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Omega-3 benefits may depend on a mutation: cf. the Inuit

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Carl Zimmer reports in the NY Times:

As the Inuit people spread across the Arctic, they developed one of the most extreme diets on Earth. They didn’t farm fruits, vegetables or grains. There weren’t many wild plants to forage, aside from the occasional patch of berries on the tundra.

For the most part, the Inuit ate what they could hunt, and they mostly hunted at sea, catching whales, seals and fish. Western scientists have long been fascinated by their distinctly un-Western diet. Despite eating so much fatty meat and fish, the Inuit didn’t have a lot of heart attacks.

In the 1970s, Danish researchers studying Inuit metabolism proposed that omega-3 fatty acids found in fish were protective. Those conclusions eventually led to the recommendation that Westerners eat more fish to help prevent heart disease and sent tens of millions scrambling for fish oil pills.

Today, at least 10 percent of Americans regularly take fish oil supplements. But recent trials have failed to confirm that the pills prevent heart attacks or stroke. And now the story has an intriguing new twist.

A study published on Thursday in the journal Science reported that the ancestors of the Inuit evolved unique genetic adaptations for metabolizing omega-3s and other fatty acids. Those gene variants had drastic effects on Inuit’s bodies, reducing their heights and weights.

Rasmus Nielsen, a geneticist at the University of California, Berkeley, and an author of the new study, said that the discovery raised questions about whether omega-3 fats really were protective for everyone, despite decades of health advice. “The same diet may have different effects on different people,” he said.

Food is a powerful force in evolution. The more nutrients an animal can get, the more likely it is to survive and reproduce. Humans are no exception. When we encounter a new kind of food, natural selection may well favor those of us with genetic mutations that help us thrive on it.

Some people, for example, are able to digest milk throughout their lives. This genetic adaptation arose in societies that domesticated cattle thousands of years ago, in such places as Northern Europe and East Africa. People who trace their ancestry to other regions, by contrast, tend to more often be lactose-intolerant.

Dr. Nielsen wondered if the Inuit had a similar evolutionary change when they shifted to a diet made up mainly of meat.

In recent years, he and his colleagues have been collaborating with researchers at the University of Greenland to study Inuit DNA. Originally, they searched for mutations that raise the risk of developing diseases such as diabetes.

But then Dr. Nielsen and his colleagues took a different tack, searching for mutations that might have provided the Inuit with some benefit.

To sharpen the focus of their search, the scientists selected 191 Greenlanders whose ancestry was 95 percent Inuit or greater. (Many Greenlanders can trace some of their ancestry to Europe because of the island’s colonization by Denmark.) The researchers looked at the DNA of these people for variations in genes important to metabolism. . .

Continue reading.

Written by LeisureGuy

17 September 2015 at 9:33 pm

Posted in Evolution, Food, Health, Science

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