By Marc Sorenson, EdD, Sunlight Institute…
Asthma is a disorder characterized by inflammation of the air passages, which cause narrowing of the airways that transport air from the nose and mouth to the lungs.[i] The mechanism by which sunlight may reduce asthma and its symptoms could be the anti-inflammatory properties of the vitamin D production that it stimulates in the skin. Inflammation is often caused by proteins called cytokines that are either pro-inflammatory or anti-inflammatory elements of the immune system.[ii] Vitamin D has the ability to inhibit pro-inflammatory cytokine production while stimulating the production of anti-inflammatory cytokines.[iii] However, there are likely other attributes of sunlight, beyond stimulating vitamin D production in the skin, that have beneficial affects.
One of the most recent studies on factors that contribute to asthma showed that living in a room without windows was associated with an increased the risk of asthma of 930%, and living in an area without adequate sunlight was associated with an increased the risk of 220%.[iv] Considering that windows filter out the UVB light that stimulates the production of vitamin D, having windows could not have reduced asthma by vitamin D production—it had to be some other factor—something that entered the room through that window glass protected the people with windows from the remarkable increase in asthma they would have otherwise had. We know that UVA light, which does pass through windows, stimulates the production of nitric oxide, which is a potent vasodilator. Could it also be a bronchodilator? This explanation, of course, is theory.
Other research that indicates a direct influence of sunlight on asthma, is one by Hart and her colleagues, which showed that controlled exposure to ultraviolet light (UVR) in mice markedly limited the development, incidence and severity of asthma symptoms such as inflamed airways and lungs.[v] These researchers exposed mice to allergens that generally brought on asthma attacks and then exposed them to sun lamps for 30 minutes. After the exposure, the allergens caused no attacks. The researchers also stated that sunlamp exposure produced a cell type in mice, that when transferred into other mice, suppressed the immune reactions and halted symptoms. This is another indication that sunlight has a healthful effect on asthma beyond vitamin D production.
Dr. Litonjua and Dr. Weiss, noting that the prevalence of asthma and allergic diseases began to increase worldwide in 1960, hypothesized that since people have increasingly spent more time indoors, there has been less exposure to sunlight, which has led to decreased cutaneous vitamin D production.[vi] This could have further led to vitamin D deficiency in pregnant women, resulting in more asthma in their offspring. But was vitamin D deficiency the cause or was it simply sunlight deficiency? Or could it have been both?
At the health resort owned by the Sorensons, we often noticed that asthmatics ceased using their inhalers after a week or two of hiking in the sunshine. One of them decreased the dosage from 6 inhalers per day to zero in about a week. Could it have been sunlight? We believe that the combination of mostly plant-based nutrition, combined with sunlight, made the difference, and the aforementioned research provides reasonable support for that opinion.
[i] Asthma and Allergy Foundation of America: Asthma Facts and Figures. Accessed 3-6-2010 http://www.aafa.org/display.cfm?id=8&sub=42
[ii] Kurtzke J. On the fine structure of the distribution of multiple sclerosis 1,25-Dihydroxyvitamin D3 inhibits cytokine production by human blood monocytes at the post-transcriptional level. Cytokine 1992;4:506-12.
[iii] Canning MO, Grotenhuis K, de Wit H, Ruwhof C, Drexhage HA. I-alpha,25-Dihydroxyvitamin D3 (l,25(OH)(2)D(3)) hampers the maturation of fully active immature dendritic cells from monocytes. Eur J Endocrinol 2001;145:351-57.
[iv] Kamran A, Hanif S, Murtaza G. Risk factors of childhood asthma in children attending Lyari General Hospital. J Pak Med Assoc 2015 Jun;65(6):647-50.
[v] Hart, P. Exposure to sunlight could reduce asthma. Newsletter of the Telethon Institute for Child Health Research 2006;3:2
[vi] Litonjua AA, Weiss ST. Is vitamin D deficiency to blame for the asthma epidemic? J Allergy Clin Immunol 2007;120:1031-35.