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| Nutrition Update | |||||||||||||||||||||||||||||||||||||||||||||
| Vitamin D: Overview Over the past decade, considerable scientific and media attention has focused on an array of potential health benefits of vitamin D beyond bone health. Vitamin D is called the “sunshine vitamin” because it can be synthesized in skin cells upon exposure to ultraviolet B (UVB) rays in sunlight. The term vitamin D refers to vitamin D2 (also called ergocalciferol) and vitamin D3 (cholecalciferol) (1, 3-4). Both forms of vitamin D function as pro-hormones (1, 3-4). To be metabolically active, vitamin D must undergo two hydroxylations in the body. First, it is transported to the liver where it is converted to 25-hydroxyvitamin D (25(OH)D) or calcidiol and then to the kidney and extra-renal sites where it is hydroxylated to 1,25-dihydroxyvitamin D (1,25(OH)2D) or calcitriol. Calcitriol, the biologically active hormonal form of vitamin D, enhances the efficiency of calcium and phosphorus absorption and is critical for bone health throughout life. The biological effects of calcitriol are mediated by vitamin D receptors. Vitamin D’s Role in Health and Disease Role in Bone Health The importance of vitamin D for bone health is well established by scientific evidence.Vitamin D helps maintain normal serum levels of calcium and phosphorus by enhancing their absorption, which in turn promotes skeletal growth and maintenance. Rickets is characterized by a failure of bone to properly mineralize, resulting in soft bone and skeletal deformities (e.g., bowed legs). Osteomalacia is a softening, weakening and demineralization of bones. A more common disease in adults resulting from long-term vitamin D (and calcium) deficiency is osteoporosis, a skeletal disorder characterized by reduced bone mass, fragility and susceptibility to fractures. Immune Regulator Vitamin D is an important immune system regulator. Vitamin D receptor ligands have been shown to increase the activity of natural killer cells and enhance the phagocytic activity of macrophages. Activated vitamin D hormone increases the production of cathelicidin, an antimicrobial peptide that is produced in macrophages triggered by bacteria, viruses, and fungi. Key to Gut Function The vitamin D receptor plays a key role in how gut flora maintain the digestive system. Without enough vitamin D3, there is more inflammation and less ability to fight infection. The vitamin D receptor is key to fighting off invading bacteria such as Salmonella by keeping inflammatory molecule NF-Kappa B from activating other inflammatory molecules. And the active form of vitamin D, 1,25-dihydroxyvitamin D3 has been shown to inhibit the development of autoimmune diseases, including inflammatory bowel disease. How much vitamin D is too much? The increasing number of vitamin D fortified foods available in the marketplace, along with the current use of vitamin D supplements, has led to concern about potential harm from consuming too much vitamin D. Prolonged sun exposure does not result in vitamin D toxicity. Dietary Reference Intakes for Vitamin D (amount/day)  A blood test for serum 25-hydroxy-vitamin D is the accepted standard. The desirable healthy blood level of 25-hydroxy vitamin D3 should be 39 to 70 ng/ml. For those with health conditions associated with low vitamin D, a serum level between 55 and 85 ng/ml may be required. Vitamin D intoxication may occur when 25-hydroxyvitamin D levels are greater than 150 ng/ml. Sources of Vitamin D “Light-exposed (wild) mushrooms can provide up to 100% of the recommended allowance of vitamin D.” Vitamin D can be obtained from sunlight, food and supplements.
*IUs=InternationalUnits. ** DV = Daily Value |
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Vitamin-D’s facts and statistics:
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