Vitamin D deficiency increases the risk and severity of asthma

Asthma is one of the most common chronic diseases, and diet and lifestyle play an important role in its increasing prevalence. Evidence also suggests that the widespread deficiency of vitamin D increases the risk of developing asthma during childhood and adolescence and is associated with more severe symptoms, according to a meta-analysis published in Pediatric Pulmonology.

Asthma is a chronic inflammatory disease of the airways that affects approximately 6–10% of the population. It is particularly common among children and adolescents, many of whom develop asthma after experiencing recurrent episodes of asthmatic bronchitis. Overall, asthma is characterized by chronic inflammation of the airways. In allergic asthma, excessive production of IgE antibodies triggers the release of histamine, causing the bronchial airways to constrict.
The primary symptoms of asthma include shortness of breath, wheezing, chest tightness, a persistent dry cough, or a productive cough with mucus, often worsening at night. If left untreated, asthma can lead to reduced lung function, impaired quality of life, and an increased risk of life-threatening asthma attacks.
Asthma is primarily treated with preventive medications, such as inhaled corticosteroids that reduce airway inflammation, together with rescue medications that open the airways during an attack. However, because these treatments are associated with a range of side effects, there is growing interest in addressing the underlying causes of asthma, including diet and lifestyle factors. It is already well established that vitamin D deficiency is widespread in the general population and that vitamin D helps regulate chronic inflammation. The aim of the new study was therefore to investigate whether blood levels of vitamin D influence both the development of asthma and the severity of the disease.

The greater the vitamin D deficiency, the more severe the asthma symptoms

The researchers searched databases including MEDLINE/PubMed, BIREME, EBSCOhost, Scopus, Web of Science, EMBASE, the Cochrane Library, and ProQuest, identifying 41 relevant studies. These studies included a total of 7,780 participants between the ages of 2 and 18 years who had either been clinically diagnosed with asthma or served as healthy controls.
The severity of asthma, including lung function, was assessed in all patients. Blood levels of vitamin D, total IgE antibodies, and various inflammatory markers were also measured. In addition, the researchers accounted for potential sources of bias that could affect the reliability of the findings.
The meta-analysis revealed that:

• Children and adolescents with asthma had significantly lower blood levels of vitamin D than healthy controls
• Children and adolescents with severe asthma had even lower vitamin D levels than those with mild asthma
• There was an inverse relationship between blood vitamin D levels and total IgE antibody concentrations, which trigger histamine release and airway constriction

The researchers therefore concluded that children and adolescents with asthma have significantly lower vitamin D levels than healthy individuals. Furthermore, the lower the vitamin D level, the more severe the asthma, a relationship that appears to be partly explained by elevated total IgE antibody levels.

Higher doses of vitamin D may cut severe asthma attacks by half

Higher daily vitamin D supplements (25–50 micrograms), when combined with standard asthma therapy, may improve quality of life and reduce the risk of severe asthma attacks requiring hospitalization by as much as 50%. This was reported in a meta-analysis published in the Cochrane Library (Yuhang Wang et al., 2022).
Although most participants continued taking their prescribed asthma medications, the researchers observed that the higher vitamin D supplementation also reduced patients' need for corticosteroid treatment, which is associated with numerous side effects.
For reference, the current recommended daily intake (RI) of vitamin D is 5-10 micrograms for children and adolescents. However, this intake is not always sufficient to achieve an optimal blood level of vitamin D, which should exceed 75 nmol/L. In addition, many children and adolescents do not receive adequate sun exposure or take the recommended vitamin D supplements.
The European Food Safety Authority (EFSA) has established the tolerable upper intake level for vitamin D at 25 micrograms per day for infants, 50 micrograms per day for children aged 1–10 years, and 100 micrograms per day for older children and adults. These amounts are no greater than the quantity of vitamin D that most children, adolescents, and adults can naturally produce from sunlight during a summer day while wearing light clothing or a swimsuit.

• During the summer months, sunlight is the body's most important source of vitamin D, which is synthesized in the skin
• It is best to increase sun exposure gradually beginning in the spring to allow the skin to develop a protective tan without becoming sunburned
• Sunscreen can be applied approximately 30 minutes after sun exposure to allow sufficient vitamin D production while still protecting the skin
• At northern latitudes, vitamin D supplementation is generally recommended during the winter months—or throughout the year for individuals who receive insufficient summer sun exposure
• Research suggests that people with asthma may require higher vitamin D intake than current official recommendations.

References:

Joelia M Ladeira et al. The Role of Vitamin D in Severity and Control of Asthma in Children and Adolescents: A Systematic Review and Meta-analysis, Pediatric Pulmonology.

Yuhang Wang et al. Efficacy of vitamin D supplementation on COPD and asthma control: A systematic review and meta-analysis. Journal of Global Health, Dec. 2022