itamin D3 deficiency is common in older adults and has been implicated in psychiatric and neurologic disorders. For example, in one study of 80 older adults (40 with mild Alzheimer's disease and 40 nondemented persons), Vitamin D3 deficiency was associated with low mood and with impairment on two of four measures of cognitive performance.6 Back Pain Musculoskeletal disorders have been linked to Vitamin D3 deficiency in a number of studies. One of the newest studies explored the role that low Vitamin D3 levels play in the development of chronic low back pain in women. Sixty female patients in Egypt complaining of low back pain lasting more than three months were studied. Researchers measured levels of Vitamin D3 in the women with low back pain and compared those levels to those of 20 matched healthy controls. The study revealed that patients with low back pain had significantly lower Vitamin D3 levels than controls. Low Vitamin D3 levels (25 OHD < 40 ng/ml) were found in 49/60 patients (81 percent) and 12/20 (60 percent) of controls.7 Bone Health One of the best known and long-established benefits of Vitamin D3 is its ability to improve bone health and the health of the musculoskeletal system. It is well documented that Vitamin D3 deficiency causes osteopenia, precipitates and exacerbates osteoporosis, causes a painful bone disease known as osteomalacia, and exacerbates muscle weakness, which increases the risk of falls and fractures. Vitamin D3 insufficiency may alter the regulatory mechanisms of parathyroid hormone (PTH) and cause a secondary hyperparathyroidism that increases the risk of osteoporosis and fractures.8 Cognitive Enhancement Scientists are developing a greater appreciation for Vitamin D3's ability to improve cognition. In a recent study, Vitamin D3 deficient subjects scored worse on mental function tests compared to individuals who had higher levels of the Vitamin.9 The researchers wrote, “In conclusion, the positive, significant correlation between serum 25(OH)D concentration and MMSE [mental state examination scores] in these patients suggests a potential role for Vitamin D in cognitive function of older adults.” Immunity Scientists have linked various aspects of immune health to a Vitamin D3 deficiency. Vitamin D3 regulates T cells, which are important to the functioning of a strong immune system. Vitamin D3 acts as an immune system modulator, preventing excessive expression of inflammatory cytokines and increasing the killing efficiency of macrophages. In addition, it dramatically stimulates the expression of potent anti-microbial peptides, which exist in immune system cells such as neutrophils, monocytes, natural killer cells, and in cells lining the respiratory tract. These Vitamin-D3-stimulated peptides play a major role in protecting the lung from infection.13 In addition, Vitamin D3 deficiency may influence development and progression of various autoimmune diseases.14 Multi-Talented Nutrient Vitamin D3 deficiency has been linked to a host of other conditions such as high blood pressure, fibromyalgia, diabetes, multiple sclerosis, Rheumatoid arthritis, and an increased risk of pre-eclampsia and insulin resistance during pregnancy.11,15-16 Most recently, low Vitamin D3 levels have been linked to an increased prevalence of early age-related macular degeneration.17 Proper Dosage In many of my patients, even after consuming 2,000 to 4,000 IU of Vitamin D3 per day, their test results indicate that their Vitamin D3 levels have not increased. These patients needed to consume 8,000 IU of Vitamin D3 per day to achieve proper blood levels of the Vitamin. Patients should, therefore, have their physicians test their serum 1,25-dihyroxy D3 levels to determine the proper level of supplementation required. Testing is very important due to the fact that, in a small number of patients, Vitamin D3 supplementation can raise calcium levels to an excessively high level. I have found this to be especially true in African American patients. Testing for 1,25-dihyroxy Vitamin D3, PTH and calcium blood levels should therefore become a part of every woman's regular blood work. Conclusion A growing number of researchers who have widely studied Vitamin D3 are almost begging the general public to consume more of this important nutrient. Due to Vitamin D3's high safety profile in doses up to 10,000 IU per day and because of the wide role it plays in our health, consuming 2,000 to 4,000 IU per day of this nutrient at times of the year when sunlight is scarce is a prudent way to improve overall health