What we need to know about the "sunshine" vitamin.

Credit: Jack Miskell

Jack MiskellFrom Health magazineNO: Chances are, you already get enough.
JoAnn E. Manson, MD, chief of preventive medicine at Brigham and Womens Hospital, Boston

The numbers dont back up the hype.
Over the past few years, studies have given hope that getting more D might be the key to preventing a range of health problems, from cancer to diabetes. But a committee I was a member of, convened by the Institute of Medicine (IOM), recently examined all the existing data and ruled that these links are inconclusive and insufficient.

Fewer people are deficient than we thought.
The IOM panel concluded that having between 20 and 30 nanograms per milliliter (ng/mL) of D in the blood is safe and healthy. But people with levels nearly twice that have been told theyre deficient.

Our bodies make—and store—plenty of D.
The IOMs new guidelines now call for an intake of 600 IU per day; most of us already get that from food, multivitamins, and everyday sun exposure. And our bodies naturally store any excess D we make, for those times when we dont get enough.

YES: Most of of us would benefit from more.
John J. Cannell, MD, executive director of the Vitamin D Council

The new guidelines are too low.
Despite the IOM ruling, I believe there are enough studies to suggest that larger doses, closer to 4,000 or 5,000 IU a day, are what people need. We know that people who have blood levels below 40 ng/mL have abnormal bone development and increased instances of cancer, cardiovascular diseases, and other chronic conditions.

You cant get enough D from food alone.
An adult would have to drink 50 glasses of milk a day or eat two to three servings of fish per meal to get that 5,000 IU per day. Taking a daily supplement and getting 5 to 10 concentrated minutes of sunshine without sunscreen is an easier alternative; obese people or those with darker skin will need more.

Theres no harm in taking extra D.
Even the IOM panel concluded you can take up to 10,000 IU a day without adverse effects.

Our advice:
Ask your doctor to check your D level. If youre below the optimal level outlined by the new guidelines, discuss taking a supplement. Though it may not help, it cant hurt to increase your intake of D-rich foods like milk, fish, and fortified cereal. Just dont ditch the sunscreen: Its not worth it to risk developing skin cancer in pursuit of more D.