Skeptics question researchers’ conclusion that recommendation to limit saturated fat unfounded

By Elizabeth Crawford

- Last updated on GMT

Skeptics question conclusion that limiting saturated fat unfounded

Related tags: Heart disease, Nutrition

A new study in Open Heart suggesting the U.S. and U.K. never should have recommended limiting saturated fat to reduce the risk of heart disease is a “rehash” of previously examined data and does not prove the advice should be overturned, according to some dietary and heart disease experts. 

The meta-analysis​ published Feb. 9 found no evidence to support the recommendation to reduce dietary fat intake to 30% of total energy and saturated fat to 10% of total energy as a way of lowering the number of deaths from heart disease, prompting the researchers to agree with the recently voiced sentiment that the advice needs to be reviewed. 

But critics of the study note that it included only randomized controlled trails available at the time the public health recommendations were made in 1977 and 1983, and therefore does not take into account the full picture. In addition, they note, the RCTs in the study have already been rigorously reviewed and add nothing new to the ongoing debate. (Read more about the controversial research on saturated fat HERE​ and HERE​.)

The study disregards “an enormous body of observational and experiential evidence”​ linking high-fat diets to plasma lipid levels, which have been linked to hardening arteries, said Thomas Sanders, a professor of nutrition and dietetics at King’s College London.

Are RCTs the gold standard for long-term behavior changes?

The researchers, led by Zoe Harcombe of the University of the West of Scotland, acknowledged some of the observational work, but reasoned that such studies could reveal only relationships, not causation. For that, “RCTs provide the best evidence,”​ they note.

Working on this premise, they reviewed six RCTs and found overall the number of deaths from all causes to be identical between the participants who lowered their fat intake and those who did not. They acknowledged slightly more participants died from heart disease in the group that did not lower their fat intake, but said the difference from the control group was insignificant.

From this they concluded “the available RCTs did not support the introduction of the dietary fat recommendations in order to reduce CHD risk or related mortality,”​ and therefore the recommendation should be reconsidered.

The authors’ conclusion, however, is open to debate, suggests Rahul Bahl, an associate editor for Open Heart with the University College London. He explains in an editorial​ that accompanies the study that some of the results reported in the meta-analysis are “controversial”​ and notes the authors’ decision to exclude from their study some research that found replacing saturated fat with polyunsaturated fat could offer some heart health benefits.  

“Small differences in the criteria used to include studies in different parts of the analysis can lead to large differences in reported results,”​ he explains.

He also suggests that RCTs might not capture the long-term benefits of changes in real world settings, and therefore observational studies should be considered before making any changes in the health recommendation.

“The existence of nutritional guidelines can be beneficial through altering the content of food available, changing how food is packaged and through setting normative standards for what is considered healthy. Small reductions in risk factors at a population level might then be expected to have large effects on the rates of the disease,”​ he said, adding: “Such mechanisms are difficult to replicate in a trial setting.”

Public policy does not require RCTs

Evidence from RCTs is not generally required for public policy, so advocating for the withdrawal of the dietary fat recommendation on this basis is unusual, Bahl also notes.

Sanders agrees that “public health guidelines do not operate in the same arena as drug trials,”​ which require evidence based data using death or disease incidence as endpoints, and therefore a demonstrated statistical significant reduction in heart disease mortality is unnecessary.

Rather “eminence based”​ data, or “the best guesses available from experts in the area at the time,”​ can be sufficient, he said.

Plus, he noted, the impact of the recommendation appears to “have turned out OK, as the [heart disease] rates fell in countries that adopted the policy of replacing saturated with polyunsaturated fatty acids.”

With that in mind, he suggested the guidance to follow a “prudent diet” ​continues to make sense – a sentiment that Bahl also espoused.

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2 comments

Missing the point

Posted by Raiden,

It's not about fat composition, it's about the foods that these fats come from.

Most of the mens and womens eating high SFA diets are getting it from lots of meat, cheese and eggs.

If you start each day with the full english breakfast, of course thats unhealthy.

On the other hand if you started the day with 75g of Dark Chocolate, that's much more healthy, even though it contains a large amount of saturated fat.

There's also the issue of PROTEIN that gets overlooked. The full english is packed with animal protein, too much of which is very unhealthy, just as much as fatty acids content.

Other high fat foods like almonds or walnuts are stunningly healthy when consumed as a snack.

The healthy diet eats meat maybe 4 times a week (sometimes fish) as a treat food, and eats plenty of green veg, red veg, yellow veg, herbs, Olive Oil, Shiitake Mushrooms, Almonds, Walnuts, Dark Chocolate, Green Tea etc.

Fats be damned, yes you need a MUFA:PUFA:SFA ratio thats sensible and Omega 3, but the type of foods they come from is most important.

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Oh dear!

Posted by P Rogers,

So never mind the science, we know better. What a dreadful exhibition of closed minds. So now we know how whistle blowers are bullied.

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