We all like sunshine, right? In fact this time of year, some people pay a pack of moola and travel great distances in search of stronger solar.

Research reports continue to tout the benefits of vitamin D (1). In several studies from 2009, researchers found that patients with low blood levels of vitamin D had worse asthma symptoms than patients with higher serum vitamin D levels. In addition, patients with low vitamin D levels didn’t respond as well to asthma therapies as the patients with higher vitamin D levels.

A study done at National Jewish Health Center in Denver, Colorado, found that that low vitamin D levels influence a number of aspects of asthma, including lung function, bronchospasm and response to steroids. Results of this study are soon to be published in the American Journal of Respiratory and Critical Care Medicine (2).

The authors noted that asthma patients commonly show variable responses to inhaled steroids and that vitamin D has been hypothesized to affect glucocorticoid response in asthma. To that end they examined 54 nonsmoking, adult asthmatics, to determine whether a relationship between serum 25-hydroxyvitamin D (vitamin D₃) concentrations and lung function, airway hyperresponsiveness and glucocorticoid response existed.

Results showed that high vitamin D₃ levels (>30ng/ml) were associated with greater lung function, while participants with vitamin D₃ levels < 30ng/ml had increased air hyperresponsiveness, impaired lung function and reduced response to glucocorticoids.

As noted on the Center for Disease Control’s website (3; http://www.cdc.gov/asthma/asthmadata.htm), children in the U.S. have one of the highest prevalence rates of asthma of any age group.

In April 2009 Harvard Medical School researchers looked at vitamin D levels in children from the Central Valley region of Costa Rica, a country known to have a high incidence of asthma. These results appeared in the May 2009 issue of the American Journal of Respiratory and Critical Care Medicine (4).

Each child was assessed for allergic markers by allergen-specific and general sensitivity tests, and assessed for lung function and circulating 25-hydroxyvitamin D levels. The 616 study participants ranged in age from 6 to 14 years.

This study found that in children with asthma, 28% had insufficient levels of vitamin D (<30ng/ml). Furthermore, vitamin D levels were significantly and inversely associated with total IgE levels and eosinophil count. And children with low vitamin D levels were significantly more likely to have been hospitalized for asthma in the previous year, had increased airway hyperreactivity and were likely to have used more inhaled corticosteroids. These children were also more likely to have markers for allergic response, including dust mite sensitivity.

Study authors Drs. Juan Celedon, MD and Augusto Litonjua, MD plan to examine whether vitamin D supplementation will help deficient patients by controlling their asthma, as a future study.

This study involving children was particularly interesting, in that it follows earlier work showing that vitamin D intake by pregnant mothers has been shown to be inversely associated with asthma symptoms in early childhood.

Also surprising perhaps is that with Costa Rica situated just 10 degrees north of the equator one might assume that no resident would be vitamin D deficient. About 90% of circulating vitamin D is produced by the body in response to direct exposure to sunlight. However, concerns about skin cancer and other potentially negative effects of sun exposure results avoidance of direct sun and the use of sunscreens, affecting the amount of vitamin D individuals make.

As noted in reference 1, below, Dr. Michael Holick states that deriving enough vitamin D from the sun is very difficult, particularly in northern climates at at this time of year. Your personal physician can check your serum vitamin D3 level and make recommendations on how to improve them. The National Institutes of Health has several vitamin D resource web pages, and Wikipedia has a vitamin D information page.

References

1. Lampe, F. and Snyder, S. (2008) Conversations: Michael Holick, vitamin D pioneer. Alt. Ther. 14, 64-75.
2. Sutherland, E.R. et al. (2010) Vitamin D levels, lung function and steroid response in adult asthma. Amer. J. Resp. Crit. Care Med. Epub ahead of print.
3. Centers for Disease Control and Prevention website, surveillance data for asthma in the U.S.: http://www.cdc.gov/asthma/asthmadata.htm
4. Brehm, J.M . et al. (2009) Serum vitamin D levels and markers of severity of childhood asthma in Costa Rica. Amer. J. Resp. Crit. Care Med. 179, 765-71.

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Kari Kenefick

Kari has been a science writer/editor for Promega since 1996. Prior to that she enjoyed working in veterinary microbiology/immunology, and has an M.S. in Bacteriology, U of WI-Madison. Favorite topics include infectious disease, inflammation, aging, exercise, nutrition and personality traits. When not writing, she enjoys training her dogs in agility and obedience. About the practice of writing, as we say for cell-based assays, "add-mix-measure".

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