Can Vitamin D Prevent Colds?

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Study Finds that Vitamin D Doesn’t Prevent Coughs, ColdsVitamin D has turned out to be the “hot” vitamin of the year. Researchers have found that the vitamin has a multifaceted role to play in the body. It’s needed to keep your bones and teeth strong. Vitamin D also helps strengthen your immune function.

Strange, then, given its ability to bolster the immune system, that vitamin D seems to have no protective effect against coughs and colds. At least, this is what two recent studies found that looked at vitamin D and the potential role it could play in preventing respiratory tract infections.

The first trial included 759 people between the ages of 45 and 75. Participants were randomized into four groups. The first group received 1,000 units of vitamin D each day, the second 1,200 mg of calcium, the third vitamin D and calcium, while the fourth group acted as control.

This was a long-term study that lasted for four years. Each winter, the researchers measured the number of days of illness amongst the participants. On average, each person taking vitamin D had the equivalent of almost two days of sickness. However, the placebo group clocked in at an average of just over a day and a half of illness. The researchers also found that there were no differences between the two groups as far as severity of symptoms were concerned. A bit of a surprise here, as many were hoping that vitamin D could offer a natural remedy to fight off the coughs and colds that seem to appear ever winter.

Of course, this is just one trial. Let’s take a look at another trial. The set-up was basically the same as the previous trial: researchers conducted a randomized controlled study to find out whether vitamin D3 supplementation could help reduce the number and duration of upper respiratory tract infections during the winter months. This trial was a little smaller, with just over 300 people participating.

Participants were randomized to receive an initial dose of 200,000 IU of oral vitamin D3. One month later, the participants received another 200,000 IU, after which point they received 100,000 IU monthly. A second group acted as a placebo. The trial lasted 18 months.

The researchers measured the frequency of upper respiratory tract infections. They also took note of the duration of the infections and the severity of symptoms.

The research team found that there were no differences between the vitamin D group and the placebo group. Both had similar measures for the number of days of missed work, the length of each upper respiratory tract infection, and the severity of symptoms. The researchers had no choice but to conclude that vitamin D played no role in helping to reduce the number and severity of upper respiratory tract infections.

The illusive cure for the cough and cold season remains undiscovered. For now, the best way to protect yourself from infections is to eat a healthy diet every day, get a full eight hours of sleep, and get some physical exercise at least three times a week. Also, don’t forget to wash your hands regularly.

Bakalar, N., “Vitamin D Fails to Ease Winter Coughs and Colds,” The New York Times web site, Dec. 2, 2013;, last accessed Dec. 5, 2013.
Rees, J.R., “Vitamin d3 supplementation and upper respiratory tract infections in a randomized, controlled trial,” Clin Infect Dis. November 2013; 57(10): 1,384-92.
Murdoch, D.R., “Effect of vitamin D3 supplementation on upper respiratory tract infections in healthy adults: the VIDARIS randomized controlled trial,” AMA. October 2012; 308(13): 1,333-9.