Nutritional factors in blood pressure.

High sodium intake, low potassium intake, high body mass index and high alcohol intake are established risk factors for high blood pressure (BP) in populations. For sodium, an overview of randomised controlled trials gave the estimate that reduction in sodium of around 70 mmol per day lowered BP on average by 2.9 mmHg systolic and 1.6 mmHg diastolic. An overview of within-population epidemiological studies (excluding INTERSALT), with correction for regression dilution, gave a pooled (simple) regression estimate that 100 mmol lower sodium was associated with BP lower by 4.5 mmHg systolic and 2.5 mmHg diastolic. In INTERSALT, across centres, average sodium excretion was significantly related to slope of BP with age, such that 100 mmol lower sodium was associated with 10 mmHg lower rise in SBP over 30 years; among individuals, previous estimates of the size of relationships of sodium and potassium to BP in INTERSALT were too low because of insufficient correction for the 'regression dilution' problem. For sodium, revised corrected regression estimates, with adjustment for age and sex, were 4.3 mmHg/100 mmol for SBP and 1.8 mmHg/100 mmol for DBP. After adjustment for other confounders, the corrected SBP-sodium regression estimate was 3.1 mmHg/100 mmol; it was 6.0 mmHg/100 mmol if body mass index was excluded from the regression model. The revised multiply adjusted regression estimate for SBP and potassium was -0.67 mmHg/10 mmol. Body mass index was positively related to BP in INTERSALT, consistent with other studies; on average, regression coefficients indicated 3.0 mmHg lower SBP and 2.2 mmHg lower DBP, for body weight lower by 10 kg.(ABSTRACT TRUNCATED AT 250 WORDS)