Saturday, January 30, 2010

Cancer patterns in Inuit populations: 1950-1997

Some types of cancer have traditionally been higher among the Inuit than in other populations, at least according to data from the 1950s, when a certain degree of westernization had already occurred. The incidence of the following types of cancer among the Inuit has been particularly high: nasopharynx, salivary gland, and oesophageal.

The high incidence of these “traditional” types of cancer among the Inuit is hypothesized to have a strong genetic basis. Nevertheless some also believe these cancers to be associated with practices that were arguably not common among the ancestral Inuit, such as preservation of fish and meat with salt.

Genetic markers in the present Inuit population show a shared Asian heritage, which is consistent with the higher incidence of similar types of cancer among Asians, particularly those consuming large amounts of salt-preserved foods. (The Inuit are believed to originate from East Asia, having crossed the Bering Strait about 5,000 years ago.)

The incidence of nasopharynx, salivary gland, and oesophageal cancer has been relatively stable among the Inuit from the 1950s on. More modern lifestyle-related cancers, on the other hand, have increased dramatically. Examples are cancers of the lung, colon, rectum, and female breast.

The figure below (click on it to enlarge), from Friborg & Melbye (2008), shows the incidence of more traditional and modern lifestyle-related cancers among Inuit males (top) and females (bottom).

Two main lifestyle changes are associated with this significant increase in modern lifestyle-related cancers. One is increased consumption of tobacco. The other, you guessed it, is a shift to refined carbohydrates, from animal protein and fat, as the main source of energy.


Friborg, J.T., & Melbye, M. (2008). Cancer patterns in Inuit populations. The Lancet Oncology, 9(9), 892-900.


Ken said...

"Inuit Greenlanders, ... have the worst longevity statistics in North America. Research from the past and present shows that they die on the average about 10 years younger and have a higher rate of cancer than the overall Canadian population."

I wonder if there is a connection with this:-

"We know that the Inuit have compensated for lower production of vitamin D by converting more of this vitamin to its most active form (Rejnmark et al., 2004). They also seem to absorb calcium more efficiently, perhaps because of a different vitamin-D receptor genotype (Sellers et al., 2003)." Population differences in vitamin D metabolism (scroll down a bit)

Increased activity of vitamin D having the effect of shortening life has an established precedent:-

Premature aging in vitamin D receptor mutant mice..
"Overall, VDR KO mice showed several aging related phenotypes, including poorer survival, early alopecia, thickened skin, enlarged sebaceous glands and development of epidermal cysts. There was no difference either in the structure of cerebellum or in the number of Purkinje cells. Unlike the wildtype controls, VDR KO mice lose their ability to swim after 6 months of age. Expression of all the genes was lower in old VDR KO mice, but only NF-kappaB, Fgf-23, p53 and IGF1R were significantly lower. Since the phenotype of aged VDR knockout mice is similar to mouse models with hypervitaminosis D(3), our study suggests that VDR genetic ablation promotes premature aging in mice, and that vitamin D(3) homeostasis regulates physiological aging"

Ned Kock said...

It is possible, but I think the more recent statistics are strongly related to their modern consumption of refined carbohydrates.

Ken said...

sI was thinking that they would be getting too much calcium now but according to this "the Inuit infrequently consume market food such as milk, dairy products".

It also says that traditional foods are still a big part of their diet, presumably the ill effects of carbohydrates would be much worse if they abandoned their largely traditional diet.

Ned Kock said...

Hi Ken.

That is a good point, but with a diet high in animal fat (the traditional Inuit diet), the negative effects of refined carbs. may be intensified. The hormonal changes caused by refined carbs. lead to significantly increased fat deposition, and decreased fat mobilization, at the same time.

So, if you consume plenty of fat (the most calorie-dense of the macronutrients in the human diet) together with refined carbs. you may end up putting on body fat very, very fast. This is one of the reasons why sumo wrestlers who are bulking up have a diet high in both ref. carbs. and fat, not only ref. carbs.

Neonomide said...

Yet Taubes had an examples of sumo diet that was actually low-fat, yet of course high in calories (which consisted of course mostly of white rice).

So can I have some ref please ? Show yours and I'll show mine. ^^