Lactose allergy

Let’s start by clarifying that, contrary to what one might believe, the disorder commonly referred to as “allergy” to  lactose … is not an allergy! Rather, it is a food intolerance  caused by  poor digestion  of this  disaccharide contained in milk.

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In reality, the only allergic form that can occur following the intake of  milk and derivatives  has nothing to do with lactose , as it concerns the  proteins of these foods .

In this regard, it would also be appropriate to make a distinction between the different allergic forms , those towards  cow’s milk proteins  ,  breast milk  (very difficult to treat) etc. But perhaps it is better not to put too many  irons  in the fire; for the moment we will simply limit ourselves to providing greater clarity on these two apparently similar and in truth completely different disorders.

Lactose intolerance and milk protein allergy are very vast topics and difficult to summarize in a few lines, therefore, we will try to focus only on some fundamental concepts for basic understanding.

Difference

In order to clearly distinguish lactose intolerance and milk protein allergy, it is essential to understand that, although the symptoms may be similar, the two disorders have  rather different etiologies and metabolic reactions.

Food intolerance

It is a NON-immune-mediated reaction (i.e. it goes beyond the mechanisms of the immune system ); intolerances   include: enzymatic deficits (such as the lack of  intestinal lactase  due to lactose intolerance), metabolic and   food poisoning . They can be linked to pharmacological properties ( caffeine  in coffee), to the release of  histamine , to individual susceptibility to particular enzymatic deficits or to  idiosyncratic phenomena . The intolerance reaction is always linked to the quantity of food ingested and the complications are limited to the  gastro-intestinal tract.

Food allergy

It is an adverse reaction to foods or nutrients  triggered by the immunological mechanism; Allergic immunological reactions are of two types: Immuno Globulin E ( IgE ) MEDIATED and NON IgE mediated, and can cause both systemic and localized manifestations, limited to the gastro-intestinal,  cutaneous  or respiratory tract. The most serious complication of the allergic reaction is  anaphylactic shock .

Allergens most frequently responsible for  food allergy

• Cow’s milk proteins (a-lactalbumin, B-lactoglubin, casein)
• Eggs( white and yolk );
• Fish;
• Soy;
• Grain;

The diagnostic process to differentiate allergy or intolerance can be very complex and, especially in children, must follow a well-defined path; this is a diagnosis often complicated by the high number of triggering mechanisms and the quantity of foods ingested in the diet NOT included in the diagnostic tests.

Lactose intolerance

Lactose intolerance (not to be confused with  galactosemia ) is a disorder that occurs after the intake of lactose (a disaccharide carbohydrate contained in  milk and dairy products ) only in subjects who do not have a sufficient quantity of lactase (an enzyme specific to intestinal cells   responsible for the splitting of lactose into  glucose  +  galactose ).

Lactose not digested  by lactase becomes a fermentation substrate of the  intestinal bacterial flora  in the  large intestine , with the relative production of: carbon dioxide (CO ₂ ), hydrogen ions (H ₂ ), methane (CH ₄ ) and organic acids; this condition causes an anomalous increase in  intestinal motility  and triggers symptoms of: bloating,  flatulence  and often also  frothy diarrhea .

Lactose intolerance is less common in the countries of NORTHERN Europe (whose populations have maintained a high consumption of milk and derivatives), while it occurs more frequently in Asia, Africa and South America (countries in which little milk and derivatives).

The pathology can be diagnosed thanks to a test called H2 breath test ; it is an analysis of the gases EXHALED after having consumed a certain quantity of lactose.

Regarding the diagnosis, we remind you that lactose intolerance is a disorder that manifests itself with extreme variability; it can be present and symptomatic, present but asymptomatic and there can even be cases of strong symptoms but with negative H2 breath test results (no gas alterations).

Note : A correlation has recently been observed between improvement of symptoms and integration/reconstitution of the intestinal probiotic bacterial  flora  .

Allergy to Cow’s Milk Proteins

We will now deal with cow’s milk allergy  , voluntarily leaving out  human milk allergy as, although it represents a very serious disorder, it is characterized by a more limited prevalence and incidence.

Cow’s milk allergy is the most common allergic form in children (which has greater intestinal permeability) and the fifth in adults; probably, the difference in prevalence and incidence between the two age groups is justifiable by a real improvement in tolerability to this potential allergen. Allergy to cow’s milk proteins manifests itself with  abdominal pain , diarrhea and  vomiting , therefore, it constitutes the first element of differential diagnosis from lactose intolerance.

The antigen  that most frequently generates the adverse reaction is the  beta-lactoglobulin protein , followed by  alpha-lactalbumin  and finally caseins ; However, it is possible that the subject may also show sensitivity to multiple proteins at the same time. 

The pathological mechanism is triggered by the recognition of the protein by the  white blood cells  which release some   specific antibodies (IgE) which adhere to the antigen; in this way (and thanks to the intervention of other specific cells:  Mast cells  and  T lymphocytes ) a sort of antigen memorization and preparation by the immune system takes place.

The second contact between the antigen and the immune system generates the allergic reaction.

There are many proteins contained in different types of milk (human,  goat’s , etc.) capable of generating allergies, therefore, the only way to render this food intended for the nutrition  of  hypersensitive infants harmless  is treatment with heat at 110°C ( special milk), which determines the definitive denaturation of the immunogenetic molecules, preventing any allergic complication even in this type of disorder.