The amount of dietary do’s and don’ts bombarding us on a daily basis may make sifting through bogus nutritional claims seem insurmountable. But have no fear—the Greatist sleuths are here to decode the latest, greatest, (and not so great) diets. This week, we’re debunking the Paleo diet.

The Breakdown

What you can eat:

  • Animal proteins (quality meats—preferably grass-fed—eggs, and fish).
  • Fruits. Vegetables (except for starchy varieties).
  • Nuts and seeds (in moderation).
  • Healthy fats (olive oil, fish oil, avocado).
  • Herbs and spices.

What you can’t eat:

  • Dairy
  • Grains
  • Legumes
  • Starches
  • Alcohol
  • Processed foods, sugars, and sugar substitutes.

Exceptions: Paleo dieters who engage in endurance events lasting 90 minutes or more can consume sweet potatoes and yams to up glycogen stores as part of training.

The Theory: Per Paleo thinking, modern human digestive systems weren’t designed to handle the refined sugars, starchy carbs, grains, legumes, and dairy products that have snuck into our diets over the past 10,000 years. The consequence? A steady expansion of our waistlines and an uptick in disease rates. Around 1975, one gastroenterologist suggested a solution: Go retro—to an era before we learned how to farm, homogenize, can, sugar, refine, fry, re-fry, and all those other techniques that make foods convenient, tasty, and bacteria-free. Since our hunter-gatherer ancestors didn’t seem to suffer from modern dietary-induced woes, the thinking went, we too might rid ourselves of our post-agricultural era illnesses by sticking to Stone Age meal plans.

Time to Go Paleo?—What The Science Says

It’s clear that a diet rich in fruits, vegetables, lean protein, omega-3, and other polyunsaturated fats improve our body’s ability to make use of food rather than store it as fat or keep it lingering in the blood stream as excess sugarBeneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes: a randomized cross-over pilot study. Jönsson, T., Granfeldt, Y., Ahrén, B. Department of Clinical Sciences, Lund, Sweden. Cardiovascular Diabetology, 2009 Jul 16;8:35.A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischaemic heart disease. Lindberg, S., Jönsson, T., Grantfeldt, Y. et al. Department of Medicine, University of Lund, Sweden. Diabetologia, 2007 Sep;50(9):1795-807.. The rationale behind eliminating starchy carbs is supported by studies finding that they spike blood sugar more severely than fructose (the sugar molecule found in fruits and veggies). And the low-carb profile Paleo adheres to does indeed dial down inflammation in tissues by altering the composition of the fatty acids they containComparison of low fat and low carbohydrate diets on circulating fatty acid composition and markers of inflammation. Forsythe, C.E., Phinney, S.D., Fernandez, M.L., et al. Department of Kinesiology, University of Connecticut. Lipids, 2008 Jan;43(1):65-77.. Numerous studies show diets mimicking what we think our ancestors ate can shrink waistlines and lower bad cholesterol levelsMarked improvement in carbohydrate and lipid metabolism in diabetic Australian aborigines after temporary reversion to traditional lifestyle. O’Dea, K. Diabetes, 1984 Jun;33(6):596-603.Evaluation of biological and clinical potential of paleolithic diet. Kowalski, L.M., Bulko, J., Wydział Nauk o Zywieniu Człowieka i Konsumpcji Szkoła Główna Gospodarstwa Wiejskiego, Warszawa. Roczniki Panstowowego Zakladou Higieny, 2012;63(1):9-15.. Oh, and when we drop legumes and grains, dairy, and refined sugars, blood pressure tends to follow suitMetabolic and physiologic improvements from consuming a paleolithic, hunter-gatherer type diet. Frassetto, L.A., Schloetter, M., Mietus-Snyder, M., et al. Department of Medicine, University of California San Francisco School of Medicine, San Francisco. European Journal of Clinical Nutrition, 2009 Aug;63(8):947-55.. So let’s take a closer look at those three problem spots.

On Legumes and Whole Grains

But (and there’s a big “but”): Legumes and whole grains have also been shown to reduce risk of disease and improve insulin sensitivity and blood glucose levels—not to mention decrease BMICereal grains, legumes, and weight management: a comprehensive review of the scientific evidence. Williams, P.D., Grafenauer, S.J., O’Shea, J.E. Smart Foods Centre, School of Health Sciences, University of Wollongong, Australia. Nutrition Reviews, 2008Apr;66(4):171-82.Cereal grains, legumes and diabetes. Venn, B.J., Mann, J.I. Department of Human Nutrition, University of Otago, New Zealand. European Journal of Clinical Nutrition, 2004 Nov;58(11):1443-61.Cereal grains and legumes in the prevention of coronary heart disease and stroke: a review of the literature. Flight, I., Clifton, P. CSIRO Human Nutrition, Adelaide, South Australia. European Journal of Clinical Nutrition. 2006, Oct;60(10):1145-59.Plausible mechanisms for the protectiveness of whole grains. Slavin, J.L., Martini, M.C., Jacobs, D.R., et al. Department of Food Science and Nutrition, University of Minnesota, St Paul. American Journal of Clinical Nutrition. 1999 Sep;70(3 Suppl):459S-463S.. So what justifies keeping them out of our bellies? Paleo proponents argue that legumes, grains, and other starches (i.e. potatoes) contain high levels of antinutrients (lectin, prolamin, phytate and saponins, for starters). These compounds, the Paleo philosophy holds, block key digestive enzymes, promote inflammation and, in some cases, lie at the root of autoimmune diseases and cancerPhytate (myo-inositol hexaphosphate) and risk factors for osteoporosis. López-González, A.A., Grases, F., Roca, P., et al. Servicio de Prevención de Riesgos Laborales, Gestión Sanitaria de Mallorca, Palma de Mallorca, Spain. Journal of Medicinal Food, 2008 Dec;11(4):747-52.. Research does show that excess consumption of some antinutrients offsets our belly’s bacteria levels and puts us at risk for inflammatory diseases like asthma, rheumatoid arthritis, and inflammatory bowel syndromeAntinutritional properties of plant lectins. Vasconcelos, I.M., Oliveira, J.T. Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Brazil. Toxicon, 2004 Sep 15;44(4):385-403.Modulation of immune function by dietary lectins in rheumatoid arthritis. Cordain, L., Toohey, L., Smith, M.J., et al. Department of Health and Exercise Science, Colorado State University, Fort Collins. British Journal of Nutrition, 2000 Mar;83(3):207-17.. But there isn’t as much science to support cutting them out completely. Some studies suggest dietary lectins from legumes and grains may bolster good bacteria inside our tummies and aid digestionCharacteristics and consequences of interactions of lectins with the intestinal mucosa. Pusztai, A. Rowett Research Institute, Bucksburn, Aberdeen, Scotland. Archivos Latinoamericanos de Nutrición, 1996 Dec;44(4 Suppl 1)10S-15S..

Dairy Deficit?

As for concerns that the Paleo diet doesn’t provide enough calcium, worriers take note: Dairy isn’t the only place you’ll find this mineral. Leafy greens like kale and spinach, for instance, trump milk, cheese, and yogurt when it comes to absorption of the bone-saving stuff. One cup of milk may contain 25 percent of our recommended daily calcium, but dairy’s acidity can actually cause our bodies to leach calcium from bones as a buffer to regulate blood alkaline levels, says Nell Stephenson, a nutrition and fitness coach and self-professed Paleoista. “You’re better off going with the 24 percent daily value of calcium a [one cup] serving of [cooked] spinach delivers,” since the natural alkalinity of veggies won’t necessitate stealing as much calcium from your skeleton.


Contrary to many misperceptions, “Going Paleo doesn’t mean eating all meat, all the time, Stephenson says. (Remember: Fish and poultry are fair game.) “Only eating meat puts the body in ketosis—an atypical reliance on fat, rather than carbohydrates, for fuel. We need carbs to function, just not in the form of bread, pasta, and bagels.” That’s why Paleo endurance athletes chow down on yams pre-race, and why Stephenson emphasizes the need to eat more vegetables and moderate amounts of fruit for adequate energy. The macronutrient ratio she recommends is 40 percent carbohydrate, 30 percent protein, and 30 percent fat.

Should I Go Stone Age?—Diet Decision

Increasing your intake of vegetables, fruits, healthy fats, and lean proteins while cutting refined sugars, processed foods, and bread can lead to some serious health benefits. To start off smart, try these tasty paleo snack ideas. But whether you want to go the whole caveman way and cut legumes, dairy, and grains is another question. Science shows this does benefit health as long as you make up for lost calcium and carbs via the right veggies and fruits. As always, speak with a nutritionist or doctor before making any drastic dietary decisions.

Special thanks to Nell Stephenson and Loren Cordain for their help on this article.