You cannot increase your body’s own lactase production once it has naturally declined. Lactase activity is controlled by your genes, and for roughly 68% of the world’s population, the gene responsible gradually dials down after infancy. But there are effective ways to improve your ability to digest lactose without relying on pills before every meal, from training your gut bacteria to choosing the right fermented foods.
Why Your Body Stops Making Lactase
Lactase is produced by cells lining your small intestine, and the gene responsible (called LCT) is regulated by a stretch of DNA in a nearby gene called MCM6. Some people inherit variants in this regulatory region that keep lactase production running throughout adulthood. Everyone else experiences a gradual slowdown that typically begins in early childhood and continues into the teens or twenties.
This isn’t a deficiency or a disease. It’s the biological default for most humans. There is currently no food, supplement, or lifestyle change that can reactivate or upregulate the LCT gene once it has wound down. The decline is epigenetic and permanent. So when people talk about “increasing lactase naturally,” the real opportunities lie elsewhere: enlisting your gut bacteria to do the work for you, choosing foods that come with their own lactase, and gradually expanding your tolerance threshold.
How Gut Bacteria Can Digest Lactose for You
Your intestinal bacteria can produce their own version of lactase, an enzyme called beta-galactosidase that breaks down lactose the same way your body’s enzyme would. Certain probiotic strains are especially good at this. Lactobacillus acidophilus is the most studied, with demonstrated lactase activity both in lab settings and in people with lactose intolerance. Other promising strains include L. rhamnosus, L. delbrueckii, and L. bulgaricus.
One particularly encouraging finding: a combination of Lactobacillus casei Shirota and Bifidobacterium breve Yakult showed benefits that persisted even after people stopped taking the probiotic. This suggests that consistent use over weeks or months can reshape your gut environment in a way that outlasts the supplement itself. The bacteria essentially set up shop in your intestines and continue producing the enzyme on their own.
To put this to work, look for probiotic supplements or fermented foods that contain these specific strains. Consistency matters more than dose. Taking a probiotic once before a pizza won’t help, but daily use over several weeks can meaningfully shift how your gut handles lactose.
Fermented Foods That Bring Their Own Lactase
Yogurt is one of the best tools for people with lactose intolerance, and the reason is simple: the starter cultures used to make all yogurt (Lactobacillus bulgaricus and Streptococcus thermophilus) contain lactase as a built-in trait of their species. When you eat yogurt with live cultures, those bacteria release their enzyme as they’re broken down in your digestive tract, helping split the lactose right where it needs to happen.
Interestingly, the bacteria don’t need to survive your stomach acid and colonize your gut for this to work. Only about 1% of yogurt bacteria make it past the upper digestive tract alive. The benefit comes from the enzyme being released as the cells break apart. This is why the key requirement is that the yogurt contains viable (living) cultures at the time you eat it. Heat-treated yogurts that have been pasteurized after fermentation lose this advantage. Both the FAO/WHO and the European Food Safety Authority recognize this effect.
Kefir offers a similar benefit and may have an edge over yogurt in one respect. Research using kefir grains found that the beta-galactosidase activity from kefir enhanced lactose breakdown in the intestine. Kefir also contains a broader diversity of bacterial and yeast strains, which can contribute additional enzyme activity. Aged cheeses like parmesan, cheddar, and Swiss are another option. The longer a cheese ages, the more lactose its bacteria consume during fermentation, leaving very little in the final product.
Training Your Tolerance With Gradual Exposure
Most people with lactose intolerance can handle more dairy than they think. The threshold is roughly 12 grams of lactose in a single sitting for many people, which is about one cup of milk or a scoop of ice cream. Below that amount, the lactose either gets partially broken down by residual enzyme activity or is managed by gut bacteria without causing symptoms.
You can expand this tolerance by introducing small amounts of dairy and slowly increasing them over time. The principle is straightforward: regular, low-level exposure encourages your colon bacteria to adapt. Bacteria that thrive on lactose gradually increase in number, improving your gut’s collective ability to handle it. This process takes weeks, not days.
A practical approach looks something like this:
- Week 1: Start with baked goods that contain milk as an ingredient, like a muffin or a slice of cake. Begin with a small portion and work up to a full serving by the end of the week.
- Week 2: Move to cooked meals containing milk or cheese, such as lasagna, mashed potatoes, or a cheese omelette. Start with a few bites and increase to a normal portion.
- Week 3: Try hard cheese or milk-based puddings like rice pudding or custard. Aim for about 25 grams of cheese (roughly matchbox-sized) or 125 ml of pudding by day seven.
- Week 4: Introduce yogurt, fromage frais, or ice cream, starting with a teaspoon and building to a small pot or single scoop.
- Week 5–6: Start with 50 ml of milk added to cereal or as a drink, working up to 200 ml over the course of each week.
If symptoms return at any stage, stay at the previous level for another week before trying again. The goal is to find a comfortable baseline, not to force your way to unlimited dairy consumption. Some people plateau at yogurt and cheese and never tolerate a full glass of milk, and that’s a perfectly functional outcome.
Spacing and Food Pairing Make a Difference
How you eat dairy matters almost as much as how much you eat. Consuming lactose as part of a larger meal slows digestion, giving whatever lactase activity you have (from your body, bacteria, or supplements) more time to work. A glass of milk on an empty stomach hits your intestines fast and overwhelms the available enzyme. The same glass alongside a full breakfast may cause no symptoms at all.
Spreading your dairy intake across the day rather than concentrating it in one meal also helps. Two small servings several hours apart are far easier on your system than a double serving at once. Fat and fiber in the same meal slow gastric emptying, which further helps by delivering lactose to your small intestine in smaller, more manageable waves.
When Lactase Supplements Still Make Sense
For meals where you can’t control the ingredients or want to eat more dairy than your tolerance allows, over-the-counter lactase supplements fill the gap. These are fungal-derived enzymes (typically from Aspergillus oryzae) measured in FCC units. Most clinical studies use around 9,000 FCC units taken just before a lactose-containing meal, which is enough to handle about 12 to 25 grams of lactose. Lower doses of around 3,000 FCC units have also been tested but appear less effective.
Supplements work best when taken right before eating, not after symptoms start. They replace the enzyme your body no longer makes, but only for that one meal. They don’t build tolerance or change your gut bacteria. Think of them as a useful backup rather than a long-term strategy. Combining supplements with the gradual exposure approach and regular fermented food intake gives you the most flexibility with the least daily effort.