Monday, July 2, 2012

Cholesterol and Saturated Fat Prevent Heart Disease – Evidence from 101 Scientific Papers - Evans

Book Review: Cholesterol and Saturated Fat Prevent Heart Disease

Posted by Tom Naughton
I receive a fair number of emails and comments from people urging me to add a section to the blog that lists studies supporting a low-carb diet. Yes, that would be a worthy project, but it’s not one I’ll have time to tackle anytime soon.

However, I’ve frequently referred people to David Evans’ Healthy Diets and Science website, which is basically a compilation of health and nutrition study abstracts, conveniently indexed by topic in the right sidebar. I don’t know where he manages to dig up all these abstracts, but there are nearly a thousand of them, spanning decades of research.

I’m pleased to announce that Evans has recently published a book with the provocative title Cholesterol and Saturated Fat Prevent Heart Disease – Evidence from 101 Scientific Papers. The content is exactly what the title promises: a list of 101 studies that dispute the hypothesis that fat and cholesterol cause heart disease, with quite a few of them suggesting that saturated fat and cholesterol are, in fact, good for us. For each study, there’s a title, a citation and a brief summary (with occasional commentary) by Evans.

Here are just a few example titles:

Diets high in carbohydrates which have a high glycemic load increase heart disease risk by 98%.

Vegetable oils implicated in increased death rates.

A high saturated fat diet gives protection from heart disease.

These are the studies you don’t often read about in the media, and of course they’re also the studies most doctors have never heard of, much less actually read. Many of them are observational studies, and I’ve pounded home the point over and over that observational studies don’t prove anything. So does that make these studies worthless as evidence?

Not at all.

As I explained in my Science For Smart People speech, if someone spots a correlation between A and B in an observational study and proposes that A causes B, one of the questions we should ask ourselves is whether or not we see a link between A and B consistently. If we don’t, it’s highly unlikely that A is causing B.

The example I gave in the speech was the observation that people who live near power lines have higher rates of cancer. Naturally, plenty of journalists and ambulance-chasing lawyers immediately concluded that power lines cause cancer. More cautious types pointed out that poor people are more likely to live near power lines, and poor people have higher rates of cancer for all kinds of reasons.

What finally put the power-line scare to rest was another observational study that found a completely opposite correlation: people who work on power lines for a living – and are therefore consistently exposed to more electrical current than people who merely live near power lines – have lower rates of cancer than the population as a whole. If proximity to power lines caused cancer, the people who work on them would have high rates of cancer. But they don’t. No consistency, no scientific validity, no cause and effect.

The same principle applies to observational studies about dietary fat and heart disease. If several observational studies show that people who eat a lot of saturated fat have higher rates of heart disease, but several other observational studies show that people who eat a lot of saturated fat have lower rates of heart disease, then it’s extremely unlikely that saturated fat causes heart disease. That’s the value of observational studies as evidence: they’re better at disproving a hypothesis than they are at proving one.

There are plenty of clinical studies cited in the book as well, and you can already guess what the evidence Evans has compiled shows: it’s not the fat in our diets that causes heart disease; it’s the sugars, refined carbohydrates, processed vegetables oils and other garbage.

For those of you who’ve written to me asking for evidence you can cite in a lecture or class paper, this is a book you need in your library. For those of you who’ve written asking for evidence that will convince your loved ones your high-fat diet isn’t going to kill you, ditto. For those of you who’ve written to tell me Fat Head is an irresponsible and dangerous film that will inspire people to eat high-fat diets and die of heart disease … well, never mind. Nothing’s going to convince you anyway.
But for those of you who are interested in the actual science, this is a great little reference.
Read the complete review of David Evans' book "Cholesterol and Saturated Fat Prevent Heart Disease – Evidence from 101 Scientific Papers" by Tom Naughton here.

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