Evidence suggests ultraviolet radiation (UVR) may play a protective role in three autoimmune diseases: multiple sclerosis, insulin-dependent diabetes mellitus and rheumatoid arthritis.
Solar ultraviolet B (UV-B) radiation (280-320 nm) has been associated with reduced risk of cancer of the breast, colon, ovary, and prostate, as well as non-Hodgkin’s lymphoma (NHL) through the production of vitamin D in papers extending back to 1980.
Vitamin D deficiency is a major contributor to chronic low back pain in areas where vitamin D deficiency is endemic.
Dietary vitamin D supplementation is associated with reduced risk of type 1 diabetes.
UV light intensity and efficiency of epidermal vitamin D3 photosynthesis may contribute to geographic and racial variability in blood pressure and the prevalence of hypertension.
Subclinical vitamin D insufficiency is characterized by mild secondary hyperparathyroidism and enhanced risk of osteoporotic fracture.
Clinical and experimental data support the view that vitamin D metabolism is involved in blood pressure regulation and other metabolic processes.
Serotonin synthesis is hypothesized to be dependent on the duration of light exposure the previous summer.
Early intervention can reduce the risk of metabolic complications caused by vitamin D hormone deficiency in patients with chronic kidney disease.
MS may be preventable in genetically susceptible individuals with early intervention strategies that provide adequate levels of hormonally active 1,25-dihydroxyvitamin D3 or its analogs.
Muscle Weakness and Falls
Specific receptors for vitamin D have been identified in human muscle tissue. Cross-sectional studies show that elderly persons with higher vitamin D serum levels have increased muscle strength and a lower number of falls.
Serum vitamin D is significantly lower in obese than in non-obese individuals and may contribute to lower serum 25-hydroxyvitamin D in obesity.
Low intake and low serum levels of vitamin D each appear to be associated with an increased risk for progression of osteoarthritis of the knee.
Vitamin D deficiency is extremely prevalent in the elderly. Most often the first symptoms are caused by myopathy with muscle pain, fatigue, muscular weakness and gait disturbances. More severe deficiency causes osteomalacia with deep bone pain, reduced mineralization of bone matrix and low energy fractures.
For adults, the 5-microg (200 IU) vitamin D recommended dietary allowance may prevent osteomalacia in the absence of sunlight, but more is needed to help prevent osteoporosis and secondary hyperparathyroidism. Other benefits of vitamin D supplementation are implicated epidemiologically: prevention of some cancers, osteoarthritis progression, multiple sclerosis, and hypertension.
Some intervention trials have demonstrated that supplementation with vitamin D or its metabolites is able: (i) to reduce blood pressure in hypertensive patients; (ii) to improve blood glucose levels in diabetics; (iii) to improve symptoms of rheumatoid arthritis and multiple sclerosis. The oral dose necessary to achieve adequate serum 25(OH)D levels is probably much higher than the current recommendations of 5-15 microg/d.
Pregnancy and Lactation
Results of studies suggest that the vitamin D supply from human milk is inadequate, and that routine vitamin D supplementation is advisable for breast-fed infants who are deprived of sunlight exposure.
Vitamin D is one of the oldest hormones that have been made in the earliest life forms for over 750 million years. Phytoplankton, zooplankton, and most plants and animals that are exposed to sunlight have the capacity to make vitamin D. Vitamin D is critically important for the development, growth, and maintenance of a healthy skeleton from birth until death.
In concert with counseling sun protection, physicians should consider discussing vitamin D intake, typically in the form of supplements.
Because vitamin D is potentially toxic, intake of >25 microg (1000 IU)/d has been avoided even though the weight of evidence shows that the currently accepted, no observed adverse effect limit of 50 microg (2000 IU)/d is too low by at least 5-fold.
Prudent nutritional support for osteoporosis prevention and treatment consists of 30 to 40 mmol Ca/d together with sufficient vitamin D to maintain serum 25(OH)D levels above 80 nmol/L (i.e., approximately 25 microg vitamin D/d).
Vitamin D Deficiency
The vitamin D status in young adults and the elderly varies widely with the country of residence. Adequate exposure to summer sunlight is the essential means to ample supply, but oral intake augmented by both fortification and supplementation is necessary to maintain baseline stores. All countries should adopt a fortification policy. It seems likely that the elderly would benefit additionally from a daily supplement of 10 micrograms of vitamin D.
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