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Vitamin D has hit the news lately, with many health-conscious folks—including reputable doctors—advocating superdoses of the vitamin, often 2,000 international units (IU) daily. But how much D do you really need?

Without a doubt, vitamin D aids calcium absorption and helps strengthen bones. But after reviewing more than 1,000 studies and reports, plus testimony from scientists, the Institute of Medicine (IOM) recently determined that 600 IU daily of D is advised for most people, except those over age 70, who may need 800 IU.

“When the IOM speaks, people like me listen,” says Dr. Mike Kern, senior vice president and quality director at John Muir Health. “I take 1,000 IU of vitamin D, but after reading this report, I might buy 600 IU next time. But as long as you stay under the daily ceilings, you should be all right.”

Some researchers believe that vitamin D may have important talents beyond strengthening bones, such as reducing the risk of cardiovascular disease and hypertension, as well as breast, colon and prostate cancer. However, the IOM review found that any health benefits beyond bone health are from studies that were inconclusive. “The results aren’t all negative— they’re mixed—so we need to look into these things further,” Kern says.

In the meantime, should you be concerned about your vitamin D intake? Perhaps. Very few foods naturally contain the vitamin. The best sources are fatty fish, cod liver oil, D-fortified milk, orange juice and cereal. Beef liver, cheese and egg yolks have small amounts. As Kern says, “There’s very little reason to recommend against vitamin D supplements, especially in the winter months when there’s less sunlight, which activates vitamin D.” 

How Much D Do You Need?

The Institute of Medicine recommends the following daily amounts of vitamin D:

Age (years) Recommended Daily Intake Upper Intake*
1 to 3 600 IU 2,500 IU
4 to 8 600 IU 3,000 IU
9 to 70 600 IU 4,000 IU
Over 70 800 IU 4,000 IU