Frequency of "Lactose Intolerance"

Recently my wife has developed what appears to be a case of lactose intolerance, where the body no longer produces the enzyme lactase necessary to break down lactose, the main sugar found in milk. I’ve done some reading up on the subject, and have come across many articles about how most of humanity is classifiable as “lactose intolerant”.

These articles often cite very similar and uncited statistics stating that the occurence of “LI” is something like 90% among people of Asian descent, 70% among people of African descent, and so on down to around 20% among people of European descent. There are often accompanying statistics about how the groups with the highest occurences (Asians and Africans) also typically develop the intolerance at earlier ages. The unstated assumption is that lactose intolerance is genetically determined.

There is simply no way that 90% of the Asian-Americans, 70% of the African-Americans, etc. of my acquaintance are lactose intolerant in the way that my wife currently is. I grew up in New York City, where dairy products are routinely consumed everywhere: cheese on pizza, butter or cream cheese on bagels, milk in Starbucks lattes (and provided every school day), ice cream from Mister Softee, etc. These foods were eaten across the entire ethnic spectrum of people I grew up and work with, which is pretty much the ethnic spectrum of the world. I don’t remember anybody having to scarf Lactaid pills or avoiding pizza due to lactose intolerance.

Even my parents, who immigrated from China in their 30s, can eat pizza or ice cream when the fancy takes them without running to the bathroom within a few hours.

This leads me to conclude one or more things are true:

[ul]These statistics were basically made up or based on dubious samplings at some earlier point in time, and have since been cribbed and propagated as fact without citation by various writers. (I understand that this accounts for up to 45% of quoted statistics on the Internet.)

[ul]The 90% figure for Asians and 70% for Africans is accurate for populations in Asia and Africa, and that the continued consumption of milk products throughout one’s life (as in a Western culture) is the main factor responsible for continuing to be able to produce lactase.

[ul]The definition of “lactose intolerance” used for the very high incidence rates is stretched out to the point of uselessness. Several sites mentioned that a milder form, “lactose deficiency”, generally meant that people could eat varying quantities of dairy without ill effect. If the litmus test is having a problem with drinking, say, a gallon of milk at a sitting, who really cares?[/ul]

Anybody with comments or insights?

Lactosed intolerance comes in many degrees.

Cheese and yogurt contain are more easily digested than raw milk. These items do not usually cause problems except in the most intense cases of LI. In addition, there is evidence that gently but frequently “challenging” the intolerance with lactose containing foods prompts the body to produce more lactase.

This site is well-cited on all these points:

I think you are observing that people have challenged their natural intolerance with very popular foods foods containing low levels of lactose. (Cream contains much less lactose than milk, ice cream is mostly cream, frozen yogurt is cultured, etc.) They would probably still feel sick if they drank a full glass of milk. This is certainly true of my level of lactoses intolerance. I’m fine with milk foods that are cooked or cultured. However in my teens I was much more intolerant than I am now.

Lactose intolerance is genetically determined. Among most mammals, lactase enzyme production is shut down during the weaning process. Lactose tolerant people have a mutation that results in the enzyme being made throughout their lifespans. As you’ve mentioned, this mutation is very common among Caucasians and very uncommon among Asians.

In America, where we’ve had a few hundred years as a melting pot, things have been mixed up a bit.

When lactose intolerance was first recognized in the 1960s as the base human standard rather than as an oddity, doctors and scientists went around the world doing studies of native populations. Although sincere and well-meant, these studies had a number of problems that became apparent in hindsight. They used too-small samples, used tests that could be administered in the field but were not as accurate as lab tests, and often used lactose loads that were so high as to cause reactions in even the most mildly intolerant people.

These tests were mostly done in the 1970s when the topic was a hot one. After they were done, LI dropped out of favor and the money to go around the world to administer LI tests to native populations disappeared. I’ve seen few studies in the past twenty years.

The standard compilation of these studies can be found in Nevin S. Scrimshaw and Edwina B. Murray: “The Acceptability of Milk and Milk Products in Populations with a High Prevalence of Lactose Intolerance,” American Journal of Clinical Nutrition, 1988;48:1080-1159. This report collects hundreds of previous journal reports and summarizes them in tables.

There is also no standard definition for “lactose intolerance.” There are about a dozen different terms used in the literature, each having some shading of different meaning. The most usual medical use of the term means someone who would test positive when given a lactose load in a clinical setting. This is not the same thing, as the OP notes, as actually having symptoms when consuming dairy products in the real world. The actual lactose loads of real-world products is lower than many people think. Cheese and butter are normally extremely low in lactose and some, like yogurt, are what is called auto-digesting.

In addition, the symptoms of lactose intolerance are produced two ways. Undigested lactose pulls water into the intestines, creating diarrhea. And undigested lactose can be fermented by bacteria in the colon, creating the gas that causes bloating, cramping, and farting. But many people have beneficial bacteria instead, which digest the lactose. These are the bacteria found in yogurt and other fermented dairy products and are easily obtained in many societies.

Nobody in the world knows just how many people are truly what the public conception of “lactose intolerant” are. The president of Lactaid once estimated his core customer base to be about 7 million in the U.S. or about 2.5% of the population at the time. This seems about right to me. I’m one of them, which is why I know a lot about it.

The largest LI site on the web is Steve Carper’s Lactose Intolerance Clearinghouse. It has a lot of the information you’re looking for on it, although in scattershot fashion. His book, Milk Is Not for Every Body, has more if you want to look deeper into the subject.

Lactose Intolerance is fairly widespread amongst Native Americans as well. As was mentioned, it manifest in varying degrees. I don’t drink milk, cheese causes no problem, and ice cream gives me a stomach ache. Ya know whut? I IGNORE the stomach ache for the rich creamy frozen goodness. Others I know can’t eat any dairy at all.


'Nother NA checking in. I didn’t go LI until I was about 30, but it hit me kinda hard at first, as I grew up consuming lots of dairy. However, I’m one of those that live culture yogurt works nicely for. Alternatively, taking either the Acidophilus capsules or the refrigerated lactase tablets from the pharmacist helps most people.

I have a friend who was LI to cows’ milk from babyhood, and to this day she can’t handle dairy. She will eat a bit of ice cream occasionally, and maybe a tiny bit of cheese, but mostly she stays as far away as possible. She’s the only one among her sibs with the problem; there’s not that much NA ancestry, but it’s on both sides, so she apparently got the wrong gene set from both parents. She also has other strong food sensitivities/allergies. She’s just lucky, I guess. :dubious:

Varying degrees… agreed. Hey, I’ve got problems handling too much ethanol, in excess. Doesn’t mean I don’t occassionally have a glass or two.

A cheeseburger - no problem. A glass of milk - well, it can get pretty fragrant, so I’ll try to keep outdoors, downwind. Or just drink black coffee instead. But no real discomfort, just slightly unpleasant for all concerned. An ice cream cone - sometimes yes, mostly no, besides leaving me with a very full feeling. So I’ll have my pie without (when come back).

Would I test positive for LI? Probably. Big deal? No.

A friend suffers from a different sort of lactose intolerance: she lost key bacteria from her digestive tract.

All the LI people I know–which are few–have been non-Caucasians.

I read something once that stated that people often don’t know they are LI. Maybe occassionally they will suffer GI problems from lactose, but because it doesn’t happen often, they never put two and two together.

I know someone who is LI who eats ice cream all the time, but stays away from cheese (no pizza) and milk.

I’m mildly lactose intolerant. The lactose has to be ingested in sufficient quantities for it to have the “need the bathroom right now!” effect. I’m fine with yoghurt, a normal-sized serve of cow’s cheese, goats cheese in any quantity, skim cows milk. Can’t be doing with too much ice-cream or too much full-cream cows milk. I only have milk with my cereal or in coffee, and then I use Lactaid milk at home or order skim-milk coffees when I’m out.
It’s not a major problem, because the only dairy products I like are hard cheeses and yoghurt, and good gelato, anyway.
I’ve been LI since I was about 15. It has gotten milder as I get older.

Sorry, forgot to add that I’m part Indian (as in Asian subcontinent Indian), so maybe it’s genetic.

My ancestry is European (mostly Italian) and I have varying reactions to dairy - cheese only bothers me in large amounts, ice cream bothers me more (but I’m also more likely to just put up with it, because I like ice cream), I have no problem with yogurt or butter, and I cook with milk sometimes with no noticeable effects. Straight milk out of a glass or on cereal… well, last time I tried that I ended up in the hospital with an intestinal blockage.

Both my brothers have genuine allergies to dairy (histamine reactions including difficulty breathing, hives, etc.) and my sister is more lactose-intolerant than I am. Weirdly, neither Mom nor Dad seem to have any difficulty at all.

I think alot of people don’t realize it. My entire (asian) family of 4 is lactose intolerant… I am the only one that admits it. I’m more intolerant then they are, but I can tell(unfortunately with my nose) that they are at least lactose deficient.

On another note. Lactaid is freaking great! The new Lactaid Fast-act works pretty much everytime for everything. I carry the stuff everywhere.

Isn’t it also possible that some people (immature brats) cultivate their lactose intolerance to make their poor, suffering siblings hate life even more? I know that when my brothers were teenagers, their main source of humor was drinking a quart of whole milk, farting in a bathroom and shoving my sister in there and blocking the door so she couldn’t get out, while laughing their heads off. Fortunately, they have outgrown this behavior.

Pizza? Cheese has very little lactose, as does live-culture yogurt and cream, so yes, it would stand to reason that someone who is lactose intolerant can eat pizza, yogurt, and ice cream with little problem.

Right—yogurt is ‘self-digesting’ because the lactobacillus acidophilus which initiates the curdling process in the first place has to break down the lactose in order to fuel its own activities. I’m a little fuzzy on exactly how cheese is made, but a similar phenomenon must occur in the cheese making process—I can eat cheese until it’s coming out of my ears, but I can tolerate only a half to three quarters of a cup or so of liquid milk before I’m trotting for the toilet. And as others have pointed out, human biochemical individuality plays an important role in a person’s response to lactose. I had a nutrition professor in college who had a friend who was so lactose intolerant that she would become nauseous if she sprinkled parmesan cheese on her spaghetti.

No, it’s a very different one. When milk is divided into Little Miss Muffet’s curds and whey, the whey portion retains nearly all the lactose (dissolved in the watery liquid). The curds are mostly casein protein. Even so, the actual cheesemaking process almost literally squeezes most of the remaining lactose-containing water out of the curds. Most aged cheeses, therefore, are very low in lactose.

The actual percentages of lactose in any given type of cheese can vary considerably, though.

The Really BIG List of Lactose Percentages.