Relations between dairy product intake and blood pressure: the INTERnational study on MAcro/micronutrients and blood Pressure.
BACKGROUND: Epidemiologic evidence suggests that low-fat dairy consumption may lower risk of hypertension. Dairy products may be distinctly linked to health, because of differences in nutritional composition, but little is known about specific nutrients that contribute to the dairy-blood pressure (BP) association, nor to underlying kidney function. METHODS: We examined cross-sectional associations to BP of dairy product intakes, total and by type, from the INTERnational study on MAcro/micronutrients and blood Pressure (INTERMAP) including 2694 participants aged 40-59 years from the UK and the USA. Eight BP, four 24-h dietary recalls and two 24-h urine samples were collected during four visits. Linear regression models adjusted for lifestyle/dietary factors to estimate BP differences per 2SD higher intakes of total-and-individual-types of dairy were calculated. RESULTS: Multivariable linear regression coefficients were estimated and pooled. In contrast to total and whole-fat dairy, each 195 g/1000 kcal (2SD) greater low-fat dairy intake was associated with a lower SBP -2.31 mmHg and DBP -2.27 mmHg. Significant associations attenuated with adjustment for dietary phosphorus, calcium, and lactose, but strengthened with urinary calcium adjustment. Stratification by median albumin-creatinine ratio (ACR; high ACR indicates impaired kidney function) showed strong associations between low-fat dairy and BP in participants with low ACR (SBP: -3.66; DBP: -2.15 mmHg), with no association in participants with high ACR. CONCLUSION: Low-fat dairy consumption was associated with lower BP, especially among participants with low ACR. Dairy-rich nutrients including phosphorus and calcium may have contributed to the beneficial associations with BP.