Could Vitamin D Help Against COVID-19?
Today I ran across mention of an old observational study of seasonal colds and flu in northern (temperate zone) and southern (tropics) India. Colds and flu had no seasonality in southern India where vitamin D from sunshine is equally available all year.
Colds and flu were seasonal in northern India closely following the months when vitamin D is not readily available from the sun which is too low on the horizon to produce vitamin D. There is not direct evidence that lower vitamin D levels allow more colds and flu, but it seems reasonable.
We have long known that vitamin D is involved in human immune system function as well as bone health. e.g. A National Institute of Health study found that persons with monohydroxy-vitamin D levels over 33ng/ml have half the risk of colorectal cancer as those with less than 12 ng/ml.
Vitamin D toxicity is possible but very rare according to the Mayo Clinic, requiring doses of 50,000 IU (1250 mcg) daily for months.
My experience in Iowa is that most persons not taking at least 1000-2000 IU (25-50 mcg) daily have vitamin D levels below 20ng/ml December through April. That is also cold and flu season.
I take 5000 IU (125 mcg) daily to keep my level at 50-60 ng/ml. That can’t hurt and it might help prevent viral infections. Over age 65, I have started working from home and am setting up TeleMedicine capabilities because of COVID-19 guidelines.
Follow your state’s health department guidelines. And extra vitamin D could help. If you have not taken any in the past, up to 5000 IU (125 mcg) daily should be safe until you have a chance to check your level.
Jay Ginther, MD