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.

Comparison of low-fat versus Mediterranean-style dietary intervention after first myocardial infarction (from The Heart Institute of Spokane Diet Intervention and Evaluation Trial).

Whether a Mediterranean-style diet reduces cardiovascular events and mortality more than a low-fat diet is uncertain. The objectives of this study were to actively compare low-fat and Mediterranean-style diets after first myocardial infarction (MI) in a randomized, controlled clinical trial and to compare dietary intervention per se with usual care in a case-control analysis. First MI survivors were randomized to a low-fat (n = 50) or Mediterranean-style (n = 51) diet. The 2 diets were low in saturated fat (< or =7% kcal) and cholesterol (< or =200 mg/day); the Mediterranean-style diet was distinguished by greater omega-3 fat intake (>0.75% kcal). Participants received individual dietary counseling sessions, 2 within the first month and again at 3, 6, 12, 18, and 24 months, along with 6 group sessions. Combined dietary intervention groups (cases, n = 101) were compared with a usual-care group (controls, n = 101) matched for age, gender, MI type and treatment, and status of diabetes mellitus and hypertension. Primary-outcome-free survival (a composite of all-cause and cardiac deaths, MI, hospital admissions for heart failure, unstable angina pectoris, or stroke) did not differ between low-fat (42 of 50) and Mediterranean-style (43 of 51) diet groups over a median follow-up period of 46 months (range 18 to 72; log-rank p = 0.81). Patients receiving dietary intervention had better primary-outcome-free survival (85 of 101) than usual-care controls (61 of 101) (log-rank p <0.001), with unadjusted and adjusted odds ratios of 0.33 (95% confidence interval 0.18 to 0.60, p <0.001) and 0.28 (95% confidence interval 0.13 to 0.63, p = 0.002), respectively. In conclusion, active intervention with either a low-fat or a Mediterranean-style diet similarly and significantly benefits overall and cardiovascular-event-free survival after MI.

Implications of chronic kidney disease for dietary treatment in cardiovascular disease.

Chronic kidney disease (CKD) often accompanies cardiovascular disease (CVD). Trends foretelling a greater burden of CKD and CVD are largely a result of increasing frequencies of obesity, hypertension, and diabetes. Nutritional therapy occupies a critical role in reducing risk factors and preventing progressive damage to the kidneys and heart. Nutritional assessment and treatment should take into account both health concerns. This review examines several diet components and eating styles for efficacy in the treatment of these conditions. A variety of dietary regimens claim to provide health benefits, but rigorous scientific validation of long-term efficacy is frequently lacking. An urgent need exists for eating styles that reduce risk of chronic diseases and that are acceptable and achievable in free-living populations. We describe our ongoing study, a randomized controlled trial comparing the American Heart Association Step II diet and a Mediterranean diet, in survivors of a first myocardial infarction. The primary end point is a composite of mortality and major CVD events. Because many in this population have CKD, indicators of kidney damage and function are prespecified secondary end points. Results of this trial should provide insight into optimal dietary interventions for persons with both CVD and CKD.