Our immune system keeps us healthy by fighting off invading pathogens while simultaneously sparing our own cells and tissues. In healthy people, the immune system is able to distinguish between the self and nonself, a concept called self-tolerance. When the body is functioning properly, the immune system maintains self-tolerance while working in the background to protect the body from infections.

In people with autoimmune disease, self-tolerance does not function correctly, causing the body to turn the powerful weapons of the immune system against self molecules, causing inflammation and injury. Autoimmune disease can be systemic, affecting multiple parts of the body, such as in diseases like systemic lupus erythematosus (SLE). They can also be organ-specific, such as in type 1 diabetes, where the immune system targets and destroys the insulin-producing cells of the pancreas.

Preclinical studies show that dietary interventions, such as elimination diets and calorie restriction in various forms (e.g., chronic caloric restriction, time-restricted feeding (TRF), and intermittent fasting, etc.) can potentially have beneficial effects on the immune system. However, more human trials are still needed to provide a better understanding of when, and in whom, these interventions are effective. It is also important to keep in mind that the efficacy and safety of diet interventions will likely vary from person to person, with some potentially being harmful for certain people.

Metabolic status in the body is intimately connected to immune function. For example, undernourished people tend to be more susceptible to infections, while the nutrient excess associated with the Western diet may be associated with increased risk of autoimmunity.^[1] This suggests that in the future, appropriate diet interventions could potentially help to reduce disease activity in people with active disease, or even lessen disease risk in those who are susceptible.

Many supplements, particularly those with antioxidant or anti-inflammatory activity, have been investigated for their ability to reduce the severity or incidence of autoimmune disease. To date, some of the more promising evidence is for vitamin D and fish oil, which were linked to reduced incidence of autoimmunity in a large randomized controlled trial.^[2] Further research is needed to better understand the way that supplements may affect the incidence or severity of autoimmunity in different people.