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Meat in the Human Diet
Human beings have been consuming meat as part of their diet for most of their existence and will likely continue this behavior until the last living animal is gone from the earth. However, public awareness of meat-associated health hazards, such as heart attacks, colon cancer, and fatal E. coli bacterial infections, has caused great concern and shifts in many people’s eating habits. The number of vegetarians has been growing worldwide, especially among better-educated and younger people. An astonishing contradiction to this trend is today’s most popular weight loss diet – the Atkins Diet – almost entirely meat. Obviously, there is still much disagreement and confusion.
There is no more important question to be answered for mankind than, “What is the proper diet for human beings?” What is the diet that allows us to look, feel, and function at our best? Not just to survive or lose weight. Is it vegetarian? Does it contain meat? How much meat? There must be a correct answer. Just like there is one diet best for horses, one for cats, one for dogs, and one for each kind of bird – there must be one diet best for people.
Why have we not discovered this diet? It is certainly not because of lack of interest. Russell Henry Chittenden, the father of American biochemistry and professor of physiological chemistry at Yale Medical School, wrote, a century ago (1904), “We hear on all sides widely divergent views regarding the needs of the body, as to the extent and character of food requirements, contradictory statements as to the relative merits of animal and vegetable foods; indeed, there is a great lack of agreement regarding many of the fundamental questions that constantly arise in any consideration of the nutrition of the human body.” You would think that after so many years of investigation using the latest scientific methods and employing modern technology that this matter of such grave importance would have been settled beyond a doubt. Coexistence today of enthusiastic advocates of “all meat” and “no meat” diets, and everything in between, proves this matter is far from settled.
I Believe, the Less Meat, the Better
Over my past 25 years of medical practice I have taken the position that meat at most should be considered a delicacy, reserved for consumption on special occasions by healthy people. The consequence of this belief is my patients lose excess weight and become healthy – and stay this way for a long lifetime. Regardless of how much others may argue the merits of their opinions on the best diet (supported, of course, by all the latest “facts”), they do not have the same glowing outcomes with their patients – I’ve seen the consequences. For me, as a practicing doctor, the bottom line is patient results. Fortunately, there is an overwhelming amount of undeniable scientific data and observations clearly supporting my conclusions. I will share this information with you.
Should We Follow Our Ancestors’ Diets?
Many scientists use the diet of our ancestors as the justification for what we should eat today. That may be a useful approach, but which ancestors are we to follow? Differences of opinion arise because throughout human history people have consumed a wide variety of foods. The early ancestors of modern humans, from at least 4 million years ago, followed diets almost exclusively of plant-foods. Beginning at least 250,000 years ago, many of the hunter-gatherer societies consumed meat as a large part of their diet.1 However, more recently, over the past 12,000 years of agricultural development, people’s diets have been mostly based upon starches, like rice in Asia, corn in North America, potatoes in western parts of South America, wheat in Europe and Northern Africa. In terms of the time line of evolution, 12,000 years, and even 250,000 years, is only a brief moment.
Out of the Garden of Eden
The Bible story of Adam and Eve’s eviction from the Garden of Eden is closely analogous to the actual shift from early plant-eating humans to hunter-gatherers.2 While in the Garden God said, “I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food.” Upon expulsion humans were instructed by God, “By the sweat of your brow you will eat your food.”
For the most part hunter-gatherers (i.e., exiles from the Garden) had a subsistence standard of living, eating foods that extended from one extreme to the other in proportions of plant vs. animal foods – from the raw flesh and fat of marine mammals – the Arctic Eskimos – to diets composed largely of wild plants of the Western Desert – Australian Aborigines.3 Hunter-gatherers took advantage of any dependable sources of food from their wild local environments. Because of the ease and dependability (compared to obtaining animals), gathering fruits and vegetables was a primary source of food for most hunter-gatherer societies – the emphasis on hunting increased in higher latitudes because of plant scarcity.4
Undoubtedly, all of these diets were adequate to support growth and life to an age of successful reproduction. To bear and raise offspring you only need to live for 20 to 30 years, and fortuitously, the average life expectancy for these people was just that. The few populations of hunter-gatherers surviving into the 21st Century are confined to the most remote regions of our planet – like the Arctic and the jungles of South America and Africa – some of the most challenging places to manage to survive. Their life expectancy is also limited to 25 to 30 years and infant mortality is 40% to 50%.5 Hunter-gatherer societies fortunately did survive, but considering their arduous struggle and short lifespan, I would not rank them among successful societies.
The Importance of Meat
So why has meat been an important part of the diet of so many of these hunter-gatherer societies?6 Throughout human history, especially before the development of agriculture-based living, acquiring food for survival was a full time job – food scarcity, even starvation, plagued most of these people, at least some of the time. Meat represented a gold mine of concentrated calories and nutrients whenever it was obtained. For those societies who found a plentiful supply, survival on a meat-based diet simply attests to the resilience and adaptability of the human frame.
Because many hunter-gatherer societies obtained most of their calories from the fat of meat does not mean meat is the ideal diet for modern people. Almost every scientist readily admits that the composition of wild game available to our ancestors was far different from the grain-fed domesticated high-fat meat people eat these days. Furthermore, even if humans have been eating meat for centuries, it has not been with the ease that wealthy Westerners acquire it today. Without refrigeration and other means of preserving meat in a near fresh state, consumption was limited to within a few days of the kill – until the meat spoiled. (With the advent of fire people learned to preserve meat by smoking it.)
During difficult times meat provided more benefits than harms, but in a society where food is plentiful and life is physically easy, meat can become a serious health hazard. A traditional Arctic Eskimo, living in a subfreezing climate, could expend 6000 calories and more a day just to keep warm and hunt for food. The high-fat animal food sources – fish, walrus, whale, and seal – from his local environment were the most practical means of meeting the demands of those rigorous surroundings. Modern Eskimos living in heated houses and driving around in their climate-controlled SUVs, still consuming a high-meat diet, have become some of the fattest and sickest people on earth. Of course, they now use a “green lure” (a $10 bill) to catch their fish (sandwich).
Our Anatomy and Physiology Provide the Undeniable Evidence3,4,8,9-13
Evolution in the animal kingdom dates back hundreds of millions of years and the evolution of humans began over 4 million years ago. The ancestors of modern humans were believed to live primarily on plant foods, eating wild fruits, leaves, roots, and other high quality plant parts with a few animal foods in their daily diet. These pre-humans ate like our nearest primate relatives, the apes of today.3 Now, biologists at Wayne State University School of Medicine in Detroit, Michigan, provide new genetic evidence that lineages of chimpanzees and humans diverged so recently that chimps should be reclassified as members of our genus Homo, along with Neanderthals, and all other human-like fossil species.7 “We humans appear as only slightly remodeled chimpanzee-like apes,” says the study.
Most apes living today eat essentially as vegetarians – consuming a diet composed of the fruits, leaves, flowers, and bark, with sporadic consumption of very small amounts of insect material (like termites) and less commonly, small animals.8 These meat-eating activities may be purely social in nature and unrelated to any real nutritional needs.
Behavior can be changed overnight, but our anatomy and physiology only evolve from selective pressures of the environment over millions of years. Food is the strongest contact with our environment. Therefore, the present state of the human body accurately reflects how our kind has eaten during most of our human and pre-human existence. These indisputable anatomical and physiological characteristics clearly identify the best diet for people today.
We Have the Mouth of a Plant-Eater
“Johnny, eat your beef, you have to get your protein.” Worried about her growing child, my mother said this to me at almost every dinnertime. “But Mother, I can’t chew it,” I tried to explain. To make her happy I mashed the bite-size piece of roast beef with my teeth into a leathery lump, still too big to comfortably swallow. Eventually, jaw tired, wanting to be excused from the table, I slipped the remains under the edge of my plate. All this distress could have easily been avoided if my mother had known enough truth about good nutrition to simply say “Of course you can’t chew that meat – you have the wrong kind of teeth, Johnny – give it to the dog.”
Our dentition evolved for processing starches, fruits, and vegetables, not tearing and masticating flesh. Our oft-cited "canine" teeth are not at all comparable to the sharp teeth of true carnivores. I lecture to over 10,000 dentists, dental hygienists, and oral specialists every year, and I always ask them to show me the “canine” teeth in a person’s mouth – those that resemble a cat’s or dog’s teeth – I am still waiting to be shown the first example of a sharply pointed canine tooth.
If you have any doubt of the truth of this observation then go look in the mirror right now – you may have learned to call your 4 corner front teeth, “canine teeth” – but in no way do they resemble the sharp, jagged, blades of a true carnivore – your corner teeth are short, blunted, and flat on top (or slightly rounded at most). Nor do they ever function in the manner of true canine teeth. Have you ever observed someone purposely favoring these teeth while tearing off a piece of steak or chewing it? Nor have I. The lower jaw of a meat-eating animal has very little side-to-side motion – it is fixed to open and close, which adds strength and stability to its powerful bite. Like other plant-eating animals our jaw can move forwards and backwards, and side-to-side, as well as open and close, for biting off pieces of plant matter, and then grinding them into smaller pieces with our flat molars.
In a failed attempt to chew and swallow pieces of food, usually meat, approximately 4,000 people die each year in the U.S.14 They choke on inadequately masticated chunks that become stuck in their throats. The Heimlich maneuver was specifically designed to save the lives of people dying from these “café coronaries.”14.
Our Digestive System Assimilates Plant Foods4,8
From our lips to our anus our digestive system has evolved to efficiently process plant foods. Digestion begins in the mouth with a salivary enzyme, called alpha-amylase (ptyalin), whose sole purpose is to help digest complex carbohydrates found in plant foods into simple sugars. There are no carbohydrates in meats of any kind (except for a smidgen of glycogen), so a true carnivore has no need for this enzyme – their salivary glands do not synthesize alpha amylase.
The stomach juices of a meat-eating animal are very concentrated in acid. The purpose of this acid is to efficiently break down the muscle and bone materials swallowed in large quantities into the stomachs of meat-eaters. Digestion of starches, vegetables and fruits is accomplished efficiently with the much lower concentrations of stomach acid found in the stomachs of people, and other plant-eaters.
The human intestine is long and coiled, much like that of apes, cows, and horses. This configuration makes digestion slow, allowing time to break down and absorb the nutrients from plant food sources. The intestine of a carnivore, like a cat, is short, straight, and tubular. This allows for very rapid digestion of flesh and excretion of the remnants quickly before they putrefy (rot). There are also marked sacculations (many sac-like enlargements that bulge out along our large intestine), like those found in all apes, which strongly supports the view that we are primarily plant-eating animals. Overall, the intestines of meat-eaters are noticeably simpler than ours.
Cholesterol Overwhelms a Plant-eater’s Liver15
Cholesterol is only found in animal foods – no plant contains cholesterol. The liver and biliary system of a meat-eating animal has an unlimited capacity to process and excrete cholesterol from its body – it goes out, in the bile, passing through the bile ducts and gallbladder, into the intestine, and finally, out with the stool. For example, you can feed a dog or cat pure egg yolks all day long and they will easily get rid of all of it and never suffer from a backup of cholesterol. Humans, like other plant-eating animals, have livers with very limited capacities for cholesterol removal – they can remove only a little more than they make for themselves for their own bodies – and as a result, most people have great difficulty eliminating the extra cholesterol they take in from eating animal products. This apparent “inefficiency” is because humans have evolved on a diet of mostly plant foods (containing no cholesterol), and therefore, they never required a highly efficient cholesterol-eliminating biliary system. The resulting cholesterol buildup, when people eat meat, causes deposits in the arteries (atherosclerosis), in the skin under the eyes (xanthelasma), and in the tendons. Bile supersaturated with cholesterol forms gallstones (over 90% of gallstones are made of cholesterol). About half of all middle-aged women who live on the Western diet have cholesterol gallstones. (See my April and May 2002 Newsletters.)
Our Requirements are for Plant Nutrients4,8
To believe we require the body parts of other animals in our diet for good health supposes the human body evolved over many millions of years on a diet predominantly of meat – and deficient in plants. This is not what is seen when the nutritional requirements of people are examined.
When plants have been for eons a plentiful and reliable part of the diet, an animal can become dependent upon specific nutrients found in these foods. For example, ascorbic acid – found preformed and ready to use in plant foods – is called vitamin C in the diet of people. Insufficient amounts of this vitamin cause scurvy. Vitamins are essential micronutrients that cannot be synthesized by the body; and therefore, must be in the food. Because ascorbic acid has not been reliably available to them, meat-eating animals have retained the ability to synthesize ascorbic acid from basic raw materials found in their meat diet – therefore, it is not a vitamin for them. (In other words it is not “vital” or essential to be preformed in their food supply.)
Because humans have lived throughout most of their evolution on diets with very little animal matter, they have had to develop or retain the ability to synthesize some substances they need that are abundantly found in meat. For example, humans, and other plant-eating animals, have the ability to make vitamin A from a precursor found in large quantities in plants, called beta-carotene. Carnivores cannot utilize beta-carotene as a precursor of vitamin A. They have no need to; throughout their evolution they have always had a plentiful supply of preformed vitamin A (Retinol) found in the meat. Carnivores have also lost the ability to synthesize Niacin, which is plentiful in meat. Remember, efficiency is necessary for survival of a species and it is inefficient to keep manufacturing processes in the body that are useless.
Our Instincts Are for Plants
For most enlightened people in modern Western nations, the idea of chasing down and killing an animal is revolting; and the thought of consuming that freshly killed flesh is repulsive. (And to eat decaying flesh, as a vulture does, would be next to impossible.) Even when meat is cooked, most people are disgusted by the thought of eating a slice of horse, kangaroo, rat, or cat. Cows, chickens and pigs are acceptable to most Westerners only because we have eaten them all of our lives. Yet even then, to make meat palatable, its true nature must be covered up with a strong flavored sauce made with salt, sugar, and/or spices – like sweet and sour, marinara, barbecue, or steak sauce. Few people enjoy boiled beef or chicken.
People do not have a negative reaction to unfamiliar fruits and vegetables. Consider, I could ask you to try an unfamiliar “star fruit” from the tropics for the first time and you would eat and enjoy it without hesitation. Why? Because your natural instincts are to eat fruits and vegetables.
You Should Eat Like You Act
So many human characteristics clearly say we evolved to be primarily plant-eaters. Do you want to read more? Our hands are made for gathering plants, not ripping flesh. We cool ourselves by sweating, like most other plant-eating animals. Carnivores cool their bodies by panting. We drink our beverages by sipping, not lapping like a dog or cat. The exhaustive factual comparisons of our body traits with that of other animals prove we have evolved over eons in an environment of plant-based foods – the only real contradiction is our behavior. The results of our aberrant behavior can be catastrophic – let me begin to explain that harm with one example about macho men.
A Man’s Behavior Contradicts His Anatomy
Men traditionally have been the hunters who carry back the slain animals to feed the village – you know, “they bring home the bacon.” Scientific research confirms meat is viewed as a superior masculine food.16 The acts of killing, butchering and eating animals are associated with power, aggression, virility, strength, and passion – attributes desired by most men – and eating meat has long been associated with aggressive behaviors and violent personalities. Men say they need more, and they do eat more meat, especially more red meat, than women. However, based on male anatomy, real men should be vegetarians.
Human males have seminal vesicles – no other meat-eating animal has these important collecting-pouches as part of their reproductive anatomy.17 The seminal vesicles are paired sacculated pouches connected to the prostate, located at the base of the bladder. They collect fluids made by the prostate that nourish and transport the sperm. Ejaculation occurs when the seminal vesicles and prostate empty into the urethra of the penis. In many ways ejaculation is the ultimate act of male performance – seminal vesicles are essential organs for proper male function and therefore, they should tell us much about his true nature.
His Aberrant Behavior Ruins His Potency
Eating meat diminishes sexual performance and masculinity. The male hormone testosterone that determines sexual development and interest has been found to be 13 % higher in vegans (a strict plant diet – no animal products of any kind) than in meat-eaters.18 Meat-eaters are likely to become impotent because of damage caused to the artery system that supplies their penis with the blood that causes an erection.19 Erectile dysfunction is more often seen in men with elevated cholesterol levels20 and high levels of LDL “bad” cholesterol21– both conditions related to habitual meat-eating.
The greatest threat to a man’s virility is from the high levels of environmental chemicals concentrated in modern meats of all kinds. These chemicals interfere with the actions of testosterone. Decreased ejaculate volume, low sperm count, shortened sperm life, poor sperm motility, genetic damage, and infertility result from eating meat with estrogen-like environmental chemicals.22 These chemicals in the meat, eaten by his mother, influence the development of the male fetus, increasing the risk that the baby boy will be born with a smaller penis and testicles, as well as deformity of the penis (hypospadia) and an undescended testicle (cryptorchism). Estimates are 89% to 99% of the chemical intake into our body is from our food, and most of this is from foods high on the food chain – meat, poultry, fish, and dairy products.23,24
A Deviant Diet Causes Deadly Diseases
The enlightened diet for humans today is centered around starchy plant foods with the addition of fruits and vegetables – the use of clean meat is limited to special occasions – like Thanksgiving and Christmas – and consumed only by healthy people.25 If your diet deviates too far from that which you evolved on over eons of time then you will likely suffer serious consequences – these are the chronic diseases affecting people living on the Western diet. Next month I will continue this discussion of the health problems produced when we attempt to live with meat as a significant part of our diet.
1) Wood B. Human evolution: We are what we ate. Nature 1999;400:219 - 220
2) Bible (New International Version): Genesis 1:29 and 3:19
3) Milton K. Back to basics: why foods of wild primates have relevance for modern human health. Nutrition. 2000 Jul-Aug;16(7-8):480-3.
4) Milton K. Hunter-gatherer diets-a different perspective. Am J Clin Nutr. 2000 Mar;71(3):665-7.
5) Nestle M. Animal v. plant foods in human diets and health: is the historical record unequivocal? Proc Nutr Soc. 1999 May;58(2):211-8.
6) Cordain I. The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. Eur J Clin Nutr. 2002 Mar;56 Suppl 1:S42-52.
7) Chimpanzees are also in the Homo species: http://news.nationalgeographic.com/news/2003/05/0520_030520_chimpanzees.html
8) Milton K. A hypothesis to explain the role of meat-eating in human evolution. Evol Anthropol 1999;8:11-21.
9) W. Collens, “Phylogenetic Aspects of the Cause of Human Atherosclerotic Disease,” Circulation (suppl II) 31-32 (1965): II-7.
10) C. Prosser, Comparative Animal Physiology , 2nd ed. Philadelphia: W. B. Saunders, 1961, p. 116
11) E. Nasset, Movements of the small intestine, P. Bard, Medical Physiology, 11 ed. C. V. Mosby, 1961, St. Louis, p. 440
12) Carpenter KJ. Protein requirements of adults from an evolutionary perspective. Am J Clin Nutr. 1992 May;55(5):913-7
13) Mills M. The Comparative Anatomy of Eating http://www.geocities.com/RainForest/2062/ana.HTML
14) H. Heimlich, “A Life-Saving Maneuver to Prevent Food-Choking,” JAMA 234 (1975): 398-401.
15) Dietschy J. Regulation of cholesterol metabolism. 3. N Engl J Med. 1970 May 28;282(22):1241-9.
16) Roos G. Men, masculinity and food: interviews with Finnish carpenters and engineers. Appetite. 2001 Aug;37(1):47-56.
Coffey D. Similarities of prostate and breast cancer:
Evolution, diet, and estrogens.
18) Allen NE. Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men. Br J Cancer. 2000 Jul;83(1):95-7.
19) Feldman HA. Erectile dysfunction and coronary risk factors: prospective results from the Massachusetts male aging study. Prev Med. 2000 Apr;30(4):328-38.
20) Bodie J. Laboratory evaluations of erectile dysfunction: an evidence based approach. J Urol. 2003 Jun;169(6):2262-4.
21) Walczak MK
Prevalence of cardiovascular risk factors in erectile
22) Rozati R . Role of environmental estrogens in the deterioration of male factor fertility. Fertil Steril. 2002 Dec;78(6):1187-94.
23) Duarte-Davidson R. Polychlorinated biphenyls (PCBs) in the UK population: estimated intake, exposure and body burden. Sci Total Environ. 1994 Jul 11;151(2):131-52.
24) Liem AK. Exposure of populations to dioxins and related compounds. Food Addit Contam. 2000 Apr;17(4):241-59.
25) Segasothy M. Vegetarian diet: panacea for modern lifestyle? Q J Med 92:531-544, 1999.