Vitamin D is known for fortifying bones but may have many other health benefits, too.
“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.