Food intolerances what they are, how to recognize them and the most accredited causes of onset.


Food intolerances are part of a larger group of disorders defined as adverse reactions to non-toxic food. Intolerances are more common than allergies.

They are classified in:

  • metabolic intolerances or “from enzymatic defects” (for example lactose intolerance),
  • from pharmacologically active substances (eg histamine, tyramine, caffeine, alcohol, solanine, theobromine, phenylethylamine, tryptamine, serotonin, also contained in foods ),
  • from unknown mechanisms such as additives intolerances (nitrite, benzoates, sulphites).

Food Intolerance or Food allergy? the differences!

Among the allergies and the phenomena of food intolerance there are some differences:

  1. What are food allergies: food allergies are adverse reactions to foods or food components with immediate onset caused by an abnormal immunological reaction mediated by antibodies of the IgE class, which react towards food components of a protein nature (allergenic substances, allergens), with release of histamine by mast cells of the gastrointestinal mucosa triggering the typical symptoms of the allergic reaction (cramps, vomiting and diarrhea, urticaria). Allergies, as they are triggered by immunological mechanisms, can also occur without intestinal symptoms but may also have serious complications and the danger of anaphylactic shock.
  2. What are food intolerances:  they are slower and arise after long periods of continuous introduction of food and then stimulation of the immune system (so an unequivocal cause and effect relationship is not visible in time), without the involvement of antibodies of the IgE class (this is the reason why to be negative for allergy tests does NOT rule out the possibility of being intolerant to tested foods: in the face of a non-IgE mediated food hypersensitivity try to understand symptoms related to the presence of a food intolerance only by the study of IgE is useless!).

When the food to which one is intolerant comes into contact with the intestinal wall, a series of reactions develops that lead to the local release of inflammatory mediators, histaminosimilar substances and immune cells with immunological memory, eventually reaching the diffusion in the circulation of cytokines (pro-inflammatory substances), leading to the development of a distant immunoflogosis. Once the maximum (subjective) tolerance level has been exceeded, a small amount of the substance that is not tolerated is sufficient for the appearance of the symptoms.

The intolerances can be cause of the symptoms or pathologies like irritable colon, digestive difficulty, intestinal meteorism, gastroesophageal reflux or stomach acid, headache, dermatitis, rash, cystitis or vaginitis, rhinitis and rhinorrhea, some form of asthma, as well as difficulties in keep the weight stable.

All these symptoms are linked to abnormal functioning of the digestive system.

What are Food intolerances: how to recognize them

The diagnosis of food intolerance, according to the Italian Superior Institute of Health, is a diagnosis by exclusion:

  • it is only possible after investigating and excluding a food allergy.
  • the investigation used to ascertain it is to identify the suspect food, eliminate it from the diet for 2-3 weeks and then reintroduce it for another 2-3 weeks.
  • If the symptoms disappear during the period in which the food is abolished and reappear at the time it is reintroduced into the diet, it is an adverse reaction to food.
  • at this point it occurs, through diagnostic tests, if the immune system is involved and if it is therefore an allergy; otherwise the disturbance is most likely due to an intolerance.

Treatment for food intolerances consists in eliminating from the diet or consuming in small quantities the foods that cause the reaction.

What are Food intolerance: the causes

For now the main causes seem to be the deficiency or absence of an enzyme.

Enzymes are protein molecules that regulate our body’s metabolic reactions.Their main function is to activate and speed up the various biological processes essential to our survival.The quantity of enzymes is not constant in living organisms, since the various alterations that can intervene are generated in humans by:

  • contaminated and / or industrialized foods and therefore devoid of enzymes;
  • from vaccines, from drugs, drugs, alcohol;
  • excess of physical stress, psychological stress;
  • toxic substances, heavy metals;
  • bad weather conditions;
  • alteration of the digestive pH due to ex. from unsuitable foods, bacterial flora, etc.

About intestinal bacterial flora (or “microbiome”), in our post “Probiotics for intestinal balance” we talk about how important it is to maintain intestinal balance and how important our gut is not only to allow the absorption of nutrients but also to prevent many diseases. In recent years there has been a noticeable increase in “food intolerances”, all of which have a condition of Leaky-gut-syndrome (intestinal permeability syndrome).

This syndrome, which has been studied for several years, derives from a functionally abnormal gastro-intestinal epithelium where microvilli – which normally allow physiological digestion and selective absorption of micronutrients – lose the ability to selectivity, allowing the passage of macro-molecules through the gastro-intestinal barrier: these molecules, larger than normal, thus enter the bloodstream and are identified as non-self by our immune system, thus triggering an immunological response.

The lack of enzymes can determine many disorders:

  • digestive difficulty;
  • low levels of energy;
  • slowing of metabolism;
  • intestinal disorders;
  • appearance of allergic forms;
  • work overload for pancreas and liver;
  • high levels of sugar;
  • less assimilation of nutrients;
  • alteration of the stimulus of hunger.

In the next post (clic here to read “Food intolerances: natural remedies) I will discuss the most widespread food intolerances (lactose, gluten) and our natural proposals to contrast them.

Dr. Laura Comollo

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