Researchers found that salt-laden foods quickly impair the ability of blood vessels to widen even in people with normal blood pressure, according to the study published in this month's The American Journal of Clinical Nutrition.
While the long term effects of this kind of impairment are unknown, the findings do show that salt has an impact even in people with healthy blood pressure, noted the study’s lead author, Kacie M. Dickinson, a researcher at the Commonwealth Scientific and Industrial Research Organization in Adelaide, Australia.
“What surprised us was that this is similar to responses seen after a meal high in saturated fats, which we know can be damage blood vessels in the long-term,” Dickinson said.
Dickinson and her colleagues studied the impact of high salt food in 16 healthy volunteers by giving eight of them a low salt serving of tomato soup and a version with 10 times more salt to the others. Each serving was about a cup.
After the snacks were consumed, the volunteers were asked to put their arms in a blood pressure cuff, which temporarily cut off blood flow as it inflated. While the cuff was deflating, the researchers used an ultrasound machine to measure how much the arteries widened as the blood rushed back through them.
The same experiment was repeated with the two groups of volunteers switched so that people who got a high salt snack the first time consumed the low salt version the second time.
Consistently, the arteries of people who got the high salt snack widened about half as much as those who consumed the low salt version. The effect passed in about two hours.
By using ultrasound to measure the ability of blood vessels to widen, scientists are able “to non-invasively detect changes in blood vessel function which is one of the earliest stages of atherosclerosis (fat accumulating in the blood vessels) which over time can lead to blockages in the blood vessels which causes heart attacks and strokes,” Dickinson said.
Substances like salt and fat may hinder the artery’s ability to widen by interfering with the workings of the blood vessel’s lining, said Dr. Emile Mohler, director of vascular medicine at the University of Pennsylvania Health System.
Normally, when the heart pumps blood through the arteries, nitric oxide is released. The gas makes the artery walls relax, which in turn allows the vessels to expand and more easily carry the rush of blood, Mohler explained.
Scientists suspect that salt and fat may somehow block the release of nitric oxide.
But, given that the study also shows that the effect passes within a couple of hours, does it matter if the arteries can’t expand as much for a short while?
Other studies have shown that this kind of impaired artery function might set a person up for atherosclerosis, Mohler said.
“The thinking is that as you go through decades where the lining is challenged and not working as well because you don’t get the release of nitric oxide, then you’re setting yourself up for cholesterol to stick to the arteries,” Mohler said.
Beyond this, we know that salt can have permanent effects, said Dr. Peter J. Counihan, an associate professor at the University of Pittsburgh’s Cardiovascular Institute.
“There’s no doubt that people with a high salt intake eventually develop high blood pressure,” Counihan said. “So, if nothing else, this study should serve as a reminder that salt is bad for you. Like everything else in life, it has to be done in moderation.”
