Lactose (=milk sugar) is contained in milk and milk products as well as in foods and dishes made from them.
Normally the binate sugar lactose is broken down in the small intestine by lactase, an enzyme constructed in the villus of the intestine and taken up into the blood system. If too little or indeed no lactase is present, the milk sugar passes undigested deeper into the bowel where bacteria turn it into gases (especially carbon dioxide and hydrogen) and short-chain fatty acids. These fermentation products in turn bring about, among other things, an increased influx of water in the large intestine which can cause symptoms such as flatulence, soft, greasy stool or diarrhea, stomach aches (sometimes like colic), but also a feeling of fullness, nausea, sour stomach, or in rare cases, blockage or vomiting. Besides this, undigested lactose tryptophan binds to itself and hinders its absorption. Because tryptophan is the raw material for the neurotransmitter serotonin and the sleep hormone melatonin, lactose intolerance can exaggerate depression, pain perception and insomnia.
How much milk sugar is tolerable?
How much milk sugar can be tolerated is very individual and depends on how much lactose is created in the small intestine.
With complete enzyme deficiency, even small parts (in the milligram range) cannot be tolerated, which seldom happens. 5-8 g of milk sugar spread over a day will, in many cases, not be well tolerated. The individually tolerated amount must be tested in each case—preferably by completely eliminating foods containing milk sugar at the beginning, then raising the milk sugar amounts by steps. Decisive for the tolerability are above all the milk sugar contents, according to the table, and the consumed amounts. A role is also played by whether or not the milk product is eaten alone or combined with other foods, which through their portion of fat, roughage and so on, can lengthen the time in the bowel, so the lactase has more time to break down the milk sugar.
The lactose contents may be split into 4 groups:
All food that does not contain any milk or milk products.
Almost lactose free (less than 1g Lactose/100g)
(e.g. cheese spread)
Medium lactose contents (1-4,5g Lactose/100g)
Small amounts are normally well tolerated in combination with other foods:
Acidified milk products
Products with lower lactose contents than milk
High lactose contents (more than 4,5g Lactose/100g)
High lactose contents: