The immune system has two major roles: recognition and response. The immune system must recognize the difference between normal, harmless cells and proteins and foreign, toxic cells and proteins. The immune system responds by destroying foreign, infected, damaged, and malignant cells whereas it tolerates normal, harmless cells.
In autoimmune disease, the immune system errs in recognizing foreign cells. Dendrites are the scavengers that must distinguish normal from abnormal cells.
Vitamin D Influence
Studies show that when vitamin D levels are normal, dendrites function normally. When vitamin D levels are low, dendrites may not recognize or develop tolerance to normal proteins and cells. This leads to the inappropriate immune response characteristic of autoimmunity. Here, the immune system targets and attacks the body’s own cells and proteins.
Autoimmunity
Autoimmunity is an inflammatory response to normal cells or proteins caused by a lack or loss of tolerance by the immune system. This inflammatory response typically causes a persistent response that can occur over years or decades before symptoms of disease develop. Factors that influence tolerance include hormones, recurrent or chronic infections (also more likely in vitamin D deficiency), and inadequate nutrition.
Studies show that other environmental factors, particularly diet, influence the activity and action of vitamin D. Inadequate vitamin D and other nutrients during immune system development (through gestation up to the second year of life) play critical roles in the development of autoimmune disease.
Multiple Sclerosis
Research into the role of vitamin D and autoimmunity was first suggested by evidence seen in specific autoimmune disease. Research shows that the further away from the equator a person spends his first 15 years of life, the higher the risk for developing MS. This observation suggests that sunlight and vitamin D early in life are essential for normal immune system development.
Type 1 Diabetes
Studies show that the risk for type 1 diabetes mellitus is greater the further from the equator an individual was born. In Finland, 40 years ago it was public health policy to administer 2,000 IU of vitamin D in the form of cod liver oil to infants through the first year of life. This was primarily to prevent rickets. Research with follow-up studies in 2001 showed that these children given cod liver oil had an 80 percent lower risk of developing juvenile diabetes. Children with low vitamin D levels who developed rickets were three times more likely to develop type 1 diabetes.
Undifferentiated Connective Tissue Disease
Individuals diagnosed with undifferentiated connective tissue disease (UCTD) may continue to have a mild undifferentiated disease course or they may go on to develop systemic lupus or other connective tissue disorders. Researchers in Italy have conducted a study showing that people with UCTD who progressed into rheumatoid arthritis, lupus, Sjogren’s syndrome, and mixed connective tissue disease had lower vitamin D levels than individuals who remained in the UCTD stage.
Vitamin D Deficiency
The Centers for Disease Prevention and Control (CDC) estimates that 60 percent of European Americans and nearly 100 percent of African Americans are deficient in vitamin D (25-OHD3) using a cutoff level of 30 ng/ml. A recent study at the Health Sciences Center in Denver suggests that 75 percent of Americans are deficient in vitamin D. Persistent vitamin D deficiency and also inadequate nutrition through adolescence amplify the risks for development of many health problems, including autoimmune diseases, obesity, high blood pressure, heart disease and cancer later in life. Vitamin D ointments are now being used with good results in the autoimmune condition psoriasis. Future therapeutic uses of vitamin D are expected.
Sunlight is the body's primary source of the hormone known as vitamin D. Experts recommend a 10 to 15-minute exposure to sunlight three times weekly without the interference of sunscreen. Although vitamin D is present in some foods, dietary intake alone is usually insufficient. Studies suggest that food supplies only about 20 percent of the body's vitamin D requirement. Food sources of vitamin include cheese, butter, margarine, fortified milk, and fortified cereals.
Resources:
James Dowd, Vitamin D: A Missing Link in Autoimmunity, Advance for Administrators of the Laboratory, June, 2009: 40-42.
Maurizio Cutolo, Vitamin D or hormone deficiency in autoimmune rheumatic disease, including undifferentiated connective tissue disease, Arthritis Research & Therapy 2008, Dec 2, 2008.
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