Diet and blood pressure: The INTERMAP and INTERMAP China Prospective Studies

Abstract

Dietary factors are important modifiable risk factors for adverse blood pressure (BP). Previous literature on relationships of dietary glycaemic index (GI) and glycaemic load (GL) to BP were not consistent and research was limited in East Asian populations. The International Collaborative Study of Macro-/Micro-nutrients and BP (INTERMAP) is a cross-sectional epidemiological study to investigate the role of multiple dietary factors in the aetiology of unfavourable BP levels, including 7 population samples from China and Japan. Eight BP, four anthropometric measures, four 24-hour dietary recalls, and two 24-hour urine samples were collected in four visits. GI values of food codes were assigned using existing national and international database of GI values following developed algorithm, and the relationships of dietary GI/GL to BP were explored. The INTERMAP China Prospective (ICP) Study is the follow-up of three INTERMAP Chinese populations with extensive data collection aiming to investigate the dietary exposure and its relation to BP changes. A BP calibration study was conducted and calibration equations were generated to make BP data comparable with different devices between the baseline and the follow-up. Findings showed that dietary GI and GL were not directly associated with BP in Chinese and Japanese populations. Among the baseline participants in the ICP Study, higher intake of dietary total protein and glutamic acid at baseline tended to be associated with smaller BP increase; higher intake of vegetable protein and glutamic acid at baseline tended to be associated with lower risk of incident hypertension (HTN). Results suggested protein intake, especially glutamic acid (the predominant dietary amino acid, especially in vegetable protein), may be associated with less BP increase with age and lower risk of incident HTN in long-term, and this may have implications for nutritional approaches to control high BP levels and slow down BP increase with age in populations.