Lactose intolerance is the most common type of food intolerance, impacting ~10-20% of the entire adult population (1).
In my gut health nutrition practice, I’ve observed that many folks with gut issues such as irritable bowel syndrome (IBS), small intestinal bacterial overgrowth (SIBO), inflammatory bowel disease (IBD) and congenital and acquired sucrase-isomaltase deficiency (CSID and ASID) are extra prone to being lactose intolerant!
If you suspect that you (or your clients, if you’re a healthcare provider) may be lactose intolerant, read on for gut health dietitian explanations of signs, symptoms, and treatment options when it comes to addressing and managing lactose intolerance.
Disclaimer: This article was written for general educational purposes and should not replace medical and dietary advice from your healthcare team.
Affiliate disclosure: This article contains affiliate links*. As an Amazon Associate, Whole-istic Living may earn a small commission on qualifying purchases at no extra cost to you!
Table of Contents
What is lactose?
Lactose is a type of disaccharide (two-unit sugar molecule) naturally found in dairy milk and certain types of dairy milk products (such as yogurt, cream, ice cream, sour cream, and soft cheeses).
On a molecular level, lactose is made up of two single-unit sugars (“monosaccharides”) – glucose and galactose – joined together.
Lactose is also a fermentable disaccharide, so it’s considered a type of FODMAP – or more specifically, the “D” in FODMAP.
Many people who are lactose intolerant – especially IBS sufferers – tend to also have other types of FODMAP intolerances and may benefit from a low FODMAP elimination & reintroduction diet (which includes lactose-free, low FODMAP dairy products).
Lactose intolerance definition
If you’re lactose intolerant, it means your gut can’t fully digest and break down lactose (milk sugar) into glucose + galactose due to lactose malabsorption.
Lactose intolerance happens when there’s missing or insufficient levels of lactase enzyme (the enzyme that breaks down lactose) in your small intestine.
So, if you consume lactose and you’re lactose intolerant, the undigested lactose molecules will travel from your small intestine to your colon (large intestine), leading to unwanted gastrointestinal (GI) symptoms that often get mistaken as IBS.
How it works: the large, undigested lactose sugars may ferment with microbes in the gut, leading to excess gas production, and/or they may also pull water into the colon, by osmosis.
Signs and symptoms
While the signs and symptoms of lactose intolerance may vary from mild to severe, lactose intolerance symptoms generally present as any or all of the following, within 10 to 90 minutes after consuming foods high in lactose (2):
- Abdominal pain/cramping
- Gas/”wind”
- Stomach rumbling/”borborygmi”
- Bloating/distention
- Diarrhea/loose stools
- Upset stomach
- Nausea, with or without vomiting
- Bowel movement urgency/incontinence
Lactose intolerance versus dairy allergy/sensitivity
Note that a lactose intolerance is GI-mediated, and it’s very different from a dairy allergy or sensitivity (these are immune-mediated reactions to proteins in dairy products, whether they contain lactose or not).
Recommended reading: Lactose Intolerance vs. Dairy Sensitivity: How to Tell Them Apart
What causes it?
Lactose intolerance can be genetic in rare cases, but most often it develops secondary to an injured or damaged intestinal brush border (2).
Alactasia
Alactasia is the genetic cause of lactose malabsorption (which correlates with lactose intolerance). This means your intestinal brush border lacks the genetic coding to produce lactase, the enzyme responsible for breaking down lactose.
As a result, you may experience severe lactose malabsorption, and the symptoms of lactose intolerance which often follow.
Alactasia is something you would experience as early on as infancy, even when consuming breastmilk (which contains lactose).
Hypolactasia
Hypolactasia is very similar to alactasia, but it indicates a deficiency (versus the complete absence) of lactase enzyme production in the small intestine.
Certain gene variants can reduce our natural ability to make lactase enzymes, but in most cases, hypolactasia is acquired later on in life, secondary to intestinal injury from gastrointestinal conditions and/or infections.
Conditions that may lead to intestinal brush border damage (and subsequent hypolactasia + lactose malabsorption) if left untreated include (3):
- Celiac disease
- Crohn’s disease
- Colitis
- Diverticulitis
- Giardia infection
- Viral gastroenteritis
- SIBO
- Dysbiosis
- Fungal overgrowth
Additionally, lactose intolerance can often follow after the following types of procedures:
- Partial or total bowel removal/resection
- Radiation, with or without chemotherapy
Regardless of what’s causing your lactose malabsorption and lactose intolerance symptoms, there are various testing options you can lean into to determine whether or not you’re lactose intolerant.
Testing options
Food-symptom logging
While food-symptom logging isn’t an official method of diagnosing lactose intolerance, it can be an economical, effective, non-invasive way to get clear on whether or not your gut is able to break down lactose.
It’s a matter of putting your detective hat on and observing how your body reacts when you consume lactose-containing foods.
How it works: Keep a detailed record of your food intake, paying special attention to how you feel (and which symptoms, if any, may show up) within a few hours of consuming foods or beverages high in lactose.
Based on your observations, and by narrowing down the culprit, food-symptom logging can help provide you with clarity on whether or not your IBS symptoms (diarrhea, abdominal pain, gas, bloating, etc.) are triggered by lactose-containing dairy.
(If you’d like a paperback food-symptom journal, consider ordering a copy of The IBS Food Diary*, designed and published by yours truly!)
Oral challenge (lactose tolerance) test
The oral lactose tolerance test is done at a doctor’s office.
It’s more invasive than food-symptom journaling in that it involves blood testing, and possibly some uncomfortable gastrointestinal (GI) symptoms (if you’re lactose intolerant).
How it works: You’ll fast for ~8 to 12 hours before drinking a high-lactose drink. Next, your doctor’s office will check your blood sugar level multiple times over the course of a few hours, at set timed intervals.
If you absorbed the lactose from the drink, your blood sugar level should rise a certain amount within certain key timeframes.
Your test would be considered positive for lactose intolerance if:
- You experience digestive symptoms during the test, after drinking the high-lactose beverage.
- Your blood glucose levels increase less than 20 mg/dL.
Stool testing
Lactose malabsorption typically leads to microbial fermentation in the intestines (4). As a result, the acidic fatty acid byproducts of undigested lactose fermentation in the gut often cause stool pH to become more acidic (5).
Stool samples with an acidic pH (lower than normal fecal pH reference range) can often be indicative of lactose malabsorption, if lactose was consumed within 8 to 12-ish hours prior to obtaining the fecal sample.
However, there are many other factors that have been shown to increase stool acidity, so this test should be considered more correlational (versus diagnostic).
Hydrogen or methane breath test
Breath tests used for diagnosing SIBO can also be useful in identifying a lactose intolerance.
How it works: Breath samples are measured periodically at set time intervals for a few hours after a high-lactose drink is consumed.
If lactose malabsorption is present, microbes in the intestines will consume and ferment the undigested lactose, leading to abnormally high levels of hydrogen and/or methane gas which will be reflected in the breath samples.
Serum gaxilose (galactosylxylose) test
A 2014 study found that checking blood levels of D-xylose post consumption of a standardized amount of a sugar called gaxilose (aka “4-galactosylxylose”) was more accurate (more sensitive and specific) compared to the hydrogen breath test or blood glucose test (6).
Intestinal biopsy
An intestinal biopsy (which directly measures levels of lactase activity in the duodenum, the first part of the small intestine) is considered to be a gold standard for measuring and diagnosing lactose malabsorption and lactose intolerance.
However, this is also the most invasive and expensive procedure for testing lactose intolerance, so it usually follows after a blood test, stool test, and/or breath test has been performed to suggest the likelihood of lactose malabsorption.
Genetic testing
While genetically-inherited lactose malabsorption is less common, there are five different single nucleotide polymorphisms (SNPs) which have been identified in the LTC/MCM6 (lactase promoter) gene and can reduce a person’s genetic coding for the production of the lactase enzyme (7, 8).
I don’t recommend starting with this test, because as mentioned earlier, most cases of modern-day lactose intolerance are acquired (versus genetically inherited).
So, even if you test negative for all of the lactose malabsorption SNPs, it doesn’t mean you don’t have lactose intolerance.
Still, lactose malabsorption needs to be confirmed before you can meet criteria for a lactose intolerance diagnosis and treatment (8).
Lactose intolerance treatment options
Lactose-free diet
A lactose-free diet is the primary treatment for preventing symptoms of lactose malabsorption and lactose intolerance.
This type of diet is made up of a balance of lactose-free foods, while simultaneously excluding foods high in lactose.
Foods high in lactose (reduce, limit, or exclude)
A lactose-free diet should limit or ideally exclude the following types of lactose-containing dairy:
- Cow’s milk
- Goat milk
- Sheep’s milk
- Cream
- Buttermilk
- Kefir
- “Half & half” (blend of cow’s milk + cream)
- Powdered milks
- Dairy-based yogurts (from cow, goat, or sheep)
- Soft cheese (ricotta, cream cheese, cottage cheese, mozzarella, etc.)
- Sour cream
- Whey
- Whey powder
- Human breast milk (in cases of genetically-inherited lactose malabsorption)
- Any processed foods containing added “lactose” as an ingredient (check ingredient list)
Lactose-containing foods/drinks
Additionally, the following types of commercially-made foods are typically (but not always) made with lactose-containing ingredients:
- Kefir
- Yakult
- Ice cream and frozen yogurt
- Sherbet
- Puddings and custards
- Nougat
- Fudgsicles
- Milk chocolate and white chocolate
- Cookies
- Pastries (muffins, cakes, etc.)
- Pancakes/waffles
- Smoothies and shakes
- Meal replacement drinks (such as Ensure & Boost)
- Meal replacement powders (such as Carnation Instant Breakfast)
- Whey-based protein powders
- Coffee creamers
- Commercially-made coffee and tea drinks
- Infant formulas
You can be proactive and savvy by reading ingredient labels (or asking for an ingredient list) before consuming these types of foods/beverages, if you’re dealing with lactose intolerance!
(Disclaimer: some people with lactose intolerance may also have other types of food intolerances such as FODMAP intolerances, sucrose intolerance, starch intolerance, histamine intolerance, or sulfur intolerance to name some common examples of what I see in my practice.
- If you aren’t feeling better on a lactose-free diet, it doesn’t necessarily mean you don’t need to be lactose free, especially if you have confirmed lactose intolerance via testing… it means there are additional layers of your metaphorical “onion” that need to be peeled/addressed.)
Lactose-free foods (lean on these!)
All types of dairy-free whole foods foods (such as fruits, vegetables, grains, beans, legumes, meat, poultry, pork, eggs, tofu, seafood, oils, and natural sugars/sweeteners) are inherently lactose-free and can collectively make up a balanced lactose-free diet.
Either way, you don’t need to go dairy-free to follow a lactose-free diet.
Lactose-free dairy options
For example, the above foods (all naturally high in lactose) can be easily replaced with the following lactose-free options, in which the lactose has been pre-digested:
- Lactose-free whole milk*
- Lactose-free 2% milk*
- Lactose-free 1% milk*
- Lactose-free skim milk*
- Lactose-free buttermilk*
- Lactose-free half & half*
- Lactose-free yogurt
- Lactose-free kefir
- Lactose-free cream cheese
- Lactose-free cottage cheese
- Lactose-free butter
- Lactose-free sour cream
Additionally, the following types of dairy products are considered naturally very low in lactose, or even lactose-free:
- Ghee (lactose-free, containing zero grams sugar per serving)
- Butter (very low in lactose, containing less than 0.5 gram of sugar per tablespoon)
- Hard cheeses (lactose-free, containing zero grams sugar per serving)
Enzyme replacement therapy
If you’re like many of my foodie clients – you love your dairy and you find it isn’t always convenient to opt for lactose-free alternatives, especially when eating on-the-go– you may want to consider trying enzyme replacement therapy for your lactose intolerance.
The lactase enzyme (which is supposed to be produced naturally, in the brush border of your small intestine) is responsible for breaking down lactose into glucose + galactose.
Taking supplemental lactase enzymes (~5 to 30 minutes before starting a meal or snack that contains lactose) can often– but not always– be a gamechanger for folks with lactose intolerance.
In my opinion, it’s worth a shot! Consult with your healthcare providers 1-1 about trying lactase enzyme replacement therapy for lactose intolerance. If it makes a difference, you may not need to follow a strict lactose-free diet, even if you’re lactose intolerant.
Prebiotics and probiotics
In many cases, people with lactose intolerance can still tolerate yogurt – even when it contains lactose. That’s because yogurt is a natural dietary source of probiotic microbes which, in some cases, have been shown to help digest lactose.
For example, the probiotic strain Lactobacillus acidophilus and various strains of the genus Bifidobacterium spp. have been shown to help digest lactose (9, 10).
Feeding probiotic microbes with prebiotic foods and herbs may also help enhance their lactose-digesting activity, indirectly.
Recommended reading: Should You Take Probiotics and Prebiotics Together?
Herbal antimicrobials/antifungals
I’ve found in my clinical practice in many cases, when you properly treat the source of the problem at the root-cause level, that the problem will often resolve in the fullness of time.
For example, if the root cause of your lactose intolerance is related to a gut pathogen, dysbiosis, or SIBO damaging the brush border of your small intestine (where lactase enzyme is supposed to be made and released), you may benefit from integrating antimicrobial herbs (or antifungal herbs, if applicable) into your regimen to eradicate the source of damage to your intestinal brush border.
Consult with your integrative/functional healthcare providers about the right protocol for you!
Gut repair foods/supplements
Functional foods and supplements shown to help heal and repair a damaged gut lining can go a long way to help you repair your intestinal brush border faster.
Some of my favorite go-to foods/supplements for reducing intestinal brush border inflammation and promoting gut repair include (but aren’t limited to) the following:
…There’s MUCH more where that came from! Consult with your functional medicine healthcare provider(s) about which herbs/supplements and functional foods will make the best allies for YOU as you navigate through your lactose intolerance and gut-healing journey.
Recommended reading:
Frequently asked questions (FAQ’s)
Is lactose free milk low FODMAP?
While all low FODMAP milk is lactose free, most (but NOT all) lactose-free milk is low FODMAP.
For example, all unsweetened lactose-free dairy milk is considered low FODMAP.
However, many types of flavored and sweetened lactose-free dairy milk can contain high FODMAP sweeteners, such as honey, agave nectar, or high-fructose corn syrup.
You can know for sure that lactose-free milk is low FODMAP if it is plain and unsweetened, or if it is sweetened exclusively with low FODMAP sweetener such as cane sugar, beet sugar, or real maple syrup.
You can check the ingredients list, or refer to our article on low FODMAP milks and milk alternatives for more information on the best low FODMAP + lactose-free milk options.
Is A2 milk lactose-free?
A2 milk is not naturally lactose-free; however, it is better tolerated than “regular” (non-A2) milk by many people who have a casein intolerance.
- That’s because A2 contains a different type of casein (milk protein) which is considered less inflammatory than the casein in standard dairy products made commercially in the United States.
However, you can occasionally find lactose-free A2 milk in natural food stores.
If you tolerate A2 milk but not regular milk, you likely are not lactose intolerant – you most likely have an intolerance to the casein in regular milk.
Is grass-fed milk lactose-free?
Much like A2 milk is not inherently lactose-free, neither is milk that comes from grass-fed cows. “Grass-fed milk” (milk from cows that were fed grass in place of corn or soy) has a different types of fatty acid profile than industrially-farmed cows whose diet was made up primarily of grain such as corn or soy). There’s no significant difference in the lactose content of grass-fed milk.
However, some dairy companies (such as Green Valley Creamery) offer grass-fed versions of lactose-free dairy products.
Is goat milk lactose-free?
Goat milk is not inherently lactose-free. If you don’t tolerate the lactose in regular goat milk, you may want to ask your healthcare providers about taking a lactase enzyme about 5 to 30 minutes before drinking a glass of goat milk.
On the other hand, if you don’t tolerate cows’ milk, but you notice that goat milk doesn’t seem to make you feel sick, you may actually have an intolerance to the casein in cow’s milk, since goat milk has a different type of casein more similar to human milk on a molecular level.
Is organic milk lactose-free?
No, not all organic milk is lactose-free; however, there are many variations of organic lactose-free milk on the market!
Recap and key takeaways
Lactose intolerance is the inability or compromised ability to digest lactose (milk sugar) from dairy products, particularly those that are high in lactose.
This condition is very common and is caused by an insufficient production of lactase, an enzyme that is supposed to be made and released in the small intestine, for digesting lactose.
Symptoms of lactose intolerance often masquerade as (and overlap with) IBS. People with lactose intolerance most often experience diarrhea, gas, bloating, stomach gurgling, nausea/vomiting, and abdominal pain/cramping within a few hours of consuming lactose.
This is because the undigested lactose molecules get fermented by bacteria in the intestines, leading to excessive gas production. The lactose also tends to pull extra water into the intestines, by osmosis, triggering the cramping and diarrhea.
While lactose intolerance can be inherited, most cases of lactose intolerance nowadays are acquired secondary to a damaged small intestinal brush border, the site where the lactase enzyme is supposed to be produced and secreted following lactose consumption.
The most common diagnostic means for identifying/confirming lactose malabsorption include food-symptom journaling, a lactose intolerance blood test, a hydrogen/methane breath test, a stool test (measuring fecal pH), a gaxilose blood test, intestinal biopsy, and genetic testing.
The degree of intolerance to lactose exists on a spectrum, and will vary from one person to another.
Treatment options for lactose intolerance include (but are not limited to) a lactose-free diet, lactase enzyme replacement therapy, prebiotics and probiotics, gut repair foods/herbs/supplements, and sometimes even antimicrobial or antifungal herbs to address the root cause(s) of the intolerance.
Always consult with your healthcare providers for medical and dietary advice related to gut issues and adverse food reactions!
Related articles
If you’d like to learn more about how to navigate milk, dairy, and dairy alternatives from a holistic nutrition and digestive health perspective, make sure to check out the following articles:
- What’s the Best Milk for IBS Sufferers?
- Ghee and IBS (Beyond FODMAPs)
- Butter is Low FODMAP – But is it IBS-Friendly?
- High and Low FODMAP Cheeses (List & Guidance)
- Homemade Low FODMAP Ice Cream for IBS Sufferers
- Holistic Guidance on Low FODMAP Milk & Milk Alternatives
- Food Allergy vs Intolerance vs Sensitivity – How to Tell the Difference
- Lactose Intolerance vs. Dairy Sensitivity – How to Tell Them Apart
Next steps
Thanks for taking the time to read this article! I hope you found what you were looking for and more.
If you’d like to continue learning about holistic nutrition for gut health, download my free gut guide on the 5 biggest diet mistakes to avoid when healing your gut here!
XX – Jenna
