Joseph F. McCaffrey MD, FACS

 

Vitamin D and the Common Cold

You have to love medical journals. The Feb 23 2009 issue of the Archives of Internal Medicine featured an article titled: "Association between serum 25-hydroxyvitamin d level and upper respiratory tract infection in the third national health and nutrition examination survey."

More clearly stated, it might have read: “There’s an association between your vitamin D level and your risk of catching a cold.”

It’s always seemed to me that medical journals like to make things about as obtuse as possible.

The study was pretty interesting, though. It looked at data collected during a national health survey of 18,883 participants. The researchers measured the vitamin D levels in specimens collected during the samples and then looked at who had reported respiratory infections (predominately colds) during the study period.

It turns out that people with low levels of vitamin D were much more likely to develop respiratory infections. The likelihood was even higher in those who had chronic problems such as asthma.

The authors are quick to point out that this study doesn’t prove that supplementing with vitamin D reduce your risk of getting an infection. They’re right, it doesn’t. Association does not prove cause and effect. It could be that healthy people are outside more and therefore have higher vitamin D levels than sickly people who are in bed more.

It could be, but it’s also true that no such explanation was identified when they reviewed the surveys. And it’s true that more and more data are showing the importance of vitamin D and its affect on immune function. Low levels of vitamin D are associated with higher rates of several different cancers as well as heart disease.

So while I agree with the authors that “Randomized controlled trials are warranted to explore the effects of vitamin D supplementation on RTI,” I’m not waiting. It will be years, if not decades before those studies are done, if they ever get done. Vitamin D is safe and I’m going to make sure my levels are in the upper range of normal.

Meanwhile we have to make a decision now. It seems silly to me to wait 20 years for the definitive studies to be done to confirm that vitamin D does in fact reduce your risk of infection. “Gee, I should have been taking vitamin D all this time,” is about the only response you could have then.

Instead, we need to look at the data and make a decision now.

They aren't definite proof, but more and more studies show an association between low levels of vitamin D and various diseases. Among those diseases are cancer and heart disease.

There’s also a growing suspicion that low levels of vitamin D at a certain point in a person’s life may increase their risk of multiple sclerosis.

Vitamin D is safe and inexpensive. My choice is to take it.

How To Increase Your Vitamin D Levels

Of course, you can also increase your vitamin D levels by getting out in the sun. UV light stimulates the skin to produce vitamin D.

Of course too much sun expose has its own problems. A reasonable approach is to use sunscreen routinely on your face (assuming you want to put off sun-damage related wrinkles as long as possible) but wait until you’ve been in the sun for 15 or 20 minutes before you apply it to the rest of you body.

However that’s not practical for everyone, especially in the winter (which may be why winter is cold and flu season. I take around 2000 units of vitamin D a day if I’m not outside and sometimes more in the winter. You might want to consider the same.

If you want to be very cautious, you can get your blood levels measured. I don’t bother. I just take it.

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 JFM-MD

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