No Magic Numbers: The Omega-3:Omega-6 (N3/N6) Ratio - Higher is Better, But as Part of the Standard American Diet Even a 1:1 Ratio Won't Protect You Against Diabesity

Eating "like an American" makes you fat and sick. No matter what the omega-3 to omega-6 ratio of your diet may be.

It is a pity. Yeah, if the latest study from the University of South Carolina was a human study, it would finally provide a definitive answer to the question how much omega-3 we actually need. Well, I should clarify: It would provide an answer to the question how much omega-3 we need with a given baseline omega-6 intake.

In view of the fact that the study duration was 20 weeks, it would yet take more than 60 (human) years to find out, whether the ratio of n-3/n-6 in the diet is in fact as irrelevant as the reslts Reilly T. Enos et al. present in their latest paper would suggest.

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Over those 20 weeks the scientists from the Departments of Pathology and Chemistry and Biochemistry fed their previously healthy C57BL/6 mice diets that contained either the regular rodent chow or one out of four high fat diets with omega-3 to omega-6 ratios of 1:1, 5:1, 10:1, and 20:1. As the scientists point out, the percentage of calories provided by each of the three macronutrients and the ratio of monounsaturated FAs (MUFAs) to PUFAs (MUFA:PUFA) were identical for the HFDs and were designed to be similar to the standard American diet.

Table 1: Diet composition of treatment diets.SFAs, Saturated Fatty-Acids; MCSFAs, Medium-Chain Saturated Fatty Acids; LCSFAs, Long-Chain Saturated Fatty Acids; USFAs, Unsaturated Fatty Acids; MUFAs, Monounsaturated Fatty Acids; PUFAs, Polyunsaturated Fatty Acids (Enos. 2014)

The only significant difference among the HFDs was the omega-6:omega-3 (The control diet (AIN-76A Mod) was used in order to match the MUFA:PUFA and omega-6:omega-3 of the 20:1 HFD.)

Ok, the rodent thing is not the only problem

None of the diets contained any long-chain omega-6 or omega-3 FAs. In human terms this would mean that we are not testing a high fish, high grass-fed beef, but a high omega-3 vegetarian diet with tons of alpha linolenic, but no Docosahexaenoic acid (DHA) or Eicosapentaenoic acid (EPA), which is the "stuff" (=long-chain omega-3 fatty acids) you would find in meats of grass-fed beef and, of course, fish.

Figure 1: Changes in body weight, visceral fat weight and adipocyte size during 20 weeks on modified "standard American diet" w/ different ratios of omega-3 to omega-6 fatty acids (Enos. 2014)

And still, based on the current paradigm, the scientists expected to see significant differences in metabolic health parameters between the high and low omega-3 to omega-6 ratio groups - at best even a complete revision of the metabolic damage the rodents suffered due to consuming a high energy + high fat diet.

It does not always work that way.

In reality, though, any therapeutic benefit produced by reducing the omega-6:omega-3 was evident only when comparing the 1:1 to 20:1 HFD. Yep, that's true, the mice on the 1:1 HFD had a lower total to HDL (TC:HDL-C) ratio and a decreased adipose tissue CXCL14 gene expression and adipose tissue macrophage infiltration, both of which would indicate that they had a lower risk cardiovascular disease.

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But there were benefits, weren't there? Yes, there were! In fact, there was even a direct link between higher EPA:AA (AA: arachidonic acid, the allegedly inflammatory and thus "bad" long-chain omega-6 fatty acid) and DHA:AA in the adipose tissue phospholipids. 

The net outcome on the other hand, was profoundly disappointing: "[...]despite these effects, and independent of the omega-6:omega-3, all HFDs, in general, led to similar levels of adiposity, insulin resistance, and AT [adipose tissue] inflammation" (Enos. 2014) - in short, it's a sad, but actually not surprising fact that the standard American diet (SAD) will make you fat and diabetic, no matter how much omega-3 fatty acids you are shoveling down.

References

• Enos, Reilly T., et al. "Reducing the Dietary Omega-6: Omega-3 Utilizing α-Linolenic Acid; Not a Sufficient Therapy for Attenuating High-Fat-Diet-Induced Obesity Development Nor Related Detrimental Metabolic and Adipose Tissue Inflammatory Outcomes." PLOS ONE 9.4 (2014): e94897.