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My Problem with the Paleo Diet

By now, most people in North America have heard of the “Paleo” trend in eating, where animal flesh is the base of almost every meal. It’s a great story based on an image that our caveman ancestors munched on mastodon meat all day.

Many people who adopt this meat-based eating style initially feel better and lose weight. They do so largely because the Paleo principles proscribe the eating of dairy, oils, and refined carbohydrates that our ancient ancestors never ate – and with that, I am in full agreement! There is also a limit to how much fat our intestines can absorb, so much of the meat fat goes out in greasy stools. 

Carbohydrates, the preferred fuels of the mammalian body, are generally on the Paleo enemies list, and, in fact, being in a state of ketosis from metabolizing fat (as opposed to carbohydrates) is viewed as a good thing. (It’s not, however, and I’ll tell you why in a moment.)

People who eat in this manner, and who like the taste of flesh in their mouth, are often enthusiastic supporters of this way of eating. Many initially get leaner and experience a lowering of cholesterol numbers, though many see their cholesterol numbers go up! They take these changes as validation of this “natural” way of eating.

I do not find it “natural” at all. Instead, I think it’s an invitation to serious disease and environmental destruction!

Here’s some of what I find problematic with the Paleo approach to eating:

Did our cave-man ancestors really eat a mostly-meat diet? Although it’s a commonly held idea with a colorful image, it’s just not true. According to Nathaniel Dominy, associate professor of Anthropology at Dartmouth College, the overwhelming majority of calories that kept our ancestors alive in ancient times were from starches, in the form of roots, tubers, bulbs, corns and wild grasses – mostly gathered by the women of the tribes (bless ’em!). (1)

All plants make and store starches and there is a reason that over the millions of years before humans appeared, our primate ancestors developed starch-digesting enzymes (amylases) in our saliva that begins digesting starches down to usable sugars right in our mouths. Our grinding teeth (not flesh-tearing fangs) and long digestive system are very efficient for processing starchy plant foods; our pancreas pours amylase-rich juice into the gut with every meal and amylases cascade off the walls of the small intestine into the food stream throughout its 22 foot length.

Carbohydrates (sugars) are clean burning fuels, leaving only carbon dioxide and water as wastes, easily excreted by the lungs and kidneys. But flesh is a “dirty” fuel, leaving urea, ketones, uric acid and other metabolic burdens that can stress the liver and build up to disease-producing levels, resulting in gout, kidney stones, and other diseases.

Burning fat-heavy fuels places one in a state of ketosis, something sought after by Paleo promoters as a “good thing.” However, keeping one’s metabolism in a state of ketosis – an emergency state the body enters during times of starvation – is NOT a good thing! It is a state of low-grade acidosis and being ketotic day after day, week after week, that forces the body to constantly dispose of an acid load which can leach calcium from the bones and precipitate kidney stones. (2)

Despite what the Paleo promoters push, we are not carnivorous apes. The Paleo diet would have us ghoulishly swallow chunks of flesh every five hours as part of our meat-based, “natural” diet. My goodness! Not even mountain lions eat flesh every 5 hours! No other primate eats flesh like this and the health consequences can be severe. 

If someone asked me how to cause a colon cancer, I’d say, “Easy. Pack the colon full of meat three times a day and let that rub against the colon wall for a few decades and see what happens.” The connection between red meat consumption and colon cancer has been evident for years. (3)

An often-overlooked consequence of a flesh-based diet is that the food you eat determines the bacteria that live in your gut. If you eat sugar on a continuous basis, you will summon up a population of sugar-eating bacteria and yeast in your gut. If you drop chunks of animal flesh down your gullet three-times a day, you will summon up a population of bacteria such as Clostridia and Peptostreptococcus that love to eat carnitine, a major constituent of animal flesh. 

“So what,” you ask? These gut bacteria turn the carnitine in meat into trimethylamine which your liver promptly oxidizes to trimethylamine oxide. This is a “molecule from hell” that drives cholesterol into the artery walls and promotes plaque formation in arteries throughout the body. That healthy-looking Paleo guy sweating in the gym is likely laying down plaque in his arteries with every steak he gobbles. People who eat a plant-based diet do not form trimethylamine, even if given a steak to eat, because they do not have the bacteria that eat carnitine. (4)

Elevated cholesterol levels may initially decrease on a Paleo diet due to weight loss and a lack of refined sugars, but before one interprets a falling total cholesterol level as a mark of improving health, remember: the question is NOT, “How high is your cholesterol level?” But, rather, “How healthy are your arteries?” 

These folks may watch their total cholesterol go down, but the real question is: What’s really happening on the inside of their arteries? Those artery walls are likely being assaulted with atherogenic, oxidized cholesterol particles with every meal, setting off a cascade of events that leads to blood clots blocking arteries, heart attacks, stroke, and early death. 

Beyond spawning artery plaques, the bacteria fostered by a flesh-based diet can also injure your gut lining and allow food proteins to leak into your bloodstream – triggering autoimmune disease from arthritis to allergies to eczema. (5)

Healthwise, far from being a “natural” health-promoting diet, I fear the Paleo diet is setting its practitioners up for an epidemic of colon cancer, clogged arteries, heart attacks, strokes, and autoimmune disease.

Ecologically, the Paleo approach is a completely elitist, non-sustainable, dietary pattern conceivable only because Western industrial meat production, driven by government subsidies, makes animal flesh grotesquely cheap.

Are the Paleo folks really proposing burgers and steaks three times a day for 9 billion people? It would take two more planets with Earth’s resources to provide such a prodigious amount of animal flesh for the entire human population, but the real problem is that it would destroy our planet’s ecosystems that are already teetering towards destruction under the pressure of industrialized meat production.

In my opinion, the so-called Paleo diet is a diet of destruction – destruction of billions of animals, leading to the destruction of the humans who eat them and, ultimately, to the destruction of our planet’s ecosystems upon which we all depend for life.

Is the Paleo diet the way of the future (or even of the past)? I don’t think so and I urge you not to be seduced by the siren-song of the Paleo promoters. Instead, there is solid evidence that a whole-food, plant-based diet – with far less death and destruction involved in its production and consumption – is the truly healing diet for people and our planet. (6)

See references below…

To your good health and happiness,

Dr. Michael Klaper


(1) “We Are What They Ate” by Jennifer McNulty.

(2) “Ketogenic Diet Side Effects”

(3) “Well-done, grilled red meat increases the risk of colorectal adenomas.” Sinha, R. et al. Cancer Research 59.17 (1999): 4320.

“—Intake of fat, meat and fiber in relation to risk of colon cancer in men.” Giovannucci E., Rimm E. B., Stampfer M. J., Colditz G. A., Ascherio A., Willet W. C. Cancer Res., 54: 2390–2397, 1994.

“Relation of meat, fat and fiber intake to the risk of colon cancer in a prospective study among women.” Willet W. C., Stampfer M. J., Colditz G. A., Rosner B. A., Speizer F. E. N. Engl. J. Med., 323: 1664–1672, 1990.

“—Relation of meat, fat and fiber intake to the risk of colon cancer in a prospective study among women.” Kune, Gabriel A. The Medical Journal of Australia 193.11–12 (2010): 648–652.

—”Red meat intake and cancer risk: a study in Italy.” Recommendations for Cancer Prevention Tavani, A. et al. International Journal of Cancer 86.3 (2000): 425–428. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. p. 116. 

“—Heme of consumed red meat can act as a catalyst of oxidative damage and could initiate colon, breast and prostate cancers, heart disease and other diseases.” Tappel, A. (2007). Medical Hypotheses 68 (3): 562–564

—”Red meat and colon cancer: dietary haem-induced colonic cytotoxicity and epithelial hyperproliferation are inhibited by calcium”. Sesink, A. L. A.; Termont, D.; Kleibeuker, J.; Van Der Meer, R. (2001) Carcinogenesis 22 (10): 1653–1659.

“—Red meat and colon cancer: dietary haem, but not fat, has cytotoxic and hyperproliferative effects on rat colonic epithelium.” Sesink AL, Termont DS, Kleibeuker JH, Van Der Meer R.Wageningen. Centre for Food Sciences, NIZO Food Research, Department of Nutrition, Quality and Safety, PO Box 20, 6710 BA Ede, The Netherlands

“Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies.” Chan DS, Lau R, Aune D, Vieira R, Greenwood DC, Kampman E, Norat T. PLoS One. 2011;6(6):e20456. Epub 2011 Jun 6.

“Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies.” Chan DS, Lau R, Aune D, Vieira R, Greenwood DC, Kampman E, Norat T. Asian Pac J Cancer Prev. 2009 Jul-Sep;10(3):429-36.

“Meat consumption and cancer risk: a case-control study.” Aune D, De Stefani E, Ronco A, Boffetta P, Deneo-Pellegrini H, Acosta G, Mendilaharsu M.

“Dietary heterocyclic amines and cancer of the colon, rectum, bladder, and kidney: a population-based study.” Augustsson, K. et alThe Lancet 353.9154 (1999): 703–707.

“Role of well-done, grilled red meat, heterocyclic amines (HCAs) in the etiology of human cancer.” Sinha, R., and N. Rothman. Cancer letters 143.2 (1999): 189–194.

(4) “Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease.” Z. Wang, E. Klipfell, B. J. Bennett, R. Koeth, B. S. Levison, B. Dugar, A. E. Feldstein, E. B. Britt, X. Fu, Y.-M. Chung, Y. Wu, P. Schauer, J. D. Smith, H. Allayee, W. H. W. Tang, J. A. DiDonato, A. J. Lusis, S. L. Hazen. Nature 2011 472(7341):57 – 63.

(5) “Protein-rich diets increase the activity of bacterial enzymes such as β-glucuronidase, azoreductase and nitroreductase, which produce toxic metabolites that trigger inflammatory responses.” Gorbach S.L. Bengt E. gustafsson memorial lecture. Function of the normal human microflora. Scand. J. Infect. Dis. Suppl. 1986;49:17–30. 

“A single dose of endotoxin increases intestinal permeability in healthy humans.” O’Dwyer, S.T., et al., Arch Surg, 1988. 123(12): p. 1459-64.

“A high-fat meal induces low-grade endotoxemia: evidence of a novel mechanism of postprandial inflammation.” Clett Erridge, Teresa Attina, Corinne M Spickett, and David J Webb. Am J Clin Nutr. 2007 Nov; 86(5):1286-92.

“Animal protein intake and risk of inflammatory bowel disease: The E3N prospective study.” Jantchou P, Morois S, Clavel-Chapelon F, Boutron-Ruault MC, Carbonnel F. Am J Gastroenterol. 2010 Oct;105(10):2195-201. doi: 10.1038/ajg.2010.192. Epub 2010 May 11.

“Are intestinal bacteria involved in the etiology of rheumatoid arthritis?” Review article. Hazenberg, M.P., et al. Apmis, 1992. 100(1): p. 1-9.

“A short review of the relationship between intestinal permeability and inflammatory joint disease.” Rooney, P.J., R.T. Jenkins, and W.W. Buchanan. Clin Exp Rheumatol, 1990. 8(1): p. 75-83.

“Reflections on the link between intestinal permeability and inflammatory joint disease.” Mielants, H. Clin Exp Rheumatol. 1990 Jan-Feb;8(1):75-83.

“A short review of the relationship between intestinal permeability and inflammatory joint disease.” Rooney PJ, Jenkins RT, Buchanan WW. Clin Exp Rheumatol. 1990 Jan-Feb;8(1):75-83.

“Normalization of leaky gut in chronic fatigue syndrome (CFS) is accompanied by a clinical improvement: effects of age, duration of illness and the translocation of LPS from gram-negative bacteria.” Maes M, Leunis JC. Neuro Endocrinol Lett. 2008 Dec;29(6):902-10.

“Small intestinal permeability in dermatological disease.” Hamilton, I., et al., Q J Med, 1985. 56(221): p. 559-67.

“Endotoxemia in psoriasis” [letter] Belew, P.W., et al., Arch Dermatol, 1982. 118(3): p. 142-3.

“Intestinal permeability in patients with eczema and food allergy.” Jackson, P.G., et al., Lancet, 1981. 1(8233): p. 1285-6.

“Intestinal permeability to 51Cr-labelled ethylenediaminetetraacetate in food-intolerant subjects.” Scadding, G., et al., Digestion, 1989. 42(2): p. 104-9.

“Intestinal permeability in patients with eczema and food allergy.” Jacobson, P., R. Baker, and M. Lessof. Lancet, 1981. i: p. 1285-1286.

“Gastrointestinal permeability in children with cow’s milk allergy: effect of milk challenge and sodium cromoglycate as assessed with polyethyleneglycols (PEG 400 and PEG 1000).” Falth-Magnusson, K., et al. Clin Allergy, 1986. 16(6): p. 543-51.

“Gastrointestinal permeability in atopic and non-atopic mothers, assessed with different-sized polyethyleneglycols (PEG 400 and PEG 1000).” Falth-Magnusson, K., et al. Clin Allergy, 1985. 15(6): p. 565-70.

“Intestinal permeability in healthy and allergic children before and after sodium-cromoglycate treatment assessed with different-sized polyethyleneglycols (PEG 400 and PEG 1000).” Falth-Magnusson, K., et al. Clin Allergy, 1984. 14(3): p. 277-86.

“Identical intestinal permeability changes in children with different clinical manifestations of cow’s milk allergy.” Jalonen, T. J Allergy Clin Immunol, 1991. 88(5): p. 737-42.

(6) “Sustainability of meat-based and plant-based diets and the environment.” David Pimentel and Marcia Pimentel. Am J Clin Nutr, 2003;78(suppl):660S–3S

“Quantification of the environmental impact of different dietary protein choices.” Lucas Reijnders and Sam Soret. Am J Clin Nutr, 2003;78(suppl):664S–8S

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