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Asthma affects a large proportion of the UK and 20% of all cases involve children.
There are many factors involved in the development of asthma and research is now highlighting the role vitamin D may play.
In this article we take a look at the evidence behind vitamin D and asthma.
Overview of asthma
Asthma is a respiratory condition involving inflammation and constriction of bronchial tubes in the lungs.
Triggers such as environmental pollution, allergens, pet hair and faeces from dust mites can irritate the respiratory tract lining, provoking a reaction.
Other factors involved include genetics, chemical exposure, stress, medications and altered immune function.
Symptoms of asthma include noisy breathing, wheezing, breathlessness, tightness of the chest and coughing.
An asthma attack describes an acute onset of asthma symptoms that can be severe and affect oxygen levels, causing a blue colour to the lips and nails.
It is estimated that around three people in the UK die from an asthma attack each day (1).
Overview of vitamin D
Vitamin D is a fat soluble vitamin, more rightly termed a hormone.
It is made from cholesterol and synthesis is stimulated when skin is exposed to UVB rays in direct sunlight.
Some foods contain small quantities that may contribute to overall levels but the best source by far is skin exposure to the sun.
Vitamin D has long been known to support bone health and research has highlighted that it may play a role in many other aspects of health.
It has been shown to support immune health, regulate actions involved in cancer development (2) and support healthy blood sugar and blood pressure.
How is vitamin D linked to asthma?
Vitamin D is known to modulate the inflammatory response – as asthma involves inflammation of the airways, there is much interest as to whether vitamin D has a therapeutic role.
Evidence clearly shows a link between vitamin D levels and asthma and many studies indicate asthmatics are often deficient in vitamin D.
A low level of vitamin D is associated with impaired lung function, airway hyper responsiveness and a reduced response to steroid medications (3).
A good maternal level of vitamin D during pregnancy has been found to reduce the risk of asthma in early childhood (4).
The link between low vitamin D levels in children and asthma is stronger than with adults.
Asthmatic children have significantly reduced levels of vitamin D compared to non-asthmatic children (5).
This leads experts to comment that vitamin D levels can be used as a strong predictor for asthma in children.
Studies into vitamin D deficiency in asthma have led to interventions with supplementation of vitamin D.
Results are mixed; some studies have found that additional vitamin D from supplements may reduce the risk of asthma exacerbations (6), particularly in children (7), whilst others have found maternal supplementation during pregnancy may give the best outcomes (8).
Benefits of vitamin D in asthma
Anti-inflammatory action – the mechanism behind airway narrowing in asthma involves inflammation and chemical messengers called cytokines. Vitamin D has been shown to modulate the inflammatory response in a variety of ways, including reducing inflammatory cytokines, and so it is thought this may be one of the ways in which it can reduce exacerbation of asthma.
Reduce response to allergens – recognising invading and foreign particles is a normal part of immune functioning and defence and in asthma it seems there is a bias towards over reacting to potential allergens causing a hyper responsiveness. Vitamin D is thought to bring back the natural balance in immune functioning and work towards preventing allergic responses that may impact asthma (9).
Strengthen response to infection – vitamin D receptors are present in many cells, including immune cells and it is thought to enhance natural defences against foreign substances and pathogens. There is a clear link between respiratory tract infections and exacerbation of asthma and adequate vitamin D levels may reduce the incidence of infections, such as colds and flu, and therefore asthma exacerbation.
Increase response to medication – steroid medication use in asthma may be enhanced by the addition of vitamin D. Several studies indicate the benefits of vitamin D alongside medication, particularly in those resistant to the effects of steroids (10). Less medication may be needed in children with a good vitamin D status (11).
How much vitamin D is beneficial?
Current European guidelines state that infants up to the age of 1 year old should have between 340iu (8.5µg) and 400iu (10µg) of vitamin D a day.
Children over the age of 1 year, adults and pregnant and breastfeeding women should have around 400iu (10µg) of vitamin D a day.
These are general recommendations and do not take into account current vitamin D status, health requirements or lifestyle.
Some studies into vitamin D and asthma use far higher levels and can range from 400iu right up to 60,000iu given once a month.
It is suggested that exposing skin to direct sunlight for around 15-20 minutes a day can provide adequate vitamin D.
In autumn and winter months the use of a high quality supplement may be recommended.
It is clear that getting adequate vitamin D may reduce the symptoms associated with asthma and cut the risk of asthma attacks.
Vitamin D deficiency is now being shown to be common and testing levels of vitamin D can be performed via a Personalised Health practitioner, this can also help with calculating daily requirements of vitamin D.
A consultation with an Amchara Personalised Health practitioner can help you understand other factors that may be playing a role in asthma.
We’re dedicated to providing you with both insightful information and evidence-based content, all orientated towards the Personalised Health approach.
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