Chapter 11. Relation of dietary fiber to blood lipids in the special intervention and usual care groups in the Multiple Risk Factor Intervention Trial

This chapter addresses relations between intake of fiber-total, soluble, and insoluble and blood lipids in the Multiple Risk Factor Intervention Trial through use of baseline data (single measurement), averages of four to five 24-h recalls and blood lipid determinations collected during annual follow- up examinations, and change from baseline to follow-up. No significant associations were observed at baseline. Consistent highly significant inverse associations were seen in analyses of follow-up measurements. Results from change data were of intermediate strength and consistency. These variations were in all likelihood due to the low reliability of a single 24-h recall at baseline for determination of dietary intake and change in intake for individuals. From follow-up data, plasma total and low-density-lipoprotein (LDL) cholesterol concentrations were lower by ≃5 mg/dL for men in the special intervention group in quintile 5 of total fiber intake (25 g/d) compared with men in quintile 1 (8 g/d), after adjustment for average body mass index and intake of alcohol, saturated and polyunsaturated fatty acids, and dietary cholesterol. Results were similar for men in the usual care group. There were no adverse effects on high-density-lipoprotein cholesterol, nor any consistent associations with plasma triglycerides. Thus, increasing dietary fiber can provide additional reduction in blood total and LDL cholesterol and consequent improvement in the lipid profile, over and above the beneficial effects of a fat-modified diet.