Autoimmune diseases are a host of conditions characterized by an abnormal immune response against normal tissues of the body. There are about 100 autoimmune diseases, and they are estimated to affect at least 3-5% of the population.
The etiology is still unclear, both genetic and environmental factors are recognized to play key roles in the disease development. Pharmacological treatments have substantially improved the disease’s control and prognosis, but a lot of them come with a wide variety of adverse effects.
One factor that can be modified is diet, which has the potential to improve clinical outcomes for several major autoimmune diseases.
Autoimmune diseases etiology
The exact causes of autoimmune diseases are unknown. The current view is that development involves multiple factors including genetic predisposition and environmental impact.
The fundamental cause of autoimmune diseases is loss of self-tolerance. For this to happen, autoreactive lymphocytes (white blood cells) must escape elimination by the body’s central tolerance mechanisms, mainly in the thymus, and travel to the periphery where they can encounter specific autoantigens.
Clinical symptoms of most autoimmune diseases are due to the responses of autoantibodies and autoreactive effector T cells against autoantigens, which causes activation of T cells and release of proinflammatory substances, called cytokines, which can activate more immune cells.
Nutritional Interventions in Autoimmune Diseases
Epidemiologic studies on the relationship between diet pattern/nutrient intake and prevalence of certain autoimmune diseases have revealed some interesting associations. They have demonstrated that a variety of diet components favorably modulate the immune and inflammatory responses involved in the pathogenesis of autoimmune diseases.
Observational studies have indicated that diet is a modifiable environmental factor for MS prevention and management. Diet-related MS risk factors proposed include low vitamin D, high fat/saturated fatty acids, childhood obesity, and diet related dysbiosis.
Low levels of vitamin D intake and low sun exposure (a major source of vitamin D synthesis) have been shown to be associated with high MS risk and disease activity. Serum vitamin D levels are typically lower in MS patients than in the healthy controls, and seasonal variations of serum vitamin D are inversely associated with clinical disease activity.
Early studies by Swank et al. revealed that MS incidence may be related to consumption of saturated fats of animal sources such as those from dairy and meat. High energy intake from fat, in particular saturated fat, increases MS risk while fruit and vegetable intake is protective in both adult and pediatric patients.
Given the inverse association between vitamin D status and MS risk reported in epidemiologic studies, together with vitamin D’s immunomodulatory function, in particular the suppressive effect on adaptive immune responses and antigen-presenting process, vitamin D supplementation in MS patients has been strongly recommended.
Moderate improvement of MS symptoms was reported in the patients receiving 1 year of low-fat diet together with increased fish intake or olive oil alone.
Curcumin, a principal component of the dietary spice turmeric, is suggested to have a protective effect for several autoimmune diseases including MS.
Diet and nutrition have long been known to impact RA initiation and progression. Studies have shown that severity of RA process adversely affects nutritional status. The nutritional status of the patients also impacts disease severity. For instance, malnourished RA patients had more active disease than those without malnutrition.
Some studies have reported that RA patients have low serum concentrations of albumin, transferrin, zinc, selenium, and folic acid. Studies have shown that lower selenium levels in RA patients is associated with the clinical disease activity.
RA patients are recommended to receive dietary education and consume adequate amounts of calcium, folic acid, vitamin E, zinc, and selenium.
A large population-based case-control study reported an inverse correlation between the Mediterranean diet and RA risk among men, but not in women. In another study high dietary quality was significantly related to reduction in plasma levels of inflammation biomarker C-reactive protein (CRP).
The Mediterranean diet showed in a systematic review that it can reduce pain levels and increase physical function in patients with RA. Monounsaturated fatty acids in the Mediterranean diet are suggested to be the key factor contributing to reduced disease activity in RA patients.
The consumption of fish has also been associated with significantly lower disease activity scores, with individuals who never ate fish or had fish less than once a month having higher activity scores when compared with those who consume fish 2 times/week.
As seen previously in MS, vitamin D levels have also been associated with disease activity. Low vitamin D levels in newly diagnosed RA patients not receiving any RA drugs were associated with reduced response to treatment and increased disease activity
Fish oil containing 1,000 mg EPA and 1,500 mg DHA for 12 weeks showed in one study reduction in disease symptoms and blood CRP levels.
Lastly, fruits and vegetables contain high levels of phytochemicals that have antiinflammatory properties.146 A recent RCT reported that female RA patients who consumed daily 500 mL of low-calorie cranberry juice containing 150 mg vitamin C, 131.92 mg proanthocyanidins, 258.75 mg total phenolics, and 0.30 mg folic acid for 90 days had reduced disease activity compared to those who did not
Inflammatory Bowel Diseases
Like in the previous conditions, vitamin D status has shown a strong association with IBD risk and disease activity.
In a retrospective study that included 504 IBD patients (403 CD and 101 UC patients), 49.8% of patients were vitamin D deficient and deficiency was associated with greater disease activity and lower health-related quality of life.
Mozaffari and colleagues evaluated the association of fish consumption and dietary intake of n-3 PUFAs with the risk of IBD. The study included 282,610 participants with 2,002 cases of IBD. They found a negative association between fish consumption and risk of CD.
In a small study with 18 mild-to-moderate CD patients, 24 weeks of supplementation with up to 5,000 IU/d vitamin D3 effectively raised serum 25(OH)D3 levels and reduced the CD activity index scores. Quality-of-life scores also improved following vitamin D supplementation.
As we can see, nutrition can have a tremendous impact in the regulation of the immune system and thus the prevalence and pathogenesis of autoimmune diseases.
It is unfortunate that there are not many studies evaluating the impact of nutrition on autoimmune diseases. But nonetheless the results so far are encouraging and show efficacy of specific nutrients or dietary patterns to decrease clinical symptoms and improve patients quality of life.
Meydani, S. N., Guo, W., Han, S. N., & Wu, D. (2020). Nutrition and autoimmune diseases. Present Knowledge in Nutrition, 549–568. doi:10.1016/b978-0-12-818460-8.00030-7