Whenever you eat strawberries, does your throat start to swell and itch? Do you also get a burning or prickling sensation in your lips, gums, tongue or inside your cheeks? Or perhaps drinking milk gives you abdominal bloating, cramps in the lower belly and diarrhoea half an hour later?
These two simple cases are very explicative of two different situations: allergy and intolerance to a given protein or other molecule in a food.
“Food allergy is a real disease, with a prevalence of 1-4% in the general population with children being more affected than adults”, says Enrico Heffler, allergist and clinical immunologist at the University of Catania, Italy, as well as General Secretary of the Italian Society of Allergy, Asthma and Clinical Immunology (SIAAIC).
“An allergy occurs when our immune system reacts to a specific protein, the “allergen”, present in a given food and wrongly considered as an “invader”, and consequently it triggers a protective response”, he explains.
The symptoms of food allergy can range from mild to severe and the clinical manifestations mainly involve the skin, the gastrointestinal tract, the cardiovascular system and the respiratory tract. Possible manifestations range from skin rashes, or hives, to anaphylaxis, a life-threatening whole-body allergic reaction that can impair breathing, causing a drop in blood pressure and affecting heart rate.
“However”, Heffler continues, “food intolerances identify a number of non-allergic diseases, usually due to enzymatic deficiencies, characterized by the inability to completely digest some food components. The two most common intolerances concern, respectively, lactose, due to the lack or reduced activity of the enzyme that breaks the milk sugar (lactose), and celiac disease, where the incomplete digestion of gluten, a protein found in wheat, rye and barley, damages the small intestine”.
The prevalence of food allergy has been increasing in the same way as that of other allergic diseases.
The last decades have shown that patients are more and more likely to perceive their disease as related to eating. This has added to the confusion between allergy and intolerance, and has led to inappropriate allergy consultancy and testing, as well as to greater health-related costs.
In this context there has been a parallel increase of the business behind tests for suspected intolerances and marketed products free from specific allergens.
In addition to the “official” and validated tests, in fact, we are seeing the growth of “non-conventional” diagnostic tests performed in private medical facilities, whose reliability and efficacy in identifying allergic diseases or food intolerances have been brought into doubt by several scientific studies.
Unfortunately, too many patients still refer to these diagnostic methods.
On the other hand, maternal diet, weaning practices and infant feeding also affect the prevalence of food allergies: earlier introduction and regular exposure to allergenic foods (such as peanuts and egg) may in fact reduce the risk of specific allergies.
The difficulty in tracing guidelines about the introduction of allergenic foods in early life nutrition has led iFAAM, a research project expected to be completed by the end of this year, to develop scientific approaches and tools for the management of allergens in food and dietary advice.
We asked Marie Bodinier, researcher in the “Allergy Team” of INRA, in Nantes, France, to clarify some of the key issues related to early life nutrition and dietary interventions for allergy prevention.
“There is mounting concern that the current recommended practice of delaying complementary foods until 6 months of age may increase the risk of immune disorders”, she explains:, “tolerance to food allergens appears to be driven by regular, early exposure to these proteins during a 'critical window' of child development”.
Breastfeeding is another important factor in allergy prevention: induction of tolerance by breast milk depends on maternal exposure to environmental and dietary antigens and on the efficiency of antigen transfer across mammary epithelium.
Bodinier concludes: “Allergy prevention guidelines are still controversial. Nevertheless, the optimal timing for introducing allergenic foods into the diet, thus reducing the risk of food allergy, is 4 to 6 months while breastfeeding should be maintained for at least 6 months where possible”.
This article is part of the communication of the ProBIO project, a support action for KBBE projects which identifies research results to facilitate their uptake into the relevant sector.
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