Lactose intolerance is one of the eating disorders that most affects the world's population, although it is not an allergy, it can often cause similar symptoms and cause doubts in the diagnosis. It consists of a disorder of the intestinal mucosa that prevents the digestion and absorption of lactose, due to the low activity or low production of the lactase enzyme.
About 70% of the world's adult population does not produce enough lactase, so they have some degree of lactose intolerance, although they are mostly asymptomatic. (1, 2)
what is lactose
Lactose is the sugar present in mammalian milk. It is a molecule too large to cross the intestinal membrane, so it needs the presence of the lactase enzyme to be transformed into its simplest components, glucose and galactose, and finally be absorbed.
If lactase enzyme activity is low or absent, undigested lactose that remains in the intestine can induce symptoms of lactose intolerance. (two)
Types of lactose intolerance
The descriptive term “lactose intolerance” includes all causes of symptomatic lactose (milk sugar) intolerance and should not be confused with milk protein allergy. Individuals with galactosemia, a genetic disorder of galactose metabolism, also cannot tolerate lactose, but their symptoms are more severe and different from those caused by lactose intolerance. These patients not only need to avoid lactose, but also galactose. (two)
Lactose intolerance, which may be due to:
a) Congenital hypolactasia/Alactasia
Hereditary alactasia is a rare condition in which lactase is completely absent from birth, due to a genetic mutation. There is no production of lactase enzyme and therefore the intestine is unable to digest lactose. Most diagnosed cases originate in Finland and the Nordic countries. It is an incurable disease, in which a lactose-free diet must be followed for life. (3)
b) Primary adult-type hypolactasia (HPTA)/acquired
Primary hypolactasia or lactase deficiency in adults, also called non-persistent lactase (LNP), is a genetically regulated phenomenon in which there is a progressive decrease in lactase enzyme activity throughout development. Activity reduction may occur shortly after weaning, around 2 to 3 years of age, or closer to adolescence, reaching about a tenth or less of the infant level.
It is the most frequent form of lactose intolerance, affecting about 70% of the world's population, with geographic and ethnic variations. It is a progressive and incurable pathology, in which lactose intake must be controlled. (2, 3)
c) Secondary hypolactasia
Hypolactasia or secondary lactase deficiency is normally associated with diseases of the small intestine that cause damage to the intestinal epithelium, leading to lactose maldigestion to varying degrees.
Illnesses such as acute gastroenteritis, untreated celiac disease, chronic intestinal inflammation, and chemotherapy treatments can trigger lactose intolerance. However, when the epithelium heals, lactase enzyme activity is restored. (2, 3)
Lactose intolerance causes digestive symptoms such as feeling of poor digestion, bloated belly, vomiting, abdominal cramps and diarrhea, with consequent dehydration and weight loss. In some cases, it can also lead to headaches, nausea and vertigo. (3, 4)
Symptoms may vary with the amount and frequency of lactose ingested. They appear slowly between 30 minutes and 2 hours after ingestion, and can last for several hours or days. (3)
The primary treatment of lactose intolerance is to reduce the intake of foods that contain lactose, namely milk and dairy products, according to the individual's degree of tolerance (4). In more severe cases, a stricter diet totally free of lactose may be necessary, namely in alactasia or congenital hypolactasia.
In the case of secondary hypolactasia, caused by intestinal disease, the lactose exclusion diet may be temporary between 15 days and 3 months, depending on the severity of the disease and the age of the patient. (3)
In either case, an evaluation and medical follow-up is recommended to determine the degree of tolerance and the level of dietary restriction necessary.
To find out which foods have or may contain lactose, see the article Allergen: Milk
Fidu products do not contain lactose or any milk-derived ingredients. We also do not handle milk or dairy products in our facilities, thus ensuring that there is no cross-contamination by traces and that our products are safe even for the most sensitive.
(1) Vieira, R. (2015). Food Allergens: A Synoptic Study. New University of Lisbon.
(2) NDA (2010). Scientific Opinion on lactose thresholds in lactose intolerance and galactosaemia. EFSA Journal, 8(9).
(3) Garcia, PB (2016). Lactose intolerance. Problematic and Food. University of Salamanca.
(4) SPAIC Food Allergy Interest Group, 2019. Food Allergy: Concepts and Advice and Precautions, 2nd Edition. Lisbon: Portuguese Society of Allergology and Clinical Immunology with support from Thermo Fisher Scientific and BIAL Laboratories.