Talk:Lactose intolerance

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This Article Creates A Distorted View Of Lactose Intolerance -- What is the Truth?[edit]

I have noticed an abundance of statistics on the interenet related to lactose intolerance.

These statistics seem to fly in the face of experience.

1. How do you come up with 70-75% of the world population (4.5 billion people) being Lactose intolerant? i believe this to be a relatively accurate estimate if you factor in the amount of people that will suffer some form of lactose intolerance with age, people tend to gain some malabsorption problem with age and a key one is lactose intolerance via a lactose persistance. 2. How accurate is this estimate? I have seen very little hard evidence except in major countries regarding Lactose Intolerance. This assumption seems to exclude Japanese from lactose tolerance, but Japanese stats show hugely increased milk consumption as do Australian dairy stats for exports to Japan. How is it the Japanese can NOW digest dairy products contrary to received scientific wisdom?

3. Indians are known to be lactose tolerant and we know of the sacred cows of India. Pakistan and Bangladesh are also of the same background. This is a huge part of the world population. Add North America and Europe. Add about half of South America.

4. China is now encouraging the consumption of milk and dairy products. So far, I have not heard of an epidemic of dead Chinese due to Lactose Intolerance.

5. Define Lactose Intolerance. The word intolerance is absolute. The implication is lactose intolerant people cannot eat and cannot digest dairy products. Obviously there are varying degrees of digestibility.

6. What are the true facts behind the statistics. What size are the samples? Where are the samples from? I have read at that the stats on Lactose Intolerance are suspect and depend upon extrapolations of data from a very few western countries.

7. Many cultures which herded cattles and goats are able to digest lactose--this includes African and Mongolian herding cultures. —Preceding unsigned comment added by (talk) 19:00, 2 July 2010 (UTC)

Re. Units... there is a comment that cheese might contain 10% of the lactose of milk. This is meaningless... is this per unit volume, per unit of dried milk solids, or something else? Meaningfull data would be helpful. —Preceding unsigned comment added by (talk) 22:57, 15 July 2010 (UTC)

ok, not only those statistics are unreliable, but the map doesn't match those statistics. And another example of wront stat: for human group "Basques", only 85 individuals examined and the result is 0.3 %. That's mathematically impossible because 1 person out of 85 would make a minimum of 1.2 %. So it's either 30 % of intolerance or the number of individuals is greater, like 285. Coeur (talk) 11:40, 30 November 2010 (UTC)

What is the source of the estimate that 75% of adults worldwide show "some decrease in lactase activity" during adulthood? I would suggest that even if this statement is factually correct - which I doubt, by the way - that is not the same as saying that lactose intolerance is the norm. Some decrease in lactose activity is not the same as being intolerant.

I am concerned that there are claims that certain cheeses have very low lactose tolerances, and the reference is the website "" - a lobbying group whose primary goal is to increase the demand for cheese. If there were links to research, that would be one thing, but the claims on the site are not backed up by research. This is Citation [31] in this section: Lactose_intolerance#Dairy_products (talk) 18:29, 8 November 2012 (UTC)

Proposed split[edit]

I've been trying to get to grips with this article in my head for a couple of hours now. I'm confused by it. Judging by the talk page, so are a lot of people. They come to the article looking for information on a medical condition, and they're confused by all the talk of percentages and what's "normal"; or they come here looking for information on an evolutionary trait, and they find only jumbled lists of statistics using inconsistent terminology. I think the core problem is that this article conflates several concepts: lactose intolerance, lactose malabsorption, lactase deficiency and lactase persistence. Not without reason of course; they're all facets of the same phenomena. But because those facets fall into different areas of academic study there are wide discrepancies in approach and terminology, discrepancies which this article makes a bit of a mess of dealing with. My proposal is that this article will only see significant improvement if it is able to commit to one approach, one set of terminology, and therefore it must be split into two:

  • Lactose intolerance, the medical condition - with a brief summary of the prevalence of lactose intolerance around the world, but mainly focusing on the biological action, diagnosis, nutrition and treatment.
  • A new article, lactase persistence, dealing with the ability to digest milk in adulthood as an evolutionary novelty in some human populations. So to start with it would consist of the current second and fourth sections (there's a lot more I'd like to add to this though).

I think the result would be two much cleaner, much more coherent, and much more understandable articles. —Joseph RoeTkCb, 19:49, 26 August 2010 (UTC)

Lactose intolerance is not a disease or a malfunction, so it does not deserve to be called a 'medical condition'. No more than menopause is a 'medical condition'. Some women are menopaused very early, others very late, but menopause is natural. Creating some sort of separate article calling this a medical condition is unscientific and un-encyclopedic.--Tallard (talk) 16:23, 25 March 2011 (UTC)

Unscientific? Perhaps. But not unencyclopedic. We have to report the consensus amongst reliable sources, and it's quite clear that the medical community--and basically everyone who isn't specifically interested in LP as an evolved trait--considers lactose intolerance as a medical condition. —Joseph RoeTkCb, 17:38, 25 March 2011 (UTC)
Those numbers still represent the minority POV of humans who have lactase persistence. It fails at NPOV.--Tallard (talk) 21:24, 25 March 2011 (UTC)
If we were to consult, oh, Sleisenger & Fordtran's Gastrointestinal and Liver Disease, Chapter 101 or The National Digestive Diseases Information Clearinghouse, June 2009 publication 09-2751, they are medical publications talking about the medical condition Lactose Intolerance. The Mayo Clinic lists it as a medical condition. National Institutes of Health as well. I'd say that since it is verifiable through reliable sources, that Tallard is not showing any sources for an opinion. Your personal opinion about it doesn't make for encyclopedic information. --Catonsunday (talk) 03:02, 29 June 2011 (UTC)

────────────────────────────────────────────────────────────────────────────────────────────────────It is true that a large body of our knowledge on the phenomenon of lactose intolerance is courtesy of medical research. Indeed awareness of the phenomenon, or condition (in the broad sense - as in 'life is a condition') likely arose from medical inquiries into why some people could tolerate milk and some reacted badly (we now know that lactase persistence is a minority condition and lactose intolerance a majority one - but this is retrospecive knowledge). A great deal of our knowledge of human biology arose as a derivative of medical inquiry, and so has been subsumed into the dominant medical paradigm of the time, including attempts to answer questions like "how can we treat this condition?" in the narrow, medical sense. Research funding is another factor: research is not cheap. The researcher may be interested in broader questions than the funder, who or which has to get a return for expenditure. We now know of course that lactose intolerance and lactase persistence are two sides of the same coin, and that the broadest relevant paradigms pertain to evolutionary biology and overlapping areas such as anthropology (both of which in turn have overlapping subsets in medicine). But this awareness is after-the-fact of a body of knowledge built up under the medical paradigm. It's not really an issue: an astute researcher will always encounter relevant information in all sorts of areas under all sorts of paradigms, some of which are sound and some outdated or even ludicrous. The trick, as a tutor once pointed out, is how to think about the information when we find it. Wotnow (talk) 20:55, 1 September 2011 (UTC)


Now, I'm not a stupid person, and I only come to Wikipedia to learn things, however, this article is horrific. I have one main concern. The rehabilitation section says something about "Secondary Lactose intolerance". I have no idea what this is, however, the primary and secondary sections don't even explain the difference between this. It ends up being extremely vague, and confusing as to why either sections exist, because they certainly don't seem to add much, or explain much, this page isn't a statistical report on lactose intolerance, simply put, put statistics with other statistics, and information with other information, and merge the two as rarely as possible, now I have to Google search to find if I might be able to rehabilitate myself :(. Sad face. Anyways, this page is shocking, people have edited and added information without maintaining a structure. For the benefit of everyone who might actually *need* good information (Students, people trying to self diagnose, or learn more about this), please address these issues. —Preceding unsigned comment added by (talkcontribs)

this confusion was due to previous vandalism which had erased an entire section explaining this classification. It is fixed now.--Tallard (talk) 16:16, 25 March 2011 (UTC)
It seems that the Nutrition section could be cleaned up and get some verifiable sources. Also, there are two paragraphs in the Classification section that seem like they don't belong, or need better explanation. They don't discuss actual classification in the second, and seems misplaced. Will look to see if there is a better place for the information. Catonsunday (talk) 03:58, 29 June 2011 (UTC)
Those two extra “Classification” paragraphs would have been moved there by me in my recent oldid 435419506 edit. They were previously under a section called “Lactase biology” which I renamed to “Lactase persistence” because the rest of it was about how lactase may or may not stop being produced as you get older. Perhaps those two paragraphs are more related to the “Mechanism” paragraph? Vadmium (talk) 02:26, 30 June 2011 (UTC).
Do you think that a "Misdiagnosis" section under diagnosis would be appropriate? It seems that it would pertain to cases that could be misdiagnosed or misunderstood, and would fit in well in that section. — Preceding unsigned comment added by Catonsunday (talkcontribs) 19:58, 1 July 2011 (UTC)
I think the final paragraph would go well under a “Misdiagnosis” section. I’m not sure that coeliac disease paragraph is about a misdiagnosis though; maybe it is actually related to the “secondary lactose intolerance” classification? Vadmium (talk) 13:00, 5 July 2011 (UTC).
I wish there would be clarification about when the intolerance develops. How long after birth is the person tolerant of lactose? How long does the tolerance last, for different groups of people?

Thanks. — Preceding unsigned comment added by (talk) 00:33, 11 September 2011 (UTC)

Proposed split sounds great.[edit]

I like the proposal a lot.

@WOW: Primary and Secondary are most likely referring to Comorbidity of lactose intolerance in a patient. Primary would be a something like an enzyme deficiency, whereas secondary would be a side effect from another disease. The disease that pops up commonly in my searches as temporarily causing lactose intolerance is Celiac disease. Also, gastroenteritis (stomach flu) and food poisoning commonly causes secondary lactose intolerance.

A page discussing Celiac disease and lactose intolerance

I edited a number questionable statements in the foods content which had spurious references. I'm sure there's more work to be done, though. Dwlocks (talk) 06:49, 7 September 2010 (UTC)

Splitting these topics would be a very bad idea, there is nothing separate about them. Lactase persistence is but a recent (in evolutionary context) condition derived from favourable genetic mutations. --Tallard (talk) 16:19, 25 March 2011 (UTC)
I don't think that just because Lactase persistence is "recent" doesn't mean it isn't worth giving it's own page. Lactase deficiency should be separated from a lactase persistence/non-persistenceLactase persistence/non-persistence page would be a wise move, especially from a research standpoint. --Catonsunday (talk) 03:18, 29 June 2011 (UTC)

Correction in Lactose intolerance frequency map.[edit]

The lactose intolerance frequency for some of the countries is marked incorrectly on the map. The table depicts the data which does not go with the markings in the map. e.g. India is shown as 60 - 80 % intolerant as per the map, while the chart shows that that only 20 % of the population is lactose intolerant: on the other hand Italy, which is at an average (northern southern as well as sicily) 80 - 90 % intolerant is 40 - 60. I am sure if it is looked into properly, a lot more anomalies can be found. Request you to please correct it.

I would like to point out that almost the entire population in Argentina and Uruguay are of exclusively European ancestry, mainly Spaniards, Italians, and Germans. In the light of this, the map shown in the article is obviously wrong to anyone who has been there or knows something about the demographics of South America. If there is no data available for those countries, they should be grayed out since they are demographically very different from they neighbors. If not that, then at least the lines delimiting the individual countries should be removed from the map, to transmit the idea that it is referring to the native population that once lived in the region. —Preceding unsigned comment added by (talk) 09:51, 22 November 2010 (UTC)

I would like to point out that almost the entire population in Argentina and Uruguay are of exclusively European ancestry

Damn lie. Argentina is about 20-30% Native, and most of its maternal lineages are Native. The same is probably true of Uruguay. (talk) 14:43, 5 January 2014 (UTC)
The map is not based on the same data as the table (see [1]). There very well could be errors, and even if not the lack of detailed sources for the statistics is problematic. But it seems to be the best freely-available map of LI available. Unfortunately preparing an alternative map is not as simple as looking up a figure for a country and colouring it in appropriately; there's lots of conflicting data that can't be really be put together. Some studies look at the modern population (useful from a medical POV) while others will only look at the indigenous people of a given area (useful from an evolutionary POV). Older studies may have methodological problems, particularly with regard to sampling, since before the 1970s the significant variation in LI between ethnicities was not widely known. Some populations have detailed stratified statistics available (e.g. the US), others only have broad regional surveys. In much of Africa, the Near East, and East Asia, doing things on a national basis would obscure considerable variation among ethnicities within a single country. Additionally, there's a range of ways you can define lactose intolerance, and although choosing one or the other could change the final figure by tens of percent, studies rarely say outright which one they are using. In other words, putting together a map that displays all the information in a way that is both accurate and consistent is a not a simple task. —Joseph RoeTkCb, 14:38, 29 November 2010 (UTC)
80-90% in italy? I'm confused, cause i'm italian and i'm the only lactose intolerant of my family (not only of my household, my entire family, grandparents, uncles, cousins)usually for breakfast italians drink cappuccino (coffe and milk), and eat fresh dairy products (mozzarella, burrata, stracchino etc.)
lactose intolerance is common,
but i do not think that affects the majority of italians. Rambaldo--Rambaldo (talk) 02:21, 29 January 2011 (UTC)
Well, as a general point, anecdotal evidence is no substitute for good statistics. It could be that you live in, or your family originally come from, an area of Italy that has a lower frequency of lactose intolerance than the national average (e.g. the north, uplands). Also, since lactose intolerance is primarily genetic, it's not surprising that the majority of the members of a family would have the same phenotype (non-lactose intolerance in this case). The typical Italian breakfast doesn't say much either: there's not enough milk in coffee to trigger symptoms in most lactose intolerant people, and cheese actually contains a very small amount of lactose because the lactose is turned into lactic acid in the fermentation process.
80–90% would be high. But if you look closely at the map south and central Italy is shaded in the 40–60% range while north Italy is only 20–40%. The table says 19% for central Italians, 41% for central Italians and 52% for northern Italians. Other studies cited in the article say 51% for northern Italians and anywhere from 4% to 72% of Sicilians. As you can see, there's a lot of variation within countries and that means the average may seem quite far off for a lot of people who are looking at a particular area. —Joseph RoeTkCb, 09:09, 29 January 2011 (UTC)
I have removed the map as I could not find (of all the sources) any that made sense. It seems rather random to me. It is better to have no map at all, than a randomly generated one. Furthermore, it made no sense that nations were split on the map along random lines. No data on most of South America, lot of europe and India that is consistent with the map. Basically, the map seems to be coded correctly only in half the world. This can hardly be called "best available" - it is outright misinformative and does not reflect the wikipedia standards. Please do not insert it without proper discussion and sources. Kniwor (talk) 06:10, 3 April 2012 (UTC)
Agreed. Someone added it back in, so I removed it again. The map is apparently from a June 2007 article in Die Zeit, but as far as I can tell, the article just uses it as an infographic and doesn't give any details of where the numbers come from (I don't know German, but used Google translate on it). The credit line on the map is "ZEIT-Grafik/Quelle: Verein für Lactoseintoleranz" (Association for lactose intolerance). The VLI has a map on their site, but I don't see any source for their numbers. So as far as I can tell, that map has no verifiable sources, and should just be deleted. 2602:304:B1B8:F420:49E4:4679:C77C:1E6 (talk) 21:58, 22 June 2012 (UTC)

Merger proposal of redundant content fork[edit]

I propose that 'Lactase persistence vs. lactose intolerance and deficiencies' be merged into 'lactose intolerance', as the former article (an orphan article created 15 December 2010) appears to be a redundant content fork covering exactly the same topic as the latter article. Qwfp (talk) 21:11, 17 February 2011 (UTC)

Delete newer redundant article--Tallard (talk) 14:42, 25 March 2011 (UTC)

Redirect Lactose intolerance to Lactase tolerance. To treat lactose intolerance as a disease makes no more sense than saying black people are a disease! Lactase persistence is the scientific oddity and the article should reflect that.--Tallard (talk) 15:18, 25 March 2011 (UTC)

redirect Came here from NPP, seems a very clear case. HominidMachinae (talk) 07:32, 11 May 2011 (UTC)

The only problem with the merger I see is that the medical community is pushing to change the condition from "lactose intolerant" to "lactose non-persistence". Maybe change the title of the original "Lactose Intolerant" page to "Lactose Non-Persistence" to keep up with the medical terminology and then combine the pages? — Preceding unsigned comment added by Stephen Glansberg (talkcontribs) 02:38, 1 June 2011 (UTC)

Lactose intolerance, or lactace deficiency should be separated from the lactase persistence/non-persistence information. The 'Lactase persistence vs. lactose intolerance and deficiencies' would be better off as lactase persistence/non-persistence in it's own page. It would make sense for the two to link to each other, but to make it clear, they would be better off in separate pages. I do believe the original vs. page is not needed. Catonsunday (talk) 03:39, 29 June 2011 (UTC)

Merge & delete There's no reason for the existence of this article. Imagine Reason (talk) 10:42, 22 July 2011 (UTC)

Merge and fork[edit]

We can add to the above Developmental regulation of lactase expression in mammals, which is good and well referenced but not really different in scope from this article. But between these two and the "Lactase persistence" section of this article I think there's easily enough material to fork off a separate lactase persistence article as I suggested above. joe•roetc 09:26, 1 September 2011 (UTC)

Greetings. What prompted me to add that article link to the 'See also' section was the map. On reading Arjamaa & Vuorisalo's 2010 article "Gene-Culture Coevolution and Human Diet", I noted that their lactose intolerance global distribution map was adapted from Wikimedia Commons. This intrigued me, and a brief search for such a map in Wikipedia/media brought me to the above article. I had noted the absence of such a map in this lactose intolerance article, which I thought was remiss: a global distribution graphic is indispensible for concept/information transmission to a broad audience. A bit more reading of this talkpage and I see there was indeed a distribution map up until 8 June 2011, after which it was deleted by a relatively new editor on 14 June 2011 on the basis of being inaccurate and misleading.
I note your own comments on the difficulty of devising a reliable map, given the methodological variations and limitations underpinning available data, and of course you make some good points, all of which I recognised from the time when I delved into epidemiological issues. The prevailing map for some time was that produced by Kretchmer in 1972, which I encountered in the early 90's and which continues to be cited. A workable solution regarding the map may well arise from answering the question: "in terms of available distribution data, what has remained stable, what has changed, and what is changing?" I must note (for some editors) that I am talking of available data, NOT phenomena for which we have yet to capture data. The latter is the arena of of primary researchers, the former that of encyclopedias such as this, and on which we need therefore concentrate our efforts.
Answering this may lead to say, three or four maps. The first could represent the distribution graphic which is relatively unchanged over recent decades. The next could represent data that has changed - or alternatively the first map could incorporate this. A second/third map could represent data that is subject to change as information comes in. Or since such information doesn't come in that fast, could be a more detailed 'blow-up' map showing variation within relevant geographic areas. Lastly, and only if practical, a map containing the overall graphics could be devised. Resolution in such a map would likely be relatively poor, but would provide instant conceptual information, which could be pursued in a more detailed map.
Of course as you say, map creation is no simple task, let alone creation of a map to portray data that on closer inspection gets quite messy. Still, just a thought. Of course for any distribution map to be created, data needs first to be tabulated, so tables per this article are also indispensible. But a good graphic, derived from such tabulated data, is almost unbeatable for maximal conceptual transmission in the shortest time. A more simple solution than the time-consuming and possibly redundant exercise I've suggested above, is to create a 'map revision' date, whereby an existing map is revised to portray most recently available data. Here one might have two maps: an 'in-use' map, and an 'under-revision' map. The maps are then interchanged at the prescribed interval. The maps would need to be notated so readers are clear. The 'in-use' map would need to clearly state that it will prevail until the next revision at date X, at which time the 'under-revision' map will be swapped. This should allay concerns of any readers/editors who spot inaccuracies or outdated data. They could be invited to provide the information they are aware of to the 'under-revision' map project. Anyone who has worked in organisations which have to continually revise policies and procedures while still functioning day-to-day will recognise this heuristic immediately. Anyway, just food for thought. By the way, a further brief search gave me the map in this 2001 article Wotnow (talk) 22:37, 1 September 2011 (UTC)

Southern South America[edit]

In southern Brazil, Argentina, Chile and Uruguai, the huge majority of the people (70-90%) have european origin (Portuguese, Spanish, Italia, German, Polish, etc.). These peoples arrived there mostly between 100-200 years ago, so they should be reasonably tolerant to lactose. How can the map show the people in this region as 80-100% lactose intolerant? Poor research IMHO. The map even show that area of south america as more lactose intolerant than northern south america, where european descendants are not as common. —Preceding unsigned comment added by (talk) 09:23, 7 May 2011 (UTC)

It's probably based on indigenous populations. And no, the map is not perfect—nor is the table—but before you rush to call it "bad research" please read what I wrote above about the difficulty of getting compatible worldwide data. It's certainly impossible to capture both the modern frequency of lactose intolerance and the (evolutionarily relevant) precolonial situation on one map. But if you disagree, by all means fix it.   jroe tkcb  10:24, 7 May 2011 (UTC)
This map has numerous problems:
  1. Map doesn't cite data source
  2. 80-100% lactose intolerance in the Chile/Argentina is wrong for the current population. If it's the indigenous population, then the US and Australia are inconsistent in showing the low LI in the current population.
  3. Intra-country variation in Brazil, Bolivia, France, Italy, Spain and Russia. I strongly doubt there is any published data showing a difference in LI between Northern/Southern Brazil or Bolivia. Spain's difference maybe could be explained by the Basque, but the map color doesn't match the figures in the table for the Basque and non-Basque Spainards. Southern France is not colored appropriately based on the table. The map incorrectly (per the table) shows Southern Italians as more lactose intolerant than Northern Italians. Russia has a substantial number of non-Slavic people in the far East, but it's still 95%+ Slavic to a point much further east than the line on the map.
  4. East African herders with low LI don't show up on the map
  5. I have a hard time believing that Canada has higher LI than the US. While Canada has slightly more Asians and Native Americans, overall the US has far more people not of Northern European ancestry. Canada probably should be the same color as the rest of Northern Europe.
The map is quite misleading in a number of areas. The problem is in the Cono Sur is only the most obvious. I'm going to remove the map from the article.Plantdrew (talk) 19:17, 14 June 2011 (UTC)

Make it clear[edit]

Lactose intolerance here refer to lactase non-persistence, its completely different from the lactose intolerance in newborns and the lactose intolerance cause by bacteria infection, or even the milk allergic. Isuzu1001 (talk) 23:47, 19 June 2011 (UTC)

What are the symptoms?[edit]

I also had trouble finding a mention of symptoms; at first glance it seems like there are no obvious symptoms apart from not getting as much nutrients. But looking closer it seems it is covered in the oddly-named “Overview” section (which the previous reader didn’t even pick up on). Surely overview is part of what the WP:lead section is meant to be. I think I’ll quickly merge the two. Vadmium (talk) 02:00, 21 June 2011 (UTC).


Does the [by whom?] tag really need to be there after the words "A counterargument to this is.."? It's a counterargument whether there's anybody out there making it or not. You don't need citations for points of practical reason. (talk) 10:47, 29 August 2011 (UTC) Tom

But if it's not a counterargument being made in reliable sources, it shouldn't be in Wikipedia. joe•roetc 11:19, 29 August 2011 (UTC)

Oi! Who deleted "my" stuff?![edit]

I spent several hours this morning researching and as a consequence edited the symptoms section. I didn't delete anything but added and clarified. I left the structure and the access to more technical information through the references. This afternoon, I returned to find the references and work deleted. It has been replaced with a lengthy "quasi-diagnostic/phramaceutical" piece that has already been tagged for lack of references.

To whoever made the changes: MedLine carries indemnity insurance I don't know if wiki does. In addition Medline carries a disclaimer for their insurance. Wiki doesn't. In my opinion it would have been a simple courtesy to have explained here the reasons for your edit. LookingGlass (talk) 20:53, 29 November 2011 (UTC)

I suppose you're talking to me? I edited your contributions to be a bit more concise, removed one of the references because it mostly duplicated the information in the other one which was much more reliable, and moved some things to more appropriate sections. Nothing was deleted or "replaced" and mine is currently the top edit so nobody could possibly have added any tags to it since.
I take it you're not aware of the edit history attached to each page. It shows every contribution, exactly what it changed, who did it, and the reasons they provided in their edit summary. Generally it isn't considered necessary to further discuss changes on the talk page unless they're particularly controversial or otherwise require discussion (which I don't think mine were).
As for insurance, to be honest I'm not sure what you're talking about. Wikipedia is an encyclopaedia, we don't give medical advice, and I'm sure that's written somewhere in the legalese down at the bottom of the page. But I don't see why that is relevant here. joe•roetc 21:56, 29 November 2011 (UTC)
Thanks for replying. Yes it looks as if it was you, however I apologize as my post scrambled two observations. Comparing your edit and mine, I can see only that you: delineated the difference between (milk)allergy and lactase deficiency (actually less of a deficiency and more a normal condition); replaced the list of symptoms with an edited text version; and made minor changes, which in my opinion muddied it. I've copied the symptom list so no problem, though why you believe a list is less clear than a sentence I don't understand. No matter, it's a subjective thing, as is eliminating any more than a link that relates to another, even if related in this instance, issue: immune system and lactase level.
As for the disclaimer my comment should not have been included as it took issue with something general. I think it's one of those things you see or don't. The disclaimer is the nub of it. Disclaimers feature prominently on medical literature, and other professional documents, and information is worded a certain way to avoid liability and damages. I guess wiki has followed/led the move away from this standard of care as it was called, in favour of an "anything goes as long as there's a legal disclaimer somewhere" approach. Times have moved on but a legal obligation could be created simply by informal opinion or advice on which someone then relied. No contract is required. Authorative advice can be given passively. It's not necessary (or wasn't under UK law) to be engaged but merely to occupy a position of authority. Perhaps wiki et all are deemed not to hold that position. LookingGlass (talk) 16:05, 2 December 2011 (UTC)

Nutritional implications[edit]

This section has some serious issues. Overall, it looks like written by some advocator of milk consumption who wants to persuade you that lactose intolerance is actually no problem at all, and that by not consuming milk you undergo the risk of several nutritional deficiencies. Some statements are simply absurd; one part basically says that "milk is fortified in some countries, therefore in these countries, if you do not consume milk, you have to find other sources, otherwise you will be deficient". If, say, in my country milk were fortified with vitamin C and I stopped consuming milk, would that mean I would develop a vitamin C deficiency? That's simply nonsense, unless there's a verifiable source saying that milk is the only main source of the mentioned nutrients in these countries. — Preceding unsigned comment added by (talk) 12:35, 13 December 2011 (UTC)

Feel free to do something about it. joe•roetc 13:35, 13 December 2011 (UTC)
I don't know any better solution than to actually delete the first paragraph, because it simply doesn't seem to be true. However, there still might be some sources proving that it is at least partly true. What is the standard policy in such a situation? (talk) 11:18, 14 December 2011 (UTC)
Yeah looking at it again you're probably right. I've gone ahead and removed it per WP:UNSOURCED. joe•roetc 12:15, 14 December 2011 (UTC)

Fork doesnt make sense[edit]

The fork is not serving the article. As stated it is two sides of one coin. So The map of lactose intolerance is also the map for lactose persistence. Do you not think the map should be in this article? Considering most people are lactose intolerant? Obviously I came a little late (before the split). But these articles probably should have been split more carefully. — Preceding unsigned comment added by Halaqah (talkcontribs) 02:42, 23 December 2011 (UTC)

I agree, a map would be useful in both articles. Although as you can see above the one that we had before (which I think the one at Lactase persistence is a straight copy of) was not very good and a lot of people pointed that out. I don't see how that invalidates the general rationale behind splitting the article into two though. joe•roetc 10:19, 23 December 2011 (UTC)
I would correct myself and agree it doesn't violate the rational,(I didnt mean to imply that to that degree. but we do need a map. And I prefer any map rather than none. I also think there is merit in the break down by ethnicity. Thats what drew me to this page to find out the relation between cultures with milk history and their lactose persistence. --Halqh حَلَقَة הלכהሐላቃህ (talk) 13:11, 23 December 2011 (UTC)

Map doesn't make sense[edit]

The map on the article is entirely unscientific. Among other things, why are continents arbitrarily divided at points that do not have any significant correlation to demographics. For example, what does the lines dividing South America or Spain in half even mean? The data itself is also very dubious. The populations of Argentina and Uruguay for instance are around 90% of European origin. It would make a lot more sense for their lactose intolerance to be lower than that of, say, Haiti or Guatemala. Someone above suggests that it might represent native populations. In that case, why are the US, Australia, New Zealand, etc. represented by their current populations? -- (talk) 18:43, 5 January 2012 (UTC)

You're not the first person to criticise it, and I agree it's far from perfect... but it is broadly correct, which is better than nothing. Basically I think ("think" because one of the problems is that there are no citations) the data is very coarse – it looks like there's just two points for South America (north and south), for example, and yes it seem likely that they've mixed studies representative of current demographics and ones restricting themselves to pre-Colombian indigenous populations. It would be great to have a better map (or even better two: one for this article with an up-to-date picture and one for Lactase persistence with a reconstructed pre-Columbian one), but see my comments above on why that's far easier said than done. I'm pretty sure the map at Lactase persistence that you also remarked on is a straight copy of the one in this article, by the way. joe•roetc 19:23, 5 January 2012 (UTC)
There's a better map, was deleted after I added it. But it makes more sense and is made by us (Austrian society for Public Health). Would be a good map for that! Here's the link: NmiPortal (talk) 14:00, 25 June 2013 (UTC)

Reference [3] seems inadequate[edit]

In the introduction the article states some frequencies with which different tribes become lactose intolerant and provides reference [3] as supporting evidence. When I looked up that publication it does not seem to mention any of the statistics given here. It talks about the correlation between lactose intolerance and a certain type of mutation in the LCT gene. — Preceding unsigned comment added by (talk) 23:16, 6 January 2012 (UTC)

From the second paragraph in the introduction section of the source in question:
The condition affects more than 75% of the population worldwide, with regional frequencies ranging from nearly 5% in northern Europe to more than 90% in some Asian and African countries.
Which (almost word for word) backs up what we're using it as a reference for in the lead. joe•roetc 07:58, 7 January 2012 (UTC)

Symptoms section[edit]

I think I might b lactose intolerant. Anyway. Is this section therefore saying a person without this issue (if it is an issue) can drink 2L of milk and nothing would happen? Like if they drank water? So therefore it is a sliding scale of symptoms. cuz I drink milk all the time, but up until the 4th glass, I thought it was normal for that to happen. --Halqh حَلَقَة הלכהሐላቃህ (talk) 11:18, 7 January 2012 (UTC)

On a net search, I can't find a reference or evidence for a link of lactose intolerance to acid reflux. Shouldn't there be a reference on the symptoms list? JohnOFL (talk) 02:59, 18 February 2012 (UTC)

Question of Degree[edit]

Lactose intolerance is also a continuum not an either/or issue like this article makes people think. This article is a little misleading. It can be a question of degree for many people.

Some people can have a small amount of milk products (such as a few drops in a cup of coffee) and not be too affected to be uncomfortable - while a larger amount may cause serious bowel problems.

Also cream has less lactose than milk so they are not necessarily the same in all lactose intolerant people. Cheese is also different.

So it is not so simple to explain to people who are not lactose intolerant.

I know because I am somewhat lactose intolerant myself. — Preceding unsigned comment added by (talk) 03:29, 29 February 2012 (UTC)

Where specifically in the article do you think this isn't made clear? joe•roetc 07:07, 29 February 2012 (UTC)

Mammilian Lactase persistence[edit]

The statement "Among mammals, lactase persistence is unique to humans –" at Lactase persistence needs strong support. Southern US farm families for generations had domesticated cats which were strongly attracted to dairy milk and routinely drank milk daily. I have never seen a cat get sick from drinking milk; perhaps they do - again it needs support since it runs counter to the experience of many rural people.
SBaker43 (talk) 01:16, 18 April 2012 (UTC)

I think this fact is well enough supported; it's stated in a number of the references, including the one actually cited in the section you're referring to ([2]).
As it happens, milk isn't good for cats or any other adult animal. It shouldn't be too hard to dig up your own sources for that. I suppose that's something that could fall under the scope of this article, actually. joe•roetc 17:45, 8 May 2012 (UTC)
References or not, "human lactase persistence" is actually quite rare among ethnic groups. But the dairy industry would much rather you believed this myth.
It's true that there are many pictures and stories involving cats liking a bowl of dairy stuff. What is actually OK for most of them is cream — thick cream that is mostly butterfat containing relatively little lactose.Daqu (talk) 22:58, 9 May 2015 (UTC)


I think the article needs to make it clear that "lactase intolerance" is not really a "deficiency" but the norm among the peoples of the world. IN evolutionary terms Lactose intolerance is the ancestral terms and lactase persistence is the mutation that became prevalent as an adaptation in cultures that have a long history of dairy consumption. The point is that it is misleading to suggest that lactose intolerance is a medical problem or condition when in fact it is the ancestral condition which is still present in the majority of the worlds population.·ʍaunus·snunɐw· 15:47, 8 May 2012 (UTC)

As usual it's semantics. Absence of lactase is indeed the norm for adults and the ancestral condition for all mammals (I hope that's clear enough in the article – it's mentioned in the lead, again in the "Terminology" section and the section and article on lactase persistence goes into more detail on the evolutionary history) but nevertheless if you try to drink a glass of milk you'll find it a deficiency.
At the end of the day though it is thought of (and formally classified, and diagnosed, and treated...) as a medical problem in Western countries where milk-drinking is the norm and there's a plethora of reliable sources that take that position. We can't ignore those any more than we can ignore the global anthropological/evolutionary perspective. There are also variants of lactose intolerance that affect infants (i.e. acquired lactase deficiency and congenital lactase deficiency) which most definitely are medical problems, sometimes life-threatening ones, wherever you are in the world. joe•roetc 17:56, 8 May 2012 (UTC)
I think there is good reason to distinguish more clearly between acquired and congential lactase deficiency that I agree are medical problems and the normal kind. This could be spelled out more explicitly in the lead I think. There is also literature in Darwinian medicine that criticize the medicalization of lactase inpersistence and the normalization of lactose tolerance (which for example has lead to nonsensical events such as the Chinese government trying to increase milk consumption in its highly lactose intolerant population using a copy of the "Got Milk" campaign).·ʍaunus·snunɐw· 18:01, 8 May 2012 (UTC)
It would be great to incorporate that literature into the article. Do you have any links? joe•roetc 18:07, 8 May 2012 (UTC)
I'll look it up. I am thinking specifically of Wenda Trevathan's "Ancient bodies modern lives" which I have at home. I'll look at how to include it if you sdon't beat me to it.·ʍaunus·snunɐw· 18:09, 8 May 2012 (UTC)
  • Here's an article we could use: "Cow's milk is accorded a high cultural value in the contemporary United States. Its white color, association with the maternal and the pastoral, and repeated mention in the Bible add positive symbolic weight to this major national agricultural commodity. Thus, it comes as no surprise that influential policy-making institutions in the United States recommend milk consumption for all U.S. groups. This is despite variation in adult populations' abilities to digest milk, which has been documented by biological anthropologists. This article assesses various U.S. “stories” about milk consumption and its relationship to biological variation against the biological anthropological explanation of variation in lactase activity/lactose tolerance. Many of these serve as normalizing discourses that ultimately pathologize biological difference and may undermine the dietary traditions of some ethnic groups. In particular, the close relationship between government and the dairy industry leads to policies that fail to seriously consider variation in digestive physiology among the diverse U.S. populations."(WILEY, A. S. (2004), “Drink Milk for Fitness”: The Cultural Politics of Human Biological Variation and Milk Consumption in the United States. American Anthropologist, 106: 506–517. doi: 10.1525/aa.2004.106.3.506)·ʍaunus·snunɐw· 15:54, 9 May 2012 (UTC)
  • Another one by the same author that also argues about China and India: Andrea S. Wiley. 2011. Milk for “Growth”: Global and Local Meanings of Milk Consumption in China, India, and the United States. Food and Foodways. Vol. 19, Iss. 1-2, 2011·ʍaunus·snunɐw· 15:59, 9 May 2012 (UTC)
  • This one is particularly critical: Wiley, Andrea S. (2007) Transforming milk in a global economy. American Anthropologist 109(4):666-677. "Large-scale milk production and consumption historically have been localized to Europe and countries with large Europeanderived populations. However, global patterns have now shifted, with dramatic increases in milk consumption in Asian countries and flat or declining consumption in European and European-derived countries. Efforts to market it around the world emphasize milk’s positive effects on child growth, and, by extension, the individual and national benefits that derive from that growth. At the same time, milk has newly emerged in milk promotions in the United States as food that facilitates weight loss. Milk has been able to achieve a global presence and continuing relevance in populations in which its consumption has been declining by continually transforming and repositioning itself as a “special” food with properties able to alleviate the health concerns seen as most salient at the time. "·ʍaunus·snunɐw· 16:07, 9 May 2012 (UTC)
I completely disagree that milk-drinking among adults is the norm in the U.S. Rather, the extremely influential dairy industry in the U.S. has for a very long time manipulated the federal government to list dairy as a "major food group" even though it is not at all that for most adults. Because the U.S. has had a lot of people of Northern European extraction, this myth has been allowed to stand.
One person above wrote: "If you try to drink a glass of milk you'll find it a deficiency." That is udder nonsense (pun intended) ! That is exactly as logical as saying that if you walk across the street without looking both ways you will find that your body's lack of armor plating is a deficiency. It is not just "semantics" at all, unless you actually look up the word "semantics" and find that its definition is the meanings of words. Yes! Meanings of words are important! They can express both truths and untruths.~
Before noticing this section I began a new one with the same point. But this cannot be said enough. And it looks to me as if the dairy industry has its own agents trying to manipulate this article.Daqu (talk) 23:14, 9 May 2015 (UTC)

Citation needed for an image?[edit]

I'm agnostic on whether we should include File:Laktoseintoleranz-1.svg in this article or not (it's already been added and removed a dozen times). It's not a good map, but it's also the best we have, and an illustration of this type is very helpful.

However, I don't think a citation needed tag is appropriate. The image is attributed, albeit not very precisely, on both its Wikipedia and Commons description pages to the German newspaper Die Zeit. Whether the newspaper cites the source of the data or not I don't know, but that's beside the point; as far as we're concerned the map comes from a reliable source so we can use it. As far as I know it's never been common practice to attribute or source images inline when they're included in an article, so I've removed the tag. joe•roetc 08:11, 21 June 2012 (UTC)

diagram lactase persistence[edit]

The diagram I added was deleted with text "nonsensical diagram". Well, it's not nonsensical, it's a very well researched diagram. I will not add it again, because I don't wanna get banned for "spamming", but I would like the community to decide, if the diagram should be used again. And if anyone really thinks it's nonsensical, ad least I'd like to hear why (after 2 years of collecting scientific data in various publications) you think so. File: NmiPortal (talk) 11:44, 23 April 2013 (UTC)

We should have an image, if possible. This one seems similar to that in the previous section, and rather different to the one in Nature here. Johnbod (talk) 12:29, 6 January 2014 (UTC)

Unclear sentence[edit]

Picky, but

"After the curdling process, lactose is found in the water-based portion (along with whey and casein), but not in the fat-based portion." Of?????? (talk) 22:06, 8 January 2014 (UTC)Ruthe74.190.202.119 (talk) 22:06, 8 January 2014 (UTC)

"quarters"? - or "quadruples"?[edit]

This line in the lede took me aback:

it prevents babies from drinking human milk, which nearly quarters its risk of Sudden Infant Death Syndrome.

Surely it's "quadruples" that's meant?Skookum1 (talk) 02:13, 3 April 2014 (UTC)

What causes the symptoms?[edit]

The article gives two causes for the symptoms of lactose intolerance.

1. “...symptoms are caused by insufficient levels of lactase in the lining of the duodenum.”

2. “ Bacteria in the colon can metabolise lactose, and the resulting fermentation produces copious amounts of gas (a mixture of hydrogen, carbon dioxide, and methane) that causes the various abdominal symptoms.”

Which one of these is correct?

Also, under the heading Symptoms the article states "These appear one-half to two hours after consumption”. So this implies that lactose can reach the colon and begin fermenting enough to produce recognisable symptoms in as little as 30 minutes! Is this possible? A test for lactose intolerance is given: the Hydrogen breath test. In this test hydrogen can be detected on the breath 2.5 hours after the ingestion of lactose. Following 2 above, how does the lactose get to the colon and then the hydrogen to the breath in 2.5 hours?

I cannot claim any expertise in this subject, but the article appears contradictory. Perhaps the hydrogen gas is produced in the duodenum? It would certainly fit better with the time scales given for the appearance of symptoms and for the testing methods used. Winstanr (talk) 11:43, 14 October 2014 (UTC)

suggestion for clarification[edit]

I did not have time to read this entire "Talk:" page, so feel free to enlighten me, "if applicable".

To me, the sentence

Congenital lactase deficiency prevents babies from drinking even human milk.

seems ambiguous. I read it as referring to "some" babies, or with the implied adverbial phrase "in some cases" missing but "understood".

Technically, however, that sentence could be interpreted as implying that all [or, almost all] [human] babies, are prevented (by congenital lactase deficiency) from drinking even human milk. IMHO, if that is not the intent, then the wording should be changed.

IMHO, either the word "some" ("some" babies), or else the adverbial phrase "in some cases" should be explicitly stated in that sentence. For example,

In some cases, congenital lactase deficiency prevents babies from drinking even human milk.


In some cases, babies have congenital lactase deficiency which prevents them from drinking even human milk.

Ordinarily, I would have just been so bold as to go ahead and make that change, but the (huge!) portion of this "Talk:" page that I did read (but it's a small percentage of the whole "Talk:" page!), has caused me to think that I might be making a mistake, if I did not seek consensus first.

Any advice? or other comments? Thanks!... --Mike Schwartz (talk) 22:50, 14 January 2015 (UTC)

Actually, the "Terminology" section of the article, already contains (as its 3rd bullet point), this:
  • Congenital lactase deficiency is a very rare, autosomal recessive genetic disorder that prevents lactase expression from birth.[footnote, "Heyman 2006"] It is particularly common in Finland.[footnote, "Behrendt 2009"] People with congenital lactase deficiency cannot digest lactose from birth, so cannot digest breast milk., *** maybe *** the revised sentence, should be something more like

In some (rare) cases, babies have congenital lactase deficiency, which prevents them from drinking even human milk.

(right?) --Mike Schwartz (talk) 23:27, 14 January 2015 (UTC)

Spelling differences[edit]

Just a trivial thing, but does anyone else think there should be a uniformity for the spelling of words within the article? Spelling "yogurt/yoghurt" both ways is cool and all, and technically correct, but I'm of the opinion that things like this distract from the article itself, and that's not cool. Thoughts anybody? RazingRazor (talk) 10:38, 19 April 2015 (UTC)

Agreed. And since "yoghurt" is a much more interesting spelling, why not let's use that one?Daqu (talk) 22:53, 9 May 2015 (UTC)

Big problem with article[edit]

A big problem with this article is that it treats lactose intolerance as a disease or disorder — exactly what the dairy industry would like you to think.

It is not a disease. Quite the contrary, almost all ethic groups other than Northern Europeans lose much of their ability to digest milk by the time they are 5 to 8 years old.

I do not dispute that some diseases may be associated with lactose intolerance. And I do not dispute that lactose intolerance may be inconvenient and undesirable for people who have come to enjoy dairy products.

Referring to "lactase deficiency" — rather than to the normal process of lessened lactase production as a child grows older — is one way that this article keeps up the misleading appearance that lactose intolerance is a disorder.

This article needs to be rewritten in a big way so as to dispel the misimpression it gives that lactose intolerance is a disorder.

From a section above: "Lactose intolerance] is thought of ... as a medical problem in Western countries where milk-drinking is the norm and there's a plethora of reliable sources that take that position. We can't ignore those any more than we can ignore the global anthropological/evolutionary perspective."

More udder nonsense! Just because many people including supposed authorities on marriage statistics have written that the chance of a woman's ever marrying if she is still single by age 40 is the same as her chance of being killed by a terrorist. There is no basis for this claim. And just as it should be treated as the myth that it is, the very same thing applies the the often-repeated lie that lactose intolerance is a disorder. (For many decades and perhaps longer, a common medical myth believed even by many physicians was that if one burned one's fingers, a good remedy was to smear butter on the burn. It turns out there is no truth to this. So, in cases where the medical community has failed to grasp some truth, there is no reason in the world that the same myth should be believed or disseminated by anyone else.

We have a huge responsibility when writing for Wikipedia to adhere to what is actually true and not perpetuate falsehoods. At one point I noticed a falsehood was being perpetuated on Wikipedia and wondered why. The references that were used for this claim in this article, as well as hundreds more websites that repeated the myth . . . all traced back to that Wikipedia article in the first place. We live in a big echo chamber. There are many special interests who are constantly trying to hijack the vehicle of Wikipedia to promote "their own version of the truth", or more accurately their own lies. We must try our best to avoid letting them do this.Daqu (talk) 23:52, 9 May 2015 (UTC)

Agree completely. This article has some european systematic bias. It's not lactose intolerance which is strange, it's lactase persistence! Anyway, some rewording should be done. (talk) 23:33, 4 August 2015 (UTC)

Adults or all people?[edit]

The lead says "inability of adults to digest lactose", but it also covers congenital LI. This is rather odd. I'm glad we have lactase persistence, but I think it's possible that this article should be replaced with "Congenital lactose intolerance" and "secondary lactose intolerance", and instead of primary lactose intolerance, "lactase persistence", cause that seems to be the most proper term. (talk) 23:49, 4 August 2015 (UTC)