Thursday, July 28, 2011

"Saturated Fat Is Bad": The Lie That Never Dies

Go ahead & eat it: you know you want to
I came across this article in Health & Fitness section of today's Globe & Mail. A reader asks Leslie Beck, a dietician, whether eating a medium rare steak is bad for him, as his wife suggests. Now, I haven't looked into the purported negative effects of grilling or cooking meat viz the generation of carcinogens. However, the overall bad science based upon assertions not backed up by the evidence make me skeptical.

Whenever I read about articles about red meat in the mainstream media, they inevitably repeat the same mantra: meat contains saturated fat, saturated fat is bad for you, and meat causes colon cancer.

But this is based upon the most simplistic understanding of human metabolism, on the one hand, and a handful of inherited prejudices connected to social power and the denigration of working class people as fat, over-eaters, lazy, etc. Let's look at the claims made by Beck in her article:

1. "Some cuts of red meat can be high in saturated fat, the type of fat that to raises LDL (bad) cholesterol in the blood."

2. "Many studies show that people who eat the most red meat – as well as processed meat (luncheon meat, bacon, hot dogs, sausages) – are at greater risk for colon cancer than those who eat little red meat."

Let's start with the first claim, that saturated fat raises "bad" cholesterol. First of all, calling LDL the "bad" cholesterol is actually a vast oversimplification of cholesterol and its role in the body. There is ample evidence that low LDL cholesterol in the brain is a prime contributor to Alzheimer's Disease and other dementias. As this 2009 study noted, the consumption of high carb and low fat diets can cause changes to blood chemistry that leads to low brain cholesterol, the impairment of neuronal function and ultimately a cascading effect that includes all the symptoms that we're familiar with - neurofibrillary tangles and the accumulation of plaque. Given that the brain - which makes up 2% of total body weight - contains 25% of the total cholesterol in our body, we shouldn't be surprised that reducing cholesterol would have a deleterious effect on brain function. It is, in fact, hypothesized that a rise in LDL cholesterol in the blood is possibly an attempted defensive response by the body attempting to overcome the depletion of LDL uptake in the brain.

"...an excess of dietary carbohydrates, particularly fructose, alongside a relative deficiency in dietary fats and cholesterol, may lead to the development of Alzheimer's disease. A first step in the pathophysiology of the disease is represented by advanced glycation end-products in crucial plasma proteins concerned with fat, cholesterol, and oxygen transport. This leads to cholesterol deficiency in neurons, which significantly impairs their ability to function. Over time, a cascade response leads to impaired glutamate signaling, increased oxidative damage, mitochondrial and lysosomal dysfunction, increased risk to microbial infection, and, ultimately, apoptosis."


But back to the main point, which was that saturated fat - in this case from meats - causes a rise in LDL cholesterol. Stephen Guyenet, a biochemist and neurologist, writing at Whole Health Source pulled together all of the studies that looked at the relationship between saturated fat and high cholesterol and examined their conclusions:

Of all the studies I came across, only the Western Electric study found a clear association between habitual saturated fat intake and blood cholesterol, and even that association was weak. The Bogalusa Heart study and the Japanese study provided inconsistent evidence for a weak association. The other studies I cited, including the bank workers' study, the Tecumseh study, the Evans county study, the Israel Ischemic Heart study, the Framingham study and the Health Professionals Follow-up study, found no association between the two factors.


As to the second claim, it's probably useful to point out that Beck is being dishonest from the start. The study she is referring to - and is trying to slide past us - groups together a whole food (i.e. unprocessed meat) with a processed food. But these are two different things. Processed meats contain all sorts of goodies - sugars, colorants, flavour enhancers, "liquid smoke", probably industrial oils (corn, canola, etc), and God knows what else. But a meta-analysis of observational studies on the relationship between eating meat and cancer found no correlation. Now, as Dr. Eades points out in his review, there are serious methodological problems with observational studies in general and meta-analyses in particular. It is problematic to prove true correlation even where a relationship is observed between two phenomenon because without isolating one factor from all others a la double-blind studies, etc the relationship could be coincidental. However, it is more effective in proving that there is no relationship between factors if there is no correlation in the data.

After sifting through all this data, what did the authors find? Absolutely nothing. No correlation between meat and/or fat intake and colorectal cancer.
"In this meta-analysis, no consistent evidence of a positive association between consumption of animal fat and colorectal cancer was observed. Specifically, we found no association between the highest animal fat intake category and colorectal cancer. Furthermore, none of the subgroup analysis (i.e., sex, anatomic tumor site, and study design) indicated positive patterns of associations."
And their conclusion:
"On the basis of the results of this quantitative assessment, the available epidemiologic evidence does not appear to support an independent association between animal fat intake or animal protein intake and colorectal cancer."


And while studies show no relationship between animal based diets and the risk of cancer, or even of diets high in saturated fat and cancer, there is definitely a relationship between high corn oil diets and cancer. So, why isn't Beck warning the reader to forego that cob of corn that he grilled alongside his steak?

I do agree with one thing she says about animal fat and fatty cuts of meat. Because we feed our meat animals primarily grain-based diets - and primarily corn based at that - we are loading them up with a food source that increases their omega 6 ratio. Industrially raised animals are also packed full of growth hormones and antibiotics. In general adipose tissues are where old chemicals go to die - or lie dormant until the fat is mobilized by the body, as any person whose ever had an LSD flashback can tell you. If you're eating industrially raised cows, pigs, etc. you probably want to go for leaner cuts. First off, industrial meats tend to be higher in fat because of their diet but that fat is also low quality fat, high in omega 6's and often perfused with nasty by-products of the industrial growth process. Because of the prevalence of corn throughout our diet - as aptly discussed in The Omnivore's Dilemma - we consume entirely too many omega 6's. As the study discussed above suggests, there is a strong relationship between omega 6 consumption and rates of cancer.

There's a large body of evidence implicating excess omega-6 fat in a number of cancer models. Reducing omega-6 to below 4% of calories has a dramatic effect on cancer incidence and progression*. In fact, there have even been several experiments showing that butter and other animal fats promote cancer growth to a lesser degree than margarine and omega-6-rich seed oils.


All of this brings us back to the fact that you should probably ignore dieticians and doctors who repeat verbatim the unvalidated prejudices of the dominant nutrition model. Ultimately, the attack on food and meat consumption is part of the same internalization of an austerity mindset that blames working class people for the economic crisis ("they bought too much stuff that they can't pay for!") and for the health crisis that is sweeping North America.
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