Last week, researchers from three different studies reported in the journal Nature identified an association between dietary salt and the development of autoimmune disease. This precedes a study published yesterday that links the consumption of processed foods with an increased risk of early death due to cardiovascular disease and cancer.
According to the Voice of America, researchers were studying the gut bacteria of 100 human subjects and found that those who ate at fast food restaurants had high levels of inflammatory T-cells. The protective, “fighter” T-cells are usually mobilized by a healthy immune system to respond to injury or pathogens. In autoimmune diseases, however, the body’s normally protective immune system, including the T-cells, begins to attack and destroy healthy tissue and organs. Previous research suggests that a subset of these cells, Th17, also play a critical role in the development of autoimmune diseases.
Researchers at Yale and colleagues at University of Erlangen-Nuremberg in Germany sought to find out whether high salt content in one’s diet might induce the destructive immune system response that marks autoimmune disease. They found that mice fed a diet high in refined salts saw a dramatic increase in the number of Th17 cells in their nervous systems that promoted inflammation. These mice developed a more severe form of an MS animal model, experimental autoimmune encephalomyelitis.
“Animals on the high salt were basically paralyzed and couldn’t move around the cage," said David Hafler, chair of the Department of Neurology at Yale and senior author of the Yale paper, in Voice of America. "So, [it was] a very dramatic difference in the extent of the disease.”
In the same issue of Nature, Brigham and Women’s Hospital and Harvard identified the key molecular pathway involved in the response to salt, and the Broad Institute outlined the regulatory network of genes that runs this autoimmune response.
“The question we wanted to pursue was: How does this highly pathogenic, pro-inflammatory T cell develop? Once we have a more nuanced understanding of the development of the pathogenic Th17 cells, we may be able to pursue ways to regulate them or their function.” said Vijay Kuchroo, a senior scientist at Brigham and Women’s Hospital and a Broad Institute associate member, in Yale News.
“Humans were genetically selected for conditions in sub-Saharan Africa, where there was no salt,” Hafler said. “Today, Western diets all have high salt content and that has led to increase in hypertension and perhaps autoimmune disease as well.”
Hafler noted that all test-tube cell biology is performed based on the salt levels found in blood and not in the tissues where immune cell ultimately travel to fight infections. That may have been a reason salt’s role in autoimmunity has gone undetected.
“Nature did not want immune cells to become turned on in the pipeline, so perhaps blood salt levels are inhibitory,” said Hefler.
Scientists have previously identified other environmental triggers that cause the gene mutations responsible for autoimmune diseases, including multiple sclerosis and lupus. Vitamin D deficiency, obesity, smoking, as well as prior infection, are considered potential triggers.
"And what the study really has demonstrated is that salt is likely or may be one of the environmental factors that was previously unknown," said Hafler.
Hefler already recommends his patients be on a low-salt, low-fat diet.
According to True Activist, the Yale study is the first to indicate that excess refined and processed salt may be one of the environmental factors driving the increased incidence of autoimmune diseases.
Dr Barbara Hendel, researcher and co-author of Water & Salt, The Essence of Life, believes too few minerals, rather than too much salt, may be the true cause of illness. Our bodies are not designed to refined, processed and bleached salts as it has no nutritional value. Mineral salts, like Himalayan rock salt or Celtic salt, she says, are healthy because they give your body the variety of mineral ions needed to balance its functions, remain healthy and heal.
David McCarron, of Oregon Health Sciences University, agrees, saying salt has always been part of the human diet, but the mineral content of our food is what has changed. Instead of eating food high in minerals, such as vegetables, nuts and fruit, people are filling up on “mineral empty” processed food and carbonated drinks.
A study published March 12 in the Archives of Internal Medicine found that consumption of meat is associated with a significant increased risk of all-cause death, as well as death from cardiovascular disease and from cancer.
"I think the overall message is that we should reduce our meat consumption and for processed meats we should definitely try to avoid or eliminate these from the diet," lead investigator Dr An Pan, of Harvard School of Public Health in Boston, told heartwire2.
In general, and women who ate more red meat were less likely to be physically active and more likely to be current smokers, to drink alcohol and have a higher body-mass index (BMI). They also tended to consume lower amounts of vegetables, fruits and grains, as well as fish and poultry.
A study published March 7 in BMC Medicine, the European Prospective Investigation into Cancer and Nutrition (EPIC) study, which surveyed almost half a million men and women across 10 countries, also addressed the association between meat consumption and mortality.
In contrast to the American study, the EPIC study found a stronger association between processed meats and cancer deaths. A very high consumption of red meat was non-significantly associated with increased cancer mortality, but not with deaths caused by cardiovascular or respiratory diseases, diseases of the digestive tract, or any other disease.
Over a mean of 12 years, high consumption of processed meat was associated with a near doubling of the risk for all-cause mortality in adults. The risk for cancer death was 43 percent higher and the risk for cardiovascular death was 70 percent higher in people eating more than 160 g/day of processed meats than in those eating 10.0 to 19.9 g/day.
While researchers pointed to the increased saturated fat and cholesterol, as well as additives (some of which are believed to be carcinogenic) in processed meats, there is something else also at play. "Another factor is the salt in processed meat products, which is linked to hypertension — a CVD risk factor," lead author Sabine Rohrmann, PhD, MPH, head of the Department of Epidemiology and Prevention at the University of Zurich in Switzerland told Medscape.