Yup’ik Eskimos, the most famous indigenous people of the US’ 49th State, have similar obesity rates to the lower 48 states, but the incidence of type-2 diabetes is only 3.3 percent, compared with 7.7 percent nationally.
According to researchers from the Fred Hutchinson Cancer Research Center and the University of Alaska-Fairbanks, this apparent reduction in diabetes risk is linked to the observation that the Eskimos’ average consumption of omega-3s from fish is 20 times more than people in the lower 48 states.
“While genetic, lifestyle and dietary factors may account for this difference,” said lead author Zeina Makhoul, PhD., “it is reasonable to ask, based on our findings, whether the lower prevalence of diabetes in this population might be attributed, at least in part, to their high consumption of omega-3-rich fish.”
Furthermore, in Eskimos with low blood levels of omega-3 fatty acids, most notably EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), obesity was found to strongly increase blood triglycerides and C-reactive protein (CRP), a measure of inflammation. Elevated levels of triglycerides and CRP increase the risk of heart disease and, possibly, diabetes.
“Interestingly, we found that obese persons with high blood levels of omega-3 fats had triglyceride and CRP concentrations that did not differ from those of normal-weight persons,” added Makhoul. “It appeared that high intakes of omega-3-rich seafood protected Yup’ik Eskios from some of the harmful effects of obesity.”
Returning to the native people of the north
The new study, published in the European Journal of Clinical Nutrition, echoes findings from the first studies in this area from 40 years ago, carried out by Dr Jørn Dyerberg and his Danish colleagues amongst the Inuit of Greenland. The Danish scientists sought to understand how the Greenland Eskimos, or Inuit, could eat a high fat diet and still have one of the lowest death rates from cardiovascular disease on the planet.
These studies led to landmark publications in The Lancet and The American Journal of Clinical Nutrition. Since then, the potential benefits of EPA and DHA have extended to include improvements in blood lipid levels, a reduced tendency of thrombosis, blood pressure and heart rate improvements, and improved vascular function.
From Greenland to Alaska
For the new study the researchers recruited 330 Yup’ik with an average age of 45. Seventy percent of the participants were overweight or obese at the start of the study. Yup’ik literally translates as “real people” from the native language.
Analysis of blood samples showed that, while CRP and triglyceride levels were observed in obese Eskimos with low omega-3 blood levels, such increased levels were not observed in people with high blood levels of EPA and DHA.
“Our findings may have important clinical relevance for the prevention of some obesity-related diseases. Obesity prevalence in the US and worldwide has been increasing over the past decades, with subsequent increases in rates of diabetes and other obesity-associated diseases,” wrote the researchers.
“It is likely that these associations are partly mediated by the positive associations of obesity with triglycerides and CRP, two biomarkers that strongly and independently predict risks of CVD and possibly diabetes.
“Chronic, high EPA and DHA intakes, similar to those of Yup’ik Eskimos, could at least partly ameliorate the obesity-associated disease risks,” they added.
What next?
The researchers called for a randomized clinical trial to test whether increasing omega-3 fat intake significantly reduces the effects of obesity on inflammation and blood triglycerides.
“If the results of such a trial were positive, it would strongly suggest that omega-3 fats could help prevent obesity-related diseases such as heart disease and diabetes,” she said.
The study was funded by the National Center for Research Resources, and the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.
Know your limitations
Harry Rice, PhD, VP regulatory and scientific affairs at the omega-3 trade association Global Organization for EPA and DHA (GOED), told NutraIngredients-USA that the study's results are "exciting given the potential implications for attenuating obesity-related disease risk.
"While the optimal way to reduce obesity-related disease risk would be to decrease BMI via weight loss, the reality is that there are individuals genetically predisposed to obesity. For those people, this research may have far-reaching implications for long-term survival," said Dr Rice.
"Perhaps as equally impressive as the results is the authors' recognition of the study's limitations, including the fact that the associations observed may not be causal and the need to replicate the results in other populations before generalizing. My experience has been that the best scientists are those that best understand their limitations!"
Source: European Journal of Clinical Nutrition
Published online ahead of print, doi: 10.1038/ejcn.2011.39
“Associations of obesity with triglycerides and C-reactive protein are attenuated in adults with high red blood cell eicosapentaenoic and docosahexaenoic acids”
Authors: Z. Makhoul, A.R. Kristal, R. Gulati, B. Luick, A. Bersamin, D. O’Brien, S.E. Hopkins, C.B. Stephensen, K.L. Stanhope, P.J. Havel B. Boyer