Epidemiological evidence of the association between dietary protein intake and blood pressure: a meta-analysis of published data.

The purpose of this study was to address the association between dietary protein intake and blood pressure (BP) by combining information from all epidemiological studies that presented quantitative estimates of dietary protein intake and BP assessment. A literature search of MEDLINE, restricted to human studies on dietary protein intake and BP, was conducted. References cited in related studies were also reviewed. The results were as follows. 1) Of eleven cross-sectional studies identified, nine were suitable for quantitative pooled analysis. In men (total sample, n=19,954 for SBP, and 19,982 for DBP), the pooled regression coefficients (betas) of SBP and DBP on dietary protein intake were -0.03 (0.001) and -0.025 (0.01) (both, p<0.01). In women (n=950), the pooled betas were -0.014 (0.01) for SBP (p<0.05) and -0.021 (0.00) for DBP (p<0.01). In the studies that reported data for both sexes (n=12,716 for SBP and 12,508 for DBP), the pooled betas were -0.029 (0.01) and -0.0156 (0.00) for SBP and DBP (both p<0.01). 2) Twenty-four-hour dietary recall and 24-h urine collection were the main methods used for diet assessment, and their pooled results were consistent with the combined results for both sexes. 3) Results from two longitudinal studies showed inverse associations between dietary protein intake and BP after 3 and 7 years' follow-up. In conclusion, a convincing cross-sectional inverse association between dietary protein intake and BP was demonstrated by the meta-analysis of nine population-based studies. The evidence from longitudinal epidemiological studies was limited. Further studies will be needed to confirm the hypothesis of the inverse dietary protein-BP association.