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 Carolinawas 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.
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.
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.