A friend recently asked for my professional opinion on the “Paleo Diet”. Because this diet is still fairly popular, I thought I would share my research of the nutritional risks and benefits with a wider audience.

Introduction

What is the “Paleo diet”?

The Paleo Diet, or Hunter Gatherer diet, refers to a way of eating that is meant to mimic the diet of our Paleolithic ancestors. Although there are several variations of this diet, the typical Paleo diet derives over 50% of energy from animal products, and is high in protein (19-35% of calories) and fat (25-58%) and low in carbohydrates (22-40%)¹. The main food sources are foods that were hunted and gathered, including wild game, fish, shellfish, eggs, nuts, fruit, and vegetables. Restricted foods are those that were not widely available during this era, and include grains, dairy, alcohol, processed foods, sucrose and legumes¹.

The Science Behind the Paleo diet

Paleo diet foods were selected for their prominence in a preagriculture Paleolithic civilization. These food choices are thought to benefit health due to their high nutrient density and soluble fiber content, low glycemic load, favorable sodium to potassium ratio, acid base balance, and low content of bioactive substances and antinutrients¹. The Paleolithic era is thought to be nutritionally superior to our current era because our Paleolithic ancestors did not suffer from the chronic diseases that plague western cultures¹. However, chronic diseases tend to occur later in life and Paleolithic peoples did not live as long as we do today. And although it has been noted that extant hunter-gatherer cultures have more years of good health and less chronic disease than people in Western civilizations, the standard American diet is known for its link to chronic disease¹.

Note that there are other, non-dietary aspects of the paleo diet that include physical activity, regular sun exposure, adequate sleep and a lack of chronic stress and pollutants¹. The purpose of this review is to narrow in on the nutrition regulations of the Paleo diet in order to evaluate the various risks and benefits of this eating pattern.

Nutrition Risks of the Paleo Diet

Restriction of Grains

One of the most controversial aspects of the Paleo diet is the elimination of grains. Without grains, followers of this diet are unable to benefit from the various health effects associated with whole grain consumption, including a decreased risk for type 2 diabetes^C, cardiovascular disease, and cancers of the colon and rectum, as well as well as decreased plasma concentration of triglycerides and LDL cholesterol⁴.

Grains are primarily a source of carbohydrate, and by eliminating grains, the Paleo diet has a carbohydrate level of only 22-40% of calories. Low carbohydrate diets have been cycling in and out of the media over the years masked as The Atkins Diet, the Zone Diet, and now the Paleo Diet. Low carbohydrate diets work to deplete liver and muscle of glycogen stores. However, in order to maintain blood sugar, both fat and muscles are broken down into ketones to be used for energy in a process known as ketosis. Converting fat to energy through ketosis does promote weight loss, although muscle is broken down for an energy source as well. Once a normal diet is resumed the body no longer has to resort to ketosis, so the weight eventually returns rendering the fad diet as unsuccessful. Studies also show that after one year, the weight loss from a low carbohydrate diet is no more than the weight loss from a low fat diet³.

Low carbohydrate diets also pose a risk for kidney disease. Although proponents of the Paleo diet are quick to point out that the diet does not seem to pose a threat to people without preexisting kidney disease¹, recent research suggests that the negative health effects of low carbohydrate diets are not always consistent with serum biochemical markers for kidney function, therefore masking underlying organ and tissue damage³.

High in animal proteins and fats

Animal based diets are linked to chronic disease including cancer, type 2 diabetes, and heart disease⁵. Because the paleo diet is relatively high in animal proteins and fats, followers of this diet may be at an increased risk of chronic disease. Diets high in meat, particularly red meat, also tend to be high in saturated fat.  Saturated fat has long been associated with an increased risk for heart disease. Supporters of the Paleo diet point out that replacing saturated fats with refined carbohydrates actually increases heart disease risk¹. However, this research does not indicate replacing whole grain carbohydrates with animal fat. A more heart healthy alternative would perhaps be to replace saturated fat laden meats with lower fat cuts of meat or even photochemical rich plant protein sources. There is also controversial research regarding the positive effects of certain types of saturated fat found in coconut oil¹. However, coconut oil is a plant source of saturated fat, so high consumptions of animal fat do not appear to have any of these health benefits.

On the other hand, plant based, vegetarian diets are linked to lower body mass indexes, total cholesterol, LDL cholesterol, and blood pressure, as well as decreased incidence of hypertension, stroke, type 2 diabetes, and certain types of cancer⁵. These plant based, vegetarian diets tend to be high in “fruits, vegetables, whole-grains, legumes, nuts, and various soy products”. Legumes are beneficial sources of protein because they contain slow release carbohydrates as well as soluble fiber⁵. Legumes can also protect against stomach, colon, and prostate cancer⁵. In contrast, the Paleo excludes grains, legumes, and soy products while promoting meat consumption.

Low in Calcium

Calcium is an extremely important mineral for bone health and is one of the essential nutrients required for normal body functioning. Because the Paleo diet excludes dairy products, one of the greatest sources of highly bioavailable calcium⁵, followers of this diet are at an increased risk of calcium deficiency. Some Paleo diet researchers believe dairy products to net acid yielding and therefore damaging to the kidneys¹, yet, as mentioned previously, research suggests that it is the restriction of carbohydrates that saturates the blood stream with acidic ketones that can pose a threat to kidney health³.

Nutritional Benefits of the Paleo Diet

High in fruits and vegetables

High consumption of fruits and vegetables has numerous documented health benefits, and there have been a number of campaigns in America that have worked to increase produce consumption. Fruits and vegetables are an excellent source of soluble fiber, as well as a variety of vitamins and minerals. In fact, fruits and vegetables have a higher micronutrient density than other food groups, including grains and dairy¹.

Choosing nutrient dense foods over energy dense foods also lends itself to weight loss and weight maintenance, because nutrient dense foods have much less calories. In addition, the soluble fiber found in these foods helps promote satiety and movement through the digestive tract, and it also aids with glycemic control¹. Various fruits and vegetables have been shown to exhibit a protection against various cancers, including prostate, lung, colon, stomach, and esophagus⁵. Because the Paleo diet encourages a high consumption of fruits and vegetables, followers may benefit from these health effects.

Animal Products that are Free Range and Grass Fed

There is an increasing amount of research being done on the health benefits of animal products that are free range and grass fed (rather than caged and grain fed). Because wild game and other animals hunted during the Paleolithic era weren’t fed grain, caged up, or pumped full of antibiotics and other additives, grass fed and free range cuts of meat and eggs are recommended in the Paleo diet. Eggs and meats from grass fed animals tend to have a lower ratio of omega-6 to omega-3, which is thought to be favorable for heart health¹.

Limiting Refined Sugars

Refined sugars are essentially empty calories, and they are hidden almost everywhere in the Western diet. Refined sugars are packed full of energy and flavor, but unlike fruit juice and other unrefined sweeteners, completely devoid of micronutrients and soluble fiber¹. High intake of refined sugars, including high fructose corn syrup, has been linked to “obesity, dyslipedemia, gout, hypertension, kidney disease, and nonalcoholic fatty liver disease”¹. Because refined sugars were not consumed during the Paleolithic era it is restricted in the Paleo diet. Therefore, followers of the Paleo diet may not be subject to the harmful effects associated with refined sugar consumption.

Discussion

While there is little argument the standard American diet is less than ideal, the current dietary guidelines for Americans reflect the latest in evidence-based research². The Paleo diet encourages a very natural way of eating and a diet high in produce and low in food additive and refined sugars is a step in the right direction. However, as with most fad diets, anytime a food group is restricted one should proceed with caution. Eliminating whole grains from the diet could potentially lead to long-term health effects such as kidney damage, as well an increased risk of cardiovascular disease or colon or rectal cancer⁴. The Paleo diet does not appear to be harmful to short-term health, especially when carbohydrate levels do not fall below the low range of the spectrum and when lean protein sources are chosen over fatty red meats. However, there is not enough evidence to warrant recommending this diet to patients over a diet high in fruits, vegetables, whole grains, and lean proteins².

Resources:

1. Carrera-Bastos P, Fontes Villabla M, O’Keefe JH, Lindeberg S, Cordain L. The western diet and lifestyle and diseases of civiliazation. Res Rep Clin Cardiol 2011; 2: 215-235.
2. “Dietary Guidelines for Americans.” Your Portal to Health Information from the U.S. Government. Web. 05 Apr. 2012. <http://health.gov/dietaryguidelines/Default.asp&gt;.
3. Frigolet ME, Raymos Barragon VE, Tamez Gonzalez M. Low-carbohydrate diets: a matter of love or hate. Ann Nutr Metab. 2011 Oct;58(4):320-34.
4. Montonen J, Boeing H, Fritsche A, Schleicher E, Joost HG, Schulze MB, Steffen A, Pischon T. Consumption of red meat and whole-grain bread in relation to biomarkers of obesity, inflammation, glucose metabolism and oxidative stress. Eur J Ntr. 2012 Mar 18. [Epub ahead of print]
5. Winston, John C. Nutrition Concerns and Health Effects of Vegetarian Diets. Nutr Clin Pract. 2010 Dec;25(6):613-20.

– Kelly