Increasing evidence supports important roles for vitamin D in the prevention of many diseases including osteoporosis, cancer, cardiovascular disease, diabetes, depression and immune disorders. The many roles of vitamin D in maintaining health and well-being are subjects of active and ongoing research, and recent discoveries have provided insight into the molecular mechanisms by which vitamin D elicits its regulatory effects.
Vitamin D is an essential fat-soluble micro-nutrient that can be naturally synthesized in the skin upon exposure to UVB radiation, or obtained through diet and supplementation. Certain medications such as antiepileptics and rifampin have been found to increase vitamin D metabolism, while others, including Questran®, orlistat, mineral oil, and ketoconazole reduce absorption or interfere with vitamin D metabolism. Vitamin D insufficiency is more prevalent among older adults and contributes to osteoporosis by decreasing intestinal calcium absorption.
Common symptoms of vitamin D deficiency include bone pain, muscle pain and weakness, while mild vitamin D deficiency often has no symptoms and can only be detected by clinical testing.
Who needs to be tested?
Vitamin D deficiency is currently under-diagnosed. Individuals who would benefit most from vitamin D testing are those with the following conditions:
• Osteoporosis or previous skeletal fracture
• Chronic musculoskeletal pain or weakness
• Low serum calcium/ phosphorus, elevated alkaline phosphatase and PTH
• CKD, renal insufficiency, or nephrotic syndrome
• Malnutrition/poor oral in-take
• Malabsorption syndromes, celiac disease, IBS
• Liver disease
Evaluation and Treatment of Vitamin D Deficiency
Measurement of 25(OH)D during the annual physical examination is prudent to maximize bone health and prevent many chronic diseases linked to vitamin D deficiency. Low vitamin D levels can be restored to recommended levels (above 30 ng/mL) by supplementing with an oral dose of vitamin D (50,000 IU) once per week for 8 weeks. Healthy vitamin D levels can be maintained thereafter by less frequent supplementation at the same dose once or twice per month.
Vitamin D testing can help diagnose and monitor health problems, but it is not without limitations. Detection of vitamin D in serum may be lower in obese individuals, as vitamin D is generally stored in the body’s adipose tissue. Other limitations include the high cost of testing. Healthcare practitioners should use good clinical judgment in determining whether older patients may be at risk for vitamin D deficiency.