What is lactose and why are people intolerant of it?
Lactose is the main sugar found in milk and other dairy products. Those who have lactose intolerance find it hard to digest the sugar, usually because their small intestine doesn’t produce lactase, the enzyme which digests lactose.
Who is affected?
Around 75% of adult humans are lactose intolerant or have reduced lactose tolerance after infancy. But tolerance varies dramatically depending on geography, affecting some ethnic groups more than others.
In Britain, the condition is most prevalent among the Asian and African-Caribbean communities, according to the NHS. Only one person in 50 of northern European descent has some degree of lactose intolerance, while around 90% of people from China have the condition.
Scientists believe this is because places in Africa and Asia historically had little access to milk, so people may not have evolved the ability to digest lactose because there was no benefit in being able to do so.
Since only 20% of us have the lactase enzyme, the rest of us rely on the microbiome (community of bugs in our gut) to do the work for us (https://www.prolongevity.co.uk/blog/surviving-covid )
Is it the same as a dairy allergy?
No. “Intolerances are different to food allergies; they are not caused by the immune system and are not life threatening,” Amena Warner, the head of clinical services at AllergyUK, told The Guardian.
Milk allergy is the second most common food allergy after peanuts. The immune system mistakes the proteins in cow’s milk for a threat and releases pro-inflammatory chemicals that trigger the signs and symptoms of an allergic reaction in response.