Vitamin D is known for fortifying bones but may have many other health benefits, too.
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“The literature of the past decade goes way beyond bone health,” says Tanya Edwards, MD, Director of Cleveland Clinic’s Center for Integrative Medicine. “The populations that have the highest vitamin D levels have a lower incidence of Alzheimer’s disease, strokes and certain cancers.”
Shorter, randomized, controlled trials already show that vitamin D has a positive effect on asthma and depression. Today, investigators are midway through a five-year NIH-funded study to see if high-dose vitamin D (2,000 IU) is better than omega-3 (1 gram) in reducing risks of cancer, stroke and heart disease. The large study involves 20,000 otherwise healthy men and women over age 65.
RDA for vitamin D ‘ultra-conservative’
Dr. Edwards believes the medical community is being “ultra-conservative” about vitamin D dosages until these large, scientifically controlled, long-term studies are completed.
“The recommended dietary allowance (RDA) of vitamin D is currently 600 to 800 international units per day. I think that is inadequate, and I feel the Institute of Medicine took a step backwards by saying you need only 20 nanograms in the blood for good bone health,” says Dr. Edwards.
Vitamin D supplements are measured in international units (IU), which convert to nanograms (ng) of 25-hydroxyvitamin D in the blood.
In her Integrative Medicine practice, Dr. Edwards tries to achieve blood levels of 50 to 80 ng of vitamin D in healthy patients. “If I’ve got a patient with disease states that have been associated with lower vitamin D levels, I may push them to levels between 60 and 90 ng,” she says.
Vitamin D toxicity rare
Very high levels of vitamin D increase the risks of hypercalcemia, or too much calcium in the body. “If you practice vitamin D medicine the way I practice vitamin D medicine — which, granted, not everybody does — you follow patients’ levels to make sure that they are exactly where you want them to be,” says Dr. Edwards. “I don’t let patients reach a level above 150, which is where I’d be concerned about hypercalcemia and kidney stones.”
The literature also links hypercalcemia to high-dose vitamin D2 rather than D3, she says. Most practitioners recommend vitamin D3, which the body metabolizes better and is less expensive than D2.
Vitamin D can be absorbed from sunshine by the skin. But if you live in Northeast Ohio, you need extra vitamin D supplements to make up for our gray days, she says.