Dietary Amino Acids and Blood Pressure: A Cohort Study of Patients With Cardiovascular Disease

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.