by Lindsey Smith, doctoral student in nutrition epidemiology at UNC Chapel Hill
***Edit: Thanks to some helpful comments from our readers, I’ve updated this post to include some (but certainly not all) of the relevant literature regarding the Paleolithic diet. The objective of this post is not to draw conclusions about the inherent “goodness” or “badness” of this diet, but shed some light on what the diet is, review existing evidence and examine some of the premises of the underlying Paleo philosophy.***
The “Paleo” diet, short for Paleolithic, is poised to become the next fad diet of our generation, following in the footsteps of the low-fat craze of the 1990’s and the Atkins obsession of the ‘00’s. Blogs dedicated to “Paleo” living have sprung up across the internet faster than you can Google “coconut flour brownies,” and self-proclaimed experts are quick to deem this diet the “natural” way to lose weight.
So what’s up with this diet?
What is it?
Food allowances on this diet vary by source, but overall boil down to a single rule:
If cavemen didn’t eat it, you shouldn’t either.
OK: meat, poultry, fish, healthy fats, fruits, vegetables, and nuts
Avoid: grains, legumes, processed foods, sugar, starch, dairy, salt, alcohol, coffee
No restrictions on energy or macronutrient (carb/fat/protein) intake, although this diet may be higher in protein than the typical Western diet.
This diet is the healthiest because it is what our bodies were evolutionarily designed to consume, and works best with our genetic makeup to promote health and longevity. Advocates argue that our genes could not have evolved quickly enough to accommodate agriculturally-derived foods. Paleo supporters also argue that eating a diet that is low in processed foods and refined starches prevents diabetes and cardiovascular disease.
An informal review of the evidence presented in scientific articles, popular media, book reviews, and blogs appears to support a positive association between Paleo and health — but with some key caveats. Key points include:
– Observational studies suggest associations with lower cardiovascular disease and associated risk factors (Lindeberg 1994; Lindeberg 2010)
– Intervention trials have shown impressive results, including improved glucose tolerance, insulin sensitivity, blood pressure, LDL cholesterol and triglycerides (Jonsson 2009)
– May be more satiating than other types of diets (Jonsson 2010)
– Proponents claim that all micronutrients can be obtained in sufficient levels in the Paleo diet; however, one analysis suggested that this diet could result in micronutrient deficiency for some consumers (Lindeberg 2010, Metzgar 2011).
Although the preliminary evidence is compelling, most of the intervention studies to date have been small and somewhat short-term. More research on a larger, ethnically diverse sample would provide more information about the effectiveness of this diet in populations and whether this diet is sustainable. A second key point is that diets containing whole grains, legumes, dairy, and moderate alcohol (i.e. vegetarianism, the Mediterranean diet) have also been linked to improved cardio-metabolic health outcomes, although it is unclear which components of these diets are producing the effects.
So, the evidence seems positive, but inconclusive. What about the premises behind “Paleo”? A few thoughts:
– First, our ancestors did not live long enough to develop chronic disease, and so it is impossible to know whether these diets were more effective in promoting health and longevity. This isn’t to say that ancestral diets were better or worse: we simply cannot know how this diet affected health in the source population (i.e. our ancestors).
– Reliance upon an “ancestral diet” requires arbitrarily selecting one set of ancestors along our evolutionary history. As Rob Dunn points out, most people link this “ancestral diet” to our most recent set of ancestors, the stone age cave-dwellers. In actuality, however, the human gut most likely evolved even earlier than these particular ancestors, during a time when most if not all of the diet was composed of vegetable matter and very little meat. (http://blogs.scientificamerican.com/guest-blog/2012/07/23/human-ancestors-were-nearly-all-vegetarians/). Even the Neandertals, it turns out, may have eaten less meat than we think http://link.springer.com/article/10.1007%2Fs00114-012-0942-0.
– Finally, some scholars have refuted the idea that humans could not have adapted to modern agricultural staples like grains and legumes, citing the rapid evolution of lactose tolerance (ie the ability to consume dairy) within the last 10,000 years. It is highly plausible that we have adapted to digest other recently introduced agricultural foods. Moreover, the timing of a food’s introduction should not be the main criteria upon which healthfulness is judged: after all, even tomatoes and Brussels sprouts haven’t been around that long—and no one is debating the nutritional quality of these foods.
Some lingering questions…
Undoubtedly, diets high in processed food and sugar are obesogenic, and if not consumed in moderation, can lead to a host of diet-related disease. However, the Paleo diet also bans foods that can very much be a part of a nutritious diet. The Paleo diet does not necessarily equal a better diet: choosing high fat meats, replacing refined sugars with syrups or fruit sugars, or simply consuming excess calories can promote weight gain and set dieters up for nutritional deficits, including vitamin D and calcium. In addition, “banning” foods of any kind can be troublesome, potentially fostering unhealthy eating behaviors and mindsets and for some. I wonder if perhaps a mindset of moderation wouldn’t be more healthy (and sustainable) in the long run?
Another key danger of diets like Paleo is that by labeling a food “Paleo,” dieters may think they can consume unlimited amounts of that food. Many blogs tout “Paleo-fied” desserts, which use coconut flour, agave, or maple syrup as a replacement for wheat flour and sugar. As with anything, a dessert by any other name is still….well, a dessert. Wouldn’t it be better to decide what to eat based on the nutrition content of a given food, rather than whether it falls in some allowed or banned food group category?
Certainly, eating a diet low in processed foods, low sugars, and unhealthy fats is intuitively more ideal than the Western diet. The evidence so far seems supportive, and for some people, following a prescribed set of rules can make it easier to eat healthfully.
However, this diet smacks closely of other popular diets which have failed to meet muster over the years. Too many people have been led astray by jumping on the proverbial bandwagon before the evidence base is fully complete; and sometimes these fads cause more harm than good. The key example is the low-fat craze of the 90’s, when the call (by nutrition scientists) to reduce diet fat resulted in a tremendous shift to low-fat and fat-free products that subbed in sugar for the fat to retain the flavor and feel. People thought that you couldn’t get fat if you didn’t eat fat, and continued to eat refined carbohydrates in unprecedented amounts. I fear the same thing could happen with Paleo, or any diet that restricts food groups without considering calories. As for the evidence? I think that only time will tell…
What do you think?
Cunningham E. Question of the Month: Are Diets from Paleolithic Times Relevant Today? Journal of the Academy of Nutrition and Dietetics 2012.
Eaton SB. The ancestral human diet: what was it and should it be a paradigm for contemporary nutrition. Proceedings of the Nutrition Society 2006. 65:1-6.
Frassetto LA, Schloetter M, Mietus-Synder M, Morris Jr RC, Sebastian A. Metabolic and physiologic improvements from consuming a paleolithic, hunter-gatherer type diet.
Lindeberg 2009. Modern human physiology with respect to evolutionary adaptations that relate to diet in the past. In: Richards MP, Hublin JJ, editors. The evolution of hominin diets: integrating approaches to the study of Palaeolitich subsistence. Berlin/Heidelberg: Elsevier. P 43-57.
Lindeberg S, Jonsson T, Granfelt Y, Borgstrand E, Soffman J, Sjostrom K, et al. A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individual with ischemic heart disease. Diabetologia 2007. 50:1795-807.
Lindeberg S 2010. Food and Western disease—health and nutrition from an evolutionary perspective. Oxford: Wiley-Blackwell.
Lindeberg S. Paleolitich Diets as a Model for Prevention and Treatment of Western Disease. American Journal of Human Biology 2012. 24:110-115.
Metzgar M, Rideout Tc, Fontes-Villalba M, Kuipers RS. The feasibility of a Paleolithic diet for low-income consumers. Nutrition Research 2011. 31:44-451.
Osterdahl M, Koeturk T, Koocheck A, Wandell PE. Effects of a short-term intervention with a paleolithic diet in healthy volunteers. European Journal of Clinical Nutrition 2007. 62:682-685.