Background: Dietary protein has been variably reported to either lower or raise blood pressure. The purpose of this study was to determine whether intakes of specific amino acids differentially associate with blood pressure.
Study design: Observational cohort study by secondary analysis of clinical trial data.
Setting & participants: Study of low-fat versus Mediterranean-style diets in patients with prevalent cardiovascular disease.
Predictor: Dietary amino acids.
Outcomes: Systolic and diastolic blood pressure.
Measurements: Dietary nutrients and cardiovascular risk factors were assessed at baseline, 3 and 6 months, and then every 6 months for 2 years.
Results: Baseline blood pressure was 119 ± 16 (SD)/72 ± 10 (SD) mm Hg (n = 92) and dietary protein intake was 80 ± 31 g/d. Independent amino acid variables (quartiles of intake) were analyzed by generalized estimating equation models with prespecified covariates for time-varying systolic and diastolic blood pressure. The odds of each 1-SD higher systolic or diastolic blood pressure (ie, 16 and 10 mm Hg, respectively) were increased per quartile of intake for methionine (ORs of 1.29 [95% CI, 1.14-1.46] and 1.21 [95% CI, 1.05-1.39], respectively) and alanine (ORs of 1.17 [95% CI, 1.05-1.30] and 1.22 [95% CI, 1.07-1.38], respectively). Quartiles of intake for threonine (ORs of 0.84 [95% CI, 0.74-0.96] and 0.87 [95% CI, 0.75-1.01], respectively) and histidine (ORs of 0.92 [95% CI, 0.86-1.00] and 0.89 [95% CI, 0.82-0.97], respectively) had inverse associations with the same degree of difference in blood pressure.
Limitations: Modest sample-size biases toward the chance of false-negative results; potential for residual confounding; colinearity between amino acids may obscure relevant relationships to blood pressure; associational findings do not establish causality.
Conclusions: Intakes of methionine and alanine were associated positively with higher blood pressure, whereas intakes of threonine and histidine had inverse associations. These amino acids merit further study for advancing dietary approaches to blood pressure reduction.
Copyright © 2012 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.