A common refrain in the doctor’s office is to eat less salt to improve your blood pressure. But that advice might be doing more for our cardiovascular health than previously thought. Cutting about one teaspoon of daily table salt from your diet could reduce your blood pressure by about the same amount as taking a prescription antihypertension medication, according to a recent study.
The idea that cutting dietary salt (aka sodium chloride) also slashes blood pressure is pretty well-established science. “There have been dozens and dozens of studies that have found the link,” says Grant Lipman, an emergency medicine specialist at wilderness medicine company GOES Health, who was not involved in the study. But the new paper is notable for demonstrating the size of the effect and the fact that the benefits held even for people who were already taking drugs for hypertension.
The study followed 213 people between the ages of 50 and 75. Unlike previous trials, however, it included some people who were already taking blood pressure medication. Participants fell into four roughly equal-sized groups: those who had normal blood pressure and did not use medication, those whose blood pressure was in the normal range because of medication, those who used medication but whose hypertension was not controlled and those with hypertension who did not take medication.
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Each participant spent one week on a high-sodium diet followed by one week on a low-sodium diet; the high-sodium diet consisted of the participants’ regular eating patterns supplemented with 2,200 milligrams of extra sodium, while the low-sodium diet was designed by the researchers to be the same for all participants. By the end of the experiment, every group’s average blood pressure dropped while its participants were on the low-sodium diet—regardless of their starting measurements. Baseline blood pressure or medication use “didn’t really matter,” says Deepak Gupta, a cardiologist at Vanderbilt University Medical Center and first author of the study, which was published November 11 in the Journal of the American Medical Association. “The reduction in blood pressure was consistent across all those groups.”
Overall, Gupta’s team found that the blood pressure reduction from cutting out about one teaspoon of table salt daily for a week was about equivalent to the drop most people experience after starting hypertension medication. Reducing the amount of salt you consume isn’t a replacement for prescription medication, however, and you should consult your doctor before stopping or starting any meds.
How, exactly, excess salt increases blood pressure is still a bit of a mystery. The prevailing hypothesis is that when a person consumes more sodium, it causes their body to hold onto more water. This in turn puts more hydrostatic pressure of the walls of the blood vessels, causing hypertension.
But scientists have not clearly demonstrated that this is the main mechanism behind salt’s blood pressure-raising tendencies. In fact, Gupta’s team plans to investigate another hypothesis. While excess fluid may still play a role, Gupta says, “one premise of our study was to see if sodium itself might also be proinflammatory and incite an immune response that actually leads to more vascular stiffening.” He hopes to publish the results of that analysis in the near future.
What is certain is that humans did not evolve to eat a high-sodium diet. “Our hominid ancestors ate probably less than half a gram of sodium a day,” says Bruce Neal, an epidemiologist and director of the George Institute for Global Health in Australia, who was not involved in the new research. But humans are hard-wired to crave salt because we need a certain amount of the mineral to survive, he says.
Sodium is essential for all sorts of bodily processes, including contracting and relaxing muscles, conducting nerve signals and maintaining a healthy internal fluid balance. “It’s a super important electrolyte,” Lipman says. Too little salt can send your body into hyponatremia, a potentially dangerous condition that causes confusion, headaches and, in rare cases, seizures or comas. Salt’s physiological importance explains why it tastes so good to us—it was hard for many of our distant ancestors to access, so eating it was a treat. But just like a spicy ghost pepper or a particularly pungent cheese, a little goes a long way.
Currently, the average person in the U.S. eats about 3,400 milligrams of sodium per day. Most of that—about 70 percent—comes from processed or restaurant food, according to the American Heart Association. Yet the Food and Drug Administration recommends consuming less than 2,300 milligrams each day. There are a few exceptions to this rule; for example, people with certain medical conditions such as kidney failure may need to increase their sodium intake. Similarly, people who are recovering from severe dehydration or diarrhea might need to consume more salt for a few days. But for the most part, people who eat a typical Western diet should try to reduce their daily sodium intake.
This presents an obvious conundrum: How do you get people to eat less salt when it is ubiquitous in our food system? Neal has been working to answer this question for the better part of two decades. His research has shown repeatedly that simply telling people to eat less salt isn’t very effective in the long term. Getting them to use a lower-sodium option instead works much better. “Cutting is hard,” he says. “Switching is easy.”
Neal believes that changing from typical table salt to a mixture of 75 percent sodium chloride and 25 percent potassium chloride—another type of salt—would be a simple, effective way to provide people with the sodium reduction they need. Such formulations are already available in many health food stores, although they are currently pricey compared with regular old sodium chloride. Making the switch might be costly on both an individual and institutional scale at first.
But Neal points out that we have changed our salt supply on a massive scale before. Iodized salt was introduced to U.S. grocery stores in 1924 in an effort to reduce the prevalence of pediatric goiters, enlarged thyroid glands, which impacted up to 70 percent of children in certain regions of the country. The intervention was a success, and today only about 5 percent of Americans develop goiters.
Perhaps one day potassium-supplemented salt will become the new lower-sodium staple. For now, though, if you’re trying to watch your sodium intake, your best bet is to cook at home and take your dinner with a grain of salt—but not too many grains.