If you have asthma or emphysema, or if just you hate blowing snot out your nose while coughing up play-doh, you want to
make sure your vitamin D level is over 30 ng/ml (or, depending on the lab’s reporting units, >60 nmol/L). A recent, thorough, well-designed study shows that the lower your vitamin D blood level (independent of the season), the more likely you are to have had a recent cold/cough/flu. The association is strongest for those that my granny would say have “weak lungs” – those people who suffer from asthma or emphysema (COPD). AND these are the people who are most likely to suffer a worse clinical outcome from having an upper respiratory infection (called a URI, in medical jargon-abbreviation).
How big a difference are we talking about? If you don’t have asthma or COPD, having the lowest vitamin D blood level means you’re roughly 40% more likely to have had a recent URI. But if you have asthma or COPD, your risk really goes through the roof – for people who have COPD = OVER TWICE the risk of a recent upper respiratory tract infection, and with asthma (brace yourself) over FIVE AND A HALF times the risk.
Sheesh. Who’s got a low vitamin D level? Everyone’s vitamin D level tries to drop in the winter-spring months (there’s usually a month or two delay in blood levels dropping as sunlight gets weaker). Studies show that anyone can have a low level, but those most likely to be low (and often very very low) are people with pigmented skin who live north of L.A. (especially if you’re lactose intolerant). Bottom line: get your vitamin D blood levels checked, and stay therapeutic all year, with supplements if necessary, regardless of the season. Taking 1,000 IU a day is a good daily dose for most people – but don’t overdo it. Mega-doses are NOT a good idea with vitamin D – the best approach is to follow/treat based on your blood levels. More studies are needed, but keeping up with your body’s vitamin D could be a cheap, easy way to avoid some nasty winter infections, especially if you have COPD or asthma.