Lactose intolerance – why milk causes stomach discomfort for many
By Dan Kauna, July 1, 2026For many people, a morning cup of hot milk tea is a daily routine. Yet, for a large number of people, this simple pleasure leads to stomach cramps, bloating, and gas.
While it is easy to assume something is wrong when this happens, science shows that this reaction is actually the biological baseline for most adults worldwide.
When humans are babies, our bodies produce an enzyme called lactase. This enzyme breaks down lactose, the natural sugar found in milk. As we grow older and stop relying on a milk-only diet, the body naturally reduces the production of this enzyme.
A study published in December 2006 explains that “In most humans, the ability to digest lactose, the main carbohydrate present in milk, declines rapidly after weaning because of decreasing levels of the enzyme.”
This means that lactose intolerance is not an illness; it is the natural evolutionary state for adult humans.
The genetic link in East Africa
If avoiding milk is the global norm, why can some Kenyans drink several cups of tea or fresh milk daily without feeling sick? The explanation comes down to genetics and history.
Thousands of years ago, specific ancestral groups in East Africa and Europe began keeping cattle for dairy. In these cultures, individuals who could digest milk throughout their lives had a better chance of surviving droughts and food shortages.
Over centuries, a genetic mutation spread through these cattle-herding communities, keeping their lactase production permanently active.
In Kenya, scientists identified this specific change as the G/C-14010 mutation. People with ancestors from traditional pastoralist communities, such as the Maasai, often carry this gene.
On the other hand, individuals whose ancestors relied primarily on agriculture or fishing are more likely to experience stomach changes after drinking milk because their bodies follow the standard human blueprint.
Managing discomfort without giving up dairy
When someone without enough lactase drinks milk, the sugar enters the large intestine completely whole. Normal gut bacteria then ferment this sugar, creating gases that cause sharp pains and severe bloating. The process also draws water into the bowel, which leads to sudden diarrhoea.
Fortunately, navigating this situation does not mean abandoning local dairy culture. Fermented options like traditional mursik or commercial lala are easier to digest because the fermentation process breaks down much of the milk sugar before consumption.
Additionally, supermarkets stock local lactose-free milk options, allowing people to enjoy their morning beverages without digestive trouble.