A topic of great discussion at this year’s 26th Annual Conference of the Australasian Society of Clinical Immunology and Allergy, was identifying the drivers behind the current food allergy epidemic in Australia. Australia has one of the highest rates of food allergy in the world, with approximately 10% of infants having a diagnosed food allergy (Allen, 2013). Though there are endless hypotheses to why the incidence of food allergy has increased so dramatically in recent decades, unfortunately, with each hypothesis, comes many unanswered questions.
At present, within the field of allergy research, the leading hypotheses for the rise in food allergy focus upon (Allen, 2014):
- Genetics – family history of allergy, filaggrin gene mutation
– Infant dietary factors – time of introduction of allergenic foods
– Hygiene – parents’ country of birth, presence of siblings or pets
– Vitamin D status
The focus of this report will be to provide an update on the current findings relating to vitamin D and the pathogenesis of allergic diseases. It is estimated up to 50% of people living within Western countries such as Australia are vitamin D insufficient, and up to 10% are vitamin D deficient (AAAAI, 2015).
Vitamin D has many roles within the body in addition to the classic action of regulating calcium and bone homeostasis. It is now understood that vitamin D is an important immunomodulator, which may play a role in food allergy and other allergic diseases such as asthma and atopic dermatitis (Searing and Leung, 2011).
Allen et al. (2013) performed a population-based cohort study to assess the vitamin D and food allergy status of 577 infants, 11 to 15 months of age, living within Melbourne, Australia, between September 2007 and August 2011. Of the infants enrolled within the study, 344 were identified to have an oral food challenge-proven food allergy, 74 infants were food sensitive but tolerant on oral food challenge, and 159 were neither food allergic nor sensitised as determined by negative skin prick tests and oral food challenges.
Upon measuring the serum 25-hydroxyvitamin D levels of these infants, it was discovered the infants of Australian-born parents, with vitamin D insufficiency, were 3 times more likely to be egg allergic and 11 times more likely to be peanut allergic, than infants with adequate vitamin D levels. Vitamin D insufficiency was also shown to increase the likelihood of food sensitivity progressing into allergy, and the risk infants would develop more than one food allergy. Though the same results were not seen for infants of parents born outside of Australia, this study provides direct evidence of vitamin D as a protective factor for food allergy development early in life (Allen et al., 2013).
The above research is not the only evidence supporting the Vitamin D hypothesis. If vitamin D is a protective factor for food allergy development, it is reasonable to suggest the incidence of food allergy will be higher among individuals who are vitamin D deficient.
Vitamin D is synthesised by the body when our skin is exposed to ultraviolet radiation from the sun. Ultraviolet radiation is strongest in equatorial regions where the sun is directly overhead, and weaker in regions further from the equator where the sun is further away. Therefore the likelihood of an individual becoming vitamin D deficient is increased if they are living in areas away from the equator where sun exposure is decreased.
Below are two diagrams which demonstrate the association between vitamin D deficiency and incidence of allergy. The first diagram demonstrates the distribution of peanut allergy among children living within the eastern states of Australia. The proportion of children with peanut allergy increases the further the population is located from the equator, where sun exposure and subsequent ability to produce vitamin D, is reduced (Osborne et al., 2012).
The second diagram is a map of the United States of America. Each state is highlighted to represent the number of adrenaline auto-injectors prescribed per 1000 people during a 12 month period. The number of adrenaline auto-injectors prescribed for individuals at risk for anaphylaxis was found to be much higher among populations living within regions further from the equator, where there is less sun exposure (Carmargo et al., 2007).
Geographical location is not the only factor which can affect an individual’s vitamin D status though. Other risk factors for vitamin D insufficiency and deficiency include (Pearce and Cheetham, 2010):
- Pigmented skin (non-white ethnicity)
– Poor nutrition
– Lack of vitamin D fortification within food products
– Lack of sunlight exposure – occupations, indoor lifestyes
– Skin concealing garments
– Strict sunscreen use – Slip Slop Slap campaign
– Infants who are exclusively breast fed – the vitamin D content of breast milk is not sufficient to meet requirements
– Certain medical conditions
Vitamin D deficiency is preventable and can be remedied with safe sun exposure, a healthy diet and appropriate supplementation. If you are concerned you or your infant may be vitamin D deficient, contact your health care professional for advice.
It is an exciting time for food allergy research. Though there remain many unanswered questions as to the cause of the current food allergy epidemic in Australia and throughout the world, new and emerging research promises further developments in food allergy prevention.
Allen, K. 2014. Are we any closer to understanding the rise in food allergy? Murdoch Children’s Research Institute. Melbourne. Accessed online September 17, 2015, http://www.ilsi.org/SEA_Region/Documents/2014%20ILSI%20SEAR%20Australasia%20Maternal%20and%20Infant%20Nutrition/ILSI%20Aust%20Maternal%20%20Infant%20Nutrition%20-%20K%20Allen%20-%20HealthNUTS%20-%20Aug2014.pdf
Allen, K., Koplin, J., Ponsonby, A. et al. 2013. Vitamin D insufficiency is associated with challenge-proven food allergy in infants. Journal of Allergy and Clinical Immunology 131, 4, 1009-1116.
American Academy of Allergy Asthma and Immunology [AAAAI]. 2015. Vitamin D and food allergy. Accessed September 16, 2015, http://www.aaaai.org/conditions-and-treatments/library/allergy-library/vitamin-d-food-allergy.aspx
Carmago, C., Clark, S., Kaplan, M., Lieberman, P. and Wood, R. 2007. Regional differences in Epipen prescriptions in the United States: the potential role of vitamin D. Journal of Allergy and Clinical Immunology 120, 1, 131-136.
Osborne, N., Ukoumunne, O., Wake, M. and Allen, K. 2012. Prevalence of eczema and food allergy is associated with latitude in Australia. Journal of Allergy and Clinical Immunology 129, 3, 865-867.
Pearce, S. and Cheetham, T. 2010. Diagnosis and management of vitamin D deficiency. British Medical Journal 340, b5664, 142-147. Accessed September 16, 2015, https://weblearn.ox.ac.uk/access/content/group/b6eb0442-7719-4f6f-b0da-f36b91c6c235/BM1%20Year%202%20Learning%20resources/Calcium%20regulation/Vit%20D%20review%20BMJ%20Pearce%202010.pdf
Searing, D. and Leung, D. 2010. Vitamin D in atopic dermatitis, asthma and allergic diseases. Immunology and Allergy Clinics of North America 30, 3, 397-409.