Dietary protein and blood pressure.

OBJECTIVE

• To review published and presented data on the relationship between dietary protein and blood pressure in humans and animals.

DATA SOURCES

• Bibliographies from review articles and books on diet and blood pressure that had references to dietary protein. The bibliographies were supplemented with computerized MEDLINE search restricted to English language and abstracts presented at epidemiologic meetings.

STUDY SELECTION

• Observational and intervention studies in humans and experimental studies in animals.

DATA EXTRACTION

• In human studies, systolic or diastolic blood pressure were outcome measures, and dietary protein was measured by dietary assessment methods or by urine collections. In animal studies, blood pressure and related physiological effects were outcome measures, and experimental treatment included protein or amino acids.

DATA SYNTHESIS

• Historically, dietary protein has been thought to raise blood pressure; however, studies conducted in Japan raised the possibility of an inverse relationship. Data analyses from subsequent observational studies in the United States and elsewhere have provided evidence of an inverse relationship between protein and blood pressure. However, intervention studies have mostly found no significant effects of protein on blood pressure. Few animal studies have specifically examined the effects of increased dietary protein on blood pressure.

CONCLUSIONS

• Because of insufficient data and limitations in previous investigations, better controlled and adequately powered human studies are needed to assess the effect of dietary protein on blood pressure. In addition, more research using animal models, in which experimental conditions are highly controlled and detailed mechanistic studies can be performed, is needed to help provide experimental support for or against the protein-blood pressure hypothesis.