Hypertension, alcohol and cations in urban black and coloured South Africans

Epidemiological evidence shows a positive relationship between alcohol consumption and blood pressure. High alcohol intake and hypertension are common in urban South African men. Relationships between mean arterial pressure (MAP), serum gamma-glutamyltransferase (GGT) as an index of alcohol intake, age, mass and levels of cations in the serum and erythrocytes were investigated in normotensive and hypertensive black and coloured men. Serum levels of potassium, magnesium and calcium and the red blood cell magnesium level were found to be significantly decreased in the black hypertensives. Serum GGT was equally raised in normotensive and hypertensive blacks and was positively correlated with systolic blood pressure in the hypertensive subjects. The coloured hypertensives were heavier, older and had significantly higher serum GGT levels than their normotensive counterparts. Serum GGT was positively correlated with MAP in the coloured subjects. No consistent relationships were found between GGT and blood cations. These data suggest that in younger black subjects alcohol is associated with systolic blood pressure only once hypertension has developed. Other factors, such as cations, may be more important than alcohol in the pathogenesis of hypertension in this group. Alcohol consumption is an important risk factor in coloured hypertensives.