Can you become lactose intolerant by not drinking milk

Photo: Christophe Papke/Getty Images/Westend61

There was a lot of cheese in my childhood: white American melted between bagel halves and pork-roll slices for breakfast, Triscuits with squat squares of Cheddar as an after-school snack, and piles of Parmesan grated over ricotta-stuffed manicotti at family dinners.

As a young adult striking out on my own, I treated homesickness with my mom’s baked macaroni and cheese: penne pasta dripping in butter, milk, gooey Colby Jack and stringy mozzarella. And my life’s constant has been a near-daily bowl of after-dinner ice cream — more often than not, mint chocolate chip — dating all the way back to my time in utero, when my pregnant mom regularly indulged her insatiable cravings for the same flavor.

All this to say: I am a person who eats dairy, often and gleefully.

But in 2016, at the suggestion of my best friend, who wanted someone to keep her accountable on her own diet, I did a Whole30. There were some unintended — and dire — consequences: At the end of the diet, I was a dairy lover who couldn’t eat any of it.

If you haven’t heard of Whole30, some information: It’s a month-long eating plan that aims to help followers hit “the reset button with your health, habits, and relationship with food.” For 30 days, you cut out soy, legumes, grains, sugars, alcohol, and, of course, dairy. In truth, it’s not all that far off from how I normally eat — most dinners include a meaty protein and a green veggie — with one glaring exception. No dairy meant no splash of milk in my morning coffee, no shredded cheese on my lunch salad, and no mint chocolate chip. But I like a challenge as much as the next girl, so I stuck it out for all 30 days.

When you reach the end of the Whole30, you’re supposed to add the forbidden food groups back into your diet one at a time. The goal is to figure out which foods are making you feel sluggish, bloated, or just generally not great, so you can ostensibly keep on avoiding them forever.

I didn’t do that part. I just jumped right back into eating what I wanted — but suddenly nothing was the same. That first bowl of ice cream I’d been looking forward to for weeks was quickly followed by sharp stomach pains and what can best be described (grossly, but accurately) as bubble gut. It happened again after my first post-Whole30 cheeseburger. Chicken parm was problematic, too. My favorite late-night writing snack, Oreos washed down with a glass of whole milk, became a veritable dance with the devil.

None of this was a problem before the Whole30, and for a while, out of willful ignorance or maybe just denial, I convinced myself it was all in my head. It couldn’t be possible, I thought, to suddenly make yourself lactose intolerant.

Well. The good news, according to gastrointestinal specialist Kim Barrett, a professor of medicine at the University of California, San Diego, is that I’m not crazy. The bad news is that dairy no longer agrees with my body’s biology. Turns out, it is possible to suddenly make yourself lactose intolerant.

“To some extent, our ability to handle lactose is a use-it-or-lose-it phenomenon,” Barrett says. The body digests lactose — a disaccharide — by using lactase, an enzyme in the small intestine, to break it down into the monosaccharides glucose and galactose, which can then be absorbed. “If you don’t have the [lactose] substrate in the diet, you start to reduce the synthesis of the lactase enzyme to digest it,” Barrett explains. “After a period of completely excluding lactose from the diet, you may not have any of those digestive enzymes present.”

This is also why it’s typical, as we age, to have a bit more trouble digesting dairy. Lactase enzymes are numerous in infancy, Barrett explains, because a baby’s primary source of energy-producing carbohydrates is breast milk or formula, both of which are loaded with lactose. But “as we move from infancy to adulthood, in most people’s diets, the amount of lactose goes down,” she says. “In response, there’s a normal developmental decline in the expression of lactase, even in people who regularly eat dairy. But if you are constantly providing a stimulus, you’ll presumably be able to keep digesting.”

On the other hand, she adds, “because lactase numbers in an adult are already teetering, removing lactose from the diet for even a short period can send it over the cliff.”  In short, by depriving my body of dairy for 30 days, I’d eliminated its ability to digest it.

Or, really, I’d eliminated its ability to digest it in the right place. The symptoms of lactose intolerance, Barrett explains, are actually caused by lactose being broken down in the wrong part of the body, by bacteria instead of lactase enzymes. “You get symptoms because the disaccharide remains in the bowel, where it’s digested by other bacteria. That process releases gases and causes bloating,” she says. “It’s happening in a part of the bowel that can’t absorb the resulting monosaccharides. Water is drawn in, which can cause diarrheal symptoms.”

All good to know, but it doesn’t exactly solve my problem. It’s been almost two years now since my 30 days of deprivation, and I’m still having issues with ice cream (though that hasn’t stopped me from eating it). And having an intestinal system that’s nearing the big 3-0 likely isn’t doing me any favors.

But Barrett says all hope is not lost. “Continuing to eat dairy may stimulate your body to produce more lactase enzymes, or it may not, but there are probably things you can do to restore a healthy balance to your gut bacteria, which will aid lactose digestion,” she says. For example, “It may help to introduce fermented dairy products, like yogurt and kefir, which have bacteria in them that contain enzymes that break down lactose. Those bacterial enzymes are also what’s added to ‘lactose-free’ milk, ice cream, and other dairy products, so they get digested in the correct part of the bowel and allow your body to take in those sugars.”

“It may never be the way it was before,” she adds, “but it could get better.”

There was some good that came out of my Whole30 experience.
I lost a couple of pounds, I discovered that Five Guys will serve you a greasy burger wrapped in iceberg lettuce in lieu of a bun, and I cut a lot of added sugar out of my diet for good. But if you’re considering the diet that’s sweeping Instagram accounts everywhere, a word of caution from someone who’s been there: Before you embark on a milkless month, consider very carefully what you’re really willing to give up.