Lazybird summary: skipping the science and the controversy: enjoy your olive (oil) salad dressing (and nuts – and even uncooked animal fat)- if you are not overweight; but feed everyone at least 3gms of simple (~30%) fish oil a day! this is easier now there is 80% fish-oil available ie 1gm caps containing 800mg marine essentials- but of course it’s far more expensive than cod liver (+- 30%) oil !! The best is to eat uncooked oily fish (eg roll-mops, sushi) three times a week- but not all can afford or stomach that?
Last month the University of South Dakota reports that the American Heart Association AHA and numerous organizations, national health agencies recommend consumption of the long-chain omega-3 fatty acids (FAs) eicosapentaenoic acid and docosahexaenoic acid (EPA and DHA) .
But last week the AHA again promotes omega6 intake eg plant oil about 15gm (135 kcalories) a day – despite epidemic obesity- in addition to promoting adequate intake of marine omega3 – EPA + DHA. Perhaps it is irrelevant that the lead author Dr Harris PhD did the research paper funded by and as a consultant to Montsanto – “Leaders in the growth of global agricultural harvest from seed technology to harvested crops” ; and another author has a research grant from Pronova- marketeer of Omacor, patent esters of EPA+DHA..
This promotion of omega6 ie longchain fatty acids FAs other than EPA and DHA contrasts with
*the historical evolutionary evidence supporting our putative original seaside 1:1 diet ratio of omega3:omega 6,
*and the fact that fish oil (at least) 3 to 4 gms a day ie about >800mg EPA + DHA a day in many observational studies up to halves all major diseases and sudden deaths; and reduces insulin resistance, arthritis, and behaviour -learning disorder in children;
*and the fact that owing to the growing scarcity and cost of fish, most non-Asian people – except fishermen – no longer take in even 100mg EPA+DHA a day.
The US Agency for Healthcare Research report of 2004 on Omega3 and CVD found: . “Based on analyses of a single 24-hour dietary recall in NHANES III, only 25 percent of the U.S. population reported any amount of daily EPA or DHA intake. Overall, a number of studies support that fish, fish oil, or ALA supplement consumption reduces all-cause mortality and various CVD outcomes, although the evidence is strongest for fish or fish oil. The potential effect of ALA, and relative effect of ALA versus fish oil, are unknown. Current data sets are too limited for adequate assessment. To address this issue … more trials are needed to confirm the effect of ALA, independent of fish oil and fish intake, on the secondary prevention of CVD outcomes…”
Following both the AHA recommendation for omega6 – 13-17gm a day- and omega3 EPA+DHA – about 800mg/day – would maintain the present degenerative-disease-associated omega6:3 ratio of ~20:1. Plant – seed- oils contain only omega6 (mainly linoleic acid) and ALA alpha-linolenic acid (omega3). But our low metabolism of ALA to EPA and DHA is further impaired by preferential metabolism of omega6 .
But.. for the non-overweight, does excess omega6 intake matter as long as fish oil intake is adequate?
Of studies published lately:
The recent landmark Israeli trial in obese teenagers showed that all diets worked for 12week weightloss, but only the lowfat diets worked for quality of life as well- not the high fat diet.
The North Atlantic trial (in Spain, Iceland and Ireland) in the overweight showed that “fish oil intake was a significant predictor of fasting insulin and insulin resistance after 8 weeks, and this finding remained significant even after including weight loss”; and “Weight-loss diet including oily fish resulted in greater triglyceride TG reduction than did a diet without fish or fish oil”
the Philadelphia trial in the obese showed that diet and exercise worked better than either alone, but by 12 months neither diet and/or exercise had made any difference in meaningful weight loss. In the Stanford trial of different diets, “premenopausal overweight /obese women assigned to follow the Atkins diet, which had the lowest carbohydrate intake with high protein/fat, lost more weight at 12 months than women assigned to follow the Zone diet, and had experienced comparable or more favorable metabolic effects than those assigned to the Zone, Ornish, or LEARN diets” .
An Edmonton metanalysis shows that “Fish oil supplementation was associated with a significant reduction in deaths from cardiac causes but had no effect on arrhythmias or all cause mortality”.
2 years ago a Guildford UK trial showed that varying the diet omega6:3 ratio from 3:1 to 15:1 “did not influence insulin sensitivity or postprandial lipase activities. Fasting and postprandial triacylglycerol concentrations were lower with an n-6:n-3 of approximately 3:1, which was achieved by the addition of long-chain n-3 PUFAs (EPA and DHA). Decreasing the n-6:n-3 does not influence insulin sensitivity or lipase activities in older subjects. The reduction in plasma triacylglycerol after an increased intake of n-3 long-chain PUFAs results in favorable changes in LDL size.”
A year ago the Italian Institute of Food Science showed that “In healthy individuals a moderate supplementation of fish oil does not affect insulin sensitivity, insulin secretion, beta-cell function or glucose tolerance. The same is true even when the habitual dietary intake of n-6 and n-3 fatty acids is taken into account.”;
and a current doyen of nutrition epidemiology , Dr Walt Willett of Harvard, wrote that “(omega)n-6 Fatty acids reduce insulin resistance, and intakes have been inversely related to risk of type 2 diabetes. Adequate intakes of both n-6 and n-3 fatty acids are essential for good health and low rates of cardiovascular disease and type 2 diabetes, but the ratio of these fatty acids is not useful. Reductions of linoleic acid to “improve” this ratio would likely increase rates of cardiovascular disease and diabetes.”
But do these opinions offset the concerns about the high omega6 intake in our fast-food western diet? Both Simonopolous and Cleland‘s 2003 book, and Steve Cunnane‘s group at Toronto University, discuss evidence linking much disease to excessive omega 6.
The latest Wiki entry on soya discusses the massive evidence against it’s recommendation as a health food owing ia to it’s transfat, phytoestrogen and cancer risk potential, and absence of EPA+DHA.
So It seems to matter less how much plant oil (from olives, nuts) is taken- as eg salad dressing or nuts – than that essential EPA+DHA at least 800mg/day (ie marine oil) is taken along with some omega6 intake.
Thus while the jury may be hung in the cases of both Marine oil vs Plant oil, and ranking of macronutrient intake, it seems clearly vital at all age from conception to dotage to raise the minimum EPA-DHA intake to above 800mg a day, plus (for adults) a maximum ~15gms of unsaturated plantseed (eg olive or nut) oil a day.
And encourage that the balance of exercise and macronutrients – protein, (uncooked) fats, and complex carbs as well as free water – maintains normal body composition ie BMI bodymass index below ~23kg/sqm at all ages except in body builders, with fat-mass below about ~15kg (25%) in average women and ~12kg (18%) in average men, and lean mass index LMI above about 17kg/sqm in women and 19kg/sqm in men.
While oily fish is becoming too scarce to be affordable for most, adequate intake of optimal plant oil is guaranteed anyway for both carnivorous and vegetarian humans who follow prudent guidelines and take some nuts, beans and avocado as well as liberal olive oil dressing on their salad or stir-fry. But a teaspoon of good fish oil a day is the bedrock of any diet.