viscous fiber (P = 0.05) and pectin (P = 0.01). Correction for measurement error increased the magnitude of these estimated effects. The ratio of total to HDL cholesterol was inversely related to the intakes of total fiber (P = 0.01), viscous fiber (P = 0.05), and pectin (P = 0.01). The magnitude of the association between IMT progression and the intakes of viscous fiber and pectin was attenuated by adjustment for serum lipids. Conclusions: The intake of viscous fiber, especially pectin, appears to protect against IMT progression. Serum lipids may act as a mediator between dietary fiber intake and IMT progression.