Vitamin D Deficiency in Asthma
Asthma is a respiratory disease characterized by airway hyper-responsiveness and inflammation Asthma has many contributing factors including genetics, environment and food allergies, nutritional status and stress to name a few. Asthma prevalence continues to increase worldwide and industrialized nations furthest from the equator have the highest prevalence. Vitamin D is not truly a vitamin it is more like a hormone in the body. It serves many functions including immune system modulation, bone health and plays an important role in wound healing. Deficiency of vitamin D have been linked to autoimmune diseases, cancer, inflammatory disease like asthma, depression, osteoporosis, periodontal disease and many more conditions. A recent article in the Journal of Allergy and Clinical Immunology suggests the reduced exposure to sunlight, resulting in decreased vitamin D production, leading to deficiency can increase the risk of asthma and atopy.
Fifty thousand years ago humans lived outside and mostly around the equator. Humans eventually began to migrate north where climate was very different. We began to live more indoors and were fully clothed which prevented sun exposure and this is still very true today. Vitamin D does not occur naturally in humans and is acquired through supplementation or exposure to sunlight. According to the US News Report, UVB rays are available when the UV index is at 3 or above which doesn’t happen in the winter for most of America (and that includes Utah). Vitamin D is formed when UVB rays come in contact with our skin and convert 7-dehydrocholesterol into cholecalciferol which is Vitamin D3. So, sun exposure is crucial in the formation of adequate vitamin D levels.
The immune system plays an important role in the pathogenesis of asthma. Many genes involved in inflammation and regulation of the immune system have been associated with asthma. The vitamin D pathway strongly impacts the function of the immune system. In human development, vitamin D plays a role in fetal lung growth and maturation. A recent study showed that higher intake of vitamin D by pregnant mothers reduced asthma rates by as much as 40% in children 3 to 5 years old. A study published in American Journal of Respiratory Critical Care demonstrated an inverse relationship between vitamin D levels in maternal blood and asthma symptoms in early childhood. This study also demonstrated that vitamin D insufficiency was relatively frequent in these asthma patients and lower vitamin D levels were associated with increased allergies and severity of asthma.
In addition to deficient levels of maternal vitamin D, genetic variation in the vitamin D receptor (VDR) and genes responsible for converting pre vitamin D to the active form have been associated with increased levels of asthma and atopy. A genetic association between these genes (IL10, CYP24A1, ILIRL1, CYP2R1 and CD86) which are involved in the vitamin D synthesis pathway and asthma have been established. The gene IL10 when working properly is associated with anti-inflammatory cell signalers which decrease inflammation. Slight mutations (called SNPs= single nucleotide polymorphisms) in IL10 gene have been associated with increased inflammation which is characteristic in asthma and altered blood levels of vitamin D.
What does this all mean? Prevention is key, expecting mothers or women who are trying to conceive may want to consider having their vitamin D levels checked. Adequate supplementation in pregnancy may significantly decrease incidence of asthma in young children.
Asthma is a condition that has many contributing factors, genetics being one of them. This research demonstrates that a relative need of vitamin D may be required for some asthmatic patients. Vitamin D levels can be tested in the blood to determine if a deficiency is present. Supplementation with vitamin D is another avenue to help regulate the inflammation in asthmatic patients. Be sure to not forget the daily dose of sunshine. Of course the bigger question is why is there so inflammation in the first place? And for that we address the numerous environmental assaults, nutritional deficiencies and other contributing factors that can make some many asthmatic patients’ lives more difficult.