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Condensed from an article by Amy Shaw, MD, Sonoma Medicine The classic disorders associated with vitamin D deficiency are the bone diseases of rickets in children and osteomalacia in adults. But over the past 15 years, scientists have discovered other diseases associated with vitamin D deficiency: osteoporosis, rheumatoid arthritis, multiple sclerosis, colon cancer, prostate cancer, breast cancer, depression, diabetes, tuberculosis, and schizophrenia. If vitamin D is so important for overall health, why is there an epidemic of vitamin D deficiency? The short answer is clothing and sunscreen, as well as human migration away from the tropics. Even when bare skin is exposed to UVB rays, the amount of melanin in the skin is a limiting factor. The darker a person’s skin, the more UVB exposure is necessary to activate vitamin D3. In actuality, the correct dose of daily vitamin D for an individual should be that amount necessary to maintain a healthy serum 25-hydroxyvitamin D3 concentration. Normal reference values cited by large laboratories have recently been adjusted to a range of 37-100 ng/ml, but other authorities recommend a serum 25-hydroxyvitamin D3 level between 50-100 ng/ml for maximum health benefits. Unfortunately, many osteoporotic patients have severe vitamin D deficiency, and unless this condition is diagnosed and resolved, bisphosphonate treatment is only marginally beneficial.
Although over the counter vitamin D3 is more potent than D2, it is challenging to get high enough doses (800-1000 IU for maintenance; 5000 IU daily for deficiency states). Once monthly oral vitamin D2, 50,000 IU, is easier for patient adherence. (For deficiency, 50,000 IU can be taken weekly for 12 – 16 weeks, until levels are normal). Patients who present with vitamin D deficiency and secondary hyperparathyroidism should be monitored for serum 25-hydroxyvitamin D3 concentrations and parathyroid levels. For patients with conditions or medications (such as phenytoin) that interfere with intestinal vitamin D absorption or vitamin D activation, very high doses of vitamin D (e.g., Rx 50,000 IU vitamin D2 one to three times weekly) may be required to maintain adequate 25-hydroxyvitamin D3 levels. The safety margin for vitamin D therapy is quite large, making vitamin D toxicity uncommon. One study reported no adverse effects in patients who took 10,000 IU vitamin D3 daily for five months.[1] In fact, vitamin D toxicity has only been observed in patients whose vitamin D3 intake is in the range of 40,000 IU per day.[2] Until more widely consumed foods, such as grains and cereals, are fortified with vitamin D, it is essential that we instruct our patients to take vitamin D supplements on a regular basis. Higher doses of vitamin D3 supplementation are usually needed to correct a pre-existing vitamin D deficiency, but that once corrected usually only 1000 IU D3 daily is required to maintain normal levels.
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