By Diana Hsieh
Recently, Dr Jaykaran Charan and colleagues of the Indian Institute of Public Health published a meta-analysis of all randomized controlled trials of vitamin D and respiratory tract infections. ...
Dr Charan combined the five randomized controlled trials he found that were conducted ... and found that the combined relative risk for a respiratory infection was about half for those taking vitamin D (relative risk = .58). The dose of vitamin D in the five trials ranged from 400 IU/day to 2,000 IU/day, with one using a single dose of 100,000 IU. The length of the trials ranged from 3 months to three years.
The authors concluded,
"On the basis of this study, we conclude that vitamin D is useful in prevention of respiratory tract infections."
Indeed, that has been the experience of many who supplement with Vitamin D, including me!
Personally, I keep my Vitamin D at about 80, and that requires taking about 2,000 IU per day. (Based on what I've read, I want it above 60 and below 100.) However, people vary wildly in their respond to consumption of Vitamin D, so I'd recommend blood testing. If that's not convenient to do through your doctor, you can order this test from ZRT lab for $65.
As for the kind of Vitamin D, be careful that it's not in some nasty oil like soy, as the capsules often are. I've used these drops from Carlson for many years. They're in coconut oil.
Also, I routinely take an extra 10,000 IU of Vitamin D when I travel -- or when I feel like a cold might be coming on. I keep an extra bottle in my travel kit for just that purpose... because wow, those respiratory infections suck!
If you want to know more about what Vitamin D does for the body... and how most people are deficient, go peruse the site of the The Vitamin D Council, starting with this page: About vitamin D.