What are the impacts of lactase deficiency?

People with lactose intolerance have a shortage of the enzyme lactase. The lactose molecules are not or are only partially broken down, and reach the large intestine in this state. The chemical process that happens there, which is responsible for the symptoms of lactose intolerance, takes place as follows: The milk sugar molecules that arrive in the large intestine are converted into different chemical elements without the involvement of oxygen; thus they ferment ‘anaerobically’.

Bacterial Breakdown Products

In addition to some short-chain fatty acids such as lactic acid and acetic acid so-called fission products are formed as the gases carbon dioxide(CO₂), methane(CH₄) and hydrogen dioxide (H₂) too. This conversion process (the so-called ‘fermentation’) has three main consequences for the human body: a) the intestinal peristalsis (intestinal movement) is stimulated through the organic acids formed in the large intestine and thereby increases the susceptibility to diarrhea.
b) the water-binding property of milk sugar (12g is enough to thicken 200ml of water) creates an osmotic pressure inside the colon (‘intestinal lumen’). Due to this pressure water and sodium (salt) flow into the intestinal cavity until osmotic equilibrium is restored. The volume of liquid in the large intestine can increase fivefold in a very short time. This is referred to as an ‘osmotic volume strain’ on the large intestine. Since these produce a laxative effect, an ‘osmotic diarrhea’ happens. c) Bacterial disintegration of milk sugar molecules leads to the formation of carbon dioxide, methane and hydrogen. These collect in the large intestine and lead to flatulence. Due to the anatomical make-up of the large intestine the gas can, in some cases, linger in the intestinal loop, resulting in a largely bloated stomach that stays for a long time. For this reason many affected people have a bulging stomach and feel overweight.

Some of the gas gets into the bloodstream through the walls of the intestine. Depending on the amount, this has veritable toxic effects on the whole body. This is recognizable as dizziness, among other things. Since the gas is exhaled through the lungs, this is where the lactose tolerance test is done: The hydrogen levels of the breath are measured and the individual tolerance to lactose is detected.

Chronic Digestive Problems

Usually a protective mucus layer is located inside the gut. Regular diarrhea decimates this, which creates an acidic environment in the intestinal lumen. As a long-term consequence ‘intestinal permeability’ (an altered permeability of the intestinal wall) develops. Thus food components can enter the organ that normally the intestinal wall wouldn’t/couldn’t let through. This side effect can be presumed to be responsible for some unspecified symptoms. There has not yet been a valid study into the long term damaging effects on the body. It is known that undigested lactose molecules are released into the bloodstream. They are not metabolized and exit the body later with urine. It is assumed that a maximum of 1% of all disaccharides take this path.

Another problem is the way lactose intolerance makes itself worse. This is because of the damaging effect chronic digestion problems have on the enzyme-carrying intestinal mucus. A consequence of milk sugar intake is that it leads to a reduction in the enzyme deposits in the affected parts of the bowels, which again causes further digestion problems.