Vitamin D regulates our natural immune system, important not only in immune deficiency diseases but also in conditions of a hyperactive immune system such as seen in autoimmune disease.
Vitamin D prevents excess cell growth as seen in cancer and allows for proper recognition of cancer cells by the immune cells. The hormonally active form of vitamin D is called Cholecalciferol (D3). It binds to nuclear vitamin D receptors (VDR) which are present in most immune cells including monocytes, macrophages, dendritic cells, NK cells, T and B cells. Every cell on the body has a VDR cell. When these VDR receptors are activated this has potent anti-proliferative, pro-differentiative, and immunomodulatory functions including both immune-enhancing and immunosuppressive effects.
Active vitamin D hormone also increases the production of cathelicidin, an antimicrobial peptide that is produced in macrophages triggered by bacteria, viruses, and fungi. Vitamin D deficiency tends to increase the risk of infections, such as influenza and tuberculosis.
Supplementation may have therapeutic clinical applications in the treatment of;
- inflammatory diseases (rheumatoid arthritis, psoriatic arthritis),
- dermatological conditions (psoriasis, actinic keratosis),
- osteoporosis, cancers (prostate, colon, breast, myelodysplasia, leukaemia, head and neck squamous cell carcinoma, and basal cell carcinoma),
- and autoimmune diseases (systemic lupus erythematosus, type I diabetes, multiple sclerosis)
- in preventing organ transplant rejection.
Vitamin D and cancer prevention
Epidemiological studies show an inverse association between sun exposure, serum levels of 25(OH)D, and intakes of vitamin D and risk of developing and/or surviving cancer. In 2005, scientists released a metastudy which demonstrated a beneficial correlation between vitamin D intake and prevention of cancer. Drawing from a meta-analysis of 63 published reports, the authors showed that intake of an additional 1,000 international units (IU) (or 25 micrograms) of vitamin D daily reduced an individual's colon cancer risk by 50%, and breast and ovarian cancer risks by 30%. Research has also shown a beneficial effect of high levels of calcitriol on patients with advanced prostate cancer.
A 2006 study using data on over 4 million cancer patients from 13 different countries showed a marked difference in cancer risk between countries classified as sunny and countries classified as less-sunny for a number of different cancers. Research has also suggested that cancer patients who have surgery or treatment in the summer - and therefore make more endogenous vitamin D - have a better chance of surviving their cancer than those who undergo treatment in the winter when they are exposed to less sunlight.
Vitamin D and the prevention of heart disease
Research indicates that vitamin D may play a role in preventing or reversing coronary disease. As with cancer incidence, a qualitative inverse correlations was found between coronary disease incidence and serum vitamin D levels of 32.0 versus 35.5 ng/mL. Cholesterol levels were found reduced in gardeners in the UK in the summer months. Heart attacks peak in winter and decline in summer in temperate but not tropical latitudes.
Carina Harkin BHSc.Nat.BHSc.Hom.BHSc.Acu.