Childhood Asthma and Vitamin D Deficiency: What You Need to Know

The concentration of vitamin D in the blood of asthmatic children is lower than that found in healthy children, suggesting that vitamin deficiency may represent a risk factor for childhood asthma. If this association is confirmed by further studies, intervention on vitamin D levels in young patients could represent a suitable strategy to counteract the symptoms of the disease.

This is reported by new research conducted by Korean researchers at the Korea University Medical Center in Seoul and published in the journal Environmental Health and Toxicology.

Childhood Asthma: The Most Common Chronic Disease in Children

Asthma is one of the most common chronic respiratory diseases in pediatric age; its prevalence is steadily increasing as is the number of patients with severe asthma and acute complications. Asthma is an inflammatory disease of the airways, and the most common symptoms are wheezing, shortness of breath, chest tightness, and coughing. Although it is now known that environmental and genetic factors contribute to the condition, the main cause is still to be determined. 

The major environmental factors that trigger the onset of asthma are dust mites, molds, animal allergens, tobacco smoke, and pollutants. Recently, numerous studies have also focused on the role of vitamin D deficiency in the onset of asthma. Besides contributing to bone growth and health, vitamin D is known to play a fundamental role in the prevention and treatment of osteoporosis as it is an essential hormone for maintaining phosphorus and calcium homeostasis. 

However, recent epidemiological studies have reported that serum vitamin D deficiency may be linked to an increased risk of autoimmune disorders and diseases such as asthma, atopic dermatitis, and allergic rhinitis. Numerous epidemiological investigations on the causes of childhood asthma have reported an association between vitamin D deficiency and increased asthma prevalence. The results of a study involving children in Qatar revealed that vitamin D levels in asthmatics were significantly lower than those of healthy children. Similarly, another study on African American children confirmed a correlation between vitamin D deficiency and asthma.

A study on children with asthma in North America also reported that vitamin D deficiency is associated with an increased rate of emergency room visits due to asthma symptoms. Vitamin deficiency in serum is more frequent among city dwellers, where sun exposure is reduced due to a “Western” lifestyle. Although vitamin D deficiency has been reduced in some countries by food fortification, many studies have shown that vitamin D deficiency is widespread even in sunny areas of the world and that supplementation and fortification are not always sufficient to prevent it.

86% of Asthmatic Children Show Vitamin D Deficiency

The results reported by the Korean study highlighted that children affected by asthma have insufficient levels of vitamin D, suggesting that this deficiency could be a risk factor for the development of the disease. During the research, which involved subjects aged between 6 and 14 years, the researchers measured and compared serum vitamin D concentrations in children with asthma and healthy children, observing that vitamin D levels in the affected children were significantly lower than in the unaffected children.

As many as 86% of children with childhood asthma showed vitamin D deficiency in serum, while only 19% of non-asthmatics had insufficient levels; results that, as stated by the authors themselves, are very consistent with numerous epidemiological studies that have examined the association between vitamin D concentrations and the risk of developing asthma. Since melanin content, age, body fat percentage, latitude, season, time spent outdoors, and use of sun protection can influence vitamin D concentration, the study examined participants’ housing types and time spent outdoors. 

However, sun exposure was found to be the only environmental factor associated with the amount of vitamin D in the blood. Regarding the link between asthma symptoms, vitamin D, and sunlight, the researchers also considered reverse causality: asthmatics tend to stay indoors more, minimizing their exposure to sunlight and thus their vitamin D levels, which, as is known, is produced by the skin through sun rays. Korean children and adolescents spend little time outdoors at school, which could promote lower serum vitamin D concentrations and, in turn, a higher prevalence of asthma.

Study Details

This study involved a total of 80 children, of whom 50 were asthmatic and 30 were healthy controls. Serum vitamin D levels were measured and compared between the two groups and were examined in relation to pulmonary function test results and environmental factors, collected through a questionnaire administered to the children. 

The results showed that vitamin D in the blood of subjects with childhood asthma (16.63 ng/mL) was significantly lower than that of healthy controls (24.24 ng/mL). Increased time spent outdoors appeared to significantly influence the increase in vitamin D levels, while no associations were observed between vitamin D levels and lung function or residential environmental factors such as housing type, floor of residence, and indoor activity time.

Further Research Will Confirm the Link Between Asthma and Vitamin D Deficiency

According to the scientists who conducted the study, these results suggest that low serum vitamin D concentration is associated with childhood asthma in Korean children, and managing the level of this nutrient could represent a promising approach to prevent disease worsening. 

The study did not consider the use of vitamin D supplements among its participants or the effect of such supplements on vitamin D levels. For this reason, the link between vitamin deficiency and the increased risk of childhood asthma needs to be further investigated. As stated by the authors themselves, the data should be interpreted with caution, and more comprehensive research will be necessary to explore the causal relationship between vitamin D levels and childhood asthma.  

Source: Yu-Ri Kim, Sung Chul Seo, Young Yoo, Ji Tae Choung. “Are children with asthma in South Korea also associated with vitamin D deficiency?” The Korean Society of Environmental Health and Toxicology.