Tuesday, February 15, 2011

The New Conventional Wisdom

Years ago our teacher told us the story of the man who made canned tuna more popular than canned salmon. As I recall, this advertising guy had the account for some brand of canned tuna, which at the time was mostly being used as pet food. Most customers preferred canned salmon. What could he do to increase the public’s preference for this brand of tuna and thereby increase its sales? He came up with a simple slogan – “Guaranteed not to turn pink in the can.” Sales of canned tuna soon outpaced those of canned salmon. Was the man lying? No, his brand of tuna didn’t turn pink in the can. Neither did salmon, of course (or any other brand of tuna), but that’s beside the point.

This story makes two important points. First, it’s most likely a myth (see Snopes), but that hasn’t stopped it from being repeated endlessly as if it were true. The sincere repetition of false information as if it were true is common. Much of what we call “Conventional Wisdom” consists of just this sort of “knowledge.” Second, the practice of taking a it’s-true-but-so-what statement and making it the basis of an advertizing or public health campaign is alive and well.

Mark Sisson calls conventional wisdom his regular nemesis. It is the commonly accepted body of misinformation known by everyone, but unsupported by actual science. Everyone knows that lard and “other saturated fats” clog your arteries and cause heart disease. Reality TV shows (there’s an oxymoron) treat us to the spectacle of heavy folks being semi-starved and forcibly exercised into becoming lean, so everyone knows (including the “experts” that gave us the Dietary Guidelines for Americans, 2010) that eating less and exercising more is the key to attaining and maintaining a healthy weight. Everyone knows that “you are what you eat” and that the key to health is “all things in moderation.” The scientific literature, however, directly refutes each of these examples of common wisdom. So why, in the face of the current epidemic of obesity and chronic metabolic diseases, have the facts not impacted what everyone knows? It might have something to do with the hundreds of billions of dollars being made every year by the diet, fitness, health, medical, pharmaceutical, food processing, agriculture, regulatory, and public health industries.

Ancel Keys’ original hypothesis was that diets high in fat raised total serum cholesterol, which then produced atherosclerosis and heart disease. This is the infamous “Lipid Hypothesis” of heart disease. Within ten years, however, Keys modified his hypothesis to say that it was the saturated fat that produced the elevation in total serum cholesterol. He and his fellow lipophobes were then joined by members of the vegetarian-industrial complex, who were eager to seize on this message to promote their own interests.

There have always been people who, for a number of reasons (many of which are not justified - see Lierre Keith’s The Vegetarian Myth: Food, Justice, and Sustainability), don’t consume animal products. Since the primary sources of saturated fat in the American diet are animal products, Keys’ message supported the more evangelical vegetarians’ purposes quite well. The roots of the organic and sustainable agriculture movements are thoroughly entwined with the vegetarian belief system. Until recently, the terms “sustainable” and “organic” were synonymous with vegetarian. As these movements grew, their implicitly (and sometimes explicitly) anti animal products messages gained a wider audience. And then there’s the edible oil industry. They were quite happy to use the lipophobes’ message to promote their industrial products – corn oil, soybean oil, cotton seed oil, and derived products like margarine and Crisco – at the expense of their principle competition – natural products like lard, butter, and tallow. Their manufactured products were low in saturated fat and cholesterol. The natural animal products were not. This became the focus of their promotional campaigns. The statement of these differences was, of course, true. The health assertions, it turns out, were not. But they weren’t about to let the facts get in the way of a great sales strategy, so in addition to their own product marketing efforts they provided funding to various vegetarian-advocacy groups, disguised as “public health interest groups,” whose messages usually failed to mention either their benefactors or their principle beliefs. More and more heavily processed, plant-based “food” items are introduced every year, all of which tout their “healthfulness” because they’re low in the cholesterol and saturated fat that “has been linked with heart disease.” Yes, they’ve been “linked,” but what does that mean? It’s as truthful a statement as “won’t turn pink in the can!” Our current conventional wisdom is the result of this unhappy mix of ideology, dogma, and politics.

Unfortunately, it seems to me that we’re forming a new conventional wisdom within the low carb / paleo / primal / grass-finished and local food communities. It, too, is unsupported by the facts. For example, one concern of today’s consumer is the use, and the presumed presence in the meat, of artificial hormones. Poultry and pork are sold with claims of “no artificial hormones.” If you look carefully, you’ll see a very small footnote which states that it’s illegal to use artificial hormones to produce poultry and pork! The statement on the label is true, but so what? And oh, by the way. If you’re concerned about the potentially harmful effects of artificial hormones that might be in the meat you consume, don’t eat soy products. (See The Whole Soy Story: The Dark Side of America's Favorite Health Food by Kaayla T. Daniel.)

Another example: The other day I was reading a grass farming book by a well-known author who repeatedly stated that “chemical fertilizer burns out the soil organic matter.” Fertilizer can actually increase soil organic matter. The biggest factor in reducing soil organic matter is tillage. If you cultivate the soil, you’ll decrease that soil’s active organic matter fraction. There’s an association here, since most tillage agriculture involves the application of fertilizer, but association does not prove causation. If you keep the soil covered with long-term, perennial grass-clover pasture you will increase the soil’s organic matter content – regardless of how you fertilize it. In yet another example, the reporter in a news story examining grass finished beef stated that since the grass the cows were eating was “rich in healthy fat,” the meat was higher in omega 3 fatty acids than grain finished beef. Studies have shown that beef from grass finished cattle does have a lower omega 6 to omega 3 ratio, but the actual amount of omega 3 fatty acids may be about the same in both (only 13 milligrams more omega 3 per 3 ounce (85.5 gram) cooked portion). 1 Pasture herbage, by the way, is low-fat – usually less than 5% ether extract (“crude fat”). I must admit, it’s hard for me to read authors or listen to speakers who make these kinds of statements. If those who carry the message of low carb / paleo / primal way of life to the agricultural community repeat these examples of the new conventional wisdom, the danger is that our farmers and ranchers may not be able to listen to us, either.

When it comes to human health assertions for grass fed and finished animal products, I’m afraid the conversation is thoroughly tainted by the old conventional wisdom. Gary Taubes has emphasized the critical role that brutal criticism plays in a healthy science. New ideas are subjected to harsh critique from one’s peers. Without this type of internal review, false ideas can contaminate the science – not just the discipline they come from, but many others as well. The realm of human nutrition hasn’t had this kind of healthy critique for more than 50 years, and the contagion of its flawed reasoning and theories has spread widely. Most research papers regarding grass based animal products contain statements that summarize either the lipid hypothesis or the calories-in/calories-out hypothesis, or both. The other day I received a newsletter from a local grass finished meat supplier which, naturally enough, listed several statements meant to describe the benefits of grass finished over grain finished beef. Here are their points, along with my comments:

"Grass fed beef has about the same amount of fat as skinless chicken and wild game, adding beef to the list of food that actually could lower your LDL cholesterol."

Grass Finished Beef, NOT Low Fat!
That grass-finished beef is low fat may be true (although there are variations due to breed, etc., that make this a less-than universally true statement), but that’s only a good thing if you believe the lipid hypothesis. The truth is that the fatty acids in beef, either grass or grain finished, will actually improve your blood lipid profile! In general beef fat is 50 percent saturated fatty acids (one third of which is stearic fatty acid, which our bodies convert to oleic acid 2 – the primary fatty acid in olive oil), 42 percent monounsaturated fatty acids (90% of which is oleic acid), and 4 percent polyunsaturated fatty acids. 3 The science has shown that, in fact, eating beef tallow instead of carbohydrates would improve your blood lipid profile and lower your Coronary Heart Disease risk! [58 percent of the fat in beef tallow will improve your LDL:HDL cholesterol ratio. The remaining 42 percent will raise LDL cholesterol, but will also raise HDL cholesterol and will have an insignificant effect on the total cholesterol:HDL ratio.] 4
What's the "Heart-Healthy" Portion of this Meal?

"Assuming you eat a typical amount of beef, in a year, by switching to Grass fed beef you could save 18,000 calories a year. Which means if you change nothing else in your diet you could lose 6 pounds a year just by changing where your beef comes from."

This is an attempt to apply the failed calories-in vs. calories-out theory of obesity. For a detailed discussion of why this theory is not correct, please see Gary Taubes’ blog post The Inanity of Overeating and his newest book, Why We Get Fat, And What to Do About It.

"4o% of American’s don’t get enough Omega-3 fatty acids, the “good fat”. Not only are they important to the brain, they also play a role in every cell and system in the body. By keeping your brain healthy you are less likely to suffer from depression, schizophrenia, attention deficit disorder and Alzheimer’s. “Good fats” are linked to lowering blood pressure, reducing heart attacks, fighting depression and reducing cancer."

The phrase “good fats” belies the lingering taint of lipophobia. Dietary fat, saturated or not, is not a cause of obesity, heart disease or any other chronic “disease of civilization.” 5 (see Grass and Cancer). Refined carbohydrates, starches, and sugars are the most likely dietary causes of cancer, Alzheimer’s disease, and the other chronic diseases of civilization. 6 Diets low in carbohydrate are necessarily high in fat, typically animal fat. So, all animal fats have been “linked” to these improvements in health. In addition, beef, grass-finished or grain-finished, is a relatively poor source of omega 3 fatty acids when compared to oily fish, like wild-caught salmon.

"Omega-6 fatty acids are vital for human health. The bad news is; a diet too rich in these Omega 6’s had been linked to obesity, diabetes, immune system disorders and cancer! In order to function well our bodies require a balance between Omega-3 & Omega-6 fatty acids. Ideally 1:1 is the best ratio, grass fed beef is 2:1, while feed lot (grain fed, store bought) beef has a ratio of over 20:1. Huge difference!"

Yes, there is a huge difference between 1:1 and 20:1. That’s a true statement. But as shown by Duckett, et al., 7 the omega 6 to omega 3 ratio in grain-finished beef can be as low as 4:1. I’ve seen the 20:1 figure cited as the ratio of the typical American diet as a whole, so it appears they got these figures confused. As I’ve discussed previously (What’s the Limiting Factor?), just how important would this difference be if dietary carbohydrates are not restricted? How likely would someone be to realize any benefit?

"5 times more CLA is found in meat raised on grass. CLA can help prevent cancer and reduce cancer-cell growth."

As stated previously, the most likely dietary cause of cancer is refined carbohydrates. Restricting those while eating beef, regardless of how it was finished, is quite likely to prevent cancer (see Grass and Cancer). Coupled with appropriate supplementation of vitamin D, the impact is likely to be far in excess of that suggested by the conjugated linoleic acid (CLA) research.

"The National Cattlemen's Beef Association has noted that grass-fed beef has eight times more vitamin B12, six times more zinc and two and a half times more iron than skinless chicken breast."

This is true of beef, regardless of how it’s finished! 8

Until the flawed and failed lipid hypothesis of heart disease and the calories-in/calories-out hypothesis of obesity are fully discarded, we won’t make meaningful progress against the epidemic of chronic illnesses we face today. That awareness, coupled with the acceptance of the fundamental requirement for animal products for optimal human health, will permit us to have a meaningful discussion about the health benefits of grass fed and finished animal products. Until then, we must guard against creating a new conventional wisdom.

References

1 S. K. Duckett, J. P. S. Neel, J. P. Fontenot, and W. M. Clapham. 2009. “Effects of winter stocker growth rate and finishing system on: III. Tissue proximate, fatty acid, vitamin, and cholesterol content.” Journal of Animal Science 2009.87:2961-2970.

2 Grundy, S. M. 1994. “Influence of Stearic Acid on Cholesterol Metabolism Relative to Other Long-Chain Fatty Acids.” American Journal of Clinical Nutrition. Dec.; 60(6 suppl.):986S-90S

3 USDA. 2010. Composition of Foods Raw, Processed, Prepared. USDA National Nutrient Database for Standard Reference. Release 23 http://www.nal.usda.gov/fnic/foodcomp/search/

4 Taubes, Gary. 2008. Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease. Anchor Books. New York, NY. pp 168-169

5 Ibid p 454

6 Ibid

7 S. K. Duckett, J. P. S. Neel, J. P. Fontenot, and W. M. Clapham. 2009. “Effects of winter stocker growth rate and finishing system on: III. Tissue proximate, fatty acid, vitamin, and cholesterol content.” Journal of Animal Science 2009.87:2961-2970.

8 USDA. 2010. Composition of Foods Raw, Processed, Prepared. USDA National Nutrient Database for Standard Reference. Release 23 http://www.nal.usda.gov/fnic/foodcomp/search/ [A comparison of “Beef, round, outside round, bottom round, steak, separable lean and fat, trimmed to 0” fat, all grades, cooked, grilled” with “Chicken, broilers or fryers, breast, meat only, cooked, roasted.”]

4 comments:

  1. Great blog post. However, Ancel Keys did not come up with the "lipid hypothesis." In name, the term "lipid hypothesis" was popularized in print by Pete Ahrens and possibly used in print for the first time by Daniel Steinberg, and in neither case was it proposed as a hypothesis directly related to diet or in any way dependent on Keys. The actual hypothesis dates to Anitschkov's 1913 cholesterol-fed rabbit model, and Anitschkov was very clear he considered the model to have metabolic and not dietary implications for humans. Keys' hypothesis was formulated as "the diet-heart question" by Ahrens and other prominent researchers in the 1960s, and it was dependent on the lipid hypothesis but quite distinct from it.

    I have a couple blog posts on this that you might be interested in.

    The Proper Use of the Term "Lipid Hypothesis"

    http://blog.cholesterol-and-health.com/2011/02/proper-use-of-term-lipid-hypothesis.html

    The Origin of the Lipid Hypothesis -- And Proposal of New Term

    http://blog.cholesterol-and-health.com/2011/02/origin-of-lipid-hypothesis-and-proposal.html

    How Conflating the Lipid Hypothesis With the Diet-Heart Hypothesis Led to the Public Condemnation of Bacon, Butter, and Eggs

    http://blog.cholesterol-and-health.com/2011/03/how-conflating-lipid-hypothesis-with.html

    Chris

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  2. Thanks for that input, Chris. And thanks for your posts and work.

    Pete B

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  3. Pete,

    Excellent points -- we have to be cautious of switching places with the anti-science lipi-phobes and becoming anti-science carb-phobes!

    When I went to the local farmers' market, the ones selling grass-fed beef ALL had marketing material pointing to how it was leaner and lower in fat.

    Cheers!

    ReplyDelete
  4. Thanks for your comment. Sorry to not reply sooner. "Technical" difficulties ... Finally figured out a "solution." Maybe time for WordPress?

    One reason I came back into the agricultural realm is exactly what you observe - the producers have "drunk the Kool-aid" of the low-fat-is-good-health cult. It's been uncomfortable as I've looked into several pieces of "new conventional wisdom," but I don't think we can afford to ignore them.

    Regards,

    ReplyDelete