Harvard Health Letter

In search of vitamin D

The right dose for bone health depends on key factors.

If you're wondering how much vitamin D will keep your bones healthy, you're not alone. Supplements of no more than 400 international units (IU) of vitamin D and 1,000 milligrams (mg) of calcium per day don't do much. A recent study in the New England Journal of Medicine said high-dose vitamin D (800–2,000 IU) reduced hip fractures by 30%. "The exact dosage that's required is still very controversial," says Dr. Jill Paulson, an instructor in medicine at Harvard Medical School.

Vitamin D is vital for bone health. It also aids calcium absorption, which is why the two are recommended together. But how much of each do you shoot for? Generally, Dr. Paulson recommends 1,000 IU of vitamin D per day (up to 2,000 IU in patients at risk for vitamin D deficiency), along with 1,000 to 1,200 mg of daily calcium in divided doses, ideally from food sources and the rest from supplements.

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