Cow's milk, cheese, yogurt, cream, and the like – all these products contain lactose and therefore pose a problem in the everyday lives of many people with lactose intolerance. In this article, we clarify what lactose intolerance means, in which foods milk sugar occurs, how it is chemically composed, and how it is processed in the body.
Lactose: Basic knowledge and chemical structure
Lactose, also called milk sugar, is a type of sugar alongside glucose and fructose. It belongs to the double sugars, the disaccharides - just like sucrose (table sugar). In its natural form, lactose is only contained in the breast milk of mammals (Seilnacht, 2013), which is a unique feature compared to other types of sugar (Schleip, 2010). Furthermore, milk sugar has only about one-fifth the sweetening power of table sugar (Fritzsche, 2009).
From a chemical perspective, lactose is a slightly sweet-tasting substance. Extracted from milk, it occurs as a white powder that is slightly soluble in water and consists of the two sugar building blocks glucose and galactose. These two monosaccharide components (simple sugars) are connected to each other by an oxygen atom (Seilnacht, 2013). This results in the molecular formula C12H22O11 and the following structural formula, which gives you a rough overview of the chemical composition.
In which foods is lactose found?
Lactose is a naturally occurring type of sugar in the milk of mammals, with the content varying in different types of milk (Schleip, 2010):
- Cow's milk: around 5 g per 100 ml of milk
- Human milk: around 7 g per 100 ml of milk
- Milk of the green monkey: around 10 g per 100 ml of milk
Lactose is a component of any cow, sheep, or goat milk products such as cheese, butter, sour cream, whey, heavy cream, quark, or milk chocolate. Furthermore, due to its properties, it is often added during the industrial production of many convenience products. For example, milk sugar is found in baking mixes, canned goods, breadcrumbs, and candies (Seilnacht, 2013), as these foods gain a higher viscosity and proteins can be enriched better. In baked goods, the use of lactose also creates a popular browning effect (Schleip, 2010). Finally, lactose is also used as a carrier substance in the production of medication (Fritzsche, 2009).
Processing in the body
Lactose serves the human body as an energy source, improves the absorption of the trace element calcium into the bones, and promotes the bacterial flora in the gut (Seilnacht, 2013). Lactose is not directly usable for humans but must be broken down in the body. In the small intestine, milk sugar is broken down into its individual components by the enzyme lactase. The split-off monosaccharides glucose and galactose can then pass through the intestinal wall and be used for metabolism (Schleip, 2010). If the body produces the enzyme lactase only partially or not at all, lactose can be processed only to a limited extent or not at all. In this case, intolerances and the well-known lactose intolerance occur (Seilnacht, 2013).
Did you know? Mammalian infants all over the world possess the enzyme lactase for the absorption of breast milk. Originally, the enzyme is then no longer produced by adult humans (Paas, 2008). Mutations and adaptations over thousands of years, however, ensured that lactase was also produced by the human body in adulthood. Since the ability to split lactose offered a great survival advantage, the mutation of the lactase gene prevailed in many parts of the world. Therefore, lactose is well digested, especially in countries with intensive dairy and livestock farming. In contrast, many people in Asia cannot tolerate milk, as the age-related decline in lactase production intended by nature prevails here (Helmich, 2022; Seilnacht, 2013).
Lactose intolerance
In Germany, 15 to 20 percent of people are lactose intolerant. In contrast, 80 to 100 percent of people in Africa or Asia cannot tolerate lactose (Paas, 2008). The intolerance to lactose can vary significantly. While some people react with strong symptoms to even the smallest amount of lactose, smaller portions can often be digested without problems. Lactose intolerance is therefore very individual (Fritzsche, 2009; Müller, 2022).
The reason for an intolerance is a deficiency of the enzyme lactase, which means lactose cannot be processed in the small intestine. The body produces lactase only in small amounts or not at all. This results in lactose passing through the large intestine in an unchanged state. The bacteria present there decompose the lactose into various metabolic products such as hydrogen and methane. This process is also referred to as bacterial fermentation, as the lactose ferments (Schleip, 2010). This can cause complaints such as abdominal pain, bloating, or diarrhea (Seilnacht, 2013). However, the symptoms range up to limb pain, skin problems, inner restlessness, headaches, dizziness, sleep disturbances, or even depressive moods (Fritzsche, 2009).
To counteract the intolerance, affected people usually consistently avoid lactose-containing foods or resort to lactose-free products. In these, the lactose has already been broken down into the simple sugars glucose and galactose, so that they contain less than 0.1 g of pure lactose per 100g - an amount that is usually tolerated even with severe intolerance (Schleip, 2010). Other dairy products such as butter and some hard cheeses contain a very small amount of milk sugar anyway, so these can often be consumed without problems (Schleip, 2010).
Another way to deal with lactose intolerance is the intake of lactase supplements. In this case, affected individuals take synthetically produced lactase before a lactose-rich meal, so that the enzyme can break down the consumed lactose. Existing symptoms caused by the intolerance can thus be avoided or at least mitigated (Fritzsche, 2009). Corresponding lactase supplements are available over-the-counter in pharmacies.
Conclusion
In lactose-intolerant people, the body does not produce the enzyme lactase at all or only partially, which means the lactose cannot be broken down into its components. The decomposition of lactose in the large intestine results in various symptoms such as abdominal pain or bloating. Usually, an intolerance can be well managed by avoiding lactose-containing foods or consuming lactose-free products. A vegan diet can also solve the problem of lactose intolerance, as no animal products are consumed. Cold-pressed vegetable and fruit juices can also be easily integrated into a lactose-free diet. Our I·DO organic juices are, of course, completely lactose-free, as they are pressed 100% from organic vegetables and fruits and are not exposed to any additives :)
Sources
Fritzsche, D. (2009). Laktose-Intoleranz. GU Ratgeber Gesundheit. 5th edition. Gräfe und Unzer Verlag.
Helmich, U. (2022). Lactose. Retrieved May 3, 2023, from: https://u-helmich.de/bio/cytologie/02/021/Kohlenhydrate/Kohlenhydrate-03-2.html
Müller, C. (2022). Laktoseintoleranz - Nicht alle Milchprodukte unverträglich. Bundeszentrum für Ernährung. Retrieved May 3, 2023, from: https://www.bzfe.de/ernaehrung/ernaehrungswissen/gesundheit/unvertraeglichkeiten-frei-von-im-trend/laktoseintoleranz/
Paas, D. (2008). Das Laktose-Intoleranz Buch - Alles, was Sie über die Milchzucker-Unverträglichkeit wissen möchten. 2nd edition. MV Verlag.
Seilnacht, T. (2013). Lactose. Retrieved May 3, 2023, from: https://www.seilnacht.com/Chemie/ch_lacto.htm
Schleip, T. (2010). Laktose-Intoleranz: Wenn Milchzucker krank macht. Trias.
