For various reasons, some Americans fail to get enough vitamin D, and it may pose health consequences beyond those commonly recognized. Vitamin D is a unique nutrient; your body produces it from sunlight exposure, and in its active form it functions as a hormone. Of its many duties, vitamin D helps regulate the immune system, and deficiency may lead to autoimmune problems, such as Hashimoto's disease.
The Vitamin That Wears Many Hats
Vitamin D is a fat-soluble vitamin that is inactive until your liver and kidneys convert it to 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D -- its active forms. Perhaps most well-known for its role in calcium balance and strengthening bones, vitamin D exerts other functions within the body. It plays a role in regulating blood pressure and glucose metabolism, and the 1,25-dihydroxyvitamin D form exerts potent immune-regulating effects.
The War Inside
Under normal circumstances, your immune cells attack foreign substances to protect you. In autoimmune conditions, the immune system goes to war against the body's own cells. When your immune system attacks your thyroid -- an endocrine gland -- it's called autoimmune thyroiditis, or Hashimoto's disease. Hashimoto's is a common endocrine disorder, occurring seven times more often in women than men, according to the National Endocrine and Metabolic Diseases Information Service. The thyroid plays a central role in metabolic function, so the symptoms of Hashimoto's go hand in hand with reduced metabolism. It causes weight gain, constipation, fatigue, cold intolerance and a slowed heart rate, to name a few.
A Link Confirmed
Researchers in Turkey conducted a study to establish a link between vitamin D deficiency and Hashimoto's disease. The study involved 540 participants, half of whom were healthy and other half who had Hashimoto's but were on a stable dose of thyroid medication. Researchers found vitamin D levels were significantly lower in the Hashimoto's group than healthy controls. The study also found the longer patients had Hashimoto's, the more severely deficient they were in vitamin D. The review was published in the May 2013 issue of the journal "Endocrine Practice."
Potential for Vitamin D Supplementation
Talk to your doctor about checking your vitamin D levels if you have Hashimoto's or any other autoimmune disease. In animal experiments, supplementing vitamin D helps prevent or at least delay autoimmune disease, according to a systematic review published in the June 2011 issue of the journal "Seminars in Arthritis and Rheumatism." If you're vitamin D deficient, this suggests correcting your vitamin D levels may improve symptoms of Hashimoto's disease. Dietary vitamin D sources include fish, eggs and fortified foods, but these may not be enough to meet your needs. Avoid supplementing vitamin D without your doctor's supervision. Too much vitamin D is toxic to the body.