Lactose intolerance is a physical response to undigested lactose in the large intestine, resulting from lactase enzyme inactivity or deficiency in the small intestine. The most obvious symptoms are diarrhoea and loose stools, abdominal pain and bloating and flatulence and wind. Lactose itself is a sugar, composed of two units: glucose and galactose, which, when digested normally by lactase, enters the blood stream via tiny blood vessels. Found in mammalian milks – human, cow, goat, sheep and products like yoghurt. Cheese, butter and double cream contain very low levels of lactose and are often tolerated by adults and older children with established lactose intolerance. It’s worth noting the different types of lactose intolerance.

Temporary, secondary or primary lactose intolerance?

Temporary or secondary lactose intolerance is the most common type and as its name suggests is short-lived.  It is sometimes called secondary because it is as a result of something else.  For example it occurs when the small intestinal lining suffers damage or inflammation eg. after a gastro-intestinal infection or surgery.   A lactose free diet may be followed for 6 weeks or until the symptoms have settled before reintroducing lactose back into the diet. This allow the intestine time to repair and for the return of normal lactase enzyme production. Primary lactose intolerance, on the other hand, is less common and refers to a permanent reduction in lactase enzyme activity. Worldwide it affects 70% of the population, with large variations in ethnic groups with only around 2% of Northern Europeans affected. In people of Asian, African and Indian decent, children as young as 2 – 3 years can loose lactose activity, but this is not normally seen in the UK.  Lactase enzyme activity reduces with age. Careful trial of varying amounts of lactose using guidance on lactose content of dairy foods is helpful to determine the amount of lactose that can be tolerated.

What about cows milk allergy?

Cows Milk Allergy (CMA) is an immune response to the proteins found in cow’s milk giving rise to symptoms which can affect the skin, gastrointestinal tract or respiratory system. It is more common in families with atopic conditions such as asthma, eczema or hayfever and is often confused with lactose intolerance, due to similar symptoms. Secondary lactose intolerance often co-exists with CMA, particular when there is severe and persistent diarrhoea and gut inflammation.