[Immunology] Fruit pectin protects allergens against degradation by stomach acid

Kofi via immuno%40net.bio.net (by kofi from anon.un)
Fri Jun 8 01:20:47 EST 2007

One mystery about allergies is how food allergens can survive the 
transit through the stomach to cause trouble when they meet the immune 
system in the intestines.  Many previous studies have suggested that 
allergens can't survive the harsh mixture of acid and pepsin in the 
stomach, however this new study explains how they can do it though both 
in vitro and in vivo human studies.  The pectin in fruit appears to 
protect allergens against the stomach's corrosive environment.

This may explain the advice given to people with yeast problems to eat 
fruits separately from other foods like meats.  The traditional reason 
for this advice is that meats and fruits have a different pH but I think 
the protective effect of pectin may play a bigger role.

Clin Exp Allergy. 2007 May;37(5):764-71. Links

A matrix effect in pectin-rich fruits hampers digestion of allergen by 
pepsin in vivo and in vitro.
Polovic N, Blanusa M, Gavrovic-Jankulovic M, Atanaskovic-Markovic M, 
Burazer L, Jankov R, Cirkovic Velickovic T.

Department of Biochemistry, Faculty of Chemistry, University of 
Belgrade, Belgrade, Serbia.

BACKGROUND: It is a general belief that a food allergen should be stable 
to gastric digestion. Various acidic plant polysaccharides, including 
pectin, are ubiquitous in fruit matrixes and can form hydrogels under 
low-pH conditions. OBJECTIVE: The purpose of this study was to 
investigate the effect of hydrogel forming polysaccharide-rich fruit 
matrixes on in vivo gastric and in vitro pepsic digestion of fruit 
allergens. METHODS: Fruit extract proteins (kiwi, banana, apple and 
cherry) and a purified major kiwi allergen Act c 2 were digested with 
simulated gastric fluid in accordance with the US Pharmacopeia. In vivo 
experiments on kiwi fruit digestion were performed on four healthy 
non-atopic volunteers by examining the gastric content 1 h after 
ingestion of kiwi fruit. The Act c 2 and kiwi proteins were detected in 
immunoblots using monoclonal anti-Act c 2 antibodies and rabbit 
polyclonal antisera. RESULTS: Crude fruit extracts were resistant to 
digestion by pepsin when compared with commonly prepared extracts. In 
the gastric content of all volunteers, following kiwi fruit ingestion 
and immunoblotting, intact Act c 2 was detected with anti-Act c 2 
monoclonal antibodies, while kiwi proteins of higher molecular weights 
were detected using rabbit polyclonal antisera. Addition of apple fruit 
pectin (1.5% and 3%) to the purified kiwi allergen was able to protect 
it from pepsin digestion in vitro. CONCLUSION: The matrix effect in 
pectin-rich fruits can influence the digestibility of food proteins and 
thereby the process of allergic sensitization in atopic individuals.

PMID: 17456224 [PubMed - in process]

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