Ever wonder how people who are lactose intolerant get enough calcium in their diet? · 3:38am Aug 2nd, 2017
I was wondering this earlier today.
So I googled it.
Turns out the answer is they don't:
Here we show that, in 2011, 3.5 and 1.1 billion people were at risk of calcium (Ca) and zinc (Zn) deficiency respectively due to inadequate dietary supply. The global mean dietary supply of Ca and Zn in 2011 was 684 ± 211 and 16 ± 3 mg capita−1 d−1 (±SD) respectively. Between 1992 and 2011, global risk of deficiency of Ca and Zn decreased from 76 to 51%, and 22 to 16%, respectively. Approximately 90% of those at risk of Ca and Zn deficiency in 2011 were in Africa and Asia.
For reference, an adult is ostensibly supposed to have an intake of 1000+ mg/day of calcium, so we're a bit short.
Another fun one:
In 1992, there were two countries in East Asia where most of the population is lactose intolerant that had significantly higher calcium intake than the rest of the lactose-intolerant world. By 2011, two other countries had joined them. Guess which countries they are?
If you guessed Japan and South Korea. with China and Mongolia joining them, give yourself a pat on the back.
Left is 1992, right is 2011. Behold the power of global nutrition initiatives! Now a mere half of the population doesn't get enough calcium! Success!
Oh, and incidentally, despite the overwhelming majority of the Mongolian population being lactose intolerant, the Mongols still manage to drink lots of milk (the Chinese, Japanese, and Koreans get their calcium from other sources - soy/tofu has quite a bit of calcium in it, as does bok choy):
Why?
Because...
Wait for it...
You don't actually have to watch the whole video, I just had to make the Crash Course World History reference to them being the exception.
You might wonder how this is possible.
The answer is that they drink fermented milk (yes, gross, I know), which is actually a traditional Mongolian drink which died out quite a bit under the USSR and then had a resurgence afterwards, in part due to promotion from various figures (including the Dalai Lama of all people) in the hopes of displacing vodka consumption. Fermenting milk reduces the amount of lactose in the product, allowing a lactose-intolerant person to consume it - this is why the Japanese can still eat stuff like cheese.
However, this distribution of calcium intake got me thinking. Here's a map of countries by lactose intolerance:
Here's a map of countries with advanced economies according to the IMF:
And if we think about historical empires, the soy-eating Chinese and the fermented-milk swilling Mongols and Turks were both pretty powerful.
I'm starting to wonder if maybe we're not giving calcium nearly enough credit.
I don't think it's the calcium per se, but more the fact that people of Caucasian descent tend to be mostly lactose tolerant, and a lot of those countries with advanced economies also have Western cultures and majority Caucasian populations.
Japan is the big exception, but their economy post-WWII is modeled on emulating (or trying to do even better) what made the West an economic success through industrialization and technology, so it stands to reason that it would also be considered advanced.
I think we could also look at some examples of advanced civilizations in pre-Columbian South America - people like the Maya, the Inca, and the Aztecs. They built impressive empires pretty much across the continent (possibly large and populous enough to actually exceed the carrying capacity of the land, which is fairly impressive if somewhat tragic in its consequences), but were almost certainly very lactose intolerant and may have had relatively calcium-poor diets.
In this day and age, we can simply take supplements - there's really no excuse for not getting enough calcium...
I feel like i should shoot Plumander a message and have her read your blog post. She seemed quite taken on the conversation about dairy products that went on in the comments section for 2 + 2 = 5.
This could almost be a sequel to that.
(and, y'know, that was actually some pretty cool info to dig up and share. i like learning offbeat facts like these - thanks!)
4620960
Oh, sure, be boring.
Obviously the real explanation is that the Eurasians kicked everyone else's butts, but the question of "Why did the Caucasians win?" is an interesting one.
Is calcium really the answer? I doubt it.
But it is an interesting coincidence.
Obviously not all advanced societies are associated with calcium - I don't think that the Aztecs or Ancient Egyptians got a whole lot of calcium - but on the other hand, the Aztecs were basically a stone-aged society which then went up against a bunch of guys on horses (which they didn't have) with metal armor (that they didn't have) with guns (which they didn't have) and lost.
And then they all died horribly of smallpox and cocoliztli afterwards.
Interestingly, there is some minor evidence that the Inca may have made some use of llama milk and cheese, and llama milk actually has a higher calcium concentration than cow and goat milk does.
Still, I doubt that calcium really explains all this.
That said, the correlation is interesting. Of course, another possibility is that more advanced civilizations are more able to consume large amounts of calcium, so the cause and effect is actually reversed (i.e. greater prosperity = more calcium). This would make some sense for places where milk isn't a staple, so greater prosperity makes it more possible to divert more resources to milk production.
4620980
Well, feel free to give her a poke!
And I'm glad you found it interesting, at least. I find it an interesting coincidence, though I doubt it is actually secretly the metal that has determined the fate of mankind.
EDIT: I forgot I was even involved in the milk discussion on 2+2 = 5. I didn't even remember it, but judging by my response, I was particularly condescending that day. I guess for me, it was Tuesday.
Also, neat little factoids there, with an interesting (if tenuous) conclusion.
4621018
It is a fun thing to muse about.
I doubt it actually has much explanatory power, even though calcium has a major impact on brain function. It is more likely something which coincidentally correlates with some actually important thing.
So you're saying that Equestria owes its high level of culture and material advancement to Applejack's share-milking cow tenants?
Just to add on, the fact that we evolved in a way that so much of the population doesn't get enough calcium would suggest to me that our pre-human ancestors (Homo erectus, et. all) or very early humans had some quantity of calcium in their diets, which later dietary trends lacked.
Which is really weird.
Why am i so perplexed by the country of Niger being aparently lactose tolerant compared to well the rest of Africa?
What happened there to make it stand out so much from the rest. :?
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4621020
I was reading something the other day about human evolution. Lactose-tolerance generally appears and spreads in a given human population after they become capable at livestock-farming (and thus get access to large amounts of milk). I'd place my bets that the correlation of calcium to advanced civilisation is more about the development of advanced farming techniques (which the Chinese would also need to develop to grow all that soy).
4621057
I wonder if it was bone? Fish bones, bonemeal et al.
4621057
4621080
Actually, this is likely a case of human ancestors being chronically malnourished by modern standards, and an issue of what "malnourished" really means.
Average human height increased by four inches in the last 150 years. This is obviously impossible from a genetic standpoint; there's no way for the entire population to spontaneously mutate to be 4 inches taller, and everyone does not share a common ancestor within the last 150 years.
The actual cause of this is likely a combination of better nutrition and less infectious disease. It is also suspected to play a role in the Flynn Effect, which is the increase in IQ by about 3 points per decade in developed countries.
There is no particular reason to believe that human ancestors were operating at their genetic maximums; indeed, we know that even modern humans do not. Caffeine, amphetamine, and nicotine can all boost human performance in various ways beyond what is natural, and caffeine doesn't even have any known long-term negative health effects (indeed, some studies suggest it may help people live longer, healthier lives). This isn't because humans evolved to be able to use these substances, but because they happen to work in various ways that makes humans operate better.
Thus, the majority of the global population not getting enough calcium may be more of a situation of "getting more calcium makes humans operate better, so that is the new standard because everyone else is substandard by comparison to those who do".
It should also be noted that human ancestors had smaller brains and generally smaller bodies, so didn't require as much calcium as modern humans do.
Incidentally, according to the Wiki article, several alleles linked to lactose tolerance appear to be extremely strongly selected for, which would suggest that there is a very large evolutionary advantage to being able to digest lactose in adulthood.
4621075
The Fulani people are cattle herders, and have been for ages and ages. Apparently they had the lactase mutation at some point in the relatively recent past, and so can digest lactose through adulthood. Note that there are actually multiple known lactase mutations; the European lactase mutation is thought to come from the Funnel Beaker people or thereabouts. The East African lactase mutations (there are actually three of them) are independent mutations which are of more recent vintage. The Middle Eastern one is yet another distinct mutation.
Also, it may not be as much of an outlier as that map indicates; other maps show a smoother distribution in the region, so it may just be a data set issue. However, Wikipedia article about lactose tolerance notes that lactose tolerance is extremely "patchy" in Africa, with nearby groups having wildly different rates of lactose tolerance, and certain pastoralist groups having very high rates of lactose tolerance. So it is possible that whatever source that map sampled from sampled from a lactose tolerant pastoral group in Niger and not in other countries, and thus happened to make it look like Niger is super good at drinking milk.
4620985
Weren't Europeans so thorough in taking over North and South American because diseases whipped out the population first?
Wanna consume calcium without drinking milk? There’s an app for that.
I'm guessing this is more about calories than calcium. When the lactase genes first showed up, the peoples who had that mutation had a HUGE new source of calories available. Those people then had a survival advantage, and pretty much took over the world from there, so the most successful societies today are largely lactose tolerant.
Also, fun fact, the Mongolians' fermented horse milk starts with a lot more lactose in it. Cow's milk doesn't have enough lactose to grow the microorganisms we think of as traditional fermentation, but horse milk does. That's why horse milk can get lightly effervescent, as well as become alcoholic.
4620985
The Spanish at that point used boiled leather armor, primarily. Completely irrelevant point, but boiled leather is a fascinating material, with a wide variety of properties depending on how you boil it.
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4621080
Eggshells are a significant source of calcium for many omnivores, which would have included early humans. Also, eating carbonate minerals is not unheard of, even today. Especially among pregnant women who get uncontrollable cravings for eating "dirt" when they don't have enough calcium.
4621094
That's a really interesting theory to read about. I live really close to where the Cahokia mound builders had an enormous city... which died out just before Europeans showed up. According to this theory, most of North America was something between a low-impact farm and a managed wilderness, with vast forests of American Chestnut producing staple quantities of carb-heavy nuts, and carefully-conserved herds of game animals. Continent-wide trade networks that reached well into the Caribbean sea, spreading culture, technology, food, artifacts... and disease.
To what degree that's true, I don't know. But it's interesting to think that the European settlers walked into Fallout: Native America.
4621094
The conquistadors actually conquered the two most important civilizations - the Aztecs and the Incas - when they were at the height of their power. It was only in the half century or so after the conquistadors took over that disease decimated the population of Mexico.
It should also be remembered that the conquisators actually allied themselves with other native groups to win; the Aztecs went down because, as it turns out, everyone else in the region wasn't overly fond of the idea of their hearts getting cut out and their bodies being thrown down their pyramids and they figured that the Spanish were a better alternative. The Inca, too, had recently subjugated groups used against them.
4621102
North America was simply never heavily populated to begin with; Cahokia was the largest city north of the Rio Grande but never had more than 20,000 people in it (and even that may be an overestimate), and it was gone before Columbus got here. The people who lived in North America didn't really have very advanced technology or agricultural techniques, which prevented them from building large cities in the first place; the Iroquois, who were one of the major powers there, had to move their villages every 4-20 years because their farming techniques quickly exhausted the local soil, forcing them to move, and they were relatively sedentary by comparison to many of the other peoples. The Comanche, who were a fairly powerful and dangerous group, were hunter gatherers, and despite being powerful for a Native American tribe are estimated to have had peak population of only 45,000 in the 18th century. The people in the Pacific Northwest were sedentary hunter-gatherers.
They were all stone-aged people, though they quickly adopted horses and European weaponry where available. They didn't have the infrastructure or wherewithal to actually produce said technology themselves, though; they had to trade for gunpowder and firearms, which made them critically dependent on the European colonists. This meant if they ran out, they needed to trade for more, and when the French got the boot, and the English stopped supplying them after the War of 1812, they were pretty much screwed when they got into conflict with the Americans as they had no ability to manufacture such things themselves (though they did have develop some ability to repair weapons by the end of the Indian Wars).
The reason why all the big cool ruins are in Mesoamerica and South America is because the North Americans were relatively primitive by comparison and their technological base simply did not support building big, persistent cities. The Pueblo people built some stuff, but it simply wasn't nearly on the scale of their neighbors to the south.
There are probably more Native Americans in the US today than there were when Columbus got here; some estimates suggest that as few as 500,000 Native Americans lived in what is today the US when the Europeans came, and it is very unlikely there were ever more than a few million.
4621094
Again, this goes back to agriculture and ultimately geography. Europeans, throughout the development of agriculture, acquired then gained some degree of immunity to various diseases from animals they domesticated (e.g. cowpox became smallpox), whereas societies lacking domesticated animals did not acquire such diseases. Thus, when Europeans meet Native Americans, European diseases helped to wipe out the Native population whereas the opposite did not occur to as great an extent.
Why did agriculture and domesticated animals arise mostly in Eurasia and not other areas like the Americas or Africa? Ultimately, the answer comes from geography and evolutionary biology. Humans co-evolved with other mammals in Africa, so most African mammals evolved to be warry of us. (This explains why horses can be domesticated but not zebras). On the other hand, by the time humans migrated to the Americas, humans had evolved to the point that they could easily hunt most domesticatable species to extinction. Humans migrated to Eurasia at just the right point in their evolution to be able to domesticate many species in Eurasia.
These arguments come from a fascinating book on the subject, Guns, Germs and Steel by Jared Diamond. As a biologist, I loved seeing evolutionary biology being applied to understand history.
4621111
Guns, Germs, and Steel is kind of a giant pack of lies, though.
The idea that Europeans had some sort of super disease immunity isn't true - death rates from smallpox actually were about the same in European and Native American populations. Likewise, the Native Americans did, in fact, have horrible diseases of their own - Cocoliztli killed more people in Mexico than smallpox did. It is likely that the disease never crossed back over to Europe not because of special immunity, but because its host species (thought to be the Vepser Mouse, which is a known carrier of several hemorrhagic fevers) is indigenous to the Americas but not Europe.
Likewise, the argument about domesticated livestock is just incorrect - the Native Americans did in fact have a number of domesticated animals, in the form of dogs, guinea pigs, llamas, alpacas, turkeys, and the like. They never domesticated reindeer, even though the Siberians did so with the same kind of animal, and they killed off the mammoths and horses - but so did the Europeans. In fact, the ancestor of the domestic cow and the domestic horse are both extinct. The Native Americans never domesticated buffalo, while the Europeans did the aurochs, despite there being little evidence that either species was more tractable than the other.
While the Native Americans lacking riding and plowing animals probably damaged their tech level, it is hard to argue that this was because such things were not available to them. Indeed, it is worth remembering that the cow and horse were actually domesticated well after humans colonized North America - the Native Americans got here about 15,000 years ago, but cows were only domesticated 10,000 years ago, and horses perhaps 5,000-6,000 years ago. Indeed, when humans colonized North America, the only animal that had been domesticated was the dog - which the Native Americans brought with them.
Diamond's arguments just don't hold up very well under scrutiny.
Well this discussion was an interesting read.
I didn't think the Philippines was lactose-intolerant. If anything, the lack of milk consumption could be attributed to the fact that that stuff is expensive to people who are at the bottom of society making $2 or less per day. Those mostly consist of very cheap instant ramen (a couple of pennies per pack) and cheap canned sardines.
Source: I'm a Filipino living in the boonies of the Philippines and working with the local equivalent of Adirondack power plant blue collar personnel who fit that description.
4621127
Diamond's hypothesis certainly is an oversimplification, but it does a good job of explaining certain key aspects of history. While there probably is some debate over the extent to which disease was a factor in European colonization of the Americas, it is certainly true that there were many more diseases passed from Europeans to Native Americans than the other way around. The earlier advent of agrarian society—both because of the greater contact with animals to pick up new diseases and the greater population densities to enable new diseases to evolve and become endemic in the population (i.e. evolve efficient human-human transmission rather than animal-human transmission)—certainly contributed to this asymmetric exchange of diseases.
While it is true that there were some domesticated animals in the Americas, the fact that the Americas lie on a North-South axis helped to constrain the spread of these animals. Because of the different climates and other geographic barriers, domesticated alpacas could not spread far from the sites of domestication in the Andes. In contrast, Eurasia has a large East-West axis which facilitated the spread and exchange of domesticated plants and animals across the continent (for example, you could have wheat domesticated in the Fertile Crescent along with horses domesticated in the Eurasian Steppes). Similarly, because of their natural climates reindeer domestication would not have been useful for the establishment of large agrarian societies in the Americas.
With regard to the timing of domestication, I think you are misunderstanding the argument. Animals in Africa had co-evolved along side with hominids since the time when hominids arose, giving these animals plenty of time to evolve behaviors to resist hunting and domestication by humans. Hominids (such as the Neanderthals and Denisovans) had migrated to Eurasia prior to modern Homo sapiens, giving some time for animals in Eurasia to co-evolve with hominids prior to being settled by Homo sapiens. In contrast, no hominids existed in the Americas prior to the arrival of Homo sapiens, which is how many of the large animal species in the Americas could go extinct faster than they could be domesticated.
4621655
The problem with this argument is that it doesn’t seem to really explain anything. Why did the Americans fall behind? Why didn’t they develop densified cities until later? It wasn’t because of a massively earlier start in the Old World for agriculture.
American agriculture began about 7,000-10,000 years BP, which isn’t substantially different from Old World agriculture, which began around 10,000-12,000 BP in the Fertile Crescent, and more recently elsewhere. In the Americas, maize was domesticated around 9500 BP, squash somewhere in the range of 8,000-10,000 BP, and potatoes and cassava between 7,000 and 10,000 BP. By comparison, China’s agriculture began about 8,000 BP, Egypt around 7,000 BP, and Europe got it around 6,000 – 8,000 BP, depending on the region.
The Americas, then, had agriculture as early or even before many parts of the Old World, and yet did not develop as advanced of civilizations. Moreover, the Egyptians only had farming for a few thousand years before they became one of the most important ancient civilizations – the Egyptian Baradi culture dates from perhaps 7,000 BP, and by 5,000 BP, the Egyptians developed writing and started building pretty significant structures. It took until about 3,400 BP for the Americas to cough up the Olmecs, and until about 2200 BP for fully developed smelting to appear in the Moche culture.
Differences in the date of agriculture starting don’t line up with this at all.
Moreover, the denser civilizations in Europe took a long time to spread – places like Britain were the hinterlands even during the Roman Empire, which was after the days of the Olmec civilization. Why did the British go from a bunch of barbarians to a world-dominating superpower in 2000 years while the Native Americans saw far less progress?
The problem with this argument is that it doesn’t seem to have stopped people from doing it in the Old World. Africa posed huge geographic challenges, but domesticated animals still came to sub-Saharan Africa from Eurasia. The Nok culture of modern-day Nigeria possessed horses, for instance, more than 3,000 years ago. The sub-Saharan Africans came to possess cattle from the Near East as well in very ancient times. Sub-Saharan Africans also acquired chickens somewhere around 1500 BP, goats around 4000 BP, and sheep by 3000 BP. Likewise, the Greeks acquired African-domesticated guineafowl by 2500 BP, and guineafowl were so heavily traded by the Turks that they came to be known as turkey-cocks and turkey-hens – which is, of course, how the North American turkey got its name.
Thus, even though there were jungles and deserts between them, the Africans and Eurasians still managed to spread their domesticated livestock across it well before modern times. This makes it hard to accept the argument that the north-south axis was really primarily responsible for this issue.
Indeed, trading across Eurasia itself was far from easy, given the gigantic deserts, mountains, and jungles in between East Asia and the rest of Eurasia.
It isn’t a particularly coherent argument, though. You can’t simultaneously argue that being around humans made African animals unsuitable to domestication while it made Eurasian ones suitable for it; they’re contradictory arguments. Moreover, there’s no particular reason to believe this is even the case.
No one ever bothered to domesticate zebras, for instance, but that doesn’t mean it is impossible to do so; indeed, people tamed zebras way back in the day. But why bother domesticating zebras when you have horses? Cheetahs were never domesticated either, despite being pretty docile creatures which get along with people pretty well – but why bother with cheetahs when you’ve got dogs? The Africans didn’t do a lot of domestication, but that doesn’t mean that they couldn’t have, just that they didn’t.
It isn't like the Native Americans didn't have any macrofauna suitable for domestication, either. They never bothered domesticating things like buffalo, mountain goats, elk, or reindeer, the last of which was something which people did domesticate in Eurasia (and buffalo and elk are today being domesticated). And it isn’t like the Eurasians didn’t drive things to extinction themselves; humans in Eurasia drove a lot of macrofauna to extinction, including the ancestors of both horses and cows, as well as the giant ice age mammals up in the north.
Diamond’s argument is for geographic determinism, but it doesn’t actually hold together.
See, this runs into some weird territory with food history and, well, 'actual' history, and ... stuff.
Basically, what it comes down to is that when you have a lot of land, but not very many people, it's more efficient to develop livestock than it is to subsist on plant agriculture. To terribly simplify things, you just need one shepherd on several acres to grow sheep, but a whole crapload of farmers to grow an acre's worth of rice.
One current theory of history is that the Black Plague hit Europe especially hard-- which resulted in a whole lot of social changes. Basically, if you've got less people to do labor, then the wages for that labor go up. And in turn, if there's less people to do labor (and theoretically more land to do it on 'cause a bunch of people are dead) then it makes sense to focus on sheep or cattle.
The one snag I run into as I kick this idea around is various herding cultures in Africa-- there's a millennia-old tradition of cattle herding down there. Of course, Africa's a big place, so I wouldn't be surprised if some ethnic groups developed a lactose tolerance while others didn't. It's the sort of thing I would do more research into if I was an actual academic. But ...
PONY SIDEBAR
I forget the exact reasoning behind it, buuuuut I vaguely recall someone on a forum I frequent theorizing about the requirements of a pony diet. Namely, as herbivores, ponies require high-energy foods to fuel high-energy sapient-thinking brains. Or ... something. It's been awhile and I don't feel like digging through untold pages of archives.
The long and short of it is, in order to fuel their incongruous sapient brains, refined sugars-- and in turn, baked goods, became an essential part of Equestrian diets, or something. :)
4622289
The Europeans were already more advanced than most other civilizations at that point, though - and much more advanced than the Africans, Americans, and the Oceanic peoples.
Moreover, the Black Death killed a ton of people in China as well. In 1200, the population of China was 120 million. In 1393, it was only 65 million.
While the Black Death certainly caused societal upheaval, it didn't push people towards herding.
Herding peoples were generally much more primitive than the agricultural people, because the agricultural people sat on the same land and could harvest year after year, while the herders moved around. They were generally pretty primitive and had a hard time really building up their tech levels, and generally had a hard time against the agriculutural civilizations, whose sedentary nature let them build up a lot more infrastructure (and thus things like metallurgy and masonry).
Almost all of the most important historical civilizations were agrarian civilizations, which displaced herders and hunter gatherers.
Hehe.
Admittedly the ponies gotta get their protein from somewhere, and given they appear to be primary vegetarian, I suspect they eat a lot of eggs and stuff made from eggs.
And possibly beans.
Granny Smith loves her six-layer bean dip.
I feel it should be clarified that Cow milk is not actually healthy for Humans.
The dairy industry has done a great job convincing people they need milk for calcium, but there are a lot of efficient plant-based sources too. As my cartons of liquefied almonds are always eager to tell me. :)
4622362
If milk wasn't healthy for humans to drink, there wouldn't have been such strong selective pressure for lactase persistence.
4622390
Yeah, they add a lot of calcium to almond milk in an attempt to stave off calcium deficiency in vegans, which is actually one of the common issues with the diet. It is possible to get enough calcium via plant-based sources (soy in particular is very rich in calcium; almonds have some calcium in them, but it isn't anywhere near what you'd get out of a similar caloric amount of milk, which is why they add calcium to almond milk - 1 cup of milk has about 100 calories and about 30% of the daily recommended amount of calcium. To get the same amount out of almonds, you'd have to eat 650 calories of them), but a lot of people don't really watch what they eat very carefully, and as a result vegans end up with some odd micronutrient deficiencies which are less common in the omnivorous populations (who avoid this problem by being a bunch of fatties instead). Globally, milk is a very important source of calcium, and the fact that it is a drink helps to get people to consume it in quantity on a regular basis, which is why spiking almond milk with more of the stuff is useful - it can fill the same role for vegans.
Vitamin D deficiency is another thing they run into, because we added a bunch of vitamin D to stuff like milk precisely to stop kids from getting rickets, and then, of course, vegans came along and stopped drinking milk, resulting in a spate of vegan children getting rickets.
Random micronutrient deficiencies is actually why the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition is not exactly fond of vegan diets for children without expert supervision; there have been increasing numbers of malnourished vegan children as a result of restrictive diets that lack certain micronutrients because a lot of people are pretty careless and don't really understand why there is always the caveat of a balanced vegan diet. Though of course, the fact that they are said experts to consult may also have something to do with their recommendation.
4622324
Hmm. Debatable. I mean, yes, Europe was indeed more advanced than Oceania, but the real cool stuff was all in the Mongol Empire(s). All the learning that was 'rediscovered' during the renaissance was really stuff the various Asian nations never forgot. :)
If you haven't read it, it's worth looking into Jack Weatherford's Genghis Khan and the Making of the Modern World. It's a rather neat read.
4622441
Oh! And as for African nations, there was also the Mali Empire of the same period, which was so rich that when their Emperor Musa went on a pilgrimage to Mecca, he disrupted the economies of every country he passed through on account of spending so much gold that the bottom fell out of the currency market.
4622398
https://nutritionfacts.org/video/is-milk-good-for-our-bones/
Sorry I took so long to respond, life's been busy.
4661294
Short-term controlled studies on calcium intake appear to indicate that consuming large amounts of calcium might have a protective effect. However, long-term studies have failed to show a strong relationship between calcium intake in general and osteoporosis.
One study claimed that milk might be associated with a higher risk of bone fracture in women; however, numerous other studies on the same subject matter have failed to find the same thing, instead finding no increased risk (and, moreover, AFAIK no study has found any sign of an increased risk in men). The most probable cause, as noted by the authors of the study, is actually reverse causation - women who are suffering from osteoporosis drink more milk because they're suffering from osteoporosis, in an attempt to treat their osteoporosis.
And indeed, this is a general issue with long-term studies - people who are suffering from osteoporosis are more likely to try and increase their calcium intake, which may or may not mitigate osteoporosis.
It is the same reason why people who drink diet sodas are fatter - it isn't that diet soda makes you fat, it is that fat people drink diet sodas.