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.”]

Tuesday, February 1, 2011

What is Grass Based Health?

Animals make us human.
Temple Grandin

. . . the Andamanese believe it is the possession of fire that makes human beings what they are and distinguishes them from animals.
Radcliffe-Brown, A. 1922.
The Andaman Islanders: A Study in Social Anthropology.
Cambridge, UK: Cambridge University Press.1

So, what does barbecue make us?

With his new opposing thumb and his king-sized cranium,
Man sallied forth with grace and savoir faire.
With Promethian desire he soon discovered fire,
And arson but a single step from there.
The wheel and gasoline, to the full-sized limousine,
Music, art and law are but a few,
But name what can compare to the artistry so rare of
the sparerib that has met the barbecue.
from The Big Band Theory. Mark Graham.2

I recently had the opportunity to attend the 7th Annual Cattlemen’s Workshop in La Grande, Oregon. It was a wonderful opportunity to connect with the region’s beef industry and learn from the ranchers, industry and University folks who were there. One lesson I learned is that “Grass Based Health” means something to everyone, but it may not mean the same thing to everyone. So I thought it was time to define what I mean by the phrase.


Grass Based Health is the concept that pasture-based livestock production systems are better for the animals, better for the farmers and ranchers, better for the land, and better for the communities they are a part of than the alternative livestock production systems. I’ll be covering all of these topics in future posts. But the fundamental principle of Grass Based Health is that our diet ought to be grass based, not grain based. Understanding and accepting this premise then forces the consideration, and re-consideration, of many other topics as well.

It’s obvious (or it ought to be!) that we lack the herbivores’ specialized ingestive and digestive anatomy that permits them to utilize cellulose. We depend on various animals to convert cellulose, the most common organic compound on Earth[3], into animal fat and high quality, complete protein. The majority of feed units consumed by all domestic livestock (beef cattle, dairy cattle, hogs and poultry, sheep and goats, horses and mules, and “other”) in the US in 1970 came from forage (54.4% of all feed units, 36.1 and 18.3 percent from pastured and harvested forage, respectively).[4] I’ll simplistically refer to all forage as “grass” from now on. A grain-finished steer spends most of his life eating grass, and is only fed grain as a portion of its diet during the finishing phase. Even then, its ration still contains grass. So, even today meat and dairy products can be described as “grass based.” I do believe that there is vast room for improving the production and utilization of grass in pasture-based production systems, and I’ll address that in future posts. 

Terms like “grass-fed,” “free-range,” “pastured,” and “organic” are all used to market food today. Quantitative and qualitative differences have been determined between grass-finished and grain-finished meats. Similar differences have been determined between the milk from dairy cows grazing pasture compared to those housed in confinement systems. Just how important are these differences? Future posts will deal with this subject, too. I am concerned, however, that the claims some make for these products are over-stated. Without addressing the biggest insult to human health – an oversupply of readily digestible refined carbohydrates – is the consumer likely to realize any of these benefits? (see What's the Limiting Factor?)

It is beyond dispute that the “natural” diet of mankind is one that is much higher in animal products and much lower in carbohydrate than what our current “experts” advise us to eat. The archeological evidence provided in the fossil record and the testimony of anthropologists concerning various hunter-gatherer cultures provides significant evidence regarding our ancestor’s diet. The ancients who 19,000 years ago produced the awe-inspiring Lascaux cave paintings in present-day southwest France were paying homage to what gave them sustenance – the auroch, the ancestor of our modern European cattle.

Loren Cordain (2000) published an analysis of the diets of hunter-gatherer populations whose diets had been assessed by anthropologists.[5] One in every five of these 229 populations subsisted on almost entirely hunting or fishing. More than 85 percent of their calories came from meat or fish, with some groups thriving entirely on meat and fish. Only 14 percent of these groups got more than half their calories from plant foods. Not a single one of these populations was exclusively vegetarian. 

Today we understand the need to avoid obesity and the chronic diseases that are associated with being overweight. The “experts” tell us that we can accomplish these goals by eating less and exercising more, and by eating diets that are low in fat and high in carbohydrates. Animal products must be restricted, according to this advice. In response to the expert’s recommendations, as published in the USDA Food Guide Pyramid, the American caloric intake averages 15% from protein, 33% from fat, and the balance from carbohydrates. In contrast, Cordain’s hunter-gatherers’ diets were high to very high in protein (19 to 35 percent of calories) and high to very high in fat (28 to 58 percent of calories). Several of these populations obtained as much as 80 percent of their calories from fat. 

There is an abundance of evidence documenting the oft-repeated experience of isolated populations who exhibited none of the various “western diseases” until the introduction of sugar and white flour to their diets (see Grass and Cancer, Good Calories, Bad Calories, and Why we Get Fat and What to Do About It, among other sources). The scientific research and observational data so strongly supports the fattening carbohydrate hypothesis and explains the phenomenon of metabolic syndrome that all but those with a vested interest ought to be convinced that the lipid hypothesis should never have been adopted as the basis of public health policy in this country, or anywhere else. And this flawed “conventional wisdom” about weight loss and what constitutes a healthy diet has contaminated all of science. Not just nutrition and human health, but disciplines as seemingly unrelated as soil conservation. I’ll write about that in the future, too.


At the end of the introduction to his newest book, Gary Taubes writes:[6]

In the more than six decades since the end of the Second World War, when this question of what causes us to fatten – calories or carbohydrates -  has been argued, it has often seemed like a religious issue rather than a scientific one. So many different belief systems enter into the question of what constitutes a healthy diet that the scientific question – why do we get fat” – has gotten lost along the way. It’s been overshadowed by ethical, moral, and sociological considerations that are valid in themselves and certainly worth discussing but have nothing to do with the science itself and arguably no place in a scientific inquiry.

Carbohydrate-restricted diets typically (if not, perhaps, ideally) replace the carbohydrates in the diet with large or at least larger portions of animal products – beginning with eggs for breakfast and moving to meat, fish, or fowl for lunch and dinner. The implications of that are proper to debate. Isn’t our dependence on animal products already bad for the environment, and won’t it just get worse? Isn’t livestock production a major contributor to global warming, water shortages, and pollution? When thinking about a healthy diet, shouldn’t we think about what’s good for the planet as well as what’s good for us? Do we have a right to kill animals for our food or put them to work for us in producing it? Isn’t the only morally and ethically defensible lifestyle a vegetarian one or even a vegan one?

These are all important questions that need to be addressed, as individuals and as a society. But they have no place in the scientific and medical discussion of why we get fat.

It is understandable that Taubes would limit his argument, especially in this book which was envisioned as a simplified and focused discussion of the causes and treatment of obesity. Taubes is to be commended for acknowledging the broader ramifications of this subject and stating that, while he’s aware of these issues he would not address them. But there’s an implication in his statement that I’d like to dispute. 

I believe that we can address, scientifically, the questions regarding the impacts of animal agriculture on “the environment,” including the issues of anthropogenic global climate change (“global warming”), water quality and water quantity. The effort will show that this science is as muddled as Taubes found the disciplines of diet, nutrition and human health to be. Some of this muddle is the result of dietary dogma contaminating the discussion. If you believe that eating animal products is bad for you, it’s easy to imagine that belief impacting your perception of environmental issues. If your environmental beliefs are informed by the incorrect 18th and 19th century image of pre-Columbian North America as an “unspoiled wilderness,” then activities by man to transform the environment are necessarily seen as degradation. If you’ve never thought of the impacts of field-crop agriculture and horticulture, it might be possible to remain ignorant of the fact that greater soil erosion occurs in annual cropping systems that in perennial pasture-based animal production systems. Pasture-based livestock production systems protect surface and ground water quality. Credible science supports the role of well-managed animal agriculture in not only protecting but actually improving the environment. Future posts will discuss these issues. This, too, is what I mean by Grass Based Health.

In the Introduction to his book, Meat: A Benign Extravagance, Simon Fairlie makes the following statement:[7]

I am not overly concerned with questions of dietary health, nor do I take any interest in the diet and dentition of our remote ancestors.

Only someone not convinced of the fundamental requirement for animal fat and protein in the human diet could label meat an “extravagance!” Fairlie’s book is one of many I’m working my way through. His book apparently is having an impact. Folks who’ve been committed to vegetarianism are being swayed by his argument that animal products can be produced in ways that are sustainable. Glad to hear it. I remember being told almost twenty years ago that animal agriculture had no place in “sustainable agriculture.” “Organic” and “sustainable” were once synonymous with vegetarian.

My initial arguments with Fairlie’s thesis are that:
  • The vast majority of the earth’s surface is best suited for producing grass for grazing.
  • A significant portion of the “grain” that is fed to livestock are by-products like brewer’s grains and oil meal. These are not suitable for humans, and not utilizing them as livestock feeds would increase the cost of the primary products.
  • The field and horticulture crops are the “extravagance,” not the animal products. And they are far from “benign.” Soil loss through erosion and soil organic matter depletion, and water quality degradation, fossil fuel use, petrochemical inputs, wildlife impact – all of these are greater in annual cropping situations than in perennial pasture-based livestock production systems. And that list does not include the impact these crops have on the human health and the cost of treating the resulting diseases.
Consider diabetes: Diabetes is one of the western diseases, now understood to be part of metabolic syndrome. The US population today is approximately 312 million people, 76.9% of whom are adults (approximately 240 million). According to the Center for Disease Control and Prevention, 105 million adults in the US have diabetes or prediabetes (26 million with diabetes, 79 million with prediabetes), as diagnosed with hemoglobin A1c.[8] Thus diabetic and pre-diabetic adults represent 44% of the US adult population. The increase in those with pre-diabetes, now equal to 1 in 3 US adults, represents a 39 % increase since 2008. The recommended plant-based diet can hardly be called benign! The CDC estimates the direct and indirect costs of diabetes at $179 billion annually. The recommended plant-based diet can hardly be called sustainable, either.

I sometimes hear those in the low-carb / Primal / Paleo community refer to “agriculture” negatively. It is important to remember that the farmers and ranchers – the people who actually steward natural resources to produce our food - have been taken in by the same official dietary guidelines as the rest of us. They are challenged by the same chronic health problems the rest of us face. They need to hear this alternative to the conventional wisdom. The average age of farmers in the US is just over 57 years.[9] Sustainability implies longevity, but the intergenerational transition of the current production models have been difficult to achieve. Is there an alternative? There can be no sustainability without profit. In western Oregon, traditional dairies are finding it difficult to break even while pasture-based dairies are making a profit. Dairymen from Europe and New Zealand have been looking at the potential for grass-based dairying in the US. Some have done more than just look. Americans spend less, as a percent of their income, on food than any other industrial country. And we spend more on medical care. We can pay our farmers or we can pay our doctors. Payin’ our doctors hasn’t worked out all that well. That, too, is what Grass Based Health is about.

Finally, if meaningful change is going to happen in our nutrition policies and all that they influence it will have to begin at the grass roots. Individuals will have to learn on their own what we should have been taught since the 1960s. They will have to apply this information to their own lives and obtain the thoroughly predictable results – improved health and weight loss. They will then pass the word along to their families and friends, some of whom will listen and adopt this appropriate way of eating and living. And so it will spread until we reach the tipping point. A grass roots movement. But "Grass Roots Healthwas already taken (and a worthwhile effort that is, too, regarding the role of vitamin D in preventing chronic diseases!). 

So now you know I called this blog “Grass Based Health,” what I mean by that phrase, and some of what I’ll be writing about in future posts.



[1] From Wrangham, R. 2009. Catching Fire: How Cooking Made Us Human. New York, NY
[2] Mark Graham. 1979 in The Mark Graham Songbook: Twenty-Five Originals From the Forked-Tongue Demon. Mark Graham. 1991.
[3] Cellulose. (2008). In Encyclopædia Britannica. Retrieved January 11, 2008, from Encyclopædia Britannica Online.
[4] Meath, M. E., D. S. Metcalfe, R. F. Barnes. 1973. Forages; The Science of Grassland Agriculture. The Iowa State University Press. Ames, Iowa.
[5] Cordain, L., J. B. Miller, S. B. Eaton, N. Mann, S. H. Holt, and J. D. Speth. 2000. “Plant-Animal Subsistence Ratios and Macronutrient Energy Estimations in Worldwide Hunter-Gatherer Diets.” American Journal of Clinical Nutrition. Mar;71(3):682-92.
[6] Taubes, G. 2011. “Why We Get Fat and What To Do About It.” 2011. Alfred A. Knopf, New York. pp 11-12
[7] Fairlie, S. 2010. “Meat: A Benign Extravagance” Chelsea Green Publishing Co.
[8] Centers for Disease Control and Prevention. 2011. National Diabetes Fact Sheet: National Estimates and General Information on Diabetes and Prediabetes in the United States 2011. Atlanta, Ga.: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention.
[9] http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Ag_Atlas_Maps/Operators/Characterists/07-M124-RGBChor-largetext.pdf