a1 Chronic Diseases of Lifestyle Unit, Medical Research Council, South Africa
a2 School of Health Sciences, Faculty of Health and Behavioural Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia
a3 Division of Diabetes and Endocrinology, University of Cape Town
a4 Biostatistics Unit, Medical Research Council, South Africa
Objective To assess the impact of a food-based intervention on blood pressure (BP) in free-living South African men and women aged 50–75 years, with drug-treated mild-to-moderate hypertension.
Methods A double-blind controlled trial was undertaken in eighty drug-treated mild-to-moderate hypertensive subjects randomised to an intervention (n 40) or control (n 40) arm. The intervention was 8-week provision of six food items with a modified cation content (salt replacement (SOLO™), bread, margarine, stock cubes, soup mix and a flavour enhancer) and 500 ml of maas (fermented milk)/d. The control diet provided the same quantities of the targeted foods but of standard commercial composition and 500 ml/d of artificially sweetened cooldrink.
Findings The intervention effect estimated as the contrast of the within-diet group changes in BP from baseline to post-intervention was a significant reduction of 6·2 mmHg (95 % CI 0·9, 11·4) for systolic BP. The largest intervention effect in 24 h BP was for wake systolic BP with a reduction of 5·1 mmHg (95 % CI 0·4, 9·9). For wake diastolic BP the reduction was 2·7 mmHg (95 % CI −0·2, 5·6).
Conclusions Modification of the cation content of a limited number of commonly consumed foods lowers BP by a clinically significant magnitude in treated South African hypertensive patients of low socio-economic status. The magnitude of BP reduction provides motivation for a public health strategy that could be adopted through lobbying of the food industry by consumer and health agencies.
(Received October 29 2007)
(Accepted July 08 2008)