Lactase: How the Enzyme Works and Who Really Needs It

“Milk makes me feel awful, but I can’t function without coffee with milk.” I hear this at the pharmacy almost every week. And the conversation almost always ends with: “Will lactase help me?”

Often, yes. But only if the problem really is lactose, and only if you take the enzyme the right way. Let’s go step by step.

What lactase is and why you need it

Lactose is milk sugar. It cannot be absorbed as it is: first, the enzyme lactase in the small intestine has to split it into glucose and galactose.

Babies have plenty of lactase because milk is their main food. After weaning, lactase activity gradually falls in most people. This is normal biology.

Some Northern European populations keep high lactase activity for life thanks to a genetic mutation. A 2017 meta-analysis estimated that 68% of adults worldwide have lactose malabsorption, with much lower rates in Northern Europe.

When lactase is low, undigested lactose reaches the large intestine. Bacteria there happily ferment it, producing gas and drawing in water. Hence the bloating, rumbling, pain and diarrhea.

Lactose intolerance or milk allergy

These are two completely different conditions, and they get mixed up all the time. Lactase only helps with the first one.

There is also secondary lactase deficiency. It happens when the lining of the small intestine is damaged: after a gut infection, or with celiac disease or Crohn’s disease. It is usually temporary and resolves once the gut recovers.

How is it confirmed? Most often with a hydrogen breath test: you drink a lactose solution and a device measures hydrogen in your breath. There is also a genetic test for the LCT gene variant. Irritable bowel syndrome can cause similar symptoms, though, so it is best to draw conclusions with a gastroenterologist.

How much lactose is in common foods

The good news: you usually don’t need to give up all dairy. According to EFSA, most people with lactose intolerance tolerate up to 12 g of lactose at once, and more if dairy is spread across the day.

Here are approximate numbers to show where that limit is.

The figures vary by producer, so check the label: in dairy products, the “sugars” line is mostly lactose.

Yogurt and kefir are often better tolerated than milk with the same amount of lactose. Live yogurt cultures produce their own enzyme that helps break lactose down. EFSA has even confirmed this claim for yogurt with live cultures.

How to take lactase correctly

Supplemental lactase works as a “backup” enzyme: it breaks down lactose in the food itself as it passes through the stomach and gut. That leads to the main rule.

Take it with food. With the first sip of milk or the first bite of cheesy pizza. Taken an hour before or after a meal, it will hardly help.

Look at units, not milligrams. Lactase activity is given in FCC units (sometimes ALU). For the claim “lactase enzyme improves lactose digestion in individuals who have difficulty digesting lactose,” the EU requires at least 4,500 FCC units with each lactose-containing meal. This is an officially authorized EU health claim.

Match the dose to the portion. Tolerance varies from person to person. A glass of milk may need more enzyme than a spoonful of cream in coffee.

Drops for milk. One form of lactase is added straight to milk, which is then left in the fridge for a day. Most of the lactose breaks down, and the milk tastes a little sweeter, because glucose and galactose are sweeter than lactose.

Lactase is on the list of substances permitted in dietary supplements in Ukraine (MoH Order No. 203), with no maximum daily dose set. We covered these rules in our article on dietary supplement requirements in Ukraine. For another popular enzyme, see our piece on bromelain.

Lactase for babies: when it makes sense

Lactase is often recommended for infant colic. I would be careful here. A 2018 Cochrane review of dietary approaches to colic found no convincing evidence that lactase reduces crying.

Primary lactose intolerance in babies is very rare. If a baby cries a lot, gains weight poorly or has blood in the stool, that is a reason to see a pediatrician, not to buy an enzyme.

When dairy and stomach trouble need a doctor

Lactose intolerance is unpleasant but not dangerous. These symptoms, however, need a doctor:

blood in the stool; unexplained weight loss; diarrhea that wakes you at night; fever; anemia; symptoms appearing for the first time after age 50; problems not only with dairy but also with bread or pasta (this could be celiac disease).

One more important point. If you have cut out dairy completely, think about where your calcium and vitamin D come from. Hard cheeses, yogurt, lactose-free milk and fortified plant drinks can help. We have a separate autumn guide to vitamin D.

Frequently asked questions

Conclusions

Lactase is for people whose symptoms really are caused by lactose. There are many of them, about two thirds of adults worldwide, although far from all have noticeable symptoms.

Giving up dairy completely is usually unnecessary: most people tolerate up to 12 g of lactose at once, hard cheeses contain almost none, and yogurt is better tolerated than milk. If you want a glass of milk or a pizza, lactase at 4,500 FCC units or more with the first bite will help.

Lactase will not help with a milk allergy. That needs a doctor and careful label reading.

About the Author

Kateryna Braitenko is a Ukrainian journalist and author specializing in writing articles for pharmaceutical publications. She holds a philology degree from Donetsk National University and a pharmaceutical degree from the National Pharmaceutical University in Kharkiv. She lives in Kyiv and continues her career, covering relevant issues in medicine and pharmaceuticals.