Metabolic Health

Notes:

This is a real banger, two RCTs didn't publish all of their data which showed seed oils increased cardio vascular risk. Academic fraud.

Our recovery and 2013 publication of previously unpublished data from the Sydney Diet Heart Study (SDHS, 1966-73) belatedly showed that replacement of saturated fat with vegetable oil rich in linoleic acid significantly increased the risks of death from coronary heart disease and all causes, despite lowering serum cholesterol.

They redid the original studies math using ALL the data and came up with contradictory findings.

Liquid corn oil was used in place of the usual hospital cooking fats (including hydrogenated oils) and was also added to numerous food items (for example, salad dressings, filled beef (lean ground beef with added oil), filled milk, and filled cheeses). Soft corn oil polyunsaturated margarine was used in place of butter. This intervention produced a mean reduction in dietary saturated fat by about 50% (from 18.5% to 9.2% of calories) and increased linoleic acid intake by more than 280% (from about 3.4% to 13.2% of calories)

the control diet did not change saturated fat intake but did substantially increase linoleic acid intake (by about 38%, from 3.4% to 4.7% of calories).

Ooph, talk about mixing variables.

As predicted, participants in the intervention group significantly lowered serum cholesterol compared with the control group (P<0.001) and compared with baseline

Seed oils lower cholesterol! It works

figure 5 - risk of death

MCE participants with greater reduction in serum cholesterol, however, had a higher rather than a lower risk of death.

figure 6 - death vs serum cholesterol

figure 7 - meta-analysis of RCT hazard ratios for different fats

Fig 7 Meta-analysis for mortality from coronary heart disease in trials testing replacement of saturated fat with vegetable oils rich in linoleic acid. Main analysis: trials provided replacement foods (vegetable oils) and were not confounded by any concomitant interventions. Sensitivity analysis: includes trials that provided advice only and/or were confounded by addition of n-3 EPA and DHA. Risk ratios were used as estimates of hazard ratios in MCE, RCOT, LA Vet, and MRC-Soy. MCE=Minnesota Coronary Experiment; SDHS=Sydney Diet Heart Study; RCOT=Rose Corn Oil Trial; LA Vet=Los Angeles Veterans Trial; MRC-Soy=Medical Research Council Soy Oil Trial; DART=Diet and Re-infarction Trial; ODHS=Oslo Diet Heart Study; STARS=St. Thomas Atherosclerosis Regression Study; LA=linoleic acid; SFA=saturated fat; ALA=α linolenic acid; EPA=eicosapentaenoate; DHA=docosahexaenoate

The clinical benefits of these serum cholesterol lowering diets, however, have never been causally demonstrated in a randomized controlled trial and thus remain uncertain.

collective findings from randomized controlled trials do not provide support for the central diet-heart tenet that the serum cholesterol lowering effects of replacing saturated fat with linoleic acid translate to lower risk of coronary heart disease or death.

the conclusions that can be drawn from non-randomized studies on this topic are limited. Together with the lack of support from randomized controlled trials (after recovery of data from the Sydney Diet Heart Study and MCE), the totality of evidence no longer provides support for the traditional diet-heart hypothesis.

They were lying the whole time, the original study publishers.

one way to interpret the unfavorable results of the two recovered trials is that high intakes of linoleic acid could have adverse effects in people who are prone to linoleic acid oxidation (such as smokers, heavy drinkers, and older adults).

figure 8 - linoleic acid vs historial intakes

Linoleic acid content of MCE diets compared with current and historical intakes in US in 2011-12 (NHANES, adults aged ≥20).58 Nutritional adequacy defined as lowest amount of dietary linoleic acid required to prevent deficiency symptoms.59 60 Pre-agricultural diets modeled from fatty acid compositions of hunter-gatherer diets.56 Pre-industrial US diets calculated from US Department of Agriculture economic disappearance data

Increasing dietary linoleic acid has been shown to increase oxidized linoleic acid derivatives in a dose-dependent manner in many tissues. These oxidized derivatives, along with other non-cholesterol lipid mediators, have been implicated in the pathogenesis of many diseases including coronary heart disease,

Whatever the explanation for key MCE data not being published, there is growing recognition that incomplete publication of negative or inconclusive results can contribute to skewed research priorities and public health initiatives.

figure 10 Diet-heart timeline: key research and policy events.

SDHS=Sydney Diet heart Study; MCE=Minnesota Coronary Experiment; AHA=American Heart Association; LA=linoleic acid

This is the saddest slide of all, 60 years of bad policy advice leading to worse health outcomes for people around the world.

Available evidence from randomized controlled trials shows that replacement of saturated fat with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. MCE findings add to growing evidence that incomplete publication has contributed to overestimation of benefits, and underestimation of potential risks, of replacing saturated fat with vegetable oils rich in linoleic acid.

Summary:

This is one of the few papers that make me mad. The research is good recalculating the actual results from the available raw data. I'm glad it got published, I'm sorry it was 60 years too late.