So You Think You’re Lactose Intolerant. But Are You Really?

(image credit: petrOlly)

[Maria’s Note: I’m super-happy to introduce Anna Zakrisson, a PhD who just joined the Experts team (learn how to join here). We often fall for fads and believing we’re lactose intolerant, when we’re actually not, has become one of them. In this article Anna will help you understand whether you’re really lactose intolerant. Enjoy!]

Am I lactose intolerant?

Telling people that they are lactose intolerant seems to be a cornerstone of many nutritionist’s advice for a happy and long life with less farting and bloating. Stop consuming lactose and all your bodily issues will be solved.

As a skeptic, this seems to me like a too easy fix for a large and varied population. Also, such one-solution-fits-all are generally too simplistic, no matter of how much I would like simple solutions to be true.

Nonetheless, lactose intolerance does exist and since I do suffer from a lively belly – could it actually be that I actually am lactose intolerant? What if the health gurus were right in my case?

I went to the doctor and it turns out that in my case there was another illness causing the stomach issues with a transient lactose intolerance as one of the symptoms. Had I just listened to the health gurus, my proper diagnosis might have been delayed.

This is my main criticism against health and fitness gurus telling everyone that they are lactose intolerant without actually running any tests or having any medical knowledge of whatsoever:

There might be more serious diseases involved that might not be discovered if all symptoms are written of only as an intolerance to something (insert lactose, gluten…) or you might need help in coping with stress, which also causes an upset belly.

There are good tests for the different types of lactose intolerance at your doctors – go and have yourself properly checked if you are worried. Do not trust the fitness industry in giving you a proper diagnosis.

Got bloating, diarrhea, or cramps? Don’t be quick to conclude you’re lactose intolerant.

Lactose intolerance is the symptoms that occur when there is not enough of the enzyme lactase in the small intestine. An enzyme is a biological catalyst that helps carrying out a chemical reaction that would otherwise be too slow for the biological system in question (here: the body).

Fast biochemical reactions are necessary for our survival. The lactase enzyme is responsible for breaking-down the lactose (milk sugar) molecule into two monosaccharide sugars namely glucose and galactose, that rather than lactose can be taken up by the intestinal lumen to later be used as a source of energy in the body.

lactose free
Did you know sea-lion milk is lactose free?
(image credit: cropped from Pedro Lozano)

Lactose exists in all mammalian milk, except for sea-lion milk. Maybe in a few years, sea-lion milk will be the new superfood giving you almost inhuman powers and health (just joking!). Well, you would certainly need such powers already to milk a sea-lion.

If there is not enough lactase sitting around in your intestine, the lactose molecule cannot be broken down and this can irritate the intestine and cause painful bloating, diarrhea and stomach cramps.

Most of these symptoms stem from bacterial fermentation of the lactose sugar (the bacteria have a real party) which creates gas, mainly carbon dioxide like during any fermentation process (Have you ever made your own beer? It bubbles a lot).

Since the symptoms of lactose intolerance are similar to many other stomach related diseases, many conclude that they are lactose intolerant even though something else might actually be causing the distress.

Thus, it can be very unwise to write your problems off as lactose intolerance since it could be something more serious that you might not find out about.


So you think you’re lactose intolerant, but what if you’re not? Beware of fitness culture B.S.

One very interesting comment from the review paper by Turnbull et al. (2015) was that for people with irritable bowel syndrome (IBS) their symptoms were often blamed on lactose and dairy products despite clear findings that the patients were neither lactose intolerant nor lactose malabsorbers.

I think that attributing all symptoms to lactose (or gluten for that matter) can result in other important reasons for your symptoms to remain undiscovered.

Turnbull et al. 2015 were very sharp in their criticism against the unnecessary and misdirected efforts of many patients with IBS to exclude all lactose from their diets (since the symptoms often stem from other factors).

They continue to discuss the multi-million dollar industry promoting alternative milk products and lactase enzyme tablets. … because there is no money in “natural” (oh, there it was again, the sarcasm).

Funnily, when the dear people of the United Kingdom were asked if they experienced food intolerances 20% claimed that they did, though when tested only 2% had actual intolerance (in double-blind placebo controlled studies). Similarly, in Germany 30% claimed an intolerance though the true level of food intolerance was at 3.6%.

Women were by far more likely to report intolerances where there were none. We are left to hypothesize as to why this might be. My bet would be on naturally fluctuating hormones that cause temporary bloating; stress and a higher level of exposure to fitness culture bullshit. But that last part is my own personal opinion. Why do you think women report so high level of food intolerances?


What type of lactose intolerant are you?

Lactose intolerance, or more correctly malabsorption, can be genetically caused (different ethnicities have different sensitivities) and it can be non-genetic (secondary lactose malabsorption).

Lactose intolerance refers to the symptoms that occur in an individual that suffers from lactose malabsorption. See the table below to not get too confused about this terminology.

Term What it means
Lactose intolerance The symptoms you get from lactose malabsorption (both genetic and non-genetic versions)
Lactose malabsorption Lack of ability to break-down lactose (milk sugar) in the intestines. This can be genetic or non-genetic.
Lactose non-persistence A genetic form of lactose malabsorption where the lactase enzyme is reduced after childhood and remains low in adults. These people often show symptoms of lactose intolerance.
Lactose persistence The genetic type that keeps high levels of the lactase enzyme into adulthood and has no problem consuming dairy products.
Cow’s milk allergy This is an allergy involving the immune system. This mostly occurs in children and often disappears when the person reaches adulthood. Since this is an allergy, this can be dangerous. Never confuse an allergy with food intolerances!


There is a particularly severe genetic form of lactose intolerance called hereditary alactasia, where you have no lactase enzyme already from birth. This is extremely rare and often fatal.


Are you lactose intolerant because of your genes?

The most common form of lactose malabsorption is called lactase non-persistence and means that the lactase enzyme levels slowly decreases in concentration as the infancy-period comes to an end. The lactase enzyme does not persist into adulthood (hence non-persistence).

In people with lactose persistence, however, the enzyme remains at high concentrations into adulthood. In some populations like in Scandinavia (where I am from), the persistent phenotype (the genetic type that expresses lactase in adulthood) dominates, thus making the population overall less sensitive to lactose.

Hence, it is incredibly stupid to come up with recommendations regarding dairy products that cover too many ethnic groups. Milk can be anything from a fantastic source of protein and nutrients (and good taste) to a source of pain and discomfort. It depends on who you are.

The world is a zone of gray-levels, never black and white. Do not let any quack tell you anything different. They are fast to sell one-solution-for-all.

am I lactose intolerant
Vermeer’s “The Milk Maid“: The Dutch have low incidence of genetic lactose intolerance.


Are you lactose intolerant because of an illness?

Often people use the term “lactose intolerance” loosely for the non-genetic form of lactase deficiency, but I prefer the term “secondary (or transient) lactose malabsorption” since it better describes the condition.

This condition can develop due to external factors such as a disease in your gastrointestinal tract (Crohn’s disease, coeliac disease [that would be real gluten intolerance], endometriosis and acute gastroenteritis), during starvation (this is relevant for the developing world), radiation treatment, post-surgery or after a proper stomach flu.

During stomach flu the lactase enzyme is flushed away with the diarrhea. I presume that the same “flushing out lactase out of the intestine” would happen during colon irrigation: maybe it is not so healthy after all… I mean, is it natural to shove a tube of water up your butt? My apologies, I was being sarcastic again.

The symptoms of transient lactose malabsorption are the same as for lactose malabsorption. However, a main difference is that secondary lactose malabsorbers can, to varying degrees, get used to consuming dairy product if their intestinal microbial flora (the bacteria) adjusts and the symptoms reduce.

Also as intestinal inflammation is reduced, the lactose intolerance may disappear entirely. Many of these inflammatory illnesses come in bouts. I know for sure that endometriosis works like this since I have this illness myself.


But what if you’re NOT lactose intolerant, and instead have a cow’s milk protein allergy?

A food allergy involves your immune system whereas a food intolerance does not. A food allergy can thus be much more dangerous and can in some instances lead to an anaphylactic shock, which means that you need to seek medical help ASAP. An anaphylactic shock can end deadly.

Intolerance” on the other hand does not involve the immune system, which means that you will get physical discomfort after exposure or consumption of a certain food, but it is not acute, i.e. has no immediate “serious” consequences. It can however lead to malnutrition over longer periods of times and cause a lot of pain and distress.

Cow’s milk protein allergy is a common condition in pre-school children (2-7 % of children under 1 year old have this allergy), but the condition often disappears as they grow older (they develop tolerance). Very few adults are allergic to cow’s milk protein.

The allergy part means that the sufferers actually get an immune system response when consuming cow’s milk. The response is fairly specific to the cow’s milk protein and these children (and a few adults) can sometimes consume sheep’s milk or other milks because they are not from a cow.

However, these responses can be very individual – please talk to your doctor! There are some examples of cross-allergies: if you are allergic to cow’s milk protein, you are often also allergic to Goat’s milk protein (90 %) and 10 % are also allergic against beef meat.

It is luckily very rare that someone with allergy to cow’s milk protein develops an anaphylactic shock, but the severe bouts of diarrhea can be terrible and eczemas and other symptoms might also occur. Even so, 15% of the acute cases do develop anaphylactic shocks, hence it is important to immediately bring your child to the ER if such symptoms occur.

The symptoms in babies can be varied and can result in diagnosis being quite tricky, so it is important that you have a really good communication with your doctor.


“Natural” solutions for little ones with cow’s milk allergy may NOT be suitable

You should not give soy-milk to children under 6 months since it contains so high levels of phytoestrogens (hormone-like compounds that – hold your hats – are NATURAL!). They unfortunately could not care less about the fact that they are natural and can mess with your baby’s own little hormones. Rice milk is extremely low in protein and has also been shown to contain so high levels of arsenic and led that in most EU countries, it is advised not to give rice milk to children under 4-5 years of age.

Almonds contain a lot of allergens and are not good to give to very small babies. Also almond milk, as well as oats milk, contains way too little protein for your little buggers to grow and get strong. There are good alternatives for babies with cow’s milk allergy. Ask your pediatrician.


What tests should you do to know if you’re lactose intolerant?

You can take the Lactose Tolerance Test (this is not a genetic test). I had to do this once. This test picks up on both hereditary lactose intolerance as well as transient intolerance.

First, I was not allowed to consume any carbohydrates at all for three days and then I had to drink a bucket load of lactose solution (the equivalent of the content of lactose contained in 1 L cow’s milk).

Through a breathing test that measures how much hydrogen gas one exhales, the doctors then observed how this lactose was broken down in my system and if everything was within the normal range. I can tell you that the lovely croissant that I ate afterwards tasted like the food of the Gods! Living completely without carbs is not my thing.

My results? I was transient lactose intolerant.

There are also genetic tests, but they obviously only pick up genetic lactose malabsorption and not the other type: secondary/transient lactose malabsorption. I do not have genetic lactose intolerance.

In case of lactose intolerance, there are tablets available that contain the lactase enzyme. They can be taken with meals to help the body break-down the lactose sugar and thus reduce the symptoms and discomfort.

How an IUD (!) cured my transient lactose intolerance

People with transient lactose malabsorption are generally not a clinically relevant group with regard to lactose intolerance (it is not dangerous) as they often discover by themselves what things they can eat and what they should be careful with. However, that does not mean that the symptoms cannot cause strong distress. If you live with chronic pain and lots of medications, the symptoms of lactose intolerance just adds to your daily hell.

When my endometriosisis very active, I have to limit my milk intake somewhat, but right now after I have received fantastic medication (an IUD) that has improved my quality of life incredibly and I can happily, merrily drink my morning latte macchiato without getting cramps.

The IUD treated my endometriosis, the intestinal inflammation decreased and this increased my tolerance for lactose. Hence, treating underlying diseases might be the way forward and not focusing on the lactose intolerance as the main problem. It might just be a symptom of something else. Thank you to the pharma industry for improving my quality of life.

I must underline once again that the world is not black and white and though this treatment worked well for me, it does not suit everyone. I have tried other medications that did not work for me, but worked fantastic for other women.

Never let quacks on a forum tell you what medications you should take! I know that this has not to do with lactose intolerance directly, but I find it important to share this as it could save many from suffering. I was an idiot and received the correct medication with much delay because I thought the IUD was bad.

I lost several years to pain and discomfort. I was stupid. I should have tried the IUD earlier. Do not be a stubborn idiot as I was. In my case a classic birth control method cured transient lactose intolerance! Yes, to science!


So are you really lactose intolerant, and if yes, what type of intolerance do you have?

You see now how dangerous it can be to confuse an allergy with a food intolerance or malabsorption and why one should never strut around proudly proclaiming such matters. These things can be serious.

I hope that I also managed to communicate that the black-and-white view of many nutritionists and “health gurus” may not be entirely correct. Not all bodies function the same way; we have different genetic backgrounds, we live in different environments, have different diseases/illnesses and are of different genders. This causes us to react very differently to medications, foods and drinks. Therefore, making sweeping generalizations such as “milk is bad” is a load of cowshit.

I am curious: Have you ever been told by a nutritionist (or similar) that you have lactose intolerance without actually having had a lactose intolerance test? Could there be other possible other explanations for your belly-ache?



Turnbull, J. L., H. N. Adams, and D. A. Gorard. “Review article: the diagnosis and management of food allergy and food intolerances.” Alimentary pharmacology & therapeutics 41.1 (2015): 3-25.

Vandenplas, Y., et al. “Algorithms for managing infant constipation, colic, regurgitation and cow’s milk allergy in formula?fed infants.” Acta Paediatrica 104.5 (2015): 449-457.

Lomer, M. C. E. “Review article: the aetiology, diagnosis, mechanisms and clinical evidence for food intolerance.” Alimentary pharmacology & therapeutics 41.3 (2015): 262-275.

Misselwitz, Benjamin, et al. “Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment.” United European gastroenterology journal 1.3 (2013): 151-159.

Pereira, Paula C. “Milk nutritional composition and its role in human health.” Nutrition 30.6 (2014): 619-627.

Brown-Esters, O., P. Mc Namara, and D. Savaiano. “Dietary and biological factors influencing lactose intolerance.” International Dairy Journal 22.2 (2012): 98-103.

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  1. This is so interesting. I avoid dairy but hate to say ‘lactose intolerant’ because I don’t think I am. I just tell people that milk upsets my stomach when in fact, milk and cheese cause me intense constipation and bloating. Not something I like to share with others. Yogurt and some ice cream doesn’t cause me issues though. I had thought it maybe was the milk protein but the article makes me believe not, so I will just keep wondering why I don’t tolerate milk well.
    I enjoyed reading the differences but wished my symptoms were there! Interestingly enough, as an infant (30 plus years ago), my mother states I could not tolerate formula so they gave me diluted whole milk! (Eek!). Thanks for the article!

  2. 23andMe told me I should be lactose intolerant a few years ago, which I scoffed at while eating a large bowl of ice cream. But now, lactose products riot in my stomach. I might be lactose non-persistence, but I didn’t really care to take the test until now. Thanks!

  3. I developed secondary lactose intolerance after having cholecystitis and needing emergency gall bladder removal. My dietary restrictions without my gall bladder are very different than when I still had it! Most changes were for the better — no more fatty foods like stuff from fast food chains or fried food, no more alcohol, both of which were easy adaptations. But I love cheese and ice cream, so I still ate those as occasional treats, and substituted almond (and now cashew) milk for cow’s milk in my everyday uses. I have other conditions now, including gastroparesis, which further complicate my dietary limitations.

    It has always bothered me when people say they have lactose intolerance or “gluten intolerance” without any clear evidence, because it complicates life for people with real food issues. I know many people in the food industry who roll their eyes at claims of food allergies and intolerances because it’s fashionable now, and they tend not to take it seriously even when it comes from someone who really needs the extra precautions. Hopefully people read this article and learn to tell the differences, consult a doctor, and act accordingly. It benefits everyone.

    1. Hi Jen, this is exactly the author’s point. She had a real issue (endometriosis) and had she thought that lactose intolerance was the culprit she might have never discovered the real issue. Thank you for sharing.

  4. I’ve never had any tests done, and I still consume dairy occasionally, but since cutting out most dairy from my diet, I’ve felt a huge difference. Whatever it is I have, whether lactose intolerance, a slight allergy or whatever, I just know that cutting back on dairy has been beneficial to me. Milk has many useful nutrients, but it also comes with drawbacks- it’s fine for people to consume it, but I really don’t see that I’m missing out.

  5. Call it what you will, but it’s not “natural” to drink the milk of another species, ESPECIALLY when you’re no longer an infant. That’s why people experience adverse effects. Period.

  6. This is honestly the most informative article I’ve read on lactose intolerance. I have seen so many with conflicting information and tons of contradictions that made reading them confusing. I’m glad there is someone out here not afraid to tell people it is okay to ask questions, don’t go with the flow and without proper testing even a doctor can get it wrong. Years of seeing different doctors, multiple specialists, having symptoms ignored, constantly being misdiagnosed, unnecessary surgeries, and being treated like a hypochondriac made me appreciate, understand and enjoy your sarcasm. Thank you!