An estimated 50 million Americans suffer from an autoimmune disease, and nearly all of them could be worsening their condition with the wrong diet. German researchers from Friedrich Alexander University and Ruhr University compared how different dietary fats affected mice with autoimmune diseases. Their findings, published in the journal Immunity, may help shape dietary recommendations for those suffering from conditions like Crohn’s disease, multiple sclerosis, and type 1 diabetes.

Autoimmune diseases emerge when the immune system mistakenly attacks healthy cells, according to the American Autoimmune Related Diseases Association. The exact cause of such physiological slip-ups is still unclear, but researchers are now beginning to learn that dietary fats could influence how these symptoms present themselves.

There are two types of fatty acids and each play different roles in the body, such as building nerve cells, producing energy, and forming cell membranes. Long-chain fatty acids, for example, are solid at room temperature and make up the most abundant component in Western diet foods like beef, pork, lamb, cheese, butter, and whole milk. On the other hand, short-chain fatty acids, typically found in fiber-rich diets, are only metabolized by gut bacteria. Omega-3 fatty acids are made of short chains, which are found most prevalently in flaxseeds, walnuts, soybeans, and leafy green vegetables.

For the study, researchers found that when mice ate foods with long-chain fatty acids, it triggered the release of pro-inflammatory T cells, which worsened the mice’s flare ups. Flare-ups are a common concern for people with autoimmune diseases, as they’re characterized by the sudden and severe onset of symptoms — they come and go depending on certain triggers. (Stress and anxiety are other triggers for flare-ups.) In a person with the autoimmune disorder Crohn’s disease, flare-ups might cause an increase in T cells attacking the lining of the digestive tract, which would lead to severe stomach pains.

When treating autoimmune disorders, doctors use immunotherapy drugs to lower the immune system’s ability to fight, which then stops it from fighting both harmful and healthy cells. The research team discovered that giving the mice short-chain fatty acids promoted the growth of regulatory T cells, which help keep the immune system in check. They ended up improving the disease in the animals.

“Most approved immunotherapies weaken or block pro-inflammatory components of the immune system,” explained the study’s lead author Ralf Linker, a researcher from Friedrich Alexander University, in a press release. “But by strengthening regulatory pathways, therapies could be further optimized.”

The study’s co-author Aiden Haghikia, a multiple sclerosis expert from Ruhr University, added, "It is now our plan to employ our gained insights to develop innovative dietary add-on therapies to established immunotherapies in multiple sclerosis."

Source: Linker RA, Haghikia A, Gold R, et al. Dietary Fatty Acids Directly Impact Central Nervous System Autoimmunity via the Small Intestine. Immunity. 2015.