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Maintaining adequate levels of vitamin D during winter months requires a daily dose of 20 micrograms, four times the current recommended dose, says a new study. The study, led by Susan Sullivan from the University of Maine, has important implications for ongoing consultations on vitamin D recommendations, with the current level of five micrograms (200 International Units) seen by many as insufficient.

Albert et al. Vitamin D: The alternative hypothesis. Autoimmunity Reviews, 2009 doi:10.1016/j.autrev.2009.02.011 

ScienceDaily (Apr. 8, 2009) - Deficiency in vitamin D has been widely regarded as contributing to autoimmune disease, but a review appearing in Autoimmunity Reviews explains that low levels of vitamin D in patients with autoimmune disease may be a result rather than a cause of disease and that supplementing with vitamin D may actually exacerbate autoimmune disease.

Hypovitaminosis D among rheumatology outpatients in clinical practice.\nMouyis M, Ostor AJ, Crisp AJ, Ginawi A, Halsall DJ, Shenker N, Poole KE.\nRheumatology (Oxford). 2008 Sep;47(9):1348-51. Epub 2008 May 22.\nPMID: 18499714 \ndoi:10.1093/rheumatology/ken203

Review: vitamin D, immunity and lupus. Cutolo M, Otsa K. Lupus. 2008;17(1):6-10. Review. PMID: 18089676 DOI: 10.1177/0961203307085879

itamin D and autoimmunity: new aetiological and therapeutic considerations. Arnson Y, Amital H, Shoenfeld Y. Ann Rheum Dis. 2007 Sep;66(9):1137-42. Epub 2007 Jun 8. Review. PMID: 17557889 doi:10.1136/ard.2007.069831

Vitamin D is a fat-soluble vitamin that is essential for maintaining normal calcium metabolism (1). Vitamin D3 (cholecalciferol) can be synthesized by humans in the skin upon exposure to ultraviolet-B (UVB) radiation from sunlight, or it can be obtained from the diet. Plants synthesize ergosterol, which is converted to vitamin D2 (ergocalciferol) by ultraviolet light. Vitamin D2 is less active in birds than vitamin D3 and may also be less active in humans (2). When exposure to UVB radiation is insufficient for the synthesis of adequate amounts of vitamin D3 in the skin, adequate intake of vitamin D from the diet is essential for health.

Vitamin D and calcium insufficiency-related chronic diseases: molecular and cellular pathophysiology. Peterlik M, Cross HS. Eur J Clin Nutr. 2009 Dec;63(12):1377-86. Epub 2009 Sep 2. PMID: 19724293 doi:10.1038/ejcn.2009.105 A compromised vitamin D status, characterized by low 25-hydroxyvitamin D (25-(OH)D) serum levels, and a nutritional calcium deficit are widely encountered in European and North American countries, independent of age or gender. Both conditions are linked to the pathogenesis of many degenerative, malignant, inflammatory and metabolic diseases. Studies on tissue-specific expression and activity of vitamin D metabolizing enzymes, 25-(OH)D-1alpha-hydroxylase and 25-(OH)D-24-hydroxylase, and of the extracellular calcium-sensing receptor (CaR) have led to the understanding of how, in non-renal tissues and cellular systems, locally produced 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and extracellular Ca2+ act jointly as key regulators of cellular proliferation, differentiation and function. Impairment of cooperative signalling from the 1,25-(OH)2D3-activated vitamin D receptor (VDR) and from the CaR in vitamin D and calcium insufficiency causes cellular dysfunction in many organs and biological systems, and, therefore, increases the risk of diseases, particularly of osteoporosis, colorectal and breast cancer, inflammatory bowel disease, insulin-dependent diabetes mellitus type I, metabolic syndrome, diabetes mellitus type II, hypertension and cardiovascular disease. Understanding the underlying molecular and cellular processes provides a rationale for advocating adequate intake of vitamin D and calcium in all populations, thereby preventing many chronic diseases worldwide.

Reducing the Burden of Disease Through Adequate Intake of Vitamin D3. A presentation at University of California, San Diego, April 9, 2008 by William B. Grant, Ph.D