martes, 6 de abril de 2010

Saturated fat

Today we’re going to talk about one of the most powerful and long-lasting myths of the last century. A myth, this is, that may have negatively affected the health of whole populations, that has guided your food choices, and has been erroneously used by medical institutions, food companies and governments.

This myth is called the ‘lipid hypothesis’. It proposes a link between saturated fat and chronic heart disease (CHD). First developed in the 1950s, the hypothesis studied the connection between blood plasma cholesterol levels and CHD.

One of the proponents of the hypothesis was Ancel Keys, an American who published his study about the issue in 1953. In his analysis he used a selection of seven countries, plotting their data on a graph with axis of “percentage calories from fat” against “CHD, deaths per 1000”.

The countries chosen for the study showed a positive correlation between the axis. From Japan, a low consumer of saturated fat with a low incidence of CHD, through Italy, England and Wales, Australia, Canada, and the US at the other end of the scale.

However. In “The Cholesterol Myths”, Uffe Ravnskov redraws the graph, this time including all the countries for which data existed at the time Keys published his study. The result is totally different; instead of a clean line, there appears a chaos of dots with apparently very little relation binding them together. Using the same logic that Keys used, we can, as other bloggers have done, prove a variety of contradictory conclusions if we ignore certain countries.

This, in fact, is exactly what Keys did. After having studied a total of 22 countries, he only included those that supported the hypothesis that he wanted to prove. (We also have to admit that even if he had included all the data from all the countries, his study would still be somewhat weak due to the failure to eliminate other variables, which is the basic rule if you want to prove a certain hypothesis).

The lipid hypothesis is still exactly that; a hypothesis; more studies refute it than support it. However, because it has been so unquestioningly accepted by institutions like the American Heart Association, many food companies, the medical establishment and the 1977 Dietary Goals for the United States, despite the lack of enough concrete evidence, it has filtered into public opinion, and has created much confusion at dinner time.

“The literature about the lipid hypothesis is impregnated with fraudulent material and designed to change negative evidence for positive evidence. This fraud is relatively easy to detect”

Russell L. Smith, PhD

So… what does this all mean for us? It means that the conventional wisdom about saturated fats is based on weak or totally incorrect studies.

From the Weston A Price Foundation:

“Saturated fats are required for the nervous system to function properly, and over half the fat in the brain is saturated. Saturated fats also help suppress inflammation. Finally, saturated animal fats carry the vital fat-soluble vitamins A, D and K2, which we need in large amounts to be healthy.”

Coming soon: Which fats should we be eating?

This post is proud to be part of Real Food Wednesdays

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