Friday, 9 February 2018

Nutrition: omega-6 to omega-3 ratio

It has been claimed that human beings evolved on a diet that had a ratio of omega-6 to omega-3 fatty acids (FA) of about 1:1; whereas today, Western diets have a ratio of 10:1 to 20–25:1, indicating that Western diets are deficient in omega-3 FA (e.g. DOI:10.1007/s12035-010-8162-0).  There is tentative evidence of omega-3 FA lowering inflammation levels in humans while omega-6 FA and their metabolites may have proinflammatory effect (but see 1).  Because of all the above, some hypothesise that the "unnaturaly" high ratio of n6:n3 is the reason why modern diets are correlated with many inflammatory disorders (e.g. cancer, atherosclerosis, and ischemic heart disease).

Many health and nutrition gurus and professionals advise that, in order to improve our health, we should eat X instead of Y because Y has a terrible omega-6 FA to omega-3 FA ratio.  To give just a couple of examples:
  • I have stumbled upon advice from Dr Michael Greger (MD) of that we should eat walnuts because they have a good n6:n3 ratio of c. 4:1
  • Thomas DeLauer advised his viewers not to eat almonds because of their high omega-6 FA and phytic acid (see 2) content.  At the same time he recommended pecans.
Pecans contain almost twice as much n-6 as almonds. Walnuts are even worse in this respect as they contain around three times as much omega-6.
It seems obvious that ratios of n6:n3 in individual products are not important (unless one follows a monotrophic (or close to monotrophic) diet which one should not).  What is important is the ratio of your cumulative daily intake of both FA groups. If you ingest x grams of almonds (n6:n3 ratio of c. 2000:1) you still get three times less n-6 than if you ingest x grams of walnuts (which boast of a much "better" n6:n3 ratio of c. 4:1). It seems reasonable that what you should do is just enjoy your almonds, walnuts, pecans or whatever else you might fancy and add some ground flaxseeds into your diet to bring the daily n6:n3 ratio closer to 1:1 ;).

  1. Omega-6 FA are still essential for the human body to function.  Moreover, there is also evidence of their anti-inflammatory effect so to consider them just proinflammatory is one-sided.
  2. "Studies examining the effects of phytic acid demonstrate that it is important in regulating vital cellular functions. Both in vivo and in vitro experiments have demonstrated striking anticancer (preventive as well as therapeutic) effects of phytic acid. Research shows anti-carcinogenic effects, albeit to a lesser extent and it acts in inhibiting cancer. In addition to reduction in cell proliferation, phytic acid increases differentiation of malignant cells often resulting in reversion to the normal phenotype." (DOI: 10.1046/j.1365-2621.2002.00620.x)

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