I’ve been following some version of a Paleo diet since January of 2012, when I was in my first year of medical school at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University. Over the past 4 years, Paleo ways of eating have become even more mainstream, and I’m often asked how I defend my decision to eat this way to other professionals in the medical community. It’s true, primary research on the Paleo diet isn’t incredibly abundant, but it’s an area of study that continues to grow. Thus far, there are 4 published randomized, controlled studies comparing Paleo to other diets in individuals with characteristics of metabolic syndrome (diabetes, obesity, high cholesterol, and high blood pressure). In other words, these studies recruited participants, randomly assigned them to eat either Paleo or another diet for a specified period of time, and compared changes in outcomes such as blood pressure, blood lipids, glucose metabolism and weight between the two groups. Below I’ll review some of the highlights of each of the four studies:
- A Paleolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischemic heart disease. Published in Diabetologia in 2007 by Lindberg et al.
- 29 men with ischemic heart disease and increased blood glucose or type 2 diabetes were randomized to Paleo or Mediterranean diet for 12 weeks.
- Participants were educated on their diets, but the amount of food consumed was not controlled (ad-libitum)
- Both groups saw significant losses in weight, but the Paleo group saw greater improvements in glucose tolerance and waist circumference compared to a Mediterranean diet.
- The Paleo group ended up eating 451 calories per day less on average than the Mediterranean group without intentionally controlling food intake.
- Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes: a randomized cross-over pilot study. Published in Cardiovasc Diabetol. in 2009 by Jonsson et al.
- 13 individuals with type 2 diabetes were randomized to either a Paleo diet or a diet consistent with guidelines for diabetes for 3 months. After the first 3 months, the participants switched diets for an additional 3 months.
- Participants had greater decreases in weight, waist circumference, HbA1c, Triglycerides, and increases in HDL on the Paleo diet than the diabetes diet.
- Long-term effects of a Paleolithic-type diet in obese postmenopausal women: a 2-year randomized trial. Published in Eur J Clin Nutr. in 2014 by Mellberg et. al.
- 61 obese, postmenopausal women randomly assigned to either a Paleo diet or a diet consistent with the Nordic Nutrition Recommendations for 2 years.
- Both groups had decreased total fat mass and waist circumference at 6 and 24 months, but the decrease was greater in the Paleo group only at 6 months. The Paleo group had greater decreases in triglycerides at both 6 and 24 months.
- Favorable effects of consuming a Paleolithic-type diet on characteristics of the metabolic syndrome: a randomized controlled pilot-study. Published in Lipids Health Dis. in 2014 by Boers et. al.
- 34 individuals with at least 2 components of metabolic syndrome were randomized to Paleo diet or a diet consistent with the Dutch Health Council guidelines for 2 weeks.
- The Paleo diet group had lower blood pressure, total cholesterol, triglycerides, and higher HDL cholesterol. The number of metabolic syndrome characteristics also decreased more in the Paleo group.
In October 2015, a meta-analysis was published in the American Journal of Clinical Nutrition in which the authors extracted data from all 4 of the above studies and analyzed it together. Generally, a meta-analysis (or systematic review) is the highest class of evidence, so the fact that enough studies have been published now to make this possible is a big step! This meta-analysis concluded that Paleo diets resulted in greater short-term improvements in waist circumference, triglycerides, blood pressure, HDL cholesterol, and fasting blood sugar than the various control diets. In another study published in June of 2015, 20 subjects were asked to follow the AHA heart-healthy dietary guidelines for 4 months followed by 4 months of a Paleo diet. The Paleo diet resulted in decreases in body weight and lowered average total cholesterol, LDL, and triglycerides and increased HDL relative to baseline and the AHA heart-healthy diet in these individuals. Though they are small, studies like this and the two above comparing Paleo to a Mediterranean diet and a diet consistent with diabetes guidelines help to put this way of eating in context with current standards of practice. Several additional studies have been published in which there is no control group, but changes in key outcomes are compared in subjects before and after a given time period following a Paleo diet. (1-3) Generally, these studies show similar positive effects, even in “healthy” individuals who don’t have signs of metabolic syndrome at baseline. This brings me to my next point – sometimes the best evidence for an individual is evidence from self-experimentation. We don’t have randomized controlled studies available to guide us in every situation, but we can each do an N=1 experiment on ourselves. Every person has a unique genetic makeup which means we all respond a little differently to food. Experimenting with different diets for a month or two is a relatively low-risk way to figure out what your own body needs for optimal health. Anyone can measure their weight, blood pressure, lipids, blood glucose, and take a qualitative assessment of how you feel before and after a dietary intervention and then use this data to devise your own optimal diet. After all, we are all different and that is part of the reason nutrition research is often so difficult to interpret in the first place! In summary, there is a small yet growing body of evidence suggesting that a Paleo diet is superior to current recommendations. For those who are still skeptical after reviewing this evidence, I recommend giving it a try and letting the results you see personally guide your decisions. Now hopefully next time someone asks you why they should try Paleo, you’ll have a little more ammunition!
- Frassetto LA, Schloetter M, Mietus-Synder M, Morris RC Jr., Sebastian A. Metabolic and physiologic improvements from consuming a paleo- lithic, hunter-gatherer type diet. Eur J Clin Nutr 2009;63:947–55.
- Osterdahl M, Kocturk T, Koochek A, Wa ̈ndell PE. Effects of a short- term intervention with a paleolithic diet in healthy volunteers. Eur J Clin Nutr 2008;62:682–5.
- Ryberg M, Sandberg S, Mellberg C, Stegle O, Lindahl B, Larsson C, Hauksson J, Olsson T. A Palaeolithic-type diet causes strong tissue- specific effects on ectopic fat deposition in obese postmenopausal women. J Intern Med 2013;274:67–76.