Q: I read in your newsletter (February) that the Institute of Medicine (IOM) used 20 nanograms/milliliter (ng/mL) as the optimum blood level of vitamin D for bone health, but that other experts use 30 ng/ml. My recent blood tests at the VA were between 20 and 30 ng/ml. Should I consider taking a vitamin D supplement?

Answer :Bess Dawson-Hughes, MD, director of Tufts HNRCA Bone Metabolism Laboratory, replies, The answer of course depends upon whom you ask. Neither the IOM nor anyone else expects that the dose needed for this reader to reach 30 ng/ml would cause harm. (The IOM sets the safe upper limit for vitamin D intake at 4,000 IU per day.) With virtually no risk and a good possibility of benefit, it would seem reasonable to take a vitamin D supplement.