What is lactose intolerance?

If you've landed here after one too many uncomfortable afternoons following a milky coffee, this is the page for you. Lactose intolerance is one of the most common food issues in the world, and one of the most manageable once you understand what's actually going on.

What lactose intolerance actually is

Lactose is the natural sugar found in milk and dairy products. To digest it, your body makes an enzyme called lactase in the small intestine, which breaks lactose down so it can be absorbed. Lactose intolerance happens when you don't make enough lactase to handle the lactose you eat.

The undigested lactose then travels to the large intestine, where gut bacteria ferment it — and that's what produces the familiar bloating, wind, cramps and looser stools.

Why it happens

Lactase levels naturally decline for many people after childhood. This is the most common form, and it's completely normal. Some populations are far more affected than others for genetic reasons. Less commonly, lactose intolerance can follow a gut illness or infection (temporary), or be part of another digestive condition.

How common is it?

Very. Globally, around 65% of people have a reduced ability to digest lactose after infancy. In Australia it depends heavily on heritage: people of East Asian, West African, Middle Eastern, Greek, Italian, and Aboriginal and Torres Strait Islander backgrounds have roughly a 70–95% chance of being lactose intolerant, while among Caucasians it's far lower, at about 1 in 20. Either way, you're far from alone.

What it means day to day

The thread that runs through this whole site: lactose intolerance does not mean giving up dairy entirely. It means learning your own threshold, choosing lower-lactose foods, using lactose-free products, and — if you want the real thing — reaching for a lactase supplement. Most people land on a way of eating that keeps the foods they love and loses the discomfort.

When to see a doctor

If your symptoms are severe, came on suddenly, include weight loss or blood in your stool, or you're just not sure what's causing them, see your GP. These can point to something other than lactose intolerance that's worth checking properly.