Vitamin D May Keep You from Getting Sick, Study Says

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Orange juice and Emergen-C may not be your only defenses against cold and flu season. A new study from Massachusetts General Hospital says vitamin D may actually be the key to staying healthy.

The research, published Wednesday in the BMJ, suggests that taking vitamin D supplements may help ward off acute respiratory infections, such as the common cold and the flu.

Doctors have long observed correlations between vitamin D deficiency and increased rates of illness, but the medical community has gone back and forth over whether upping vitamin D intake actually prevents people from getting sick. Mass General’s study suggests, however, that it does.

The Mass General team, working with Queen Mary University of London researcher Adrian Martineau, gathered data from roughly 11,000 people in more than a dozen countries, who each participated in one of 25 randomized controlled trials. After studying each individual’s data, they found that those starting with the lowest levels of vitamin D benefitted most from daily or weekly supplements—suggesting that the dietary aids do offer some protection against respiratory infections.

Participants who began with very low blood vitamin D levels saw their risk of respiratory disease decrease by half. All subjects, regardless of initial vitamin D, saw some immunity benefit.

“Most people understand that vitamin D is critical for bone and muscle health,” Carlos Camargo, the study’s senior author, said in a statement. “Our analysis has also found that it helps the body fight acute respiratory infection, which is responsible for millions of deaths globally each year.”

If you suffer from vitamin D deficiency, you may consider adding a supplement to your routine. (It’s best to consult a doctor before taking any supplement, since they are not subjected to the same regulatory scrutiny as drugs and may interact with other things you’re taking.) You can also find vitamin D in foods including fatty fish, some mushrooms, egg yolks, and liver, or boost levels naturally by getting some fresh air—while wearing sunscreen—each day.