(i’m not sure where to post this, but seeing as it’s a question, here it is.) quote from cecil’s column here
i’ve seen it mentioned a few times in this thread (Why Do People Drink Milk?) that most of non-europeans are lactose intolerant without any objections. so is this true or false? as far as i can see from the supermarket shelves milk is selling very well so the 90% figure surely do not hold water here.
or am i misinterpreting something? i assume lactose intolerant equals no more than a glass of milk for you.
I’m not an expert in this, but I think there are different degrees of lactose intolerance, and if you drink milk continously from childhood through adulthood your body might continue to make the enzyme, but if you stop drinking it for any significant length of time it will stop. Although in some cases it stops anyway.
I also think some milk products are less troublesome than others.
Most folks can tolerate trace amounts of the stuff, such as found in breads and baked goods.
Then there’s the whole issue of mixed-race folks - a lot of “blacks” in America contain a hefty dose of “white” genes, for example, so I would expect lactose intolerance would be more common in Africa than in Americans of (largely, but not exclusively) African descent. And some African tribes, such as the Masai, drink milk all their lives as a major part of their diet. Likewise, while most Asians in Asia historically did not drink milk past weaning, some groups such as the Mongols did (I think they were big on horse milk, though)
Latinos as milk intolerant? I would like some study about that because many people in Latin America have some European ancestor, which would make them more milk tolerant in general than Native Americans.
Are we including people from the Indian subcontinent as Asians? Because I don’t think I’ve ever met an Indian who is lactose intolerant, though I’m sure that there are plenty - but does the 90% apply here too?
Anthropologist Marvin Harris devotes a chapter to milk drinking and lactose intolerance in his book Good to Eat (aka The Sacred Cow and the Abominable Pig), citing studies that show that, at least until the relatively recent mixing of populations, folks in the Americas, Cgina, and a lot of sub-saharan Africa were largely lactose-intolerant. The folks that weren’t – Europeans, Mediterranean and Middle-East types, and cow-raising folk in Africa – on the contrary, drank a lot of milk. It all depends on whether you’ve domestcated cows or goats (or, in the cases of some nomads, believe it or not, use horse milk). Apparently it’s worthwhile to get calcium and fats from the milk of other animals, and people with milk supplies tend to breed for lactose tolerance.
(i.e. – if you can’t digest milk, you’re more likel;y to die). Now that people can travel and mix more freely, and can get nutrition in other ways, you can look for an unravelling of this. Might explain why my WEuropean-ancestored wife is lactise-intolerant.
Good thing you’re not an expect, because this is completely incorrect.
Primary lactose intolerance is a purely genetic condition (not a disease) that results from the gradual reduction in the production of the lactase enzyme that digests lactose. Once the reduction starts it continues, with no known means for restarting it or increasing its production. The gene that triggers the reduction is found on chromosome 2. It is this gene that is found in 70% of the world’s population and in its highest percentages in Asian, African, and Aboriginal peoples (including Australians and Native Americans). There appears to be a correlation between the age at which a population starts becoming LI and the percentage of LI in that population. For populations nearing 100% LI, the loss of lactase appears as early as the age of weaning. In Northern European populations, which low percentages of LI, the condition was first reported as “adult-onset LI” because there were so few known cases in children.
The classic study on percentages of intolerance is 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. It is actually a meta-study, examining every percentage study done on every population worldwide up to that time.
But, as stated, in the real world many peoples in these populations can drink milk and milk products without symptoms.
Why? Several reasons.
Low levels of lactase is not the same as no lactase. There may still be enough lactase produced to handle occasional foods with dairy products.
Many dairy products have naturally low levels of lactose. Butter and aged cheese have only 1% of lactose or less.
Some dairy products are auto-digesting. Yogurt, kefir and all other varieties of dairy that contain live bacterial cultures have the type of bacteria that manufacture their own lactase. There is almost always enough lactase in the food to digest the lactose in it.
And human intestines contain many types of bacteria as well. Some of these bacteria digest lactose, some ferment it. The fermenting kind produce the gas that is associated with the cramps and flatulence that plague sufferers of LI. But if the bacteria digest lactose then dairy products can be well tolerated even by those with little lactase. And the dairy foods with live bacterial cultures tend to colonize the digesting bacteria in the intestines.
The gene for continued lactase production is the dominant one. Mixed populations - and the world is increasingly mixed - will tend toward being able to have dairy. American blacks are already showing this.
Additionally, the percentages reported in studies may be wrong. Virtually all the population studies were done in the 1970s and early 1980s, shortly after doctors first realized that LI was a natural condition and not a pathological one (caused by problems to the intestines). There were no DNA tests in those days. The researchers gave subjects huge amounts of a lactose solution to drink and then tested the subject’s blood to see whether a spike in sugar appeared, indicating that the lactose had been digested and taken into the bloodstream. Non-digesters would show a “flat curve” of sugar instead of a spike.
But these studies are now known to be unrealistic (technically, there are not physiologic) meaning that they do not reproduce normal body conditions. A huge amount of lactose in water will hit even those with moderate amounts of lactase production like a storm surge in front of a hurricane. People who would not normally get symptoms from any usual meals would show symptoms from these tests.
Better and more physiologic tests have been developed today, but LI is a dead subject for grant funding: nobody will ever get the money to go out and test all the world’s populations over again.
So we don’t know. Maybe when everybody’s DNA is encoded into an identity chip we’ll have a database that will reveal the true percentages. In the meantime, researchers distinguish between LI, a condition in which people show symptoms after ingesting dairy, and such names as lactase deficiency or hypolactasia for those who have reduced lactase production and may or may nor show symptoms.
Just to cover all the bases, I should throw in that there also exists “secondary lactose intolerance” which is pathological: any of a hundred types of damage, disease, surgery, drugs, alcoholism, etc. can stop lactase production. Production can sometimes come back when the intestines have healed, but the lack is sometimes permanent. These people will normally show symptoms from any amount of dairy. Of course, secondary LI is independent of ancestry.
Well, no - the difference is I condensed a complex subject into a sentence or two, and you went and eleborated on it for paragraphs.
I never said lactose intolerance was a disease, and if you read my posts it should be clear that inheritance is involved. You even provided an explanation of why intolerance might increase after ceasing to consume dairy products - if you consume things like yogurt with colonizing bacteria, then stop, you might lose those colonies and therefore some of your body’s ability to handle the lactose.
Not a good ethnic choice to demonstrate this, as so many African populations retain the lactase production into adulthood - the American blacks not only mixed with Whites and Native Americans, they also mixed people from different tribes. More illustrative of this would be Mestizo or people mixed Asian descent.
Ugh! What a horrible, horrible thought! The idea that human “identity” will be reduced to numbers in a database, even numbers based in genetics, makes me want to vomit. Genes are not the sum total of a human being!
All in keeping with my statement that there are different levels of intolerance.
OK, Broomstick, if you really want to nitpick, let’s go to the mats.
Your original quote was:
In other words, enzyme production depends on continued milk drinking. This is what I said was wrong. And it is certainly wrong, as all studies on this have shown it to be false.
This is also an entirely different physiological function than bacteria in the colon producing lactase. You can’t just switch over from one to the other and say, see, I was right all along.
Only a tiny number of African populations retain lactase production into adulthood. And all of them are groups or tribes who have a cultural need for dependency on milk that allowed the spread of the mutation that results in lactase persistence. The number of American blacks who are descendants of these particular tribes is minuscule.*
Like every other bit of technology ever produced in all human history, DNA mapping will allow for some beneficial applications and some detrimental ones. There is nobody alive who has any idea of what the percent of each will be.
*Cites: On nomadic milk-drinking tribes: Gebhard Flatz, “Genetics of Lactose Digestion in Humans,” Ch. 1 in Advances in Human Genetics, Harry Harris and Kurt Hirschhorn, eds. NY: Plenum Press, 1987. On lactose tolerance percentages in Africa, either the Carper book or the Scrimshaw & Murray paper it uses as the source for its tables.
are you saying the percentages quoted in the OP is wrong because it’s based on a faulty study, but it is still generally correct since LI is subject to your gene makeup as opposed to adaptation?
does the existence of these lactose digesting bacteria account for the large number of non-europeans drinking milk? i’ve skipped your other reasons based on the assumption that milk is selling well, so people must be drinking lots of it; and that the mixed population is still a minority.
Something I ran across online a couple of years ago that seems to be relevant to this discussion. Apparently, somebody studied the genetics of human ethnicities and found that there are 5 races. One of these includes Europeans, Middle Easterners, North Africans, and people of India. (Of course, the phylogenic tree is an oversimplification because there has been so much interracial breeding over the millennia.)
I would really like to cite the page, but I found it before September 2001 and when I went back looking for it after September 2001 it had conveniently disappeared.
Anyway it looks to me like the ability to digest milk arose in the common ancestor of all these people.
The one thing that phylogenetoc trees tells us with great certainty is that here is no evidence thatthere were ever separate human races with anything remotely approaching discrete breeding, over the millenia or over hundreds of millenia. There are not 5 races, there are not 4 races. Genetically speaking there are no races.
I’m saying that the percentages reported overall may be too high to reflect the prevalence of LI in normal physiologic situations - in other words, having dairy products in moderation as part of a meal is known to produce far fewer and milder symptoms than drinking a glass of lactose solution.
That’s one reason why Asians and other groups probably can have dairy. Bacterial digestion may be another. Nobody knows for certain because the formal tests necessary have never been carried out.
OTOH, my understanding from much reading is that the consumption of dairy products in Asia and Africa is far lower per capita than in northern Europe or the U.S. With increased used a threshold may be reached and symptoms may become more common. Regular milk-drinkers in every culture are a self-selected minority.
aryk29, while you’re wrong on the issue of race, on cultural terms you may be correct. One school of thought is that the same farmers who brought the Indo-European languages up from the Caucasus/Middle East to northern Europe also brought their lactase persistent genes and their low-lactose varieties of dairy - butter, yogurt, kefir, cheese etc. Once in the north, the ability to drink milk and get an adequate supply of calcium selected for those who had the lactase persistent gene. Again, this is controversial because there is simply not enough information about these time periods to say anything solid.
