Too much of this ingredient leads to autoimmune diseases, new research shows. Here's how to cut back.

Too much of this ingredient leads to autoimmune diseases, new research shows. Here's how to cut back.

Scientists are looking at how salt affects our cells, and they're finding more reasons to avoid htoo much of it.

Adobe Stock

For more than a century, doctors have warned that too much salt in your diet can lead to high blood pressure, heart disease and stroke - and many of the reasons for these effects are well known. But recently scientists have been looking deeper, into the cellular level, and they are finding additional reasons to minimize sodium intake; it is bad for immune cells, creating patterns of gene expression and activity seen in a variety of autoimmune diseases such as multiple sclerosis, lupus, rheumatoid arthritis, and type-1 diabetes.

Salt is a major part of the ocean from which life evolved on this planet. We carry that legacy in our blood, which tastes salty. It is an important element for conducting electrical signals along nerves and balancing water and metabolites transported throughout our bodies. We need to consume about 500 milligrams of salt each day to maintain these functions, more with exercise and heavy sweating as that is a major way the body loses salt. The problem is that most Americans eating a modern western diet consume about 3400 milligrams, 1.5 teaspoons per day.


Evidence has been accumulating over the last few years that elevated levels of sodium can be harmful to at least some types of immune cells. The first signal came in monocytes, which are immune cells that travel to various tissues in the body, where some of them turn into macrophages, a subset of white blood cells that can directly kill microorganisms and make chemical signals that bring other types of immune cells into play.

Two years ago, Dominik N. Müller from the Max-Delbrueck-Center in Berlin, Germany and Markus Kleinewietfeld, an immunologist at Hasselt University in Belgium, ran a study where they fed people pizza and then measured their immune cell function. “We saw that in any monocytes, metabolic function was down, even after a single salty meal,” Kleinewietfeld says. It seemed to be the cellular equivalent of the sluggish feeling we get after eating too much. The cells were able to recover but more research is needed to answer questions about what dose of sodium causes impairment, how long the damage lasts, and whether there is a cumulative effect of salt toxicity.

Kleinewietfeld and his colleagues have hypothesized that too much salt could be a significant factor in the increased number of autoimmune diseases and allergies over the last few generations.

The latest series of experiments focused on a type of T cell called T regulatory cells, or Tregs. Most T cells release inflammatory mediators to fight pathogens and, once that job is done, Tregs come along to calm down their hyperactive brethren. Failure to do so can result in continued inflammation and possibly autoimmune diseases.

In the lab, Kleinewietfeld and his large team of international collaborators saw that high levels of sodium had a huge effect on Tregs, upregulating 1250 genes and downregulating an additional 1380 genes so that they looked similar to patterns of gene expression seen in autoimmune diseases.

Digging deeper, they found that sodium affected mitochondria, the tiny organelles inside of cells that produce much of its energy. The sodium was interfering with how the mitochondria use oxygen, which resulted in increased levels of an unstable form of oxygen that can damage cell function. The researchers injected those damaged Tregs into mice and found that they impaired the animals' immune function, allowing the inflammation to continue rather than shutting it down.

That finding dovetailed nicely with a 2019 paper in Nature from Navdeep Chandel's lab at Northwestern University, which showed in mice that inhibiting the mitochondrial use of oxygen reduced the ability of Tregs to regulate other T cells. “Mitochondria were controlling directly the immunosuppressive program, they were this master regulator tuning the right amount of genes to give you proper immunosuppression,” Chandel said. “And if you lose that function, then you get autoimmunity.”

Kleinewietfeld's team studied the Treg cells of humans and found that sodium can similarly decrease mitochondrial use of oxygen and immunosuppressive activity. “I would have never predicted that myself,” Chandel says, but now researchers can look at the mitochondria of patients with autoimmune disease and see if their gene expression also changes under high salt conditions. He sees the link between the patterns of gene expression in Tregs generated by high salt exposure and those patterns seen in autoimmune diseases, but he is cautious about claiming a causal effect.

Kleinewietfeld and his colleagues have hypothesized that too much salt could be a significant factor in the increased number of autoimmune diseases and allergies over the last few generations. He says a high salt diet could also have an indirect effect on immune function through the way it affects the gut microbiome and the molecules made by microbes when they break down food. But the research results are too preliminary to say that for sure, much less parse out the role of salt compared with other possible factors. “It is still an exciting journey to try to understand this field,” he says.

Additionally, it is difficult to say precisely how this research in animals and human cell cultures will translate into a whole human body. Individual differences in genetics can affect how the body absorbs, transports, and gets rid of sodium, such that some people are more sensitive to salt than are others.

So how should people apply these research findings to daily life?

Salt is obvious when we sprinkle it on at the table or eat tasty things like potato chips, but we may be unaware of sodium hidden in packaged foods. That's because salt is an easy and cheap way to boost the flavor of foods. And if we do read the labeled salt content on a package, we focus on the number for a single serving, but then eat more than that.

Last September, the U.S. Food and Drug Administration (FDA) began a process to update labels on the content of food, including what is meant by the word “healthy” and how food manufacturers can use the term. Many in the food industry are resisting those proposed changes.

Chandel cautions against trying to counter the effects of salt by reaching for foods or supplements full of antioxidants, which, in theory, could reduce the harmful effects on mitochondria caused by a heavy hand with the salt shaker.

Until labels are updated, it would be prudent to try to reduce sodium intake by cutting down on packaged foods while making your own food at home, where you know just how much salt has been added. The Mayo Clinic offers guidance on how to become more aware of the sodium in your diet and eat less of it.

Chandel thinks many people will struggle with minimizing salt in their diets. It’s similar to the challenge of eating less sugar, in that the body craves both, and it is difficult to fight that. He cautions against trying to counter the effects of salt by reaching for foods or supplements full of antioxidants, which, in theory, could reduce the harmful effects on mitochondria caused by a heavy hand with the salt shaker. “Dietary antioxidants have failed in just about every clinical trial, yet the public continues to take them,” Chandel says. But he is optimistic that research will lead us to a better understanding of how Tregs function, and uncover new targets for treating autoimmune diseases.

Bob Roehr
Bob Roehr is a biomedical journalist based in Washington, DC. Over the last twenty-five years he has written extensively for The BMJ, Scientific American, PNAS, Proto, and myriad other publications. He is primarily interested in HIV, infectious disease, immunology, and how growing knowledge of the microbiome is changing our understanding of health and disease. He is working on a book about the ways the body can at least partially control HIV and how that has influenced (or not) the search for a treatment and cure.
For Kids with Progeria, New Therapies May Offer Revolutionary Hope for a Longer Life

Sammy Basso is one of around 400 young people in the world with progeria.

Courtesy of Basso

Sammy Basso has some profound ideas about fate. As long as he has been alive, he has known he has minimal control over his own. His parents, however, had to transition from a world of unlimited possibility to one in which their son might not live to his 20s.

"I remember very clearly that day because Sammy was three years old," his mother says of the day a genetic counselor diagnosed Sammy with progeria. "It was a devastating day for me."

But to Sammy, he has always been himself: a smart kid, interested in science, a little smaller than his classmates, with one notable kink in his DNA. In one copy of the gene that codes for the protein Lamin A, Sammy has a T where there should be a C. The incorrect code creates a toxic protein called progerin, which destabilizes Sammy's cells and makes him age much faster than a person who doesn't have the mutation. The older he gets, the more he is in danger of strokes, heart failure, or a heart attack. "I am okay with my situation," he says from his home in Tezze sul Brenta, Italy. "But I think, yes, fate has a great role in my life."

Keep Reading Keep Reading
Jacqueline Detwiler-George
Jacqueline Detwiler is a contributing editor to Popular Mechanics and former host of The Most Useful Podcast Ever. She writes about science, adventure, travel, and technology. For stories, she has embedded with high school students in Indianapolis, jumped out of a plane with a member of the Red Bull Air Force, and travelled the country searching for the cure for cancer. Most recently, she trailed the Baltimore Police Department's Crime Scene Investigation team for a book for Simon & Schuster's Masters at Work series.
Want to Motivate Vaccinations? Message Optimism, Not Doom

There is a lot to be optimistic about regarding the new safe and highly effective vaccines, which are moving society closer toward the goal of close human contact once again.

Photo by Christine Jou on Unsplash

After COVID-19 was declared a worldwide pandemic by the World Health Organization on March 11, 2020, life as we knew it altered dramatically and millions went into lockdown. Since then, most of the world has had to contend with masks, distancing, ventilation and cycles of lockdowns as surges flare up. Deaths from COVID-19 infection, along with economic and mental health effects from the shutdowns, have been devastating. The need for an ultimate solution -- safe and effective vaccines -- has been paramount.

On November 9, 2020 (just 8 months after the pandemic announcement), the press release for the first effective COVID-19 vaccine from Pfizer/BioNTech was issued, followed by positive announcements regarding the safety and efficacy of five other vaccines from Moderna, University of Oxford/AztraZeneca, Novavax, Johnson and Johnson and Sputnik V. The Moderna and Pfizer vaccines have earned emergency use authorization through the FDA in the United States and are being distributed. We -- after many long months -- are seeing control of the devastating COVID-19 pandemic glimmering into sight.

Keep Reading Keep Reading
Monica Gandhi
Monica Gandhi MD, MPH is a Professor of Medicine and Associate Chief in the Division of HIV, Infectious Diseases, and Global Medicine at the University of California, San Francisco (UCSF). She is also the Director of the UCSF Center for AIDS Research (CFAR) and the Medical Director of the HIV Clinic ("Ward 86") at San Francisco General Hospital. Her research focuses on HIV and women and adherence measurement in HIV treatment and prevention. She is now conducting research on mitigation strategies for COVID-19.