Most of us aren’t inherently dairy intolerant, but we can go through periods where we become more sensitive to lactose in our diet, says Amanda Avery, an associate professor in nutrition and dietetics at the University of Nottingham.
She says that when people talk about being “dairy intolerant”, they’re usually referring to lactose, the sugar found in milk and dairy products, such as milk, cheese and yoghurt. In most people, that sugar is broken down by an enzyme called lactase, which is found in our small intestine. It helps our bodies digest and absorb lactose without causing discomfort. “We’re born with plenty of lactase. But as our diets diversify, our lactase levels decline,” says Avery. “If there is minimal milk in the dairy diet then lactase levels may be zero, thus people from some cultural backgrounds and countries where dairy intake is negligible may be intolerant.”
People who don’t produce enough lactase may find themselves having gastrointestinal symptoms such as abdominal pain, bloating and loose stools when they consume dairy. Some people can find their lactase activity is temporarily reduced when their gut function is disrupted by antibiotics or stress. This can lead to “transient lactose intolerance” – a period where your body struggles to digest dairy even if you weren’t previously sensitive.
If people cut out dairy and then reintroduce it, they might also experience abdominal symptoms for a short period while their lactase activity is being restored, says Avery. But this doesn’t necessarily mean you’re permanently intolerant. It could just be your gut enzymes playing catchup. “Good practice, even if you do think you are slightly intolerant, is to try to keep a little dairy in your diet – cheese or yoghurt should be OK. Cheese has very little lactose, and in yoghurt, much of the lactose is broken down by the bacteria. Even having a little bit of milk in your tea helps,” says Avery.
So, is it true that we’re all a little bit intolerant to dairy? No, but our ability to digest it can definitely fluctuate. For many, it’s not a lifelong intolerance but a temporary reaction.