Why Am I Suddenly Lactose Intolerant? Experts Explain

Lactose intolerance might bring up fears: never eating cheese or ice cream again?! It’s incredibly common, and your risk of becoming lactose intolerant increases as you age. If you’re asking, Why am I suddenly lactose intolerant?, there are a few potential culprits, plus effective management strategies.

You’re attending a family reunion, and your cousin made your favorite dish from childhood: homemade mac and cheese. You devour a plate, only to experience stomach cramps a few hours later.  If this never happened to you while growing up, but seems to be happening more often these days, it may mean you’ve developed a lactose intolerance. Fortunately, if you’re wondering about the cause of a sudden lactose intolerance, there is usually a relatively easy answer (as far as health questions go). Plus, there are many effective management strategies you can try, some of which may even allow you to enjoy that mac and cheese in moderation.

Understanding lactose intolerance

“Lactose intolerance is when your body can't break down or properly digest lactose,” says Shelley Balls, MDA, RDN, LDN. “It happens when your small intestine does not make enough of a digestive enzyme called lactase.”

If lactase had an official job description, its main responsibility would be to break down lactose, the primary sugar found in dairy. Once broken down, lactose is easier to digest. When someone has a lactose intolerance, that enzyme is “sleeping on the job”—and you can’t put digestive enzymes on a performance improvement plan.

A lactose intolerance can occur at any age, and it doesn’t discriminate. In fact, it’s quite common, with over 65% of the world’s population having some degree of lactose intolerance.

When defining what lactose intolerance is, it’s also important to establish what it’s not. It’s commonly confused with a milk allergy, but these two conditions are quite different. Balls explains: “A milk allergy causes an autoimmune system response to milk and milk products.” Milk allergies are more common in children and often extend to include sheep and goat milk, not just cow’s milk. By contrast, lactose intolerance isn’t an autoimmune response, and typically only creates adverse reactions to products made with cow’s milk.

Symptoms of lactose intolerance

Most people with lactose intolerance experience symptoms within a few hours of ingesting a dairy product. The exact symptoms and severity depend on the level of your intolerance and the amount of lactose consumed.

Symptoms that may serve as signs of dairy intolerance include:

• Bloating
• Diarrhea
• Fatigue
• Gas
• Headaches
• Joint Pain
• Nausea
• Stomach cramps
• Stomach gurgling
• Stomach pain
• Vomiting

But lactose enzyme production doesn’t just impact your digestive system. Over time, lactose intolerance may cause a lack of calcium and vitamin D, possibly increasing the risk of osteoporosis and vitamin D deficiency. Fortunately, calcium is also found in fortified foods, beans, supplements, and leafy greens. Vitamin D can also come from the sun or a supplement.  It’s worth noting that too much lactose consumption may also lead to osteoporosis.

Can you develop lactose intolerance later in life?

Let’s say you used to love ice cream on a summer’s day and lived for pizza nights. But ice cream and those cheesy pizzas don’t agree with you anymore, yet you were never diagnosed with a lactose intolerance when you were younger.

Turns out, there’s a good chance you are developing a lactose intolerance later in life. “As you age, your body has a harder time producing enough lactase, which can increase lactose intolerance symptoms,” explains Balls. This decline in lactase production is a natural part of aging, but it doesn’t make the potential breakup with our dairy favorites any easier.

Causes of lactose intolerance

So the chance of lactose intolerance increases as we age, but what causes it to begin with? Turns out, it’s influenced by a variety of factors, including genetics, other medical conditions, prolonged dairy abstinence, and aging. The factors at play typically depend on which of the three types of lactose intolerance you experience.

Primary lactose intolerance

The most common form, primary lactose intolerance, occurs when there’s a decline in lactose enzyme activity as you age. While this decline first begins in infancy, symptoms don’t typically manifest until adolescence or early adulthood. There is a strong genetic component to this type, meaning some people are predisposed to develop primary lactose intolerance.

Secondary lactose intolerance

If a lactose intolerance is identified later in life, it’s probably secondary lactose intolerance. Secondary lactose intolerance occurs when the small intestine cannot produce enough lactase because of a disruption in the gut.

Many inflammatory diseases, infections, and other medical conditions could be to blame, such as:

• Bacterial overgrowth
• Celiac disease
• Crohn’s disease
• Gastroenteritis, is inflammation in the stomach and intestines
• Intestinal infections
• Ulcerative colitis

Secondary intolerance can also stem from chemotherapy, radiation, antibiotics, and some gastrointestinal surgery. Unlike with a primary intolerance, secondary lactose intolerance is often temporary. When you address the underlying condition, you can restore lactase levels over time.

Congenital and developmental lactose intolerance

A third and rare type of lactose intolerance is congenital and developmental. Okay, yes, technically, these are two different types, but both of them occur in infancy and stem from someone being born with little to no lactase enzyme.

The cause of congenital lactose intolerance is genetic, though researchers are still working out why it occurs. Developmental lactose intolerance is easier to explain; this type occurs due to a premature birth. Babies born at 28 to 37 weeks of gestation typically have an underdeveloped small intestine, meaning they don’t have enough lactase enzyme.

Diagnosing lactose intolerance

“Lactose intolerance can be diagnosed a few different ways,” says Balls. She adds that a doctor will probably start by asking about your symptoms to determine if symptoms are actually due to lactose intolerance or something else and which diagnostic tests to complete.

And yes, we said “doctor” for a reason. While some people may try to self-diagnose lactose intolerance, the DIY approach isn’t the best. Instead, a qualified functional medicine provider can more accurately assess symptoms.

Tracking dairy consumption and symptoms

To help identify food patterns related to your symptoms, a doctor may ask you to keep a food diary. And we promise this diary doesn’t include long, rambling paragraphs about your day. Instead, it’s a concise list of the foods you ate, the time of day you ate, and any symptoms you felt after.

If you’re keeping a food diary, remember that lactose intolerance symptoms usually occur a few hours later, so it may be beneficial to note the specific time your symptoms occurred, too.

Elimination diet

An elimination diet is a natural way to determine what foods are causing symptoms. A functional medicine provider may have you temporarily remove dairy from your diet for four to six weeks and keep track of any changes. Afterward, you can slowly reintroduce foods, flagging (and avoiding) any ones that exacerbate symptoms.

Medical tests for lactose intolerance

The third and most common way to diagnose lactose intolerance is with a medical test. There are a few tests doctors may order:

• Hydrogen breath test: Measures hydrogen levels after consuming lactose
• Lactose tolerance test: Measures blood glucose response to lactose consumption
• Stool acidity test: Used mainly for infants and young children

Hydrogen breath tests are the most common, since your levels of hydrogen, a gas found on your breath, are higher if your body can’t absorb lactose. Thanks to its effectiveness, the functional medicine providers at Parsley perform the food marble test, a type of hydrogen breath test.

Foods that contain lactose

Most of us can probably round up the usual suspects to avoid when you’ve got a lactose intolerance: Milk, cheese, butter, yogurt, and ice cream. Anyone with a lactose intolerance should also read the ingredient labels of anything they consume carefully. Why? Because there are many sneaky, hidden sources of lactose.

“Lactose can sneak into foods you wouldn’t expect,” says Jennifer Pallian, Bsc, RD.  She points out some hidden sources of lactose, including:

• Baked goods
• Breakfast cereals
• Custards
• Gravy mixes
• Instant soups
• Mashed potatoes
• Margarine
• Pancakes
• Protein bars and powders
• Processed meat
• Processed sausages
• Puddings
• Salad dressings
• Waffles

When reading a food label, check for whey, casein, and milk solids, three lactose-derived ingredients. Pallian adds that people with lactose intolerance should read the ingredients list on medications too, since some can contain lactose.

Managing lactose intolerance

Being lactose intolerant doesn’t sentence you to a life of bland recipes and no cheese. Instead, you can work with a functional medicine provider to develop a management plan that includes delicious recipes and even small portions of your favorite dairy products, if you can tolerate them.

Adjusting your diet

“A great way to manage lactose intolerance is by making simple swaps in your diet,” says Pallain. She recommends cutting high-lactose foods and replacing them with alternatives. Instead of drinking regular milk in your coffee, for example, you could opt for a plant-based alternative. Some of the best plant-based milks include soy, almond, oat, coconut, rice, and cashew.

If your lactose intolerance is mild or moderate, you may be able to enjoy small portions of lactose. Pallain explains, “Most people with lactose intolerance can still handle small amounts (up to about 100 mL, a little less than half a cup, of milk) without major issues.” She adds that eating these small portions of lactose with a bigger meal can help, since the other nutrients could slow digestion, giving the lactase enzymes more time to do their job.

Taking lactase supplements

Giving up dairy can be hard—I, for one, would be so sad without my celebratory Friday night ice cream. Luckily, many people with a lactose intolerance don’t have to give up lactose entirely. Instead, they can take a lactase enzyme supplement before eating a meal or snack high in lactose. “These supplements break down lactose into simpler sugars, making dairy much easier to digest,” says Pallain.

Although these supplements are often effective, clinical trials suggest they don’t work for everyone. The bottom line? Trying a lactase supplement could be a good idea, but be open to looking for dairy alternatives if this supplement doesn’t work for you.

Improving gut health

Bifidobacterium animalis, a probiotic strain, can help improve lactose digestion and reduce lactose intolerance symptoms. That may sound like a random fact to share at dinner parties, but that good old Bifidobacterium has a big impact on your lactose intolerance. Its impact suggests a healthy gut microbiome may help with lactase enzyme production. Other probiotic strains, like Lactobacillus bulgaricus and Streptococcus thermophilus, have also been shown to help.

To boost gut health, Pallain often recommends Greek yogurt to those with lactose intolerance. Greek yogurt is a win-win since it contains gut-healthy probiotic strains and has lower lactose levels than other yogurts.

Ensuring proper nutrition without dairy

Lactose is a key part of a healthy diet because it contains high amounts of calcium and vitamin D. Calcium supports bone health and prevents osteoporosis, while Vitamin D helps the body absorb calcium.

Fortunately, there are non-dairy sources of both. For calcium, lactose-free sources include:

• Apples
• Bok choy
• Broccoli
• Chia seeds
• Kale
• Pinto beans
• Salmon
• Sardines
• Soybeans
• Tofu
• Turnips

Vitamin D is also found in sunlight, as well as in foods like trout, salmon, mushrooms, sardines, broccoli, apples, bananas, lentils, edamame, and sunflower seeds.

Alternatively, opting for calcium and vitamin D supplements can be useful, especially if your diet alone doesn’t provide enough of these nutrients.

What happens if you ignore lactose intolerance?

We often tend to dismiss this condition as “just lactose intolerance.” But ignoring it can lead to problems down the line. The first disruption will probably be digestive discomfort, thanks to dairy sensitivity symptoms like bloating, gas, and diarrhea. Over time, you could even experience chronic inflammation and gut irritation as a result. There’s also the risk of nutrient deficiency and osteoporosis, especially for women as they age.

Frequently Asked Questions (FAQs)

Can you become lactose intolerant all of a sudden?

It’s possible to suddenly become lactose intolerant if a medical condition, inflammation, or medication damages your small intestine. The small intestine is responsible for creating a lactase enzyme, which absorbs and digests lactose.

What are the top 10 worst foods for lactose intolerance?

The worst foods for lactose intolerance include milk, cheese, ice cream, and yogurt. Less obvious but still harmful choices can include breakfast cereals, processed meats, pancakes, waffles, many baked goods, and many soups.

How to flush dairy out of your system quickly?

To eliminate dairy quickly, consider removing all sources of dairy from your diet. You can also make helpful lifestyle changes, like walking after meals and eating smaller portions of dairy products.

Why am I lactose intolerant when I never was before?

As you age, your body’s ability to digest lactose can decrease. For many, this leads to a lactose intolerance diagnosis in their early 20s or late adolescence. Should a lactose allergy develop after that, it could be due to an infection, inflammatory disease, gut imbalance, or another medical condition.

Conclusion

If you wake up one day with a lactose intolerance that wasn’t there before, there are many possible reasons—and many effective management strategies. When it comes to any dairy intolerance, remember:

• The cause matters: A genetic predisposition for reduced lactase enzyme activity causes primary lactose intolerance. A secondary lactose intolerance, however, is due to small intestine damage.
• Management is multi-pronged: No matter the cause, lactose intolerance management has many potential moving parts, such as swapping in dairy alternatives, using lactase supplements, and improving your overall gut health.
• Diagnosis occurs at the doctor’s: You can’t self-diagnose a lactose intolerance. Instead, a healthcare provider can run tests, assess your symptoms, and determine the cause. For a whole-person approach to lactose intolerance, consider working with a functional medicine provider.

The team at Parsley Health is well-versed in determining the root cause of lactose intolerance and creating a management plan that suits your unique lifestyle and dietary preferences.