Inuit have unique genes for metabolising omega-3 fats

Decades of advice on the protective effects of omega-3 fatty acids are being challenged by a study of the genomes of the Inuit population in Greenland.

The traditional diet of the Inuit primarily consists of proteins and fat from fish, with a comparatively low amount of vegetables and carbohydrates as a result of the extremely cold climate and sparse vegetation of the Arctic. The rate of heart attack and stroke is low among Arctic peoples, and this has
lead health experts to conclude that omega-3 fatty acids are protective.

A new study has investigated whether this protection against heart attack might also be genetic. Researchers compared the genomes of 191 Inuit in Greenland, 60 Europeans and 44 ethnic Chinese to look for genetic changes that could benefit the Inuit population in their harsh environment.

'When we did that, it pointed directly to one group of genes where we had an extremely strong signal. They regulate how much of these omega-3s and omega-6s you make yourself naturally,' said Professor Rasmus Nielsen from the University of California, Berkeley, one of the authors of the paper, which was published in the journal Science.

Almost every Inuit in the study had variations in enzymes called fatty acid desaturases (FADS). These modulate
fatty-acid composition, which may also affect the regulation of growth hormones. In contrast, only 25 percent of Chinese and two percent of Europeans had the same variations. Inuit people who had two copies of this variant gene not only had different levels of fatty acids in their blood, they were also, on average, one inch shorter and ten pounds lighter than those without the gene.

These variations may help to explain why some people are able to metabolise fats more effectively than others and what effects the same diet may have on different populations.

'The
genetic network is rewired to make fewer of these [fatty acids] themselves,' Professor Nielsen told the New York Times. 'This clearly shows that you can't extrapolate [dietary effects] from the Inuit to other populations.'

Further research will be needed to show the full implications of having these variations, said Professor Nielsen. 'The regulation of fats in your body is a really complex network. You turn one knob, and it just changes everything everywhere else.'