The Paleo diet - a nutritional overview - December 2014
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The Paleo diet – a nutritional overview
December 2014
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Table of Contents
Introduction ……………………………………………………………………………………………………………………………………..3
Guidelines for the diet..…………………………………………………………………………………………….……………………….3
Physiology …………………………………………………………………………………………………………………………………………4
Increased meat consumption…………………………………………………………………………………………………….………5
Elimination of legumes.…………………………………………………………………………………………………………….….……7
Elimination of dairy ………..………………………………………………………………………………………………….……………..7
Impact on gut health………………………………………………………………………………………………………………………….8
Other impacts ……….………………………………………………………………………………………………………………………….8
Conclusion………………………………………………………………………………………………………………………….…………..10
References ……………………………………………………………………………………………………………………….…………….10
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Introduction
A very easy measure to determine the popularity of anything these days is to find out how often it
was searched for on Google. During prime ‘diet’ week (the first week of the year) in 2013 the paleo
diet was the most frequently searched diet on Google (Experian, 2013), showing that a concept that
has been around for several decades is still an option that many people consider when wanting to
lose weight. With celebrity endorsements from Tom Jones, Gwyneth Paltrow and Megan Fox, there
are suggestions in the media that the paleo diet is gaining in popularity.
Although the diet has had increased media exposure over the past few years the diet concept is not
new. In 1975 Walter Voegtlin published a book called ‘The Stone Age Diet’ which first introduced
the idea of paleolithic nutrition in the modern day. In 1985 two anthropologists called S. Boyd Eaton
and Melvin Konner proceeded to investigate the effects of such a diet on the human body. For the
remainder of the 20th century the paleo diet was dwarfed by popular diets such as the Atkins diet,
the Hollywood diet and various shake-based diets. It was not until 2005 when a book called ‘The
Paleo Diet for Athletes: A Nutritional Formula for Peak Athletic Performance’ by Loren Cordain was
published that the paleo diet was brought back into public attention. By 2010 the diet had gained
momentum, with athletes endorsing the benefits it could provide, and with two further publications
– one again by Cordain, entitled ‘The Paleo Diet’, and the second, a top-selling book called ‘The
Paleo Solution’ by Rob Wolf.
The term ‘paleo diet’ is very wide-ranging however in paleolithic times there was not just one diet.
Diets varied depending on the local availability of food, the tools and techniques available for
preparing food, and also a matter of taste. In tropical climates the diet would be rich in gathered
plants (which is thought to have included grains and tubers) whereas in higher latitudes the diet
mostly comprised of animal protein, as plants were not as abundant but animals could be hunted.
Guidelines for the diet
The main concept of the paleo diet is to eat like our caveman ancestors did. It is often used as a
weight loss method however quite a number of people who choose to follow the paleo diet do so as
a long term lifestyle choice rather than for short term weight loss success. ‘Paleolithic’ refers to the
period of time beginning more than 2 million years ago and continuing until around 10,000 years
ago, when the Neolithic period began and humans started cultivating cereal grains and
domesticating animals (Frassetto et al. 2009). Those following the diet can eat as much as they like
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of: grass-produced meats, fish and seafood, fresh fruits and vegetables, eggs, nuts and seeds, and
‘healthy’ oils such as olive, walnut, coconut and avocado. The diet does not allow the consumption
of: cereal grains, legumes (including peanuts), dairy, refined sugar, potatoes, processed foods, salt
and refined vegetable oils. Supporters of the paleo diet believe that human health started to
deteriorate when agricultural practices were put in place. They believe that the modern diet may
lead to chronic conditions such as cardiovascular disease, obesity and type 2 diabetes (Klonoff,
2009).
Theoretically, for millions of years humans have eaten meat, fish, poultry, and the leaves, roots and
shoots of various plants. Grains, potatoes and beans were not eaten for several reasons. Firstly, in
their natural state grains and beans are not easily digestible, and require to be cooked. Secondly, it is
thought that the potato has only been harvested for the past 35,000 years and so would not have
been available to paleolithic people. In 1985 Eaton and Konner estimated that the percentage of
energy from each macronutrient group in paleolithic human diets were: 21% fat, 34% protein and
45% carbohydrate. Further research lead to an amendment of these figures, so in 1997 revised
figures were published: 22% fat, 37% protein, 41% carbohydrate. A ration of plant to animal energy
subsistence of 65:35 was assumed by anthropologist Richard Borshay Lee (Lee, 1968).
It is questionable as to how accurate the modern day paleo diet is compared to the diet of our
paleolithic ancestors. Initially it was thought that some pre-agricultural humans ate wild game, fish,
uncultivated plant foods and, when available, honey. It is thought that grains were for emergencies
and there were no dairy products, oils, salts, processed foods, nor empty calories (Eaton, 2000).
There is however evidence to suggest that humans have been processing cereal grains for food for
the past 200,000 years (Murphy, 2007). Starch granules have been discovered on the surface of
stone tools from 100,000 years ago in Mozambique (Mercader, 2009). Starch granules have also
been discovered on paleolithic grinding tools in North-Eastern Europe and the Mediterranean ,
suggesting that the production of flour was a widespread practice across Europe from at least
30,000 years ago (Revedin et al. 2010). Starch grains have been recovered from dental tartar of
Neanderthal skeletons in both Iraq and Belgium, suggesting that in both warmer and cooler climates
Neanderthals made use of the plants foods available to them (Henry et al. 2011).
Physiology
One of the arguments for following the paleo diet is that our bodies are not equipped to deal with
some of the foods we eat nowadays, however the human body has a slightly different physiology
than it did in the paleolithic era. Human tooth size remained unchanged until about 100,000 years
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ago. Since then the size of teeth has been reducing by a rate of 1% every 2000 years. It is thought
that this reduction in tooth size is due to the introduction of cooking meat and vegetables, so the
teeth were no longer required to chew raw foods (Brace et al. 1987). Brain size has increased
notably, and evidence indicates that rapid brain evolution occurred with the emergence of Homo
erectus 1.8M years ago, and this is associated with important changes in diet, body size, and
foraging behaviours (Leonard, 2007).
Increased meat consumption
The Paleo diet is not well suited to vegetarians due to the high prominence of meat and fish in the
guidelines. There are concerns over the increased intake of meat (particularly red meat) and the
impact on health. Figure 1 shows the current government guidelines for UK which recommends that
meat and other non-dairy protein sources should account for about 27% of your daily food intake
(Public Health England) however in comparison to this most guidance information on the Paleo diet
generally promotes meat and fish as the basis of the diet (see figure 2), at 37% in accordance with
Eaton and Konner’s 1997 publication.
Figure 1: The ‘Eatwell’ plate. Public Health England
5Figure 2: Paleo food pyramid. www.allpaleodiet.com
A large-scale study conducted by researchers at Harvard School of Public health found that meat
consumption is associated with an increased risk of cardiovascular and cancer mortality. The study
also indicated that substituting red meat in the diet with other protein sources such as legumes,
poultry, fish and nuts was associated with a lower risk of mortality (Pan et al. 2012). The compounds
of concern within meat include saturated fats, nitrites, and carcinogens such as Heterocyclic amines
(HCAs), which are formed during cooking.
Countries with a higher percentage of dietary fat from animal sources show higher levels of breast
cancer. In Japan, a country where the intake of fat from animal products is relatively low, affluent
women who eat meat daily are at an 8.5 times greater risk of breast cancer than the less affluent
women who rarely or never eat meat (Hirayama, 1978). It is thought this may be due to higher fat
consumption, which can affect the levels of hormones in the body. A study of 90,655 women
showed that increased red meat and high fat dairy consumption during premenopausal years
resulted in an increased risk of breast cancer (Cho et al. 2003). Other studies have indicated that
daily red meat eaters have an increased risk of colon cancer compared to those who rarely eat meat
(World Cancer Research Fund, 2007). When red meat consumption is increased more dietary protein
reaches the colon, and results in increased fermentation to products that include harmful
nitrogenous metabolites (Gill et al 2002).
6Elimination of legumes and pulses
The elimination of grains and legumes from the diet is disputed by many nutritionists, as both
observational and experimental research has shown that whole grains and legumes can impart
multiple health benefits to humans, including a reduced rate of coronary heart disease and stroke,
and improved glucose control (Flight et al. 2006)(Venn et al. 2004). Refined grains, however, have
been shown to have the opposite effect and increase inflammation (Masters et al. 2010).
The paleo diet does not include legumes and pulses because it is thought that paleolithic humans did
not consume these food groups. Both legumes and pulses display important nutritional
characteristics, and are becoming an increasingly popular alternative to meat due to the high levels
of good quality protein and micronutrients, as well as being a more environmentally sustainable and
cost effective option. High plant protein diets have positive effects on human health and decrease
the number of hazardous metabolites in the colon (Russell et al., 2011). The World Health
Organisation recommends that people increase their consumption of legumes, as well as vegetables,
whole grains and nuts, to reduce obesity, which is contrary to the theory behind the Paleo diet.
A study conducted by Harvard School of Public Health showed that replacing one serving of red meat
per day with a legume-based meal resulted in a 10% reduction in mortality risk. This study was
conducted over the course of 22 years. The researchers estimated that 9.3% of deaths in men and
7.6% of deaths in women could have been prevented if they had consumed less than 0.5 servings of
red meat each day (Pan et al. 2012).
Elimination of dairy
The paleo diet also eliminates all dairy produce, on the basis that a paleolithic human would not
have consumed milk and milk products. Excluding consumers who may have an allergy, dairy
products play a positive role in many aspects of human health, including cardiac health, dental
health, weight management and as an important source of many vitamins and minerals. Fermented
dairy foods can also aid gut health (Ebringer et al. 2008).
7Impact on gut health
Diets that are high in protein and low in carbohydrates are popular ways to lose weight, and the
paleo diet generally fits in to this category. These diets have a reasonably high success rate for
weight loss due to increased feelings of satiety. In the short term these diets can improve insulin
sensitivity too, along with other health benefits of weight loss. Sustaining a high protein, low
carbohydrate diet however could have adverse consequences, particularly to gut health. A study
conducted by the Rowett Institute of Nutrition and Health, University of Aberdeen, found that in a
study of 16 obese men, after 4 weeks the weight loss diets high in protein and low in carbohydrates
and fibre resulted in a significant decrease in faecal cancer-protective metabolites and an increased
concentration of hazardous metabolites (Russell et al. 2011). The balance of flora in the gut is
altered significantly when the human body starts to follow a specific diet such as the paleo diet.
Other impacts
One consideration for consumers who are thinking about moving to the Paleo diet is the cost. Meat
and fish play a major role in the diets of most people following the Paleo lifestyle, and many
guidance books and websites about the diet recommend organic grass-fed meat where possible,
which adds a premium to the weekly food shop. If however, somebody moves to the Paleo diet
after a lifestyle which involved eating out in fast food restaurants and ‘on the go’ then they may find
the paleo diet the same price, if not cheaper. Paleo diet forums recommend buying in bulk (e.g.
buying a side of lamb) however this depends on storage facilities in the home and would require a
change in shopping habits for most people. Eating out on the paleo diet can be problematic however
some people who choose to follow the diet long term as a lifestyle exercise a relaxed attitude
towards eating out, and try to eat ‘paleo’ for the rest of the time.
Another consideration of the paleo diet is the environmental impacts. About 35% of the paleo diet
is made up of meats and fish, and if every person in the world were to follow this diet the
environmental impact would be noticeable. Livestock production impacts on air and water quality as
well as greenhouse gas emissions. A recent study into the environmental costs of meat production
shows that beef production has the largest impact on land use, water use and greenhouse gas
emissions (Eshel et al. 2014). Figure 3 shows how the different types of meat compare in terms of
environmental resource required for production in the USA, as calculated in the 2014 study. This
8reflects current farming practices however if the paleo diet were to become more popular these
values would alter to keep up with demand for meat.
Figure 3: Percentage of the overall national environmental burdens exerted by the individual animal categories (Eshel et
al. 2014)
If all meat was sourced locally using sustainable farming methods the situation would be different,
however with meat buying behaviours often seeking the cheapest prices most of the meat
purchased in supermarkets is not local or sustainably farmed.
9Conclusion
Whilst the historical accuracy of the Paleo diet is under scrutiny most nutritionists agree that it is a
good idea to cut down on the consumption of processed foods such as white bread, sugary cereals
and packaged reformed meats. The Paleo diet bans more than just highly processed foods, and the
removal of grains, legumes and dairy from the diet is a controversial idea – as is any diet which
eliminates entire food groups. It is generally agreed amongst nutritionists that a diverse diet is best
for overall health. The human body requires more than fifty essential nutrients for growth and cell
maintenance. Most of these essential nutrients must be supplied from food sources, and a diet
consisting of a range of food types is most likely to provide the balance of nutrients required for
optimal human health.
In terms of short term weight loss the Paleo diet could be useful to some people. There are scores of
stories about weight loss on the Paleo diet (as with all diets) and a recent study carried out by
researchers in Canada showed that the variation in weight loss across different diets is small, and
that the most important element to weight loss success is to stick to the diet, whichever one the
individual may choose (Johnston et al. 2014). This only takes into consideration weight loss however,
not wider health issues, and is for short term dieting only.
It is true that the paleolithic human did not eat chips, hotdogs and chocolate however they also did
not make pizza bases made from cauliflowers, dairy-free cheesecake, or almond flour pancakes,
which appear in Paleo diet books and websites. It seems that although the principle of the paleo diet
is simple, it is very difficult to draw a line at what was and was not eaten by our ancestors.
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