I’d be lying if I said I didn’t enjoy having this particular debate. Someone – not a fan of the Paleo Diet – points out that the diet’s higher protein content is proof that the diet is dangerous citing multiple studies linking higher protein to cancer, CVD, and all-cause mortality.1-3
I have this “dance” down pat. I simply shrug my shoulders and say, “Makes sense. Too bad vegetables are bad for us as well.” I get an incredulous look and a “How can you say that?” response. “Vegetables are a carbohydrate and so are jelly beans. And jelly beans are bad for you.” My frustrated opponent chastises me for drawing a ridiculous conclusion by lumping all carbohydrates together.
Gotcha! Almost invariably I’m able to point out that the high protein diets in their studies were based on processed meats like fast food hamburgers and bologna, not lean meats. “Aren’t you doing the same with all proteins?”
Its remarkable how much current literature and popular diets focus on nutrient ratios, from the “carbs are bad for you” Atkins diet to the 55-65% carbohydrate ratio of the popular food pyramid. It seems one of the hottest topic in nutrition today is the ideal ratio of carbohydrate to fat to protein.
But this debate can miss a very important point.
Throughout our entire evolution, our ancestors had no idea what carbohydrates, protein, and fats were. I am certain that when offered a mango, no hunter-gatherer ever muttered the words “No thanks, I’m watching my waistline. I don’t need the carbs right now.”
All they understood was what was edible and what was not.
The biography of Ishi – the last true North American hunter-gatherer – provides a great example of this awareness. Even while trying to adapt to western civilization, he refused to consume milk or butter. In his very limited English he explained that dairy “ruined his singing voice.”4
This is, in my opinion, one of the greatest strengths of the Paleo Diet. It doesn’t miss the point. While the Paleo Diet is lower than a Western diet in carbohydrates, it is not a low carb or a high protein/fat diet. That’s because not all carbohydrates, protein, and fats are made the same. A high protein or higher carbohydrate diet can be healthy or unhealthy depending on the foods.
The focus of the Paleo Diet is not on ratios, but on eating the foods we evolved to eat. The ratio is a by-product.
A healthy Paleo Diet in fact doesn’t have an ideal ratio.
In their 2009 review of plant-animal subsistence ratios of hunter gatherer societies, Dr. Cordain and his team were quick to point out that the plant-animal ratio varied greatly.5 Societies living close to the equator could get more than 55% of their calories from plant sources, while more polar societies (such as Eskimos) derived almost all of their calories from animal sources.
As a result, the macronutrient ratios could be vastly different. Hunter-gatherer societies ate anywhere between 22-40% carbohydrates, 19-35% protein, and 28-58% fat (though it’s worth pointing out that even those broad ranges are lower carbohydrate and higher protein/fat than the Western diet).6
So it’s somewhat ironic that despite showing such broad ranges, much of the early criticism of the Paleo Diet was over macronutrient ratios.
In 2002, Dr. Cordain described a sample one-day Paleo menu in one of his early reviews. His sample menu was 23% carbohydrate, 38% protein, and 39% fat.7 Those numbers have been cited repeatedly by critics of the diet.
But again, they missed the point.
The point of the review was not to establish exact macronutrient ratios. Dr. Cordain could have easily laid out a sample Paleo menu that was higher or lower in carbs, protein, or fat. The point was to show that the sample menu consisted of nutrient dense and healthier foods than a typical Western Diet.
Let me give a real world example of why focusing on ratios over foods can be so dangerous.
My wife recently told me about a friend of hers who describes himself as a “Paleo Diet fanatic.” He unfortunately has a habit of lecturing others on their food choices including my wife. Yet, a large portion of his diet consists of bacon, butter, and coconut oil. And he avoids fruit.
His diet may be many things, but I wouldn’t personally call it Paleo. I’m unaware of any hunter-gatherer society that ate butter as a staple and gave the local fruit tree a wide berth.
When my wife asked her friend why he eats the way he does, his answer was all about macronutrients. Carbohydrates are bad for us because they cause cancer and all fats are good because they put us in ketosis.
Addressing both of those points fully is beyond the scope of this article, but let me give a cursory overview of carbohydrates and cancer to show why it’s so dangerous to make generalizations like that about macronutrients.
Cancer has been increasingly associated with elevated levels of the hormone Insulin-Like Growth Factor 1 (IGF-1), a potent promoter of growth and cell division.8-11 As its name implies, IGF-1 shares many commonalities with insulin. The pathways that raise insulin and insulin itself cause an increase in IFG-1 and lower its inhibitor Insulin-Like Growth Factor Binding Protein-3 (IGFBP-3).12, 13
If insulin raises IGF-1 and its common knowledge now-a-days that eating sugary foods spikes insulin, it’s easy to draw the conclusion that carbohydrates promote cancer.14
But that would be a mistake. A better way to determine how diet may influence both insulin and IGF-1 is to look at the glycaemic load – a measure of the ability of individual foods to raise blood sugar levels.15, 16 High glycaemic load foods have been linked to cancer in many studies.17-21
When we look at the glycaemic load of individual foods instead of carbohydrates in general we see a very different picture. For example, the fruits and vegetables promoted by the Paleo Diet all have a low glycaemic load despite being composed mostly of carbohydrates.16 Fruits and vegetables have certainly been shown to be protective against cancer.22
Likewise, foods on the Paleo-no fly list such as refined grains and soft drinks have a very high glycaemic load and may promote both IGF-123 and cancer.17-21 Interestingly, milk also has a low glycaemic load value but still strongly raises insulin and IGF-1.24
There are still many great discussions to have about the Paleo Diet. For example, the fact that most Palaeolithic foods don’t exist in the same form anymore, so how do we best approximate them? Likewise, should individuals eat different diets depending on whether they have more equatorial or polar heritages? Even macronutrient ratios are a good question to explore.
But all of these questions are the minutia not the focus. While addressing them we can never lose sight of the foundation – eat the foods we evolved to eat. Otherwise, we start snacking on sticks of butter and think it’s a good idea.
Trevor Connor is Dr. Cordain’s last mentored graduate student and will complete his M.S. in HES and Nutrition from the Colorado State University this year and later enter the Ph.D. program. Connor was the Principle Investigator in a large case study, approximately 100 subjects, in which he and Dr. Cordain examined autoimmune patients following The Paleo Diet or Paleo-like diets.
1. Nilsson, L.M., et al., Low-carbohydrate, high-protein diet score and risk of incident cancer; a prospective cohort study. Nutrition Journal, 2013. 12: p. 10.
2. Pan, A., et al., Red Meat Consumption and Mortality Results From 2 Prospective Cohort Studies. Archives of Internal Medicine, 2012. 172(7): p. 555-563.
3. Zhou, J. and H. Xu, LOW CARBOHYDRATE AND HIGH PROTEIN DIETS AND ALL-CAUSE, CANCER AND CARDIOVASCULAR DISEASES MORTALITIES: A SYSTEMATIC REVIEW AND META-ANALYSIS FROM 7 COHORT STUDIES. Acta Endocrinologica-Bucharest, 2014. 10(2): p. 259-266.
4. Kroeber, T., Ishi in two worlds; a biography of the last wild Indian in North America. 1961, Berkeley,: University of California Press. 255 p.
5. Cordain, L., et al., Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets. Am J Clin Nutr, 2000. 71(3): p. 682-92.
6. McDowell, M.A., et al., Energy and macronutrient intakes of persons ages 2 months and over in the United States: Third National Health and Nutrition Examination Survey, Phase 1, 1988-91. Adv Data, 1994(255): p. 1-24.
7. Cordain, L., The nutritional characteristics of a contemporary diet based upon Paleolithic food groups. Journal of the American Nutraceutical Association, 2002. 5(5): p. 15-24.
8. Safarinejad, M.R., N. Shafiei, and S. Safarinejad, Relationship of insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) gene polymorphism with the susceptibility to development of prostate cancer and influence on serum levels of IGF-I, and IGFBP-3. Growth Hormone & Igf Research, 2011. 21(3): p. 146-154.
9. Yu, H. and T. Rohan, Role of the insulin-like growth factor family in cancer development and progression. Journal of the National Cancer Institute, 2000. 92(18): p. 1472-1489.
10. Christopoulos, P.F., P. Msaouel, and M. Koutsilieris, The role of the insulin-like growth factor-1 system in breast cancer. Mol Cancer, 2015. 14(1): p. 43.
11. Zhu, S., et al., Insulin-like growth factor binding protein-related protein 1 and cancer. Clin Chim Acta, 2014. 431: p. 23-32.
12. Cordain, L., The Paleo diet : lose weight and get healthy by eating the foods you were designed to eat. Rev. ed. 2011, Hoboken, N.J.: Wiley. xv, 266 p.
13. Attia, N., et al., The metabolic syndrome and insulin-like growth factor I regulation in adolescent obesity. Journal of Clinical Endocrinology & Metabolism, 1998. 83(5): p. 1467-1471.
14. Freedland, S.J., et al., Carbohydrate restriction, prostate cancer growth, and the insulin-like growth factor axis. Prostate, 2008. 68(1): p. 11-9.
15. Runchey, S.S., et al., Glycemic load effect on fasting and post-prandial serum glucose, insulin, IGF-1 and IGFBP-3 in a randomized, controlled feeding study. Eur J Clin Nutr, 2012. 66(10): p. 1146-52.
16. Foster-Powell, K., S.H. Holt, and J.C. Brand-Miller, International table of glycemic index and glycemic load values: 2002. Am J Clin Nutr, 2002. 76(1): p. 5-56.
17. Augustin, L.S., et al., Dietary glycemic index and glycemic load, and breast cancer risk: a case-control study. Ann Oncol, 2001. 12(11): p. 1533-8.
18. Woo, H.D., et al., Glycemic index and glycemic load dietary patterns and the associated risk of breast cancer: a case-control study. Asian Pac J Cancer Prev, 2013. 14(9): p. 5193-8.
19. Sieri, S., et al., Dietary glycemic index and glycemic load and risk of colorectal cancer: results from the EPIC-Italy study. Int J Cancer, 2014.
21. Eslamian, G., et al., Higher glycemic index and glycemic load diet is associated with increased risk of esophageal squamous cell carcinoma: a case-control study. Nutr Res, 2013. 33(9): p. 719-25.
22. Block, G., B. Patterson, and A. Subar, FRUIT, VEGETABLES, AND CANCER PREVENTION – A REVIEW OF THE EPIDEMIOLOGIC EVIDENCE. Nutrition and Cancer-an International Journal, 1992. 18(1): p. 1-29.
23. Salmeron, J., et al., Dietary fiber, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. JAMA, 1997. 277(6): p. 472-7.
24. Hoyt, G., M.S. Hickey, and L. Cordain, Dissociation of the glycaemic and insulinaemic responses to whole and skimmed milk. Br J Nutr, 2005. 93(2): p. 175-7.