Why it Fails
The Paleo diet can be an improvement on the eating habits of many people of today. It eliminates processed foods and refined carbohydrates, fast foods and fried foods and it embraces fruits and vegetables, nuts and seeds in their natural states. Unfortunately, it also encourages large amounts of meat in spite of the well-known connection between meat consumption and chronic disease and it limits carbohydrate ingestion to relatively low amounts. Evidence illustrating the negative link between high-meat low-carbohydrate consumption and robust health is mighty. Let’s look at the potential health problems that can arise from eating a long-term Paleo diet.
The Paleo diet rejects legumes, one of two food groups associated with longevity. The longest-living peoples in the world, residents of Blue Zones, have traditionally eaten diets based on legumes. In fact, Blue Zone populations tend to eat about four times as many legumes as the average modern person. These healthy populations have been discovered in pockets around the globe – Okinawa, Japan; Icaria, Greece; Sardinia, Italy; Loma Linda, California; Nicoya Peninsula, Costa Rica. These people not only live much longer than the majority of people on earth, with a high proportion of them living to be over 100 years old, but they live well, enjoying vibrant health throughout their long lives. The diet in Okinawa is based on soybeans. Lentils, garbanzo beans and white beans are the cornerstones of Icaria and Greek citizens. Black beans are eaten daily in Nicoya. Peas and beans of all kinds are emphasized in Loma Linda. Studies show that a higher intake of legumes is the most important dietary predictor of survival amongst the elderly, regardless of where they live. Every 20 gram daily serving of legumes (about one heaping tablespoonful) results in an 8% reduction in risk of early death. Imagine what eating a whole cup of legumes can do! The significance of this finding remains after controlling for age, ethnicity, gender and smoking. (1)
The Paleo diet also rejects grains, the other major food group associated with longevity. Many recent studies have weighed in on this issue. A 2016 review of 45 different studies concluded that whole grain consumption reduced risk of cardiovascular disease, coronary heart disease, cancer, respiratory disease, infectious disease, diabetes and early death from all causes. Researchers calculated that eating 90 grams of whole grain daily reduced the risk of early death from all causes by 17% (2). A 2016 meta-analysis (a method of analyzing separate but similar experiments by pooling results to test their strength) used the data from 14 studies (encompassing 788,076 participants) to show that, compared to those eating the least amount of grains, those that ate the most whole grains had a 16% reduced risk of early death from all causes and an 18% reduced risk of cardiovascular-related death. These researchers calculated that for each 16 gm increase in whole grain intake there was a 7% reduction in premature death (3). A 2015 study followed more than 100,000 men and women for more than twenty years and found that those who regularly ate grains had a 9% lower overall rate of early death and a 15% lower death rate from heart disease. These researchers stated that even one 28 gram serving of whole grains per day has the ability to lower overall risk of early death by 5% and the risk of death from heart disease by 9% (4). These studies vary in their calculations of the precise extent of the lowering of risk but they all agree that consumption of grains leads to lower rates of many chronic health problems and lower risk of early death from all causes. What does it take to eat 28 grams of whole grains? Simple choices include one slice of whole-grain bread or half a cup of cooked brown rice. It is clear however that the more whole grains you consume, the more benefits you will enjoy.
The Paleo diet encourages the daily consumption of an abundance of meat. Evidence on the negative effect of eating meat on life expectancy is plentiful. In 1999 five prospective studies that had compared the death rates from common diseases in vegetarians and non-vegetarians with similar lifestyles were reviewed and analyzed with the conclusion that early death from coronary heart disease was 24% lower in vegetarians than in non-vegetarians (5). The eminent Adventist Health Study 2 in 2013 found that, compared to meat eaters, vegetarians lowered their risk of early death by 12% and vegans lowered theirs by 15%. Vegetarian diets showed reductions in cardiovascular mortality, non-cardiovascular non-cancer mortality, renal mortality, and endocrine mortality. (6). An earlier study of Seventh Day Adventists from California revealed that men who eat beef three or more times a week are 2.3 times more likely to die of coronary heart disease. The lifetime risk of coronary heart disease was decreased by 37% in male vegetarians compared to non-vegetarians (7). A 2017 study followed 536,969 participants and looked at their ingestion of processed and unprocessed red meat (beef, lamb, pork) and white meat (poultry, fish) as well as their intake of heme iron and nitrate/nitrite from processed meat. An increased risk of early mortality from all causes and death due to nine different causes was associated with red meat intake. Increased death associated with nitrate and heme iron intake from processed meat was estimated to be 24%. Consumption of unprocessed poultry and fish were associated with lower mortality rates (8). The National Institutes of Health followed over 500,000 retired people over more than 8 years and discovered statistically significant elevated risks of cancer for esophageal, colorectal, liver, and lung cancer in those eating the most red meat. Individuals eating the most processed meat had a 20% higher risk for colorectal and a 16% higher risk for lung cancer compared to participants eating the lowest amount of meat (9).
What about the Paleo diet pattern of restricting carbohydrates? Studies completed over the last decade show the folly of restricting healthy carbohydrates. In 2007 the diet of 22,944 healthy adults was assessed and followed for five years. Higher carbohydrate intake was associated with significant reductions in total mortality especially that of cardiovascular and cancer mortality (10). The Women’s Lifestyle and Health Cohort study in Sweden looked at 42,237 women and found that both decreasing carbohydrate intake and increasing protein intake were associated with increased total mortality and particularly cardiovascular mortality (11). A meta-analysis of four low-carbohydrate studies encompassing 272,216 subjects reported a 31% higher risk of early death from all causes in those eating a low-carbohydrate diet (12). A Harvard School of Public Health study followed over 4000 men and women who had survived a heart attack. Eating a diet higher in animal protein and fat and lower in carbohydrate was associated with a higher risk of cardiovascular-related death and early death from all causes. Those eating a plant-based low-carbohydrate diet showed no increase in early death risk (13). Lastly, the source of food plays a part in mortality risks. An analysis performed by the Harvard School of Public Health of nearly 130,000 subjects found that a low-carbohydrate diet based on animal-sourced food was associated with higher all-cause mortality in both men and women, whereas a vegetable-based low-carbohydrate diet was associated with lower all-cause mortality and cardiovascular disease mortality rates. (14).
The scientific investigations listed in this article are by no means the only ones that have enlightened us on the health risks of following a Paleo diet over a long time. But there is enough evidence here to make a strong case for limiting foods sourced from animals and embracing whole plant foods.
1 Darmadi-Blackberry, I., Wahlqvist, M.L., Kouris-Blazos, A., Steen, B., Lukito, W., Horie, Y., Horie, K. Legumes: the most important dietary predictor of survival in older people of different ethnicities. Asia Pac J Clin Nutr. 2004; 13(2): 217-220.
2 Aune, D., Keum, N., Giovannucci, E. et al. Whole grain consumption and risk of cardiovascular disease, cancer, coronary heart disease, respiratory disease, infectious disease, diabetes, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies. BMJ 2016; 353:i2716
3 Zong, G., Gao, A., Hu, F., Sun, Q. Whole Grain Intake and Mortality From All Causes, Cardiovascular Disease, and Cancer: A Meta-Analysis of Prospective Cohort Studies. Circulation 2016;133:2370-2380.
4 Hongyu, W., Flint, A.J., Qi, Q., van Dam, R.M., Sampson, L.A., Rimm, E.B., et al. Association Between Dietary Whole Grain Intake and Risk of Mortality – Two Large Prospective Studies in US Men and Women. JAMA Intern Med. March 2015; 175 (3):373-384.
5 Key, T.J., Fraser, G.E., Thorogood, M., Appleby, P.N., Beral, V., Reeves, G., Burr, M.L. et al. Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies.
Am J Clin Nutr 1999; 70(suppl):516S–24S
6 Orlich, M.J., Singh, P.N., Sabaté, J., Jaceldo-Siegl, K., Jing Fan, J., Knutsen, S., Beeson, W.L., Fraser, G.E.
Vegetarian Dietary Patterns and Mortality in Adventist Health Study 2. JAMA Intern Med. 2013 Jul 8; 173(13): 1230–1238.
7 Fraser, G.E. Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists. Am J Clin Nutr. 1999 Sep; 70(3 Suppl):532S-538S.
8 Etemadi, A., Sinha, R., Ward, M.H., Graubard, B., Inoue-Choi, M., Dawsey, S.M., Abnet, C.C.. Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study. BMJ. 2017 May 9; 357:j1957.
9 Cross, A.J., Leitzmann, M.F., Gail, M.H. et al. A Prospective Study of Red and Processed Meat Intake in Relation to Cancer Risk. PLos Medicine. Dec. 11, 2007.
10 Trichopoulou, A., Psaltopoulou, T., Orfanos, P., Hsieh, C.C., Trichopoulos, D. Low-carbohydrate-high-protein diet and long-term survival in a general population cohort. Eur J Clin Nutr. 2007 May; 61(5):575-581.
11 Lagiou, P., Sandin, S., Weiderpass, E., Lagiou, A., Mucci, L., Trichopoulos, D., Adami, H.O. Low carbohydrate-high protein diet and mortality in a cohort of Swedish women. J Intern Med. 2007 Apr; 261(4):366-74.
12 Noto, H., Goto, A., Tsujimoto, T., Noda, M. Low-carbohydrate diets and all-cause mortality: a systematic review and meta-analysis of observational studies. PLoS One. 2013; 8(1):e55030.
13 Li, S., Flint, A., Pai, J.K., Forman, J.P., Hu, F.B., Willett, W.C., Rexrode, K.M., Mukamal, K.J., Rimm, E.B. Low carbohydrate diet from plant or animal sources and mortality among myocardial infarction survivors. J Am Heart Assoc. 2014 Sep 22; 3(5):e001169.
14 Fung, T.T., van Dam, R.M., Hankinson, S.E., Stampfer, M., Willett, W.C., Hu, F.B. Low-carbohydrate diets and all-cause and cause-specific mortality: two cohort studies. Ann Intern Med. 2010 Sep 7; 153(5):289-298.