including one in San Diego County, isn’t such a negative after all.
The sodium consumed with salt is widely supposed to raise blood pressure and increase the rate of cardiovascular disease. But that position, endorsed by the American Heart Association and the Centers for Disease Control, has been disputed in recent studies in peer-reviewed journals that fail to find health risks for most Americans in their salt consumption.
Now a study published today points to an unexpected benefit of salt: It fights infections.
Sodium deposits build up where skin infections take place, increasing the activity of immune cells called macrophages that consume microbes, the study found. The phenomenon was noticed first in mice. When infected mice were fed a high-salt diet, the macrophages were activated, speeding healing of feet infected with Leishmania major.
Sodium also builds up in the skin of older people, suggesting the same mechanism is at work in humans, said Jens Titze, the study’s senior author and a researcher at Vanderbilt University in Nashville, Tenn.
Titze says he agrees that excessive salt consumption has harmful effects. But the story is incomplete, and salt has hitherto unsuspected health benefits.
“That’s the game-changer here,” Titze said in a Monday interview. “It’s a completely different science. The most important finding here is that tissues can accumulate massive amounts of sodium locally to boost immune response wherever needed. It’s a biological principle.”
In evolutionary terms, the ability to fight infection is critical to survival at any age, Titze said. But in the modern age of medicine and longevity, salt’s harmful effects become more pronounced. Moreover, salt deposits in skin appear to play a role in autoimmune diseases.
The study was published in the journal Cell Metabolism. (If the link doesn’t work, try again later until the online version is live).
That salt accumulates in the skin has been known for years, and scientists such as Titze have been trying to understand why.
Salt’s properties as an anti-infective have long been advocated in popular medicine. A salt cure was key to Jane Goodall’s acceptance in Africa when she began to do research on chimps in the 1960s. Her mother, Vanne, recommended a saline drip to cure a deep leg wound on a native African, thus winning acceptance.
“Every morning and every afternoon, the patient sat down with a large bowl of blood-warm salted water which he dripped very slowly over his sores,” Goodall wrote in her book, In the Shadow of Man. “After three weeks the swelling had gone and the wounds were clean. Subsequently, it was only a matter of time before he was completely healed.”
Another science dogma shaken