A team of scientists from Yale University in the U.S and the University of Erlangen-Nuremberg, in Germany, say junk food diets could be partly to blame for disease.
‘This study is the first to indicate that excess refined and processed foods, particularly salt, may be one of the environmental factors driving the increased incidence of autoimmune diseases,’ they said.
Junk foods at fast food restaurants as well as processed foods at grocery retailers represent the largest sources of sodium intake from refined salts.
The Canadian Medical Association Journal sent out an international team of researchers to compare the salt content of 2,124 items from fast food establishments such as Burger King, Domino’s Pizza, Kentucky Fried Chicken, McDonald’s, Pizza Hut and Subway. They found that the average salt content varied between companies and between the same products sold in different countries.
U.S. fast foods are often more than twice as salt-laden as those of other countries. While government-led public health campaigns and legislation efforts have reduced refined salt levels in many countries, the U.S. government has been reluctant to press the issue. That’s left fast-food companies free to go salt crazy, says Norm Campbell, M.D., one of the study authors and a blood-pressure specialist at the University of Calgary.
Many low-fat foods rely on salt–and lots of it–for their flavor. One packet of KFC’s Marzetti Light Italian Dressing might only have 15 calories and 0.5 grams fat, but it also has 510 mg sodium–about 1.5 times as much as one Original Recipe chicken drumstick. (Feel like you’re having too much of a good thing? You probably are.
Bread is the No. 1 source of refined salt consumption in the American diet, according to the Centers for Disease Control and Prevention. Just one 6-inch Roasted Garlic loaf from Subway–just the bread, no meat, no cheeses, no nothing–has 1,260 mg sodium, about as much as 14 strips of bacon.
How Refined Salt Causes Autoimmune Disease
The team from Yale University studied the role of T helper cells in the body. These activate and ‘help’ other cells to fight dangerous pathogens such as bacteria or viruses and battle infections.
Previous research suggests that a subset of these cells – known as Th17 cells – also play an important role in the development of autoimmune diseases.
In the latest study, scientists discovered that exposing these cells in a lab to a table salt solution made them act more ‘aggressively.’
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.
They were also more likely to develop a severe form of a disease associated with multiple sclerosis in humans.
The scientists then conducted a closer examination of these effects at a molecular level.
Laboratory tests revealed that salt exposure increased the levels of cytokines released by Th17 cells 10 times more than usual. Cytokines are proteins used to pass messages between cells.
Study co-author Ralf Linker, from the University of Erlangen-Nuremberg, said: ‘These findings are an important contribution to the understanding of multiple sclerosis and may offer new targets for a better treatment of the disease, for which at present there is no cure.’
It develops when the immune system mistakes the myelin that surrounds the nerve fibres in the brain and spinal cord for a foreign body.
It strips the myelin off the nerves fibres, which disrupts messages passed between the brain and body causing problems with speech, vision and balance.
Another of the study’s authors, Professor David Hafler, from Yale University, said that nature had clearly not intended for the immune system to attack its host body, so he expected that an external factor was playing a part.
He said: ‘These are not diseases of bad genes alone or diseases caused by the environment, but diseases of a bad interaction between genes and the environment.
‘Humans were genetically selected for conditions in sub-Saharan Africa, where there was no salt. It’s one of the reasons that having a particular gene may make African Americans much more sensitive to salt.
‘Today, Western diets all have high salt content and that has led to increase in hypertension and perhaps autoimmune disease as well.’
The team next plan to study the role that Th17 cells play in autoimmune conditions that affect the skin.
‘It would be interesting to find out if patients with psoriasis can alleviate their symptoms by reducing their salt intake,’ they said.
‘However, the development of autoimmune diseases is a very complex process which depends on many genetic and environmental factors.’
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