Tuesday, March 18, 2014


It is no secret that there has always been healthy rivalry and competition, not only between Oxford and Cambridge but also between Cambridge and Harvard. These are great institutions. They are not Ivy League for nothing. 
Their latest battle ground is an interesting article, published in the March 18th edition of the Annals if Internal medicine entitled " Association of dietary, circulating, and supplement fatty acids with coronary risk. A systematic review and meta-analysis."  The lead author is Dr Rajiv Chowdhury.
This paper is a meta-analysis of 45 prospective observational studies and 27 Randomised controlled trial on the issue of dietary PUFA intakes, levels of circulating PUFA, and intake of fatty acid dietary supplements.

Relative Risk (95% CI) for Coronary Events, Top vs Bottom Third of Total Dietary Fatty Acid Intake Levels in Prospective Cohort Studies*
Fatty Acid TypeRR (95% CI)
Saturated1.02 (0.97–1.07)
Monosaturated0.99 (0.89–1.09)
Long-chain omega-30.93 (0.84–1.02)
Omega-61.01 (0.96–1.07)
Trans1.16 (1.06–1.27)

Relative Risk (95% CI) for Coronary Events, Top vs Bottom Third of Circulating Fatty Acid Levels in Prospective Cohort Studies*
Fatty Acid TypeRR (95% CI)
Saturated1.06 (0.86–1.30)
Monosaturated1.06 (0.97–1.17)
Long-chain omega-30.84 (0.63–1.11)
Omega-60.94 (0.84–1.06)
Trans1.05 (0.76–1.44)

The authors ( Cambridge U ) concluded and I quote "We found essentially null associations between total saturated fatty acids [SFA] and coronary risk," in studies looking at dietary fat intake and those focusing on circulating fatty-acid levels, nor were there significant associations between CV risk and dietary intake of long-chain omega-3 and omega-6 polyunsaturated fatty acids. Other findings suggested that dietary supplements containing those fatty acids don't significantly reduce coronary risk. 

From across the pond ( even as the article go to press ), the Harvard boys, represented by Dr Eric B Rimm (Harvard School of Public Health, Boston, MA) said, "My colleagues were quite surprised at the findings. We uncovered a serious mistake in their review of PUFA that likely will change the results substantially." And the parts of the meta-analysis focusing on PUFA didn't summarize the relevant studies correctly, which leaves  "the results are in serious question.They added "Moreover, the group's conclusion about saturated fat "has little context, because it likely represents the result of when you exchange saturated fat in your diet for refined grain. Thus, saturated fat is no better or worse than eating white bread. We have known that for decades, so is not new."
The Harvard boys were supported by their neighbours from Tufts U, Dr Alice H Lichtenstein (Tufts University, Boston, MA) replied by email, "the majority of the evidence suggests that replacing saturated fat with polyunsaturated fat reduces heart disease risk, whereas replacing saturated fat with carbohydrate does not. This new study only assessed one factor, an indicator of dietary fat, and not the whole picture, making the conclusions questionable."

Is this a question of one up manship, or scientific facts, you decide. Anyway, it is a meta-analysis, so no one should go out now and change their practice patterns. It should spur us on to look for more information including an international randomised controlled trial, but this is unlikely to happen. For one, the world economy is still not in good health and so money for large trials is scarce. And two, who will fund something where you may not be able to patent and make money from. So................

Well, if you look at the tables, the margins are thin. I will not go start a trans-Atlantic war on this.
As always, moderation is the best. Eat no trans-fat, plenty of "polyunsaturated fatty acids as we have in fishes, and a controlled amount of saturated fats as we grow older or should we have other cardiovascular risks. 

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