Hi Dr. Cordain,
Just finished The Paleo Diet for Athletes; I have found it extremely useful so thank you! In the meantime, I noted Chris Kresser has recently been promoting the consumption of Kefir: //chriskresser.com/kefir-
If you are able to comment I would be very interested in your views! I entirely understand if you are unable or unwilling to comment. Suspect you probably get a few emails like this!
Keep up the good work!
Dr. Cordain’s Response:
Good to hear from you and many thanks for your kind words about The Paleo Diet for Athletes. I note that Chris Kresser has recently become quite a spokesperson for contemporary Paleo Diets, as he recently appeared on the Dr. Oz TV program, espousing the dietary benefits of both dairy products and legumes in contemporary Paleo diets. A brief check of Chris’s scientific publication record on PubMed for “Paleo Diets,” or any other topic for that matter, comes up with absolutely zilch — zero ! — nothing ! — no publications whatsoever! This evidence (or lack thereof) lends little credibility to Chris’s claims as an expert in diet, nutrition or anthropology — much less Paleo Diets. He has simply never put forth his ideas in peer review, scientific journals. Nevertheless, the presence of scientific publications or advanced degrees don’t always guarantee expert advice; rather good ideas and rationale thought, supported by solid data frequently do. Chris’s advice that legumes and dairy are indeed “Paleo” foods that should be regularly consumed in contemporary diets mimicking the nutritional characteristics of our pre-agricultural, hunter gatherer ancestors is ill founded at best.
The Paleolithic period or Old Stone Age is generally defined as the time span in which human ancestors first began to manufacture stone tools (about 2.5 million years ago to 3.2 million years ago) until the beginnings of agriculture in the Middle East about 10,000 years. During this period all humans and our hominid ancestors lived as hunter gatherers and only consumed wild plant and animal foods available in their environments.
Because it is difficult or impossible to milk wild mammals, humans couldn’t have consumed the milk of another species until they were domesticated, beginning about 10,000 years ago. Even though 10,000 years ago seems to be incredibly distant from a historical perspective; on an evolutionary time scale it only represents about 330 human generations.1 Hence, dairy products (milk, butter, cheese, yogurt, kefir etc.) are very recent introductions into the human diet and never were components of Paleolithic diets.1 In support of this notion is the very recent evolutionary appearance of genes which allow certain human populations on the planet to digest milk without gastro-intestinal upset.2 In fact, about 65 % of the world’s people are lactose intolerant and cannot drink milk without digestive discomfort. By fermenting dairy products, it is possible to reduce their lactose content, but not all fermented dairy products (yogurt, kumiss, sour milk etc) are completely lactose free. So the question comes up, should people consuming contemporary Paleo Diets be regularly consuming a food (kefir or for that matter any dairy product) for which our species has scant evolutionary experience? I have fully addressed this issue in an entire chapter in my most recent book, The Paleo Answer.3
It is not the lactose in milk that is the sole reason to avoid dairy. Except for calcium, milk and dairy products are relative nutritional lightweights in the 13 nutrients most lacking in the U.S. diet.1, 3 Of seven food groups (seafood, meats, fresh vegetables, fresh fruits, milk, whole grains and nuts), milk ranked 5th for the 13 nutrients most deficient in the U.S. diet. Seafood, meat, fresh vegetables, fresh fruits and nuts provide humans with all known nutritional requirements4 and represent the major food groups that conditioned the human genome for more than 2.5 million years of evolutionary experience.3 No mammal on earth has a nutritional requirement for the milk of another species, nor do we.
Besides its poor nutritional value and indigestibility for 65% of the world’s people, milk and other dairy products may produce a variety of adverse health effects including: 1) a high insulin response and insulin resistance, 2) an increased risk for cardiovascular disease, 3) an increased risk for acne, 4) an increased risk for many autoimmune diseases including multiple sclerosis, rheumatoid arthritis, Crohn’s disease and ulcerative colitis, 5) an increased risk for food allergies, 6) an increased risk for breast, ovarian, prostate and testicular cancers, 7) an increased risk for senile cataracts 8) dairy products’ high calcium content impairs zinc and iron absorption, and finally 9) increased dairy consumption doesn’t reduce the risk for bone fractures – so why consume them?. The mechanisms underlying these adverse health effects are fully outlined in my chapter on the topic, including more than 100 references to support this information.3
If you think milk is just a healthy white liquid that is “Good for Every Body,” think again! The following non-comprehensive list contains hormones and bioactive substances found in cow’s milk which are either known to, or suspected of causing a number of the deleterious health effects associated with milk and dairy consumption.3
- Insulin, Insulin like growth factor 1 (IGF-1), Insulin like growth factor 2 (IGF-2)
- Insulin like growth factor binding proteins, 1 to 6 (IGFBP-1, 2, 3, 4, 5, 6),
- Betacellulin (BTC), Growth hormone (GH), Growth hormone releasing factor (GHRF), Transforming growth factor alpha (TGF α), Transforming growth factor beta 1 (TGF-β1), (TGF-β2), Platelet derived growth factor (PDGF)
- Estrogens (Estrone, Estradiol-17β, Estriol and Estrone sulfate), Progesterone, 20 alpha-dihydropregnenolone, 5α androstanedione, 5 α pregnanedione, 20α- and 20β-dihydroprogesterone, 5α-pregnan-3β-ol-20-one, 5α-androstene-3β17β-diol, 5α-androstan-3β-ol-17-one, androstenedione, testosterone, and DHEA acyl ester
Bioactive Proteins and Peptides
- Relaxin, Thyrotropin releasing hormone (TRH), Luteinizing hormone releasing hormone (LHRH), Somatostatin (SIH), Gastrin releasing peptide (GRP), Calcitonin, Adrenocorticotropic hormone (ACTH), Prolactin, Thyroid stimulating hormone (TSH), Lysozyme, Lactoperoxidase, Lactoferrin, Transferrin, Immunoglobulins (IgA, IgM, IgG), Proteose-peptone, Glycomacropeptide, Plasmin, α Casein, β Casein, κ Casein, α Lactoglobulin, β Lactoglobulin, Bovine serum albumen (BSA), Gastric inhibitory polypeptide (GIP), Glucagon-like peptide-1 (GLP-1), Antitrypsin, Plasminogen activator inhibitor-1, α(2) antiplasmin , Butyrophilin, Xanthine oxidase, Mucin-1, Mucin-15, Adipohilin, Fatty acid binding protein, CD36, Periodic acid Schiff 6/7
Bioactive Peptides formed in gut from Milk Proteins
- Casomorphins, α Lactorphin, β Lactorphin, Lactoferroxins, Casoxins, Casokinins, Casoplatelins, Immunopeptides, Phosphopeptides.
Loren Cordain, Ph.D., Professor Emeritus
1. Cordain L, Eaton SB, Sebastian A, Mann N, Lindeberg S, Watkins BA, O’Keefe JH, Brand-Miller J. Origins and evolution of the western diet: Health implications for the 21st century. Am J Clin Nutr 2005;81:341-54.
2. Cordain, L., Hickey, M. , Kim K. Malaria and rickets represent selective forces for the convergent evolution of adult lactase persistence. In: Biodiversity in Agriculture: Domestication, Evolution and Sustainability, Gepts P, Famula T, Bettinger R et al. (Eds.), Cambridge University Press, Cambridge, UK, 2011, pp 299-308.