If you’ve ever tired an elimination diet, you’re probably familiar with the nerves that comes along with re-introducing your old favorites—and the worry that maybe you’ve “lost” your ability to digest them at all.
This is especially true when it comes to dairy. After all, lactose intolerance symptoms like bloating, diarrhea, and gas can be more than a little inconvenient. But is there any truth to the idea that hitting pause on the ice cream and milk for a while can leave you susceptible to these annoying results when you try them again?
Unfortunately, yes. Cutting out high-lactose foods really can give you lactose intolerance symptoms when you re-introduce them—at least, temporarily. But you can retrain your body to digest this tricky sugar, which is excellent news if you decide you just can’t do life without milkshakes.
Here’s why quitting dairy could hurt your ability to digest lactose—and how to rebuild your tolerance.
The link between dairy tolerance and your microbiome
The truth is, about three-quarters of the world’s population are already “lactose maldigesters,” explains Dennis Savaiano, PhD, Meredith Professor of Nutrition Policy at Purdue University, who’s studied lactose digestion for four decades. This means your body doesn’t produce very much lactase—the enzyme that breaks down lactose—on its own.
Up until ages three to five, we all have pretty high levels of intestinal lactase. After that, there’s a steep drop-off for most. (About one-quarter of the world’s population has a genetic mutation that allows them to keep producing lactase in high doses, says Savaiano—lucky them.)
If you’re wondering how it is that more than a quarter of the population can still tolerate a latte—despite being maldigesters— there’s an explanation. Our gut bacteria actually produce lactase for us. And the more dairy we give them, the more lactase they produce.
“The bacteria in our colon need to be fed in order to survive,” explains Savaiano. “So whatever you feed them, those bacteria are going to prosper. Individuals who are used to eating lactose in their diet have more lactase enzyme [than people don’t eat lactose-containing foods]—we think six to eight times more—and are more efficient at digesting it so they don’t get symptoms.”
If you’re a maldigester and you stop eating high-lactose foods, though, you have the potential for intolerance when you decide to start eating it again. “You would change your colon bacteria to reduce the number of lactose-digesting bacteria, and hence if you reintroduced lactose in a large dose, you would have symptoms,” says Savaiano.
How to re-introduce dairy into your diet
Don’t worry, this doesn’t mean you can never have a cow’s milk cappuccino again if you’ve been favoring Oatly for months. Savaiano conducted a study to test exactly how the gut adapts when it breaks a lactose hiatus, and the results were encouraging. “We took [maldigesters] and either fed them lactose in water three times a day with their meals [for 10 days], or sugar water three times a day with their meals,” he says. “And what we saw is that as we fed them lactose in water, their colon bacteria adapted to produce far more lactase activity, and their maldigestion went down dramatically.”
There are a few keys to doing this effectively IRL, though. First, it’s all about the dose: You don’t want to start with a huge amount of lactose. Savaiano suggests drinking about a half cup of milk three times a day—eventually, you should be able to tolerate a full cup at a time. It’s also important to couple high-lactose foods with other foods, he says, because this slows down transit. That way, you’re not overloading your digestive system with a ton of lactose all at once. (And setting yourself up for tummy trouble.)
The type of dairy you’re eating matters, too. Hard cheeses and yogurt don’t actually have very much lactose at all. The cheesemaking process strains out most lactose along the way, and the bacteria in yogurt contain quite a bit of lactase on their own, explains Savaiano. So most people can actually eat these foods without much trouble—but they also won’t help you adapt much to eating high-lactose foods.
If you’ve already given up dairy (or are just thinking about it), don’t let the potential for developing lactose intolerance freak you out. Take it slow when you reintroduce it, and you’ll regain your ability to break it down in no time.
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