Heart attack, stroke... What if food allergens also weakened our arteries?

Rhinitis, asthma, urticaria, or extreme anaphylactic shock... There are many expressions of allergy. And some of us harbor the antibodies that cause allergies, even if we don't have any of these symptoms. “This sensitization without obvious immediate allergy is considered benign and not pathological by doctors,” explains Professor Gisèle Kanny, allergist and immunologist at the Nancy CHRU. A paradigm that could be called into question...

Explanations: the majority of immediately expressed allergies are linked to the presence of type E immunoglobins (IgE), antibodies which attack the responsible allergen (pollens, milk, egg, etc.). However, just because a person develops IgE to a type of allergen does not mean they have signs of allergy. However, a study published at the end of the year in the Journal of Allergy and Clinical Immunology suggests that awareness of certain foods without allergy symptoms is linked to an increase in cardiovascular risk.

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Recent studies have highlighted a possible link between the presence of IgE to alpa-gal, an allergen present in red meat, and the quantity of atherosclerotic plaques in the arteries. Researchers at the Medical University of Virginia, in the United States, therefore sought to find out if this could concern other food allergens. Indeed, sensitization to certain foods is quite common. “Approximately 15% of adults produce IgE antibodies in response to cow's milk, peanuts and other foods,” note the authors of the study.

The scientists used data from the US National Health and Nutrition Examination Survey (NHANES) and a multi-ethnic atherosclerosis cohort to study nearly 5,000 adults over time. Their results show that people sensitized to dairy products were at high risk of death and cardiovascular events. This remained true even when known risk factors for heart disease, such as smoking, high blood pressure, high cholesterol and diabetes, were taken into account. The risk associated with other allergens such as peanut and shellfish were also significant, but lower.

How can we explain the increase in cardiovascular risk? We now know that atherosclerotic plaque, the cause of cardiovascular disease, is linked to inflammation and not only to an accumulation of cholesterol in the arteries. However, allergic diseases are immunological disorders characterized by the development of type 2 inflammation and IgE responses. “We are not sure of the role that this type 2 inflammation plays in the genesis of the plaque. However, a literature review dating from 2022 hypothesizes that certain patients could develop sensitization with IgE against oxidized cholesterol. These IgE will activate a whole bunch of cells, macrophages, mast cells, which can enter the plaque and allow it to grow or make it unstable. Which will increase the cardiovascular risk,” explains Dr Luc Colas, allergist and immunologist at Nantes University Hospital.

But all this remains hypothetical. The authors of the study themselves point out that the mechanisms involved have not yet been understood. Environmental and genetic factors could also enter into the equation. “It is difficult at this stage to draw clinical recommendations from this study. We are in the field of research,” insists Professor Gisèle Kanny.

On the other hand, if the mechanism of the inflammatory pathway is confirmed, it could be interesting to see if the drugs developed in allergy to counter IgE or type 2 inflammation have a protective action against cardiovascular mortality. “Medicines exist. But will they be effective? We could look at patients treated with these drugs for years and retrospectively look at whether they had more or fewer cardiovascular events than their reference population. This could already give us the beginnings of an answer,” concludes Dr Luc Colas.