Relationship to blood pressure of combinations of dietary macronutrients: Findings of the Multiple Risk Factor Intervention Trial (MRFIT)

Background: Elevated blood pressure remains a widespread major impediment to health. Obesity and specific dietary factors such as high salt and alcohol intake and low potassium intake adversely affect blood pressure. It is a reasonable hypothesis that additional dietary constituents, particularly macronutrients, may also influence blood pressure. Methods and Results: Participants were 11 342 middle-aged men from the Multiple Risk Factor Intervention Trial (MRFIT). Data from repeat 24-hour dietary recalls (four to five per person) and blood pressure measurements at six annual visits were used to assess relationships, singly and in combination, of dietary macronutrients to blood pressure, adjusted for multiple possible confounders (demographic, dietary, and biomedical). Multiple linear regression was used to assess diet blood pressure relations in two MRFIT treatment groups (special intervention and usual care), with adjustment for confounders, pooling of coefficients from the two groups (weighted by inverse of variance), and correction of coefficients for regression-dilution bias. In multivariate regression models, dietary cholesterol (milligrams per 1000 kilocalories), saturated fatty acids (percent of kilocalories), and starch (percent of kilocalories) were positively related to blood pressure; protein and the ratio of dietary polyunsaturated to saturated fatty acids were inversely related to blood pressure. These macronutrient-blood pressure findings were obtained in analyses that controlled for body mass, dietary sodium and ratio of sodium to potassium, and alcohol intake, each positively related to blood pressure, and intake of potassium and caffeine, both inversely related to blood pressure. Conclusions: These data support the concept that multiple dietary factors influence blood pressure; hence, broad improvements in nutrition can be important in preventing and controlling high normal and high blood pressure.