Research demonstrates a new damaging effect of salt intake on the circulatory system
1 December 2011
29 June 2010
A new study published (Ref. 1) today provides increasing evidence to suggest that our high salt intake has direct damaging effects on small blood vessels (capillaries) that may be independent and additive to the effect of salt in raising blood pressure.
The study demonstrated that a modest reduction in salt intake, as currently recommended in the United Kingdom and the United States, not only lowers blood pressure but also increases skin capillary density in white, black, and Asian individuals with mildly raised blood pressure.
Furthermore; the study found that the greater the reduction in salt intake, the greater the increase in the number of small blood vessels (capillary density). A reduction in capillary density and the microcirculation is thought to lead damaging effects on the brain, possibly increasing the likelihood of dementia. In the heart, the reduction in cardiac function may increase the likelihood of heart failure.
The findings suggest that a reduction in salt intake could have major cardiovascular benefits potentially independent of the blood pressure fall that occurs.
Graham MacGregor, Professor of Cardiovascular Medicine at the Wolfson Institute of Preventive Medicine and Chairman of CASH comments:
“The new research provides further evidence that our high salt intake can directly damage the circulatory system, both additive and independent of blood pressure. These results provide even more support for the current recommendations to reduce salt intake to less than 6 g/day in adults and much less in children.”
1. He FJ, Marciniak M, Markandu ND, Antonios TF, MacGregor GA. Effect of Modest Salt Reduction on Skin Capillary Rarefaction in White, Black, and Asian Individuals With Mild Hypertension. Hypertension. 2010;56:253-259.* *Published online Jun 28, 2010; DOI: 10.1161/HYPERTENSIONAHA.110.155747.
Microvascular rarefaction occurs in hypertension. We carried out a 12-week randomized double-blind crossover trial to determine the effect of a modest reduction in salt intake on capillary rarefaction in 71 whites, 69 blacks, and 29 Asians with untreated mildly raised blood pressure. Both basal and maximal (during venous congestion) skin capillary density were measured by capillaroscopy at the dorsum and the side of the fingers. In addition, we used orthogonal polarization spectral imaging to measure skin capillary density at the dorsum of the fingers and the hand web. With a reduction in salt intake from 9.7 to 6.5 g/day, there was an increase in capillary density (capillaries per millimetre squared) from 101+/-21 to 106+/-23 (basal) and 108+/-22 to 115+/-22 (maximal) at the dorsum, and 101+/-25 to 107+/-26 (basal) and 110+/-26 to 116+/-26 (maximal) at the side of the fingers (P_0.001 for all). Orthogonal polarization spectral imaging also showed a significant increase in capillary density both at the dorsum of the fingers and the web. Subgroup analysis showed that most of the changes were significant in all of the ethnic groups. Furthermore, there was a significant relationship between the change in 24-hour urinary sodium and the change in capillary density at the side of the fingers. These results demonstrate that a modest reduction in salt intake, as currently recommended, improves both functional and structural capillary rarefactions that occur in hypertension, and a larger reduction in salt intake would have a greater effect. The increase in capillary density may possibly carry additional beneficial effects on target organs.