Native Greenlanders consume a specialized diet that’s high in fat and proteins – mostly from seals and whales that eat fish containing omega-3 fatty acids. Now, an analysis of their genetic makeup reveals how they’re uniquely adapted to their extreme environment: The Inuit possess a number of genetic variations that help control fat metabolism, cholesterol, and also weight and height. The findings, published in Science this week, suggests that people differ in how we physiologically respond to diets.
"The original focus on fish oil and omega-3s came from studies of Inuit. On their traditional diet, rich in fat from marine mammals, Inuit seemed quite healthy with a low incidence of cardiovascular disease, so fish oil must be protective," UC Berkeley’s Rasmus Nielsen said in a statement. "We’ve now found that they have unique genetic adaptations to this diet, so you cannot extrapolate from them to other populations. A diet that is healthy for the Inuit may not necessarily be good for the rest of us."
The large international team analyzed the genomes of 191 Greenlandic Inuit who have less than 5% European ancestry, and then compared these results to 60 European and 44 Han Chinese individuals. The researchers were looking for mutations that occur in a significant portion of the Inuit but in few or no other groups. That would suggest the mutations were useful for Inuit survival, but not essential for others.
The team identified a number of mutations that help counteract the effects of eating a lot of marine mammal fat. One cluster of mutations occurs in genes that control the conversion of omega-6 and omega-3 fatty acids into polyunsaturated fatty acids. The mutations decrease the production of these fatty acids, which are abundantly available from the Inuit diet already.
Additionally, since growth is partly regulated by an individual’s fatty acid profile, some of these genetic mutations influence height. While height is controlled by many genes, these mutations have some of the strongest effects ever seen. They reduce height by 2 centimeters, or nearly an inch.
These mutations appear to be at least 20,000 years old, and they likely arose in Siberians living in the Arctic. Selection for these genes began before the Inuit population diverged from Native Americans – back when their common ancestors lived around the Bering Strait land bridge connecting Asia and North America.
“We think it is a quite old selection that may have helped humans adapt to the environment during the last ice age, but the selection is far stronger in the Inuit than anywhere else,” added joint lead author Matteo Fumagalli of University College London. “It’s fascinating that Greenlanders have a unique genetic makeup that lets them better use their traditional food sources.”
Ukkusissat, Greenland. Photo by Malik Milfeldt