A low salt diet is usually recommended for people who have high blood pressure.
The study referred to here investigated the effect of salt reduction on vascular function by measuring artery flow-mediated vasodilation (widening of blood vessels) (Dickinson KM, et al, 2009).
The researchers compared measurements after 2 weeks of an usual-salt diet with a low-salt diet (1/3 of the salt) after 2 weeks in overweight and obese people with normal blood pressure. Blood pressure was also measured.
The results showed that the systolic blood pressure went down on the low-salt diet. What also improved was the endothelium-dependent vasodilation and it was concluded that salt reduction provides additional cardio-protective effects beyond blood pressure reduction.
Dickinson KM, et al. Effects of a low-salt diet on flow-mediated dilation in humans. Am J Clin Nutr. 2009 Feb;89(2):485-90.