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Evidence for Dietary Guidelines?

Evidence for Dietary Guidelines?

They had hard evidence when they implemented our dietary guidelines… They did nothing with it.

What would you say if those who formed our modern guidelines were liars? That’s a pretty outrageous claim, but sadly, it is the truth. They spent all their time demonizing fat but had no evidence to do so. In fact, there was clear confirmation at the time that saturated fat was not harmful and did not lead to heart disease. Good going guys…

 

Good job - you had evidence against your guidelines and did nothing with it


In 1977 the United States government implemented the very first dietary guidelines after several epidemiological studies hinted at the correlation between heart disease and saturated fat intake. However, in the realm of scientific research, epidemiological studies are the weakest kind of evidence. They are usually just the beginning for further research.

These kind of studies look at general trends of disease over large populations. They are not randomized controlled trials (RCTs) where they give subjects the intervention to look at the outcomes. RCTs boil down the cause of something to one variable while epidemiological studies have no control for variables. Despite this fact, politicians made the move forward. I guess scientific proof doesn’t matter to them.

The United Kingdom soon followed the US with its guidelines introduced in 1983. Ever since then, both countries have promoted a diet low in fat and especially low in saturated fat (less than 10% of caloric intake).

If randomized controlled trials are the standard for medical care, then why did we change the diet of millions of people without it? That is great question, and we may never know. Money. Power. Special interest. Who knows. But the one thing we do know is that they had no reason to give these recommendations.

Summary

The article I looked at this week was quite enlightening. The researchers go through every one of the randomized controlled trials available in the 70’s that show the relationship between saturated fat / cholesterol intake and heart death. The conclusion was obvious. There was no statistically significant risk with the consumption of saturated fat.[1]

Zoe Harcombe, one of my personal heroes on this topic, led a team of researchers in the UK and US to discover what evidence they based dietary guidelines on. Feel free to take a look at the article for yourself and follow along. [Click here for the file.]

Harcombe Z, Baker JS, Cooper SM, Daview B, Sculthorpe N, DiNicolantonio JJ, Grace F. (2015). Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis. Open Heart 2: e000196. doi: 10.1136/openhrt-2014-000196.


Usually I have a whole list of bullet points about the most important facts of an article, but this time there are really only two:

  • Evidence available in the 70’s showed no difference in all cause mortality with a higher amount of diet calories coming from saturated fat. The risk ratio was 0.996.
  • Evidence available in the 70’s showed no difference in heart related mortality with a higher amount of diet calories coming from saturated fat. The risk ratio was 0.989.

Yep, it’s that simple. The evidence showed no improvement to the risk of death by lowering total fat / saturated fat intake. Their claims in the 70’s which led to guidelines that changed the diet of hundreds of millions of people were not substantiated by clinical research! Ahhh, what a crazy world we live in today.

Finding the studies

The researchers went through all of the randomized controlled trials that were published at the time. They had criteria at the beginning of the search that narrowed things down. They looked at studies that met the following criteria:

  • Were published before 1983
  • Lasted at least 1 year
  • Were in the data bases MEDLINE and Cochrane Library
    • Other resources available at the time were “grey literature sources” (i.e. could not be relied on).

This narrowed the list to 98 studies total. The researchers read through each one of these to narrow the list further. They excluded studies that were non-controlled trials, that included drug interventions, that were on non-human subjects, that looked at more than 1 variable, that did not look at diet and heart relationships, and that did not include dietary fat interventions. They then went through some other qualifications that eliminated more studies. All-in-all, this left them with 6 fully qualified, randomized controlled trials to look at.

Check out the figure below which outlines their qualification process:

 

Flowchart describing the criteria process for narrowing down applicable studies


You can find the 6 studies that were analyzed for this meta-analysis in the References section of this post.
[2][3][4][5][6][7] There were 7 total dietary interventions with the 6 studies. Each one looked at the effects lowering fat intake had on the incidence of heart failure (or general death).

Results

As stated above, there was no significant variation between those given the dietary interventions of lower fat and those who weren’t. This was a huge finding because no studies were conducted specifically looking for the impact of the stated guidelines. Those in power of making our standard diet felt they were right without conducting trials to make sure. This was the first time a group of researchers set out to find the validity of their claims. Again, they found absolutely no grounding for their recommended diet. For this conclusion we have to look at the risk ratios.

“Risk ratio” is a way of comparing the risk of some event happening between two groups. In this context they measured risk of all cause mortality (general risk of death) and the risk of heart deaths. They do this by looking at the risk given by each individual study and then averaging out the results with the proper weighting involved. The two groups were those given an intervention and those remaining on a non-controlled diet.

 

Risk ratios from the individual studies


The intervention groups were the ones given a diet low in fat to specifically see the outcomes of that kind of diet. The control groups were the ones left alone for comparison. A risk ratio above 1 means that the control groups showed “better” outcomes – meaning that those remaining on a normal fat diet had better chances of survival. A risk ratio below 1 means that the groups given an intervention had a better chance of survival.

The overall total of all of these studies showed a risk ratio of 0.996 for all cause mortality and 0.989 for heart mortality. Those ratios are right on the line of 1. That means there was no difference in deaths between those given a low-fat diet and those who were not.

Cholesterol lowering effects

One point I have been harping on for a long time is that high cholesterol does not cause heart disease. This article also supports that claim. Each of the diet interventions of lower fat or saturated fat showed a decrease in cholesterol levels. Despite each group lowering their cholesterol, there was no change in their rates of heart deaths. It appears to be a 50/50 chance of whether or not you die of heart complications.

Those that had a normal diet died just as much as those with a lower fat diet. If you are interested in learning more about cholesterol (it’s roles in the body and why it does not cause heart disease), then check out our other article on it. Click here to see it. Anyway, the point is that although people lowered their cholesterol, that did not save them from heart death. We seem to be looking at all of the wrong causes…

Check out the summary of the cholesterol changes below, and you can see that each group did, indeed, lower their cholesterol. Each line correlates with the same studies as the picture above.

 

Each group lowered their cholesterol

Summary

  • Evidence available in the 70’s showed no difference in all cause mortality with a higher amount of diet calories coming from saturated fat. The risk ratio was 0.996.
  • Evidence available in the 70’s showed no difference in heart related mortality with a higher amount of diet calories coming from saturated fat. The risk ratio was 0.989.

At the time dietary recommendations came out, there were a multitude of studies showing their is no extra risk of heart disease in people who ate more fat. Why they decided to go with their recommendations anyway may remain a mystery forever. It is time we eliminate the dietary guidelines of today because politicians had no reason to implement them in the first palce.

References:

[1] Harcombe Z, Baker JS, Cooper SM, Daview B, Sculthorpe N, DiNicolantonio JJ, Grace F. (2015). Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis. Open Heart 2: e000196. doi: 10.1136/openhrt-2014-000196.

[2] Rose GS, Thomson WB, Williams RT. (1965). Corn Oil in Treatment of Ishaemic Heart Disease. British Medical Journal 1(5449): 1531-1533.

[3] Research Committee. (1965).  Low-Fat Diet in Myocardial Infarction: A Controlled Trial. The Lancet 286(7411): 501-504.

[4] Medical Research Council. (1968). Controlled Trial of Soya-bean Oil in Myocardial Infarction: Report of a Research Committee to the Medical Research Council. The Lancet 292(7570): 693-700.

[5] Dayton S, Pearce ML, Hashimoto S, Dixon WJ, Tomiyasu U. (1969). A Controlled Clinical Trial of a Diet High in Unsaturated Fat in Preventing Complications of Atherosclerosis. Circulation 40(1S2): II-1-II-63.

[6] Leren P. (1970). The Oslo Diet-Heart Study. Circulation 42(5): 935-942.

[7] Woodhill JM, Palmer AJ, Leelarthaepin B, McGilchrist C, Blacket RB. (1978). Low Fat, Low Cholesterol Diet in Secondary Prevention of Coronary Heart Disease. Drugs, Lipid Metabolism, and Atherosclerosis. Advances in Experimental Medicine and Biology 109: 317-330.

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