Saturday, 19 November 2011

Vitamin D and Northern Natives


Annual average exposure to erythema-inducing UV radiation at ground level. Source: Jablonski & Chaplin, 2000. At high northern latitudes, vitamin D can be obtained only from one’s diet, notably fatty fish. Yet many northern native peoples consume little fish. Have they evolved a different vitamin D metabolism?

I’ve just published an article on population differences in vitamin D metabolism, specifically about northern native peoples. Comments are welcome.

Abstract

Vitamin-D deficiency seems to be common among northern native peoples, notably Inuit and Amerindians. It has usually been attributed to: 1) higher latitudes that prevent vitamin-D synthesis most of the year; 2) darker skin that blocks solar UVB; and 3) fewer dietary sources of vitamin D. Although vitamin-D levels are clearly lower among northern natives, it is less clear that these lower levels indicate a deficiency. The above factors predate European contact, yet pre-Columbian skeletons show few signs of rickets—the most visible sign of vitamin-D deficiency. Furthermore, because northern natives have long inhabited high latitudes, natural selection should have progressively reduced their vitamin-D requirements. There is in fact evidence that the Inuit have compensated for decreased production of vitamin D through increased conversion to its most active form and through receptors that bind more effectively. Thus, when diagnosing vitamin-D deficiency in these populations, we should not use norms that were originally developed for European-descended populations who produce this vitamin more easily and have adapted accordingly.


References

Frost, P. (2011). Vitamin D deficiency among northern Native Peoples: A real or apparent problem? International Journal of Circumpolar Health, early view

http://www.ijch.fi/aheadofprint.php

Jablonski, N.G. and G. Chaplin (2000). The evolution of human skin coloration
, Journal of Human Evolution, 39, 57-106.

8 comments:

Anonymous said...

Seems that females did the wandering back then but then, maybe it is just propaganda.

Unknown said...

Very interesting hypothesis.
You paper is extracted and available now in 64 languages (including French), along with several others on Inuit and vitamin D: http://www.vitamindwiki.com/tiki-index.php?page_id=1836

Ben10 said...

You have a long way to go in the main stream education. My mom in France told me she was watching a documentary about the 'human origin(s)' last summer, she told me how vitD level variation with latitude explained the color of european skin etc. I didn't bother to argue. That was probably a french translation of a History channel or a BBC documentary.
Why this? it's not monsense. It's politic. You have to understand that in France, the elite in control of the media has brainwashed the population for 40-50 years now. Antiracist organazitions have lobbied to pass laws. People in France have actually been sued and IMPRISONNED Not for their ACTION, but for their OPINIONS. The culmination of this appears in this statement, from the LICRA, stating:
"Racism is not an OPINION, it's a FELONY".

Yes, no kidding:
http://www.licra.org/communique/racisme-nest-pas-opinion-cest-d%C3%A9lit-0

Now you understand why 'races' must at all cost be the result of natural processes unrelated to human behavior: Light, or VitaminD are NOT 'racist' entities, it's a darwinian, therefore a random process with no' evil' intention behind.
Sexual selection, on the other hand, is a human behavior, natural, but nonetheless driven by Man. Anybody can then make a case that this behavior was imprinted in european males as a normal process of natural selection through a few thousand years of practice, which LICRA would call 'racist' practices. But if sexual selection is true, it will be hard for LICRA to label Cro-Magnon as racists or criminals. The racism of Cro-Magnons was not an OPINION, not a CRIME, it was a normal survival behavior that some of their descendants today may still inherit as an archaic character, which expresses more or less strongly and completely indenpendantly of their will. Treating modern europeans, whose only crime is to inherit some characters from their ancestors, IS the crime.

Sean said...

The Inuit are likely well adapted to eating their traditional diet but not Western foods. Even just adding moderate amounts of things like refined carbohydrates to their dietary mix may interact to damage health. But the health problems of Inuit and Amerindians are a happy hunting ground for vitamin D enthusiasts packing an observational study ( eg Vitamin D deficiency and disease risk among aboriginal Arctic populations).
Good thing that the 'vitamin' D proponents' arguments are being answered.

Inuit health issues are most likely down to their diet. The idea that many generations in an unforgiving environment would not have led to the evolution of adaptations for meeting the specific challenges of that environment, including low vitamin D production, is far fetched.

Peter Frost said...

Anon,

We see the same pattern in more recent human populations. It's called patrilocality, i.e., the female moves in with the male's clan. Often, this happens because the female has literally been abducted from another group.

Unknown,

64 languages?

Ben,

There are three main barriers to acceptance of the sexual selection explanation:

1. Among many evolutionary scientists, there is a strong prejudice against sexual selection. They see it as a "catch-all" explanation that is used to explain anything and everything. That was Greg Cochran's reaction. I don't think he even bothered to read my article in EHB.

2. Among the general public, there is surprisingly little knowledge of evolutionary theory. People understand that organisms evolve over time, but the mechanism for change -- natural selection -- is often poorly understood. When I talk with journalists, I often have to spend more time explaining evolution than explaining my own work.

3. In most mammals, sexual selection acts on males, and not on females. That's why females generally have a less ornamental and more "functional" appearance in most species and even in many human populations.

Sean,

Our Western diet is a big factor, but there are other causes of illness among the Inuit. The high rate of suicide among the Inuit, for instance, seems to reflect a higher incidence of "suicide ideation," and we see this kind of ideation even among Inuit who have no serious problems in life.

The trigger seems to be just inactivity and lack of a clearly defined purpose. The Inuit used to live in an environment where most of the day was spent doing specific goal-directed tasks. When those tasks are absent, thoughts of suicide seem to take over.

Ben10 said...

Peter, regarding point number 2, 'the lack of knowledge in the general population...'
European nations were composed of farmers, who were familiar with the concept of selective breeding for basically all farm animals. Dogs breeds were very well known. In addition to that, human genetic selection in family trees were also very well known and appreciated. The concept of sexual selection was not different. 'Beautiful women', from the common or from the nobility, was as much a genetic concept than a social concept. Evolutionary concepts were almost embedded in this knowledge, why would people have difficulties to understand the mechanisms of evolution if they dealt with them every day? it is way more easy to understand than, say, newtonian gravitation. The only problem is when you touch the point of finalism or causality. I have a big problem with it myself and so you can just NOT go there.

Peter Frost said...

Ben10,

Yes, we used to be familiar with breeding, both in farm animals and in humans. But today most of us have no contact at all with farm life.

We are also less familiar with human breeding. Generation intervals are longer and most people no longer remain in the same community as their parents'. So they cannot follow the transmission of mental, behavioral, and personality traits from one generation to the next.

Greg Cochran wrote a post on this phenomenon:

http://westhunt.wordpress.com/2011/10/21/local-knowledge/

Sean said...

Dietary Reference Intakes for Calcium and Vitamin D (2011)
p.492
. "These factors help to explain why latitude alone does not appear to predict serum 25OHD concentrations in humans. In a Finnish study, healthy subjects living above the Arctic Circle (latitude 66°N) did not have lower serum 25OHD levels than subjects living in southern Finland; in fact, the group living above the Arctic Circle had higher levels. Both groups achieved mean serum 25OHD levels above 90 nmol/L during the summer, whereas the mean serum 25OHD level at the winter nadir was 56 nmol/L in the south and 68 nmol/L in those living above the Arctic Circle (Lamberg-Allardt et al., 1983).

"large-scale pooled analysis (n = 2,285) found a statistically significant two-fold increased risk for pancreatic cancer in participants with serum 25OHD levels at or above 100 nmol/L compared with those with levels between 50 to 75 nmol" Dietary Reference Intakes for Calcium and Vitamin D (2011) p.436

What do the National Acadamies know ?