Studies Show Possible Role of Vitamin D in Asthma, Influenza and COPD. How Much Proof Do We Need?

Article by Arnie Gitomer

The evidence supporting the role of vitamin D supplementation in preventing various health problems continues to accumulate. Most medical professionals have now adopted a much higher recommended daily intake level than the old 400 IU. Blood tests have shown that a surprising majority of Americans actually have low vitamin D levels. While it is true that vitamin D is one of those vitamins that can be toxic in excess, the focus now is on "are we getting enough" rather than "are we getting too much."

Yet some remain cautious. Some remain skeptical, demanding ironclad "proof" that vitamin D is as important to health and disease prevention as it seems. Proof is fine, but when the upside is potentially great, and there is little downside, are you doing yourself a disservice by sitting on the sidelines?

Here is an example. There was one recent study showing that vitamin D reduced inflammation in the lungs of mice exposed to a certain irritant, indicating a possible role in humans relative to asthma and COPD. Yes, it was in mice. And it was short term. But that does not mean it should be ignored. Details of that study are presented below.

Another study, on Japanese school children, designed to show if vitamin D would prevent influenza, ended up revealing an 83% reduction of asthma attacks in the subgroup of children with asthma.

So, whether or not you consider these studies "proof," if you or a loved one had health problems related to lung inflammation, why would you not take extra vitamin D?

First, I will provide information on the schoolchildren study, and then the mice study.

"Vitamin D. In a study designed to determine whether vitamin D supplementation can prevent influenza, 430 Japanese children (mean age, 10 years) were randomly assigned to receive, in double-blind fashion, 1,200 IU/day of vitamin D3 or placebo for 15–17 weeks, beginning between December 1 and December 15 and continuing until the end of March. One hundred ten of the children had a previous diagnosis of asthma. Within that subgroup, 83% fewer children in the vitamin D group than in the placebo group suffered an asthma attack during the study (p = 0.006)." (Gaby, Alan R., MD. Nutritional Medicine. Alan R. Gaby, M.D., 01/2011.)

Here are the details of the second study:

In the first study of its kind, results of a University of Nebraska Medical Center research study suggest that vitamin D may be important for humans exposed to agricultural organic dust. In the study, researchers found a significant decrease in lung inflammation in mice exposed to hog barn dust that received high doses of vitamin D.

“We found that the relatively high vitamin D treatment group had significantly decreased lung inflammation. The mice still got inflammation but didn’t get it as bad,” said Jill Poole, M.D., associate professor in the UNMC Department of Internal Medicine and principal investigator of the study.

Past studies in the U.S. have shown relationships with vitamin D and various airway inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD).

“We know that vitamin D changes the expression of key molecules that respond to the dust, and through this response, we think vitamin D may be helpful in lessening disease brought on by agricultural dust,” Dr. Poole said.

Workers on today’s farms are exposed to a variety of high levels of agricultural organic dust – dust that comes from feed, bedding and livestock, which includes mold, pollen, bacteria, pesticides, and chemicals. Exposure can lead to inflammation in the lungs and a risk of developing COPD.

Over time, exposure to organic dust can result in serious respiratory illnesses, such as organic dust toxic syndrome (ODTS) and Farmer's lung.

Dr. Poole said initial exposure in humans to organic dust induces an intense airway inflammatory response that wanes over time, but repetitive exposure causes an increased risk of lung function decline, persistent inflammation and progressive respiratory impairment.

Researchers used unique mouse models that were exposed to hog barn dust. One group received a high vitamin D diet and the other a low vitamin D diet.

Though there are a lot of things researchers still need to figure out, based on the initial findings in mice, Dr. Poole hopes that those with or without lung disease exposed to agricultural dust consider taking vitamin D. She also recommends they ask primary care providers to check vitamin D levels to find out if they are deficient.

“Since vitamin D is inexpensive, readily available and safe, if you don’t take more than 4,000 IUs daily, there’s no downside,” she said. “We’re learning more and more about vitamin D and its benefits for a variety of health issues.

“I think there should be awareness in the farming community about the potential benefit of vitamin D. How important it is for sure we don’t know yet. But it may help the immune system.”

The study, published in the Journal of Biochemical and Molecular Toxicology, was funded by the National Institute of Health Institute of Environmental Health Sciences and the National Institute for Occupational Safety and Health (NIOSH) Agricultural Safety and Health Center at the UNMC College of Public Health.

Dr. Poole said limitations of the study were it involved mice, not humans, and the study didn’t measure exposure over a long period of time. She said more studies in humans are warranted to determine vitamin D levels in farmers and if vitamin D supplementation could improve health outcomes