Objective: To determine the blood pressure responses in elderly normotensive men and women to dietary sodium and to the diunsaturated fatty acid dihomogammalinolenic acid (DGLA), which is derived from linoleic acid.
Design: Blood pressure responses were assessed in 66 subjects (36 male, 30 female; mean age 65 years) on two diets differing by approximately 70 mmol/day sodium, combined with daily supplements of either 1 g DGLA or 1 g safflower oil, giving a four-group parallel design. After a common period of salt restriction and salt supplementation, two sets of parallel groups continued with either salt or placebo tablets. The study was blinded, except for dietary adjustments based on 24-h urinary sodium excretion values measured once every 2 weeks. Blood pressures were also measured automatically once every 2 weeks.
Results: Urinary sodium excretion (sodium intake) correlated significantly with systolic and diastolic blood pressures. A strong interaction with sex (P < 0.001 for systolic blood pressure) reflected greater responsiveness in women to changing sodium intake. A second major determinant of blood pressure responsiveness was the waist: hip ratio, an index of central obesity; this correlation was independent of the initial sodium intake, initial blood pressure or body mass index. The waist: hip ratio was a powerful predictor of blood pressure changes with sodium intake in women only; women with android fat distribution were, similarly to men, less sensitive to dietary sodium. Daily supplements of 1 g DGLA doubled the concentration of DGLA in plasma but did not influence blood pressure.
Conclusions: Among elderly normotensive subjects, women responded to changes in sodium intake with greater changes in blood pressure than men did. Furthermore, this response was strongly related to the gynaecoid distribution of body fat.