Vitamin D is important for a healty immune system as well as proper bone metabolism and muscle strength; blood tests are used to determine the need for supplements.
Several studies have shown a link between higher levels of Vitamin D and a lower incidence of multiple sclerosis. Similarly, studies have shown low blood levels of vitamin D are associated with numerous autoimmune diseases. Vitamin D offers benefits for autoimmune diseases because of its ability to influence T cell development and inactivate Natural Killer cells. Besides its beneficial effects on immunity, which include cancer prevention, vitamin D helps the body absorb calcium, ensuring proper bone metabolism, and it has also been shown to improve muscle strength, particularly leg muscle strength. The question of how much vitamin D is enough is of prime importance for patients with autoimmune diseases.
Sources of Vitamin D
Vitamin D is absorbed through the skin from sunlight or from supplements and foods fortified with vitamin D. The body then converts it into 25-OH vitamin D and then into the active hormone 1,25-dihydroxy vitamin D (1,25OH-D).
- The recommended daily dose of vitamin D is 200-600 IU.
- The optimal blood range for 1, 25 hydroxy vitamin D is 75-125 nmol/L.
Studies show that most people in the United States do not get adequate vitamin D, especially in the winter months. Studies show that the action of vitamin D in the body also depends on adequate sources of calcium from a normal to high calcium diet.
Because of the widespread use of sunscreen and a trend towards limited exposure to sunlight, the incidence of vitamin D deficiency has reached epidemic levels. Blood tests are available for measuring vitamin D levels with tests for 1, 25 hydroxy vitamin D. This test is necessary for determining if a vitamin D deficiency exists. Serum levels in the optimal range have been associated with improved bone health and muscle strength, as well as protection against numerous cancers,
- The recommended dose of vitamin D3 supplementation is 800-1,000 IU daily.
- However, some people need at least 5,000 IU vitamin D3 daily to bring levels into the optimal range.
- According to the Life Extension Foundation, toxicity is unlikely at daily intake levels less than 10,000 IU (250 mcg).
Vitamin D Toxicity
Blood tests are important to guard against toxicity. Excess vitamin D can cause dangerous blood calcium levels, poor muscle and nerve function. Long-term elevations of vitamin D can increase the risk of kidney stone. Patients taking extremely high doses of vitamin D should be monitored for signs and symptoms of toxicity, including nausea, vomiting, poor appetite, constipation, weakness, heart arrhythmias, and elevated levels of cholesterol, calcium or liver enzymes. People with kidney disease and patients using digoxin or other heart medications should check with their doctor before using vitamin D.
Vitamin D and the Immune System
The highest concentration of vitamin D is found in the immature immune cells of the thymus and the mature CD-8 T Lymphocytes. Studies show that vitamin D3 supplements can either prevent or markedly suppress experimental autoimmune encephalomyelitis, rheumatoid arthritis, systemic lupus erythematosus, type I diabetes, and inflammatory bowel disease.
With adequate calcium, vitamin D stimulates transforming growth factor-beta1 and interleukin-4 production, which in turn may suppress inflammatory T-cell activity.
Resources:
Hector F. Deluca and Margherita T. Cantorna, Vitamin D: Its role and uses in immunology, FASEB J. 15, 2579-2585, 2001.
Tiesha D. Johnson, Guarding Against the Dangers of Vitamin D Deficiency, Life Extension Journal, May 2007: 43-50.
Janet Raloff, Vitamin Boost, From muscle strength to immunity, scientists find new vitamin D benefits, Science News Online, Oct 9, 2004, accessed May 8, 2007.
