Fasting involves a controlled, temporary abstinence from food or a severe restriction of calories, including methods like intermittent fasting (IF), time-restricted eating, or periodic, longer fasts. Autoimmune diseases are conditions where the body’s immune system mistakenly attacks its own healthy tissues, leading to chronic inflammation and tissue damage. The potential of using fasting as a therapeutic intervention is of scientific interest, primarily due to the metabolic shifts that occur when the body is deprived of its regular fuel source. This article explores the emerging scientific evidence for how fasting might influence the complex processes of an overactive immune system.
The Immune System Response During Fasting
Fasting triggers a significant metabolic shift that directly impacts the immune system, moving the body from a growth-oriented state to a repair-and-survival mode. The activation of autophagy is a cellular cleanup process where damaged cells, old proteins, and dysfunctional organelles are broken down and recycled. This “housekeeping” mechanism is thought to remove aged and potentially self-reactive immune cells.
Prolonged fasting cycles, typically lasting two to four days, have been shown in both animal and early human trials to induce a depletion of white blood cells. Upon refeeding, blood stem cells are triggered to produce a new, potentially healthier population of immune cells. This process effectively creates a less reactive immune system by recycling damaged immune components and generating new cells.
Fasting also influences the body’s inflammatory signaling molecules, known as cytokines. Studies suggest that intermittent fasting can lead to a reduction in pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). Fasting may also increase anti-inflammatory markers, helping to suppress the chronic low-grade inflammation that drives autoimmune pathology. This shift in the cytokine balance is a primary mechanism by which fasting is believed to calm the overactive immune response.
Clinical Evidence for Specific Autoimmune Conditions
Research into fasting’s effect on autoimmune diseases is promising, though still largely preliminary, with various protocols yielding different results. For Multiple Sclerosis (MS), studies using a Fasting-Mimicking Diet (FMD) showed positive outcomes in animal models and small human trials. Patients with relapsing-remitting MS who completed FMD cycles followed by a Mediterranean diet reported improvements in quality of life, physical, and mental health. Another small trial using intermittent calorie restriction (500 calories two days a week) found a reduction in the pro-inflammatory hormone leptin and an increase in regulatory T-cells, suggesting a shift toward a less inflammatory state.
In Rheumatoid Arthritis (RA), a number of older and recent studies suggest that therapeutic fasting can lead to short-term improvements in disease activity. Fasting periods, sometimes lasting seven to ten days, have been linked to a reduction in inflammatory markers like C-reactive protein (CRP) and IL-6, along with reported decreases in joint pain and stiffness. However, the benefit is often transient, and the positive effects tend to diminish if the fast is not followed by a sustained anti-inflammatory diet.
Evidence for Systemic Lupus Erythematosus (SLE or Lupus) is mostly derived from animal models, which suggest fasting may be protective. In lupus-prone mice, fasting dramatically reduced levels of the pro-inflammatory hormone leptin, which in turn promoted an expansion of regulatory T cells (Tregs). Tregs maintain tolerance and prevent the immune system from attacking the body’s own tissues. While human data is sparse, these mechanistic findings provide a rationale for further investigation into fasting’s potential to reduce systemic inflammation in Lupus patients.
Fasting’s Influence on the Gut Microbiome
The gut microbiome is intricately linked to immune system function and the development of autoimmune disease. An imbalance in this community, known as dysbiosis, is frequently observed in autoimmune conditions and contributes to systemic inflammation by compromising the gut barrier. Fasting alters the availability of nutrients, which forces a rapid shift in the composition of the gut microbiota.
This change in environment often favors the growth of beneficial bacteria. Specifically, fasting can enhance the abundance of bacteria that produce Short-Chain Fatty Acids (SCFAs), such as butyrate. SCFAs are metabolites produced when gut bacteria ferment dietary fiber, and they play a direct role in strengthening the intestinal barrier and communicating with the immune system.
By increasing SCFA production, fasting helps to reduce intestinal permeability and dampen the flow of inflammatory signals from the gut to the rest of the body. This mechanism provides a pathway for fasting to modulate systemic inflammation, offering a potential benefit for autoimmune conditions. The gut-mediated effects of fasting are a significant area of current research, suggesting that the timing of food intake impacts both metabolism and the microbial environment that governs immune health.
Essential Safety Considerations and Contraindications
Fasting, even in its milder forms like intermittent fasting, is not suitable for everyone. Strict contraindications include pregnancy, breastfeeding, and a history of or current struggle with an eating disorder, as any form of dietary restriction can be triggering. People with Type 1 Diabetes are at a significantly higher risk of complications, such as hypoglycemia or diabetic ketoacidosis, and should not attempt fasting without highly specialized medical supervision.
Other populations who should avoid fasting or proceed with extreme caution are those who are underweight, have low blood pressure, or are dealing with an active infection. Fasting can interact unpredictably with many medications used to manage autoimmune diseases, including immunosuppressants and steroids, leading to changes in drug effectiveness. Any individual with an autoimmune disease considering a fasting regimen must first consult with their rheumatologist or primary care provider. Self-treating a chronic, complex condition with a dietary intervention like fasting can be hazardous and may lead to a worsening of symptoms or a disease flare.