Is asthma a disease of sunlight/vitamin D deficiency?

Yes. Asthma, to a great extent, is caused by sun avoidance and consequent vitamin D deficiency.

Asthma, a devastating respiratory illness, is increasing rapidly in the US. The latest statistics I have show that the overall prevalence of asthma increased 75% from 1980-1994, and asthma rates in children under the age of five increased more than 160%.[1]

There is little doubt that the profound increase in asthma in the last few decades has been caused to a great extent by our societal exodus from sunlight exposure along with the increased use of sunscreen, which can inhibit up to 99% of vitamin D production by the skin.[2]

Drs Litonjua and Weiss, in a medical hypothesis presented in 2007, made a strong case for vitamin D deficiency as a major player in the increase in asthma incidence among both children and adults.[3] They hypothesized the following:

1. “… as populations grow more prosperous, more time is spent indoors, and there is less exposure to sunlight, leading to decreased cutaneous vitamin D production.”
2. “Vitamin D has been linked to immune system and lung development in utero, and our epidemiologic studies show that higher vitamin D intake by pregnant mothers reduces asthma risk by as much as 40% in children 3 to 5 years old.”
3. "Vitamin D deficiency has been associated with obesity, African American race (particularly in urban, inner-city settings), and recent immigrants to westernized countries, thus reflecting the epidemiologic patterns observed in the asthma epidemic."

Other research demonstrates that vitamin D reduces the production of inflammatory chemicals (chemokines) in the respiratory passages,[4] which would dampen the asthmatic response.

Another study assessed the asthma risk of children whose mothers had the highest vitamin D consumption during pregnancy, and compared them to children whose mother had the lowest levels. The high-vitamin D group showed an impressive reduced risk of asthma of 52-67%.[5] The researchers believe that inadequate vitamin D levels in the fetus leads to improper development of the lungs and immune system.

Still other research, conducted on three-year old children whose mothers were in the highest quartile (fourth) of vitamin D consumption during pregnancy, showed them to have a 61% reduced risk of a “recurrent wheeze,” a symptom of asthma, when compared to those whose mothers were in the lowest quartile.[6] Each 100-IU increase in vitamin D consumption resulted in a 19% risk reduction. That's about the amount that could be produced in the summer sunlight in one minute, or a good tanning bed in half a minute! How sad that these women have been frightened out of the sunlight, the natural way to produce vast quantities of vitamin D.

[1] Centers for Disease Control. Surveillance for Asthma - United States, 1960-1995, MMWR. 1998; 47 (SS-1).
[2] Matsuoka, L. et al. sunscreens suppress cutaneous vitamin D3 synthesis. Journal Clini Endocrinol Metab 1987; 64:1165-68.
[3] Litonjua AA, Weiss ST. Is vitamin D deficiency to blame for the asthma epidemic? J Allergy Clin Immunol 2007;120:1031–1035.
[4] Banerjee, A. et al. Vitamin D and glucocorticoids differentially modulate chemokine expression in human airway smooth muscle cells. Br J Pharmacol 2008; 155: 84–92.
[5] Devereux, G. et al. Maternal vitamin D intake and early childhood wheezing. Am J Clin Nutr 2007;85:853-59.
[6] Camargo, C. et al. Maternal intake of vitamin D during pregnancy and risk of recurrent wheeze in children at 3 y. Am J Clin Nutr 2007;85:788-95.