Food Intolerances: Let's Clarify

In recent decades, the widespread conditions of overweight and obesity have favored the spread of a worrying and erroneous idea that they are themselves the consequence of presumed pathologies such as food intolerances or allergies.

On social media, restrictive dietary regimes based on diagnostically dubious tests or rather questionable therapeutic approaches aimed at weight loss have become increasingly widespread.

In reality, there are no (rigorous and sufficient) scientific evidences that support or demonstrate the alleged link between food intolerances and obesity/overweight.

Food allergies and intolerances are adverse reactions to foods, which are unwanted and unexpected clinical manifestations resulting from the consumption of a food.

Adverse reactions to food can be classified as:

Toxic: bacterial contamination, toxin contamination, contamination from synthetic chemicals

Non-toxic (due to hypersensitivity):

various types of immunomediated reactions > among these, food allergies (celiac disease, nickel allergy)

non-immunomediated reactions > food intolerances

Food allergies can manifest with immediate or delayed symptoms: symptoms, ranging from mild to severe, occur from a few minutes to a few hours after ingestion of the responsible food.

To identify food allergies, various diagnostically validated tests exist:

• skin allergy tests (prick test, prick by prick, patch test)

• serological tests (PRIST or RAST)

• molecular diagnostics

All are performed in a laboratory and prescribed by a competent physician. Therefore, be wary of "non-conventional" and improvised professional figures.

Once the allergy is diagnosed, an elimination diet is applied, meaning the exclusion of the food or foods responsible for the reaction.

Food intolerances are also unwanted and sudden reactions triggered by the ingestion of one or more foods. They present with symptoms very similar to food allergies but are characterized by non-immunomediated and dose-dependent mechanisms.

Abdominal bloating, altered bowel movements, dyspepsia, abdominal pain, and vomiting are the most common symptoms, manifestations affecting the gastrointestinal tract. However, hives and itching of the skin can also occur. In general, they present with less severe symptoms than allergies.

There are various types of intolerances: enzymatic, pharmacological, and derived from undefined mechanisms.

Lactose intolerance is due to a deficiency of the lactase enzyme (the enzyme responsible for digesting lactose, a sugar present in milk and its derivatives); it is very common in the adult population, especially in the Mediterranean area.

Symptoms (bloating, diarrhea, abdominal pain) generally regress with the exclusion of lactose from the diet, but since it is a dose-dependent condition, small amounts of the food may be tolerated.

Being a genetically determined condition, it can be diagnosed with a DNA test or through the Breath test (evaluates the presence of H2 in exhaled air after lactose intake).

Pharmacological intolerances are reactions determined by the pharmacological effect exerted by some substances present in foods such as biogenic or vasoactive amines, such as:

  histamine > wine, tomatoes, canned foods, sardine fillets, aged cheeses

  tyramine > aged cheeses, wine, beer, brewer's yeast, herring

  serotonin > bananas, tomatoes

  dopamine, noradrenaline, phenylethylamine > chocolate

Other substances such as caffeine, alcohol, theobromine (tea and chocolate), theophylline, and tryptamine present in tomatoes and plums, potato solanine, chili pepper capsaicin are also implicated in these types of reactions.

Celiac Disease (or gluten intolerance) is a chronic inflammation of the small intestine, triggered by gluten ingestion in genetically predisposed individuals. The prevalence in the general Italian population is about 1%, a number certainly underestimated.

The diagnosis is made with a blood draw through the dosage of anti-transglutaminase antibodies (IgA and IgG) and anti-endomysium antibodies (to confirm).

Gluten intolerance causes serious damage to the intestinal mucosa such as atrophy of the intestinal villi; the only therapy that guarantees a celiac good health is a gluten-free diet, carefully followed for life.

In 2010, a syndrome called "Gluten Sensitivity" or better "non-celiac gluten sensitivity (NCGS)" was described, a disorder characterized by symptoms related to gluten ingestion in non-celiac subjects. Given the many pathogenetic and diagnostic aspects still unclear, it is preferable to avoid total and long-term elimination of gluten (elimination is applied for 6-24 months and then gradually reintroduced).

Finally, among the food intolerances triggered by undefined mechanisms, there are reactions related to the intake of additives used in the food industry such as colorants, thickeners, preservatives, antimicrobials, antioxidants (among the most common: benzoates, nitrites, nitrates, sulfites, sodium glutamate).

Regarding the diagnostic approach, since intolerances can manifest with symptoms similar and overlapping with food allergies, it is essential first of all to exclude that they are allergies and then proceed with careful anamnesis.

In case of gastrointestinal disorders, it is advisable to consult an expert doctor and beware of anyone proposing unreliable and scientifically unvalidated food intolerance diagnosis tests.

Unvalidated tests include: IgG4 assays, cytotoxic tests, Alcat tests, electrical tests (vega-test, Voll electroacupuncture, bioscreening, biostrengt test, sarm test, moratest), kinesiological tests, dria tests, hair analysis, iridology, bioresonance, pulse test, auricular cardiac reflex.

Dr. Concetta Mauriello

Sources and further information:

  Position Statement on "Allergies, Food Intolerances, and Nutritional Therapy for Obesity and Metabolic Diseases"

  Shared Document Ten Rules for Managing Food Intolerances