The prevalence of asthma has increased significantly since the 1970s. In 2011, 235-300 million people globally were diagnosed with asthma, and caused 250,000 deaths. Worldwide, the rise in prevalence of allergic diseases has continued with the rise of industrialization. It is estimated that 40-50% school children currently suffer from allergens. Asthma morbidity is especially high among African-American kids. Several risk factors including urban environment with air pollutants and unique allergens, lower socio-economic status, and poor diet predispose these children to have more severe symptoms of the disease.
Natural vitamin D production is determined by the UV component of sunlight which permits vitamin D synthesis in the skin. However, darker skin population has better protection (melanin) from UV light, which by blocking the rays also prevents vitamin D synthesis.
The Nutrition Journal published a study “Outdoor exposure and vitamin D levels in urban children with asthma.” Sonali Bose at el. investigated several questions in this study whether outside exposure of children in Baltimore can change vitamin D amounts in the blood and whether vitamin D is associated with Asthma and outdoor allergy. One hundred twenty-one children 2-6 years of age were recruited to participate in this longitudinal study, they were followed for 3 to 6 months. Sonali Bose at el. assessed the amount of hours children spent outside, the amount of vitamin D in the serum, asthma and allergy symptoms through questionnaires, daily diaries and allergic markers (IgE in the blood).
The study showed that more than half of the participants had low vitamin D level in the blood (less than 30ng/mL). Twenty-three percent of children were found to have levels even below 20ng/mL, and 8% were found to have below 15ng/mL, which is associated with risk of rickets. Vitamin D was found to be higher in fair-skinned kids compare to African American kids. Scientists suggested a socio-economic status played a big role in this vitamin D diversity; also, as mentioned earlier, amounts of melanin in the skin may play an important role as well. Children were found to play outside on average for about 3 hours, and the highest was about 5 hours a day, which still surprisingly didn’t show any more vitamin D in the blood than in those who played 3h/day or less. In other words, boys and girls who spent 5h or more outside still had vitamin D deficiency. Also to prevent seasonal bias, scientists sampled the blood during all 4 seasons, which showed similar results over the whole 4 seasons. It is suggested that with industrialization, sunshine became less available for kids, and spending more hours outside is not the answer anymore for repletion of vitamin D. The research team recommended to parents to increase vitamin D through supplemental intake.
Additionally, scientists found statistically significant inverse correlation between vitamin D levels and total IgE concentrations. IgE plays an essential role in hypersensitivity, which manifests various allergic diseases, such as asthma, allergic rhinitis, and food allergy, some types of chronic urticarial and atopic dermatitis. Additionally IgE is known to play a major role in allergic conditions, such as anaphylactic reactions to certain drugs and bee stings. The study results suggest the higher amounts of vitamin D in the blood may decrease amounts of IgE marker and decrease risk and/or severity of allergies.
Even though the study did not have the highest level design, Bose at el. showed a definite association between vitamin D levels and allergy marker-IgE. Obviously vitamin D deficiency is not the only missing element that induces allergies and asthma, but it is already known that vitamin D deficiency is an initiator for several industrialized disorders, including asthma. It is also easy to see that deprivation of vitamin D after winter may cause more severe symptoms of allergy in the spring time. Vitamin D deficiency is growing at the same speed as obesity, diabetes and allergies in this country. Several studies showed supplementation of vitamin D can easily increase vitamin D concentration in the blood, as do mushrooms (read article for more information on this topic).