Vitamin D is synthesized in the body using sunlight. But, due to decreasing outdoor activity time, weather, sunscreen blockers, and other metabolic conditions, the body's production of vitamin D and blood levels are frequently low.79 In fact, it has been proposed that annual fluctuations in vitamin D levels explain the seasonality of influenza.80 All of these factors point to the value of taking a daily vitamin D supplement to keep levels optimal for maximum health.<br /> <br /> <br /> <br /> Vitamin D is known to provide significant support for healthy bone density.81-86 Vitamin D receptors are widely distributed in the body, including colon, prostate, breast and ovary, where vitamin D acts to inhibit the excessive growth of body cells and tissues and helps cells mature normally. Scientists have found that vitamin D regulates healthy cell division and differentiation, and has profound effects on human immunity, as well as a role in heart disease, high blood pressure, diabetes and metabolic syndrome and many other conditions.87-90 <br /> <br /> Vitamin D is actually more of a hormone that affects over 2000 genes (about 10% of all genes) in the human body. Current research suggests that vitamin D deficiency as a major factor in the pathology of at least 17 varieties of cancer as well as heart disease, stroke, hypertension, autoimmune diseases, diabetes, depression, chronic pain, cognitive loss, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects, periodontal disease, and much more.<br /> <br /> <br /> <br /> These findings also link a deficiency of vitamin D to a host of common age-related problems. The current RDA is only 400 IU, and this will be raised shortly. As a result of startling evidence of a widespread vitamin D deficiency, about 75% of the population, and up to 90% of African American subgroups, prominent nutritional scientists are calling on Americans to increase their vitamin D intake to 2000 -5000IU per day and higher. When the skin is properly exposed to the sun it produces about 10,000 IU vitamin D. This is equivalent to ~50 glasses of milk, or up to 50 OTC calcium or multivitamins! Currently, most experts in the field believe that intakes of between 1000 and 4000 IU for adults will lead to a more healthy level of serum 25(OH)D, at approximately 75 nmol/L. <br /> <br /> For further information please see http://healthscienceresearch.com/?p=1770