Obesity masks the relationship between dietary salt intake and blood pressure in people of African ancestry: the impact of obesity on the relationship between sodium and blood pressure.

Previous studies conducted to investigate the relationship between sodium intake and blood pressure in our African population have yielded contradictory results. With the high prevalence of obesity in this population, it is possible that these contradictory findings are due to the masking effects of obesity on this relationship. We measured 24-hour ambulatory blood pressure and 24-hour urine excretion on 547 South Africans of African ancestry. A multivariate regression analysis revealed no independent relationship between 24-hour sodium excretion and blood pressure in the total population sample, but when participants were stratified according to body mass index (BMI) status, there was a significant association between 24-hour sodium excretion and blood pressure in the normal-BMI participants but not in the overweight/obese participants. We concluded that dietary salt intake, indexed by 24-hour urinary sodium excretion, was associated with increased ambulatory blood pressure but this relationship was masked because of a high proportion of overweight/obese individuals in this population.