Celiac disease, wheat allergy and gluten sensitivity or non-celiac gluten sensitivity are common disorders related to gluten consumption. A considerable proportion of as high as 3%–10% of the human population in wheat-consuming part of the word suffers from one of these disorders.
 
Celiac disease and wheat allergy are the most serious forms of gluten intolerance. Celiac disease is an autoimmune disorder and is one of the most frequent food intolerances. Wheat allergy occurs mainly due to immune-mediated reactions from the ingestion of gluten proteins that give rise to immunogenic peptides in sensitive individuals. And all who suffers from celiac or wheat allergy knows, a lifelong gluten-free diet is the only accepted medical treatment for these disorders. Such a diet includes the complete elimination of wheat, barley, and rye products beside any food and non-food items that are cross-contaminated with these cereals.
 
Several dietary and non-dietary alternative therapies to gluten-free diet have been proposed. However, the effectiveness of these alternative therapies are yet to be proven. Since gluten-free diet is generally effective for clinical improvement in most patients, most of the alternative therapies identified do not replace, but are recommended as adjuncts to gluten-free diet.
 
Among dietary alternative therapies, the consumption of gluten-specific proteolytic enzymes supplements before/after a meal to hydrolyze proline-rich peptides in gluten has gained attention due to its apparent success in eliminating the immunogenicity triggered by these peptides. These gluten-specific exogenous enzymes must tolerate strongly acidic gastric pH conditions and be active to hydrolyze gluten
peptides effectively before they reach the upper small intestine, where the immunogenic reactions start occurring. To date, several microbial and plant enzyme groups have been identified.
 
The researchers from New Zealand propose actinidin as a candidate for “detoxifying” gluten. The actinidin molecule is found at relatively high levels in green kiwifruit (Actinidia deliciosa). It consists of a single chain of 220 amino acids. As with the other fruit thiol proteases (papain and bromelain), the physiological function of actinidin in green kiwifruit is unknown, and it is clearly not essential, as other cultivars of kiwifruit contain much lower amounts of the enzyme.
 
Laboratory studies using rats showed that actinidin enhances the digestion of wheat gluten and gliadin. Thus, it is to be expected that actinidin will digest gluten proteins in the human stomach, which could result in a reduction or elimination of immunogenic peptides. This suggests that consumption of green kiwifruit, and possibly also papaya and pineapple, could be used as an alternative way to reduce the adverse effects of consumption of gluten-containing products.
 
However, the researchers underline that there is still need for more evidence to determine if the increase in gastric digestion when these fruits are consumed is translated to a reduced or eliminated presence of immunogenic peptides in the small intestine.
 
 
Further reading
Jayawardana et al., Possibility of minimizing gluten intolerance by co-consumption of some fruits – A case for positive food synergy?, Trends in Food Science & Technology, https://doi.org/10.1016/j.tifs.2019.10.003, 2019.