Intolerance to milk components

The public "belief" that milk causes an inflammatory process and an increase in mucus production has not been confirmed [152,153]. It has been shown that respiratory symptoms was not associated with milk intake [152], and concluded that consumption of milk does not seem to exacerbate the symptoms of asthma, but in a few cases people with cow's milk allergy may have asthma-like symptoms after milk consumption [153]. However in cells from another tissue; mucin producing cells of gastric mucosa, alpha-lactalbumin stimulates mucin synthesis and secretion [154].

Milk allergy

Most milk proteins, even proteins present at low concentrations, are potential allergens. A person may be allergic to casein or whey proteins or to both. Milk allergy may arise in small children (0–3 years) and it is estimated that 2–5% of the children has milk allergy [155]. After the age of three years it is no longer a problem for most children.

Milk allergy reactions may either be of the type 'rapid onset' or the 'slower-onset' type. The rapid type comes suddenly with symptoms of e.g. wheezing, vomiting, anaphylaxis. The slower-onset reactions are more common and symptoms develop over a period of hours or days after ingesting milk, and may include loose stool, vomiting, fussiness, reduced weight gain etc. As these symptoms are more general, this type is difficult to diagnose.

Cow's milk allergy may be treated by completely avoiding milk proteins. Epitopes on milk proteins have been shown to be both conformational and linear epitopes, widely spread throughout the protein molecules. Due to the great variability and heterogeneity of the human IgE response, no single allergen or particular structure has been found to be a major part of milk allergenicity [156].

An interesting study from Germany showed that the children of farmers had less allergy, in spite of the fact that these children were drinking more whole- milk than other children not living on farms[157].

Intolerance to milk proteins

There has been speculation if milk proteins may have a role in Attention Deficit Hyperactivity Disorder (ADHD), autism, depressions and schizophrenia in some cases. There are major supports to the hypothesis that ADHD may be linked to increased levels of neuroactive peptides and increased urinary peptide levels [158,159]. A diet free of milk, milk products and gluten may in many cases give reduced ADHD symptoms [158]. Further, opioid peptides derived from food proteins (exorphins) have been found in urine of autistic patients [160]. This area of investigation is important and large scale, good quality randomised controlled trials are needed.

Lactose intolerance

The lactose concentration in bovine milk is about 53 g/l [9]. People often confuse a milk allergy with lactose intolerance, but they are not the same thing. Lactose intolerance is common in many adults throughout the world, and is caused by deficiency of intestinal lactase (hypolactasia). Lactose maldigestion occurs in about 75 % of the worldwide population and about 25 % of the US population [4]. In Scandinavian counties it varies between 2% and 18% [4]. Avoiding all lactose is seldom necessary, and persons with hypolactasia can usually ingest limited amounts of milk without having annoying symptoms. Individual differences in gut micro flora may be one reason for large variations in amounts of milk that is tolerated. To ingest milk with a meal may also improve tolerance. Instead of drinking regular milk, fermented milk may be an option, because fermented milk contains less lactose than fresh milk, and that it also may contain bacterial lactase that may be activated when the fermented milk reaches the gut [161].