Lactose and Lactase

By Christiane Pies, MSc
(Translated from German by Ute Marie Allison)

Lactose and Lactase

Lactose is the most important energy source during the first years of a baby’s life. It makes sure that the physiological gut flora can develop and that the calcium in milk can be
best utilised by the body. In the food industry lactose also plays an important role. Due to its chemical and technological properties lactose is frequently used in the production of industrial food products like baked products, sweets, meat preparations like pates, low fat foods, convenience foods, spice mixtures and artificial sweeteners. Lactose works as a binder and a carrier for
aroma substances. It ensures a better firmness and a higher volume of these foods. A lot of medication also contains lactose as a filler or for taste correction. To enable absorption by the body the disaccharide has to be split into its two monosaccharides. Lactase is the necessary enzyme, which can split the ß-glycosidic bond between galactose and glucose.

Frequency and Prevalence
A lack of lactase is the world’s most frequent ‘enzyme deficiency’. About two thirds of the world’s human population loose the ability to split lactose after weaning – as do most mammals. Interestingly there is a characteristic North-South gradient. In Scandinavia only 3-8% of the population show a loss of lactase after weaning. In Germany about 13-14% and in Austria about 20% of the population is lactose intolerant.

However, this number is on the increase through the rising number of immigrants from the Mediterranean. In the Mediterranean the percentage of the population with lactose intolerance is rising to about 70%, and in Africa close to the equator about 98% of the population show lactose mal-digestion. It is assumed that the distribution of lactose intolerance has a connection to sunshine. In Northern countries the population has to manage on much less sunshine than the population near the equator. The human organism needs UV-rays for the production of vitamin D, which is needed for the efficient absorption of calcium from food. With their ability to digest lactose, which also promotes calcium absorption, people in countries with less sunshine could prevent calcium deficiencies. A long time ago a coincidental mutation, which is responsible for permanent lactase production, must have been successful in light-skinned Northern Europeans and Americans. This created the tolerance of milk and milk products and later enabled the development of the milk industry.
Please note: In about 75% of lactose intolerant people fructose intolerance can also be found.

Please ask the laboratory for more information.

Forms of Lactose Intolerance
In lactose intolerance we generally distinguish between two forms.

1. Primary lactase deficiency
This is the most frequent form of lactase deficiency. It is hereditary. Whilst in Western European countries lactase intolerance usually only occurs at adult age, in a great number of the world’s population the decline of lactase activity even happens in infants. Older people practically always have lactose intolerance. Primary lactase deficiency most frequently occurs in South-East Asia, Central Africa and in the Mediterranean. A very rare form of primary lactase deficiency is Congenital Lactase Deficiency (CLD). In this autosomal recessive hereditary disease lactase activity is lacking even directly after birth. Because mother’s milk contains a lot of lactose these babies suffer from severe watery diarrhoea, dehydration and malnourishment. A strictly lactose free diet has to be maintained because even the smallest quantities of lactose can cause severe development damage for newborn babies.

2. Secondary lactase deficiency
Secondary forms of lactase intolerance can occur when the surface of the small intestinal epithelium is damaged by disease. The cause of the damage is insignificant. As soon as the absorption surface is diminished a functional limitation of lactase activity follows because the enzyme occurs in the microvilli.

The following diseases can lead to a loss of lactase activity:

1. Bacterial dysbiosis in the small intestine, overgrowth syndrome
2. Celiac disease
3. Radiation induced enteritis (radiation in tumour therapy)
4. Infectious enteritis and infectious diseases
5. Reduced contact times with accelerated intestinal passage

What is the Cause of the Symptoms in Lactose Intolerance?

Lactase splits lactose into its two components, galactose and glucose. These two monosaccharides are absorbed in the small intestine. In contrast, unsplit lactose remains in the intestine. This lactose reaches lower intestinal areas and is then fermented by gut bacteria. The fermentation products are methane, carbon dioxide and short chain fatty acids, which lead to symptoms like gas, wind and osmotic diarrhoea. In addition to that the gut bacteria can produce a number of biologically active substances. This is the reason for symptoms of lactose intolerance not limited to the GI tract.

Symptoms of Lactose Intolerance

  • diarrhoea/diarrhoea like problems
  • mushy stool
  • tummy rumbling
  • bloating
  • vomiting
  • constipation
  • wind
  • feeling sick after food
  • tummy ache
  • belching
  • colic like pain

(These problems can occur as early as 15-30 minutes after the lactose containing meal, a few hours later or even in the morning of the following day.)

Non-specific complaints

  • chronic tiredness
  • joint pain
  • depressive moods
  • restlessness
  • subjective feeling ill
  • nausea
  • headache
  • exhaustion
  • nervousness
  • feeling low
  • feeling tense
  • sleep problems
  • skin impurities
  • lack of concentration
  • deficiency symptoms
  • fatigue

(from Schleip, Laktoseintoleranz, Trias-Verlag)


Because milk and milk products can cause the problems described, diet recommendations have so far concentrated on avoiding or reducing milk, milk products and foods containing lactose.

The following foods are free of lactose

  • meat
  • fish
  • fruit and veg
  • potatoes, pasta, rice
  • pulses
  • grains
  • mineral water, fruit juices tea, coffee
  • plant oils
  • eggs

Until recently it was difficult for the consumer to find out which foods contained added lactose. A declaration of lactose as a carrier substance for aromatic substances or as an emulsifier in processed foods was not regulated by law.  However, on the 25th November 2005 the EU rule 2003/89/EG was put into force. According to this lactose has to be declared in the ingredient list. 

Numerous milk and milk substitute products are commercially available which are mostly based on soya or rice. Some manufacturers also offer lactose free milk and milk products.

One problem, which can occur in lactose-intolerant people, is calcium deficiency since milk and milk products are the best sources of the mineral calcium in human diet. Calcium has, for example, important properties in the stabilisation of cell membranes, the transmission of nerve signals and in blood clotting. It is also very important for the stability of bones and teeth. Because lactose intolerant people have a lower supply with milk and milk products, there is the danger of acquiring osteoporosis.

Generally the demand for calcium can also be met with plant food like kale, spinach, broccoli and soya beans. However, calcium from these sources is not as readily available for the human organism because of the oxalic acid content. It might be wise to supplement calcium in combination with vitamin D3, which supports the absorption of calcium.

To prevent symptoms and for a better tolerance of products containing lactose the enzyme lactase can be supplemented in tablet or capsule form. It should be taken before meals. Each patient has to find out their own individually-appropriate dose. With a lactase supplement eating out, when the patient has no influence on the ingredients, is much easier for sufferers.

In the UK lactase supplements are available for example from Solgar: Lactase 3500; or from BioCare: Lactase Enzyme. It can also be beneficial to add Okoubaka, a very useful homeopathic remedy to counteract the typical symptoms of food intolerance.

Lactobacilli can also make a valuable contribution. They produce lactase, the enzyme which is lacking in the gut of lactose intolerant people. Please make sure that the lactobacilli supplement of your choice has been produced lactose free. These lactobacilli should also be resistant enough to survive the stomach passage.

– M. Ledochowski, Bair, H., Fuchs, D., Laktoseintoleranz, J. Ernährungsmed., 2003, 5 (1)  Ausgabe für Österreich, 7 – 14.
– Sonntag, S., Phänomen „Laktoseintoleranz – Laktasemangel“, OM & Ernährung, 2006. Nr. 115, S. 14 – 17.
– Stuparsky, A., Milchzuckerunverträglichkeit Laktoseintoleranz, Umwelt & Gesundheit, 2003 (3), 104 – 108.
– Schleip,T. Laktoseintoleranz, Trias-Verlag, 2004.

Christiane Pies, MSc
Head of Science
Dr. Hauss Laboratory
Kieler Str. 71
24340 Eckernförde
043 51- 71 26 81