12 January - 20 June 2016

Vitamin C and exercise-induced asthma

19 June 13

Vitamin C consumption may have a beneficial effect on respiratory symptoms encountered after exercise, according to a meta-analysis published in the journal BMJ Open by Dr Harri Hemila from the University of Helsinki.  Exercise-induced bronchoconstriction (EIB) is a temporary narrowing of the airway which can occur during or after exercise, resulting in a decline in forced expiratory volume (FEV) and affecting around 10% of the general population to about 50% in some fields of competitive athletics.   Formerly, this condition was called exercise-induced asthma.  Symptoms include coughing, wheezing and shortness of breath.  Hemila identified three suitable trials (Schachter and Schlesinger, Cohen et al and Tecklenburg et al), through Medline and Scopus.  The studies were all randomised, double blind and placebo controlled trials and involved a total of 40 participants who each consumed between 0.5g and 2 g of vitamin C before exercise according to the individual study.  Despite the differences in age of participants, the continent and decade in which each trial was carried out and other trial-specific details, the apparent effect of vitamin C remained both constant and significant; there was a 50% reduction in post exercise FEV.  The study notes that pathophysiology of EIB is not fully understood.   However the author states that respiratory water loss can cause the release of inflammatory mediators, such as histamine and prostaglandins, which can cause bronchoconstriction.  Hemila states that previous research has indicated that vitamin C influences the production of various prostanoids in lung tissue, and vitamin C deficiency increases the level of bronchoconstrictor PGF. Animal studies have found that vitamin C decreases contraction caused by PGF, histamine and carbamylcholine.  Hemila also notes how previously, vitamin C has been found to halve the incidence of common cold episodes in people enduring heavy short-term physical stress, which indicate that vitamin C might also have other effects on people under heavy physical exertion.  In conclusion Hemila states that whilst the studies included in this current meta-analysis were small, and limited, and as such it is not possible to say with certainty that this effect will remain true in other populations, such promising results indicate that further research should take place. 

RSSL's Functional Ingredients Laboratory provides vitamin analysis in a wide range of matrices including drinks, fortified foods, pre-mixes and multi-vitamin tablets.  It provides a full vitamin and mineral analysis service to assist with labelling, due diligence, claim substantiation and stability.

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