Investigation into adverse reactions to mycoprotein

Abstract

Quorn® is a novel food produced from mycoprotein filaments from the Fusarium species ATC20334 (formerly Fusarium graminearum) bound together using egg protein. It has been available in the United Kingdom since 1985 and over 15 million packs have been sold in this country.

A small number of individuals have reported adverse reactions following ingestion of this foodstuff including vomiting, skin rashes and even anaphylaxis. There have been no fatalities but reactions are uncomfortable and unpleasant. Possible underlying causes included a true immunologically mediated food allergy to either mycoprotein or egg, a toxic effect of mycotoxins known to be produced by this species, causing delayed gastric emptying and vomiting or a directly irritant effect of the foodstuff on the mucosa of the upper gastrointestinal tract. 140 individuals who had experienced such a reaction were contacted and invited to participate in an investigation into its aetiology. Subjects were invited to complete a postal questionnaire detailing the precise nature of their reaction, past medical and drug histories and asking whether they would be prepared to participate in more invasive investigations. These investigations entailed providing a blood sample for detection of IgE, IgG and IgA antibodies to mycoprotein and egg proteins, and undergoing either upper gastrointestinal endoscopy or isotope solid phase gastric emptying studies pre and post oral challenge with mycoprotein. An in house ELISA assay for IgE, IgG and IgA antibodies was developed. 89/140 replied to the questionnaire and 54 sent a blood sample. 32/54 subjects were female with age range 18-82 years.

Affected subjects had a significantly elevated mean concentration of IgG antibodies to mycoprotein compared with normal controls and these levels approached those seen in controls with intestinal diseases such as Crohn's disease, ulcerative colitis and Coeliac disease.

Three subjects agreed to have endoscopy, all had evidence of minor upper gastrointestinal pathology pre-challenge. There was no difference in either the macroscopic or microscopic appearances of the mucosa post- challenge and in particular, no excess of neutrophils or eosinophils. One subject had isotope gastric emptying studies which were normal at baseline and did not change post- challenge. There is no evidence of a true food allergy directed against either mycoprotein itself or the egg protein binders used in its manufacture. There is no evidence of any serious immunological abnormality in those affected. However, anti-mycoprotein antibodies produced by subjects have a greater affinity for binding mycoprotein in vitro than those produced by disease controls. This is unlikely to explain the reaction but may imply some increased susceptibility in affected subjects. Within the constraints of a small sample size, there was no evidence of any direct irritant or inflammatory reaction on the gastric mucosa when small doses of cooked mycoprotein are ingested. There was however, a high prevalence of minor upper gastrointestinal pathology noted on endoscopy of affected subjects, but this may be a chance finding.

Although sample size was too small to make useful comments, gastric emptying was not abnormal before challenge and was not affected by mycoprotein ingestion. The underlying aetiology of these reactions remains obscure and at present, the best advice to be given to those affected is to avoid mycoprotein- containing foods.