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This study presents a review of the influence of different environmental factors on autoimmune diseases.

The interplay between environmental factors and genetic susceptibility triggers autoimmune disease onset. Risk factors such as Epstein–Barr virus infection and coffee, tobacco, and alcohol consumption have been extensively reviewed. A review in the journal Frontiers in Immunology has focused on other autoimmune factors with conflicting research findings.

Vitamin D Deficiency and Autoimmune Diseases

Multiple sclerosis (MS) patients exhibit deficient or insufficient vitamin D, regardless of geographical localization. The cause may be low active vitamin D or a lack of vitamin D receptor (VDR) availability. To exert its anti-inflammatory effect, vitamin D must bind to a VDR, forming a VDR–D complex that further binds to the retinoid X receptor, which is activated by a retinoic acid metabolite. This process suggests that vitamin D and A supplementation might improve MS by triggering an anti-inflammatory cascade. Moreover, active vitamin D has immunomodulatory effects.

Systemic lupus erythematosus (SLE) patients frequently demonstrate low vitamin D levels. However, deficiency in these patients is often attributed to sunlight avoidance because of photosensitivity or renal insufficiency. A prospective cohort study demonstrated that vitamin D and its metabolism gene allele CYP24A1 are linked to the risk of developing SLE.

Low vitamin D levels are also reported in alopecia areata (AA) patients and are associated with increased disease severity. Low VDR amounts are also noted in their serum and scalp.

Obesity as a Risk Factor for Multiple Sclerosis and SLE

Obesity is a proinflammatory state in which expanded adipose tissue and its resident immune cells release increased proinflammatory cytokines. Obesity is an MS risk factor. Studies show a two-fold weight increase (averaging 3%) in MS vs. controls. A large prospective study on children demonstrated a significantly increased MS risk with higher body mass index (BMI). Several nucleotide polymorphisms related to genetically elevated BMI are a risk factor for MS.

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Obese women are at significantly increased risk for SLE. Obesity during adolescence is linked to double SLE incidence in adulthood. AA has also been associated with obesity. Studies report a higher BMI in these patients vs. controls, and a higher BMI was also linked to disease severity in males. AA patients demonstrate lower adiponectin levels, which correlate with disease severity.

Nutritional Factors and Disease Course

The Mediterranean diet is suggested for autoimmune diseases as it potentially reduces inflammation. In contrast, the Western diet may negatively impact the disease course.
Magnesium deficiency is an MS risk factor. MS patients demonstrate low iron and magnesium levels. Studies show that most SLE patients have inadequate nutritional intake. High fiber intake in SLE is linked to reduced disease activity. A vegetarian diet is associated with lower odds of SLE. Dietary protein, biotin, and folate deficiencies are associated with AA onset and progression.

Source

Touil, H., Mounts, K., & De Jager, P. L. (2023). Differential impact of environmental factors on systemic and localized autoimmunity. Frontiers in Immunology, 14. https://doi.org/10.3389/fimmu.2023.1147447