In the largest study yet of the association between vitamin D and respiratory infections, people with the lowest blood vitamin D levels reported having significantly more recent colds or cases of the flu. The risks were even higher for those with chronic respiratory disorders such as asthma.
Vitamin C has been used for the prevention of colds for decades, but little scientific evidence supports its effectiveness. In contrast, evidence has accumulated that vitamin D plays a key role in the immune system.
The wintertime deficiency of vitamin D, which the body produces in response to sunlight, has been implicated in the seasonal increase in colds and flu, and previous small studies have suggested an association between low blood levels of vitamin D and a higher risk of respiratory infections.
The newest study analyzed blood levels of vitamin D from almost 19,000 adult and adolescents, selected to be representative of the overall U.S. population.
How much D is enough?
Dr. Mecola also wrote that the late winter average vitamin D level is only about 15-18 ng/ml, which is considered a very serious deficiency state. It’s estimated that over 95 percent of U.S. senior citizens may be deficient, along with 85 percent of the American public.
It’s not so surprising then that the average American adult typically gets two colds per year. And those who are seriously deficient may suffer at least one additional one. But that’s under the current, now outdated, guidelines for normal vitamin D levels. I strongly believe you could avoid colds and influenza entirely by maintaining your vitamin D level in the optimal range.
So what is the optimal level of D?
Dr. Mercola’s chart below provides a good estimation.
To see Dr. Mercola’s report on these medical findings, go here.
Source: Mercola.com Newsletter, March 21, 2009.