Wednesday, 30 October 2013

Good Week for Saturated Fat!!

Saturated fat has had some good press the last couple weeks. 

Dr. Perlmutter was on the Dr. Oz show extolling the benefits of butter. 

BMJ published a review article by British cardiologist Asseem Malholta in which he states that saturated fat and cholesterol are not the major issue causing heart disease. (1)

Catalyst, as news show on the ABC network in Australia aired part 1 of a 2 part series with many doctors and researchers who believe that saturated fat and cholesterol do not cause heart disease. (Part 2 will be on next week) It included a quote from George Mann, a retired professor of biochemistry and medicine at Vanderbilt University who worked on the Framingham heart study:

"One of the Framingham researchers became so dismayed with the results, he wrote a scathing review of the whole diet-heart hypothesis, saying that people had been misled 'by the greatest scientific deception of our times, the notion that animal fat causes heart disease'."

Recent Research


A 2010 meta-analysis published in the American Journal of Clinical Nutrition Concluded that:(2)

" A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD."

Earlier this year a group examined data from The Sydney Diet Heart Study which was done in the 1970's.  In this study the experimental group decreased the saturated fat in the diet and increased the amount of omega 6 polyunsaturated fat. (polyonsaturated fats are the ones the various health agencies claim are heart healthy) 

 When originally published in in the 70's it did not include any data on Cardiovascular deaths.  I find this rather odd since it was called the Sydney Diet HEART Study.  Since the CVD deaths data was omitted I have seen this study used to support the theory that saturated fat causes heart disease since cholesterol was lowered in the low saturated fat group.

When the data was recovered and analyzed it showed that the group eating more saturated fat had lower  rate of CVD deaths than the group eating more polyunsaturated fats which led to the conclusion:(3)

" Advice to substitute polyunsaturated fats for saturated fats is a key component of worldwide dietary guidelines for coronary heart disease risk reduction. However, clinical benefits of the most abundant polyunsaturated fatty acid, omega 6 linoleic acid, have not been established. In this cohort, substituting dietary linoleic acid in place of saturated fats increased the rates of death from all causes, coronary heart disease, and cardiovascular disease. An updated meta-analysis of linoleic acid intervention trials showed no evidence of cardiovascular benefit. These findings could have important implications for worldwide dietary advice to substitute omega 6 linoleic acid, or polyunsaturated fats in general, for saturated fats."

 If all this is true why did all the health organizations start giving our dietary recommendations to cut saturated fat in the first place?

 Some bad science.

In the 1950's a researcher named Ancel Keys presented an observational study comparing the percentage of fat in the diet to death from heart disease in 6 countries shown below.  Thanks to Peter from Hyperlipid for the graphs.

As you can see Keys graph showed a correlation between fat intake and heart disease, it is almost a perfectly straight line.  There were a few problems with his study.  First it was an observational study so although it can show correlations it cannot provide any information on cause and effect.  I discussed the limitations of observational studies in a previous post.

Keys used 6 countries (Japan, Italy, England and Wales, Australia, Canada and the USA) in his study but there was data for 22 countries available when he did his study.  Using 6 other countries  shows a negative correlation between fat in the diet and deaths from heart disease.

  When all 22 countries are plotted on a graph they are all over the place and there isn't much of a correlation.  There are countries like the Netherlands that eat a lot of fat and a low rate of heart disease deaths.  In Finland they eat less fat than the Netherlands yet they have rate of heart disease deaths over 3 times as high.  The red dots below are data added from some hunter gatherer populations that eat a high fat diet and have very low rates of heart disease ( Masai, Inuit, Tokelau and a few others)


Politics in the American Heart Association

Keys study was initially met with skepticism.  The American Heart Association (AHA) did not immediately accept the diet heart hypothesis.  They acknowledged the correlation in the study but that did not mean there was any proof that reducing fat in the diet would reduce heart disease deaths.  Clinical trials needed to be done that showed a reduction in dietary fat would lead to lower heart disease deaths before they could give a diet recommendation to the American people.  By 1961 the AHA had changed its position and was now recommending a low fat diet.  Does this mean that the clinical trials had been done that proved a high fat diet caused heart disease?  No, those trials had not been done.  What had changed was that now Keys and a few other like minded people were on the AHA committee that made the decision to support Keys research.

The government will makes things better, right??

In 1968 a Senate Select Committee on Nutrition and Human Needs was formed headed by George McGovern.  Originally its mandate was to eliminate malnutrition but in the 70's they started looking into the link between diet and chronic disease.  At the time there was a controversy in the scientific community as to whether lowering the amount of fat in the diet would lead to improvements in health.  The committee  sided with Keys and the AHA despite protests from other researchers.  When the dissenting researchers told McGovern that there wasn't enough evidence to make these recommendation McGovern replied,

 “we Senators don’t have the luxury that a research scientist does of waiting until every last shred of evidence is in.”  

The following clip is from Tom Naughton's documentary "Fathead":

They were so sure that the theory that saturated fat causes heart disease was right they decided to release the guideline without proof they were correct.  They assumed that once the research was done it would validate the theory. ( You know what they say about assumptions )  For the last 40 years they have done study after study spending billions of dollars but have yet to prove that the theory is correct.  During that time people have been following that advice and we have become fatter and sicker.  Obesity and diabetes rates are skyrocketing.  I am hoping that the recent will convince people that the natural saturated fat we have been eating for thousands, if not millions of years is healthy and that the man made vegetable oils, sugars and refined grains that we have only been eating for about 100 years are the real problems in our diets. 

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