Let’s start by specifying that, contrary to what one might believe, the disorder commonly defined as “allergy” to lactose … is not an allergy! But 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 as a result of the intake of milk and derivatives has nothing to do with lactose , since 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 much meat on the fire; for the moment we will simply limit ourselves to shedding more light on these two apparently similar and actually completely different disorders.
Lactose intolerance and milk protein allergy are very vast and difficult topics 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 superimposed, the two disorders have quite different etiology and metabolic reactions.
Food intolerance
It is a NON immune-mediated reaction (ie it is outside the mechanisms of the immune system ); intolerances include : enzymatic deficiencies (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 gastrointestinal tract.
Food allergy
It is an adverse reaction to food or nutrients triggered by the immunological mechanism; allergic immunological reactions are of two types: Immuno Globuline 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( egg white and yolk );
- Pesce;
- soybeans;
- Grain;
The diagnostic procedure to differentiate allergy or intolerance can be very complex and, especially in children, must follow a well-determined path; it is a diagnosis often complicated by the high number of triggering mechanisms and the quantity of foods ingested with 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 of intestinal cells responsible for the breakdown of lactose into glucose + galactose ).
Lactose undigested by lactase becomes a substrate for fermentation 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 abnormal increase in intestinal motility and triggers symptoms of: bloating, flatulence and often also foamy diarrhea .
Lactose intolerance is less common in the countries of NORTH Europe (whose populations have kept the consumption of milk and dairy products high), while it occurs more frequently in Asia, Africa and South America (countries in which little milk and milk are consumed). derivatives).
The pathology can be diagnosed thanks to an examination called the H2 breath test ; it is an analysis of the EXPIRED gases after having taken a certain amount 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 may even be cases of strong symptoms but with negative H2 breath test results (no alteration of gases).
Note : A correlation has recently been observed between improvement of symptoms and integration / reconstitution of the intestinal probiotic bacterial flora.
| Lactose in food | ||
| Foods containing lactose | Foods containing small amounts of lactose | Lactose-free foods |
| Whole , partially skimmed or skimmed milk (of any animal species) | Milk supplemented with lactase (highly digestible) | Soups, broths, pasta and rice |
| Powdered or condensed milk | Burro | Common bread |
| Panna | Aged cheeses | Meat and fish of all kinds (boiled, baked , roasted ) |
| Ricotta , dairy products, spreadable cheeses | Sorbets | Vegetables and fresh vegetables |
| Ice creams | Foods containing whey | Fruit |
| Milk-based drinks ( milkshakes , smoothies) | Some cured meats | Soy milk , tofu and derived foods |
| Yogurt (in variable quantities depending on the bacterial strain used for fermentation) | Milk bread or some special breads | Desserts and creams without milk |
Allergy to Cow’s Milk Proteins
We will now deal with cow’s milk allergy , voluntarily omitting 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 (who have 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. The allergy to cow’s milk proteins manifests itself with abdominal pain , diarrhea and vomiting , therefore, it is the first element of differential diagnosis from lactose intolerance.
The antigen that most frequently generates the adverse reaction is the beta-lactoglobulin protein , then the alpha-lactalbumin and finally the caseins ; it is however possible that the subject manifests sensitivity even to several 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 storage 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 , etc.) capable of generating allergy, therefore, the only way to make this food harmless for the nutrition of the hypersensitive infant is the 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.
