August 25, 2012

Lactose tolerance favors obesity

While the lactose tolerance allele may have some positive health effects, notably because milk is one of the few good dietary sources of calcium, it seems to correlate also with some negative effects, namely obesity.

Ricardo Almon et al., Association of the European Lactase Persistence Variant (LCT-13910 C>T Polymorphism) with Obesity in the Canary Islands. PLoS ONE 2012. Open access ··> LINK [doi:10.1371/journal.pone.0043978]

Canary Islands, in spite of its subtropical geography, is one of the regions of the European Union where milk is most consumed, at levels comparable to Scandinavia. 

Although there is a strong correlation between being lactose tolerant and milk consumption it is not fully clear yet if it is excess milk consumption what makes people obese or an unknown collateral effect of the European lactase persistence allele.

Interestingly the correlation, very strong, is only found for obesity and not for being overweight:

Fig. 1 - BMI classification by LCT genotypes (LP: n = 330; LNP: n = 221)

8 comments:

  1. Nonsense. It's the calories.

    The highest rate of diabetes in the US is among the Pima Indians of the US (in contrast to the low rate among the Pima Indians of Mexico). Both groups are lactose intolerant, but have a different diet, thanks to American government food subsidies.

    So one wonders if many in the Canary Islands who are lactose intolerant can afford other sources of protein or high calorie foods... Are the lactose intolerant descendants of the Arab/Berber immigrants poorer than the Spanish/European descended population? Do they eat a high fish/fiber/bean diet of their ancestral home rather than European type foods?

    Was the study only among the native Canarians, whose genetics are different?

    and how much of the milk is eaten as yogurt, which can be tolerated by many with lactose intolerance?

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    1. Sorry, Boinky, but Blogger Spam Filter sent your comment to the spam folder again. Nothing I can do but to approve it ex-post-facto, as I did.

      Notice that this paper does not deal with diabetes but obesity, related maybe but different illnesses (actually I recently learned that diabetics lose weight initially in fact). It should also be caused by things totally unrelated to milk consumption, for example fructose syrup consumption in sodas and bakery.

      Also to have the known "European" lactose tolerance allele is not synonym of being lactose tolerant, much less vice versa. For example Central Italians only have the genotype at the frequency of 21% but they have the phenotype at the level of 82%, instead among Tajiks the genotype is as high as 51% but actual lactose tolerants are only 18% - see here.

      Said that, I'd agree that the percentages of people without the genotype seem rather high for Spain's levels and that may be caused by Guanche blood (North Africans have lower levels of the allele than Spaniards).

      "Was the study only among the native Canarians, whose genetics are different?"

      Nobody knows anymore who are "Native Canarians", as you say. The blend was completed long ago and now there are just Canarians. You can read the details in the link anyhow, because it is an open access paper, no particulars are reported anyhow.

      "and how much of the milk is eaten as yogurt, which can be tolerated by many with lactose intolerance?"

      The paper only mentions high consumption of "milk", no mention of dairies in general. Milk usually means unprocessed milk. What is less clear is how much of it is low fat and how much is full. The paper only mentions this high consumption in a few lines comparing it with Norway and close to Sweden. You can research the source yourself, if you are so interested.

      Milk is used, mixed with beer, among the Dinka of South Sudan for "fattening contests" which usually end up killing the "winner". It's therefore no surprise for me to find that milk can be a cause of obesity, after all full milk has more than 30% of fat (dry residue), and that's a lot of fat (WHO recommends not eating more than 20% of fat but the healthy levels should probably be set quite lower, specially for high calorie diets).

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  2. Sorry in advance for commenting on an old post.

    One thing I've never heard mentioned regarding L.persistence and obesity (it's not "lactose tolerance"; everybody is "tolerant") is the nature of the selection process.

    The effect of lactase persistence is the access to sugar in milk. For a group to evolve this trait, they must have been starving for calories.

    Thus, if we have two dairying groups, the one which is constantly on the brink of starvation will evolve to be lactase persistent. The well-fed group will have no reason to evolve the trait; most modern Japanese can handle a few glasses of milk per day, so any benefits from solely milk consumption will be experienced by all groups.

    Empirically, I think this looks true for europe. Northwesterners (anglos dutch etc) seem to have higher obesity rates than easterners (slavs). NWers also have more hemochromatosis and subclinical iron overload, which is something that would have evolved in proportion to milk consumption (calcium inhibits iron absorption, necessitating higher baseline levels).

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    1. Well, if you lack lactose tolerance, you just can't eat non-fermented dairies of any sort, because it gives you tummy issues like diarrhea. So it's not just about the sugars but also about the fats and proteins (and calcium, milk is about the only food that is calcium-rich in the calcium/phosphorus balance theory) that are available in milk and derivatives such as non-hard cheese and such. Many cultures developed fermented alternatives such as yogurt (Turkics), buttermilk (Arabs, Berbers) or hard cheese (Italians), among many others, but in Western Europe it seems the solution was rather to adapt biologically... or die trying.

      Alternatively, and this should be considered very seriously because genetic facts do support it, a Basque-like population expanded from approx. France in the Chalcolithic with that pre-existent genetic trait and made it overwhelming: i.e. there was not so much "selection" but "founder effect".

      In any case milk is a great source of calories, but not just for the sugar: fat and protein are surely much more important, the problem with lactose (the sugar) is that, unless you can digest it, it gets in the way of nutritionally exploiting all the rest of the milk.

      English people do not have high obesity rates at all, there seems to be a rather sharp cut between Britain and continental NW Europe in several aspects and one of them is this trait (notice that white US-Americans are rather German than British by ancestry, although both, and that is very noticeable in traits like this one, also height). French are also in the lean and short side of things, of course diet is suspected to be important in the overweight issue, because if you eat "properly" rather than just sausages, hamburgers, pizza and doritos, then you are more likely to remain lean and fit. The English are well known for eating a lot of fish (since Vikings only but they do now anyhow) but they also have paladins of easy quality nutrition like that famous TV chef whose name I can't recall right now, the French do have the custom of small servings and a good deal of "Mediterranean diet" (although also a lot of cream). Diet is important here, although I'd say that the North-Central continental (and Scandinavian) region of Europe has a tendency to oversize: in height only if healthy diet/sporting or also in width if not-so-healthy. So you get "curvy" Angela Merkel in Berlin but "bony" Theresa May in London (not any coincidence because there is a pattern beyond those two examples).

      "calcium inhibits iron absorption": that's new for me. I'm more used to the "old" theory of calcium/phosporus balance, in which milk is about the only food that is rich in calcium (also dried figs it seems), while other animal food is phosphorus-rich (veggies are rather balanced), this phosphorus imbalance was supposed to cause osteoporosis issues, as well as aid the development of cancer. On the other hand if you have iron absorption issues you should get anemia, right?, and that's not an issue for most people.

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    2. "Well, if you lack lactose tolerance, you just can't eat non-fermented dairies of any sort, because it gives you tummy issues like diarrhea."

      That's simply not true. I can find the studies if you wish, multiple ones done on Japanese people and African Americans, finding that the majority can drink one or two glasses of milk a day without issue, provided gut bacteria adaptation. I think this is also the reason so many ancient steppe males come up as lactose "intolerant" (aka really just lactase nonpersistent, and even then only judging by the known alleles which are flawed)

      Multiple studies also show that there is a drastic difference between what is clinically considered lactose intolerance, and what is actually symptomatic (aka diarrhea, gas) lactose intolerance. The claims of intolerance are massively inflated; the majority of people are lactose tolerant, only a minority (Arab, India, Europe, Africa) are lactose digestive.

      That's not to mention that other fresh dairy products (fresh cheese, butter, cream) have much less lactose because it's water soluble.

      Perhaps the typical Japanese wouldn't be able to drink a half gallon challenge, but two glasses of milk in a day would be no problem at all--empirically proven by anyone who's seen Japanese school lunches (kids lose lactase ability very quickly). And realistically, there's no nutritional advantage to drinking much more than that.

      The British Isles do have high obesity rates compared to the rest of N.europe. A simple google search confirms this, although maybe it's not the English exactly, and rather the more Celtic descended peoples, idk.

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    3. https://www.ncbi.nlm.nih.gov/pubmed/21462112

      Calcium inhibits iron absorption, both heme and nonheme, and NW Euro populations have the highest hemochromatosis incidence, at 0.6%: https://en.wikipedia.org/wiki/Iron_overload#Epidemiology

      In an obscure paper I can't find right now, 10% of American whites had subclinically high iron levels, though I don't know if diet was controlled for (whites probably eat more ruminant meat).

      The logical conclusion is that a high-milk, and therefore high-calcium diet, would have selected for this. With Britain being the epicenter of obesity, lactase persistence, and hemochromatosis in northern Europe, it seems logical that these things had some interselection with each other.

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    4. I know the experience of lactose intolerance can vary, and that tolerance can be developed, but I've also met people who were lactose intolerant (very oddly so, as both his parents were tolerant) and just didn't want to even try milk at all, once they identified their issue. In ancient Rome raw milk was considered a purge, not a food, at least not for adults.

      As for iron overload, the article you linked to explains that it is hereditary and that, even in the most affected areas, only affects half percent of the population, what is a very small fraction in contrast to the almost 100% who are lactose tolerant. Also the article says nothing about calcium being involved: it's genetics, blood transfusions, excess dietary iron, hormonal issues, etc. but not a word about calcium. So IMO, in general calcium is a good thing for bones and the overall metabolism (although calcification of parts of your brain is not good, this is not caused by "excess calcium intake").

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    5. By "the article you linked to", I meant the Wikipedia article.

      The other one says: "a thorough review of studies on humans in which Ca intake was substantially increased for long periods shows no changes in hematological measures or indicators of iron status."

      Also it'd be about iron underload ("Fe decificency"), not overload, i.e. about ANEMIA.

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