and Evolution of the Western Diet:
Health Implications for the 21st Century
Cordain et al
American Journal of Clinical Nutrition
Vol. 81, No. 2, 341-354, February 2005
There's no getting around it, this is a LONG article, and probably not the read for everyone. I posted this paper for a few reasons: (A) Because Loren Cordain has done so much to promote not only the Paleo Movement, but to raise awareness for human health. (B) He is a fantastic scientist, researcher, and writer. And, what he writes about is fact. (C) To give you, the reader, some scientific ammunition to shut someone down when they doubt the facts of the
Paleo ~ Primal Lifestyle.
This paper is an
in-depth look at the implications of the foods commonly eaten and recommended
in society today versus what was eaten during our Hunter-Gatherer period in
history. Loren Cordain, author of The Paleo Diet, and seven other contributors,
have constructed a detailed look at the problems ingesting these foods yield and
the resulting negative results on human physiology. I have shortened the
original manuscript, but I can be founding its entirety, along with the 172
scientifically cited references HERE
There is growing
awareness that the profound changes in the environment (eg, in diet and other
lifestyle conditions) that began with the introduction of agriculture and
animal husbandry ≈10000 y ago occurred too recently on an evolutionary time
scale for the human genome to adjust. In conjunction with this discordance
between our ancient, genetically determined biology and the nutritional,
cultural, and activity patterns of contemporary Western populations, many of
the so-called diseases of civilization have emerged. In particular, food
staples and food-processing procedures introduced during the Neolithic and
Industrial Periods have fundamentally altered 7 crucial nutritional
characteristics of ancestral hominin diets: 1) glycemic load, 2) fatty acid composition, 3) macronutrient
composition, 4) micronutrient density, 5) acid-base balance, 6) sodium-potassium
ratio, and 7) fiber content. The evolutionary collision of
our ancient genome with the nutritional qualities of recently introduced foods
may underlie many of the chronic diseases of Western civilization.
Genetic traits may
be positively or negatively selected relative to their concordance or
discordance with environmental selective pressures. In the affected genotype,
this evolutionary discordance manifests itself phenotypically as disease,
increased morbidity and mortality, and reduced reproductive success
Increasingly, clinical trials and
interventions that use dietary treatments with nutritional characteristics
similar to those found in preindustrial and preagricultural diets have
confirmed the beneficial health consequences predicted by the template of
evolutionary discordance theory.
With the advent of
agriculture, novel foods were introduced as staples for which the hominin
genome had little evolutionary experience. This allowed for quantitative and qualitative
food and nutrient combinations that had not previously been encountered over
the course of hominin evolution.
products, cereals, refined sugars, refined vegetable oils, and alcohol make up
72.1% of the total daily energy consumed by all people in the United States,
these types of foods would have contributed little or none of the energy in the
typical preagricultural hominin diet.
In the United States, chronic illnesses and health
problems either wholly or partially attributable to diet represent by far the
most serious threat to public health.
- Sixty-five percent of adults aged +20y in the United
States are either overweight or obese, and the estimated number of deaths
ascribable to obesity is 280,184 per year.
- More than 64 million Americans have one or more types
of cardiovascular disease (CVD), which represents the leading cause of
mortality (38.5% of all deaths) in the United States.
- Fifty million Americans are hypertensive
- 11 million have type 2 diabetes
- 37 million adults maintain high-risk total cholesterol
concentrations >240 mg/dL)
- In postmenopausal women aged >50 y, 7.2% have
osteoporosis and 39.6% have osteopenia Osteoporotic hip fractures are
associated a 20% excess mortality in the year after fracture.
Cancer is the second leading cause of death (25%
of all deaths) in the United States, and an estimated one-third of all
cancer deaths are due to nutritional factors, including obesity.
In the 5–7 million-year period since the evolutionary
emergence of hominins and studied hunter-gatherers, there would have been no
single universal diet consumed by all extinct hominin species. Rather, diets
would have varied by geographic locale, climate, and specific ecologic niche.
However, there are universal characteristics of preagricultural hominin diets
that are useful in understanding how the current Western diet may predispose
modern populations to chronic disease. Increasingly, clinical trials and
interventions that use dietary treatments with nutritional characteristics
similar to those found in preindustrial and preagricultural diets have confirmed
the beneficial health consequences predicted by the template of
evolutionary discordance theory.
NUTRITIONAL CHARACTERISTICS OF PRE- AND POST AGRICULTURAL DIETS
the development of agriculture and animal husbandry, hominin dietary choices
would have been necessarily limited to minimally processed, wild plant and
animal foods. With the initial domestication of plants and animals, the
original nutrient characteristics of these formerly wild foods changed, subtly
at first but more rapidly with advancing technology after the Industrial
Revolution. Furthermore, with the advent of agriculture, novel foods were
introduced as staples for which the hominin genome had little evolutionary
experience. More importantly, food-processing procedures were developed,
particularly following the Industrial Revolution, which allowed for quantitative
and qualitative food and nutrient combinations that had not previously been
encountered over the course of hominin evolution. In contrasting, pre- and
post-agricultural diets, it is important to consider not only the nutrient
qualities and types of foods that likely would have been consumed by preagricultural
hominins but to also recognize the types of foods and their nutrient qualities
that could not have been regularly consumed before the development of
agriculture, industrialization, and advanced technology. Food types that would
have generally been unavailable to preagricultural hominins are: dairy
products, cereals, refined sugars, refined vegetable oils, and alcohol. And
although they make up 72.1% of the total daily energy consumed by all people in
the United States, these types of foods would have contributed little or none
of the energy in the typical preagricultural hominin diet. Additionally,
mixtures of these foods make up the ubiquitous processed foods (eg, cookies,
cake, bakery foods, breakfast cereals, bagels, rolls, muffins, crackers, chips,
snack foods, pizza, soft drinks, candy, ice cream, condiments, and salad
dressings) that dominate the typical US diet.
After weaning, the
consumption of milk and milk products of other mammals would have been
nearly impossible before the domestication of livestock because of the
inherent difficulties in capturing and milking wild mammals and are
therefore relative newcomers to the hominin diet.
- Because wild cereal grains
are usually small, difficult to harvest, and minimally digestible without
processing through grinding and cooking, the appearance of stone
processing tools in the fossil record represents a reliable indication of
when and where cultures systematically began to include cereal grains in
Ground stone mortars, bowls,
and cup holes first appeared in the Upper Paleolithic (from 40000 y ago to
12000 y ago), whereas the regular exploitation of cereal grains by any
worldwide hunter-gatherer group arose with the emergence of the Natufian
culture in the Levant ≈13000 BP.
- Cereal grains were rarely
consumed as year round staples by most worldwide hunter-gatherers, except
by certain groups living in arid and marginal environments.
- There was little or no
previous evolutionary experience for cereal grain consumption throughout
- 85.3% of the cereals consumed
in the current US diet are highly processed refined grains
With the invention of
mechanized steel roller mills and automated sifting devices in the latter
part of the 19th century, the nutritional characteristics of milled grain
changed significantly because the germ and bran were removed in the
milling process, leaving flour comprised mainly of endosperm of uniformly
small particulate size.
The per capita consumption of
all refined sugars in the United States in 2000 was 69.1 kg, whereas in
1970 it was 55.5
This secular trend for
increased sugar consumption in the United States in the past 30 y reflects
a much larger worldwide trend that has occurred in Western nations since
the beginning of the Industrial Revolution some 200 y ago
evidence of crystalline sucrose production appears about 500 BC in
northern India. Before this time, honey would have represented one of the
few concentrated sugars to which hominins would have had access. Although
honey likely was a favored food by all hominin species, seasonal
availability would have restricted regular access.
In the past 30
y with the advent of chromatographic fructose enrichment technology in the
late 1970s, it became economically feasible to manufacture high-fructose
corn syrup (HFCS) in mass quantity.
available in 2 main forms, HFCS 42 and HFCS 55, both of which are liquid
mixtures of fructose and glucose (42% fructose and 53% glucose and 55%
fructose and 42% glucose, respectively). On digestion, sucrose is
hydrolyzed in the gut into its 2 equal molecular moieties of glucose and
In the past 90y, a striking
increase in the use of vegetable oils occurred.
Specifically, consumption of salad
and cooking oils increased 130%, shortening consumption increased 136%,
and margarine consumption increased 410%.
These trends were made possible by
the industrialization and mechanization of the oil-seed industry.
To produce vegetable oils from
oil-bearing seeds, 3 procedures can be used:
1) rendering and pressing
2) expeller pressing
3) solvent extraction.
Oils made from walnuts, almonds,
olives, sesame seeds, and flax seeds likely were first produced via the
rendering and pressing process between 5000 and 6000 y ago.
Margarine and shortening are
produced by solidifying or partially solidifying vegetable oils via
hydrogenation, a process first developed in 1897 which produces novel transfatty acid isomers (trans elaidic acid in particular) that
rarely, if ever, are found in conventional human foodstuffs.
In contrast with dairy products,
cereal grains, refined sugars, and oils, alcohol consumption in the
typical US diet represents a relatively minor contribution (1.4%) to the
total energy consumed.
The earliest evidence for wine
drinking from domesticated vines comes from a pottery jar dated 7400–7100
Because of seasonal fluctuations
in fruit availability and the limited liquid storage capacity of
hunter-gatherers, it is likely that fermented fruit drinks, such as wine,
would have made an insignificant or nonexistent contribution to total
energy in hominin diets before the Neolithic.
The total quantity of salt
included in the typical US diet amounts to 9.6 g/d and about 90% comes from manufactured salt that is
added to the food supply.
The systematic mining,
manufacture, and transportation of salt have their origin in the Neolithic
Period, and the earliest salt use is argued to have taken place in China,
Collectively, this evidence
suggests that the high salt consumption (≈10 g/d) in Western societies has
minimal or no evolutionary precedent in hominin species before the
Fatty Domestic Meats
Before the Neolithic period, all
animal foods consumed by hominins were derived from wild animals.
with the advent of animal husbandry, it became feasible to prevent or attenuate
the seasonal decline in body fat (and hence in SFAs) by provisioning
domesticated animals with stored plant foods.
it became possible to consistently slaughter the animal at peak body fat
advances in food-processing procedures allowed for the storage of concentrated
sources of animal SFAs (cheese, butter, tallow, and salted fatty meats) for
later consumption throughout the year.
Technologic developments of the
early and mid 19th century—such as the steam engine, mechanical reaper,
and railroads—allowed for increased grain harvests and efficient transport
of both grain and cattle, which in turn spawned the practice of feeding
grain (corn primarily) to cattle sequestered in feedlots.
In the United States before 1850,
virtually all cattle were free range or pasture fed and were typically
slaughtered at 4–5 y of age.
By about 1885, the science of
rapidly fattening cattle in feedlots had advanced to the point that it was
possible to produce a 545-kg steer ready for slaughter in 24 mo and
that exhibited "marbled meat".
Wild animals and free-range or
pasture-fed cattle rarely display this trait.
Marbled meat results from
excessive triacylglycerol accumulation in muscle interfascicular
adipocytes. Such meat has a greatly increased SFA content, a lower
proportion of n–3 fatty acids, and more n–6 fatty acids.
Modern feedlot operations
involving as many as 100,000 cattle emerged in the 1950s and have
developed to the point that a characteristically obese (30% body fat)
545-kg pound steer can be brought to slaughter in 14 mo.
Although 99% of all the beef
consumed in the United States is now produced from grain-fed, feedlot
cattle, virtually no beef was produced in this manner as recently as 200 y
Accordingly, cattle meat (muscle
tissue) with a high absolute SFA content, low n–3 fatty acid content, and
high n–6 fatty acid content represents a recent component of human diets.
RAMIFICATIONS OF FOODS
The novel foods
(dairy products, cereals, refined cereals, refined sugars, refined vegetable
oils, fatty meats, salt, and combinations of these foods) introduced as staples
during the Neolithic and Industrial Eras fundamentally altered several key
nutritional characteristics of ancestral hominin diets and ultimately had
far-reaching effects on health and well-being. As these foods gradually
displaced the minimally processed wild plant and animal foods in
hunter-gatherer diets, they adversely affected the following dietary
indicators 1) glycemic load, 2), fatty acid composition, 3) macronutrient composition, 4) micronutrient density, 5) acid-base balance, 6) sodium-potassium ratio, and 7) fiber content.
1. Glycemic load
- Assesses blood glucose
raising potential of a food based on both the quality and quantity of
- Refined grain and sugar
products nearly always maintain much higher glycemic loads than
unprocessed fruits and vegetables.
- Unrefined wild plant foods
like those available to contemporary hunter-gatherers typically exhibit
low glycemic indices.
- Sugars with a high glycemic
load that lead to Insulin Resistance are 39% of the total energy in the
typical US diet.
- Acute elevations in blood
glucose concentrations, along with increases in hormones secreted from the
gut, stimulate pancreatic insulin secretion causing an acute rise in blood
Substantial evidence has
accumulated showing that long-term consumption of high glycemic load
carbohydrates can adversely affect metabolism and health and may elicit a
number of hormonal and physiologic changes that promote insulin
- Diseases of insulin
resistance are frequently referred to as ‘diseases of civilization’ and
include: obesity, coronary heart disease, type 2 diabetes, hypertension,
- In addition, myopia, acne,
gout, polycystic ovary syndrome, epithelial cell cancers (breast, colon,
and prostate), male vertex balding, skin tags and acanthosis nigricans can
all be related to regular consumption of HGL foods.
- In addition to
high-glycemic-load carbohydrates, other elements of Neolithic and
Industrial Era foods such as milk, yogurt, and ice cream, may contribute
to the insulin resistance and underlying metabolic syndrome diseases.
Despite having relatively low
glycemic loads, they are highly insulinotropic, with insulin indexes
comparable with white bread.
Dietary fructose may
contribute to insulin resistance via its unique ability among all sugars
to cause a shift in balance from oxidation to esterification of serum
nonesterified free fatty acids.
- Although sugars and
grains with a high glycemic load now represent a dominant element of the modern
These foods were rarely or never consumed by average
citizens as recently as 200 y ago.
acids fall into 1 of 3 major categories: 1) SFA (saturated) 2)
MUFA (monounsaturated) and 3) PUFA (polyunsaturated)
essential PUFAs occur in 2 biologically important families, the n6 PUFA
and the n3 PUFA.
- Substantial evidence now indicates that
to prevent the risk of chronic disease, the absolute amount of dietary
fat is less important than is the type of fat.
Western diet frequently contains excessive saturated and trans fatty
acids and has too little n3 PUFA than n6 PUFA.
PUFA may reduce the risk of CVD via many mechanisms, including reductions
in ventricular arrhythmias, blood clotting, serum triacylglycerol
concentrations, growth of atherosclerotic plaques, and blood pressure
dietary intakes of n3 fatty acids are also therapeutic in preventing or
ameliorating many inflammatory and autoimmune diseases.
much of the early work on the link between diet and CVD focused primarily
on dietary fats and their effect on total and LDL-cholesterol
concentrations, there are many other dietary elements that can operate
synergistically to promote atherosclerosis.
- As was
previously mentioned, carbohydrates with a high glycemic load encourage
a proatherogenic blood profile by elevating triacylglycerols and
small-dense LDLs, while reducing HDL cholesterol.
is not just a “plumbing” problem involving excessive LDL cholesterol in
the blood from excessive dietary SFAs, but also from chronic
inflammation, which is essential in the formation of atherosclerotic
recent study suggested that the blood concentration of the inflammatory
marker C-reactive protein (CRP) is a stronger predictor of CVD than is LDL
- The 6
major sources of SFAs in the United States diet are fatty meats, baked
goods, cheese, milk, margarine, and butter. Five of these 6 foods would
not have been components of hominin diets before the advent of animal
husbandry or the Industrial Revolution.
of the inherently lean nature of wild animal tissues throughout most of
the year and the dominance of MUFAs and PUFAs, high dietary levels of SFAs
on a year round basis could not have exerted adverse selective pressure
on the hominin genome before the development of agriculture.
trend toward a higher ratio of n6 to n3 PUFA was exacerbated as meat from
grain fed cattle and livestock became the norm in the US diet over the
past 100 y.
- In the
current US diet, the ratio of n6 to n3 PUFA has risen to 10:1, whereas the
ratio in hunter-gatherer diets predominant in wild animal foods has been
estimated to be between 2:1 and 3:1.
- The invention of the
hydrogenation process in 1897 (44) allowed vegetable oils to become
solidified and marketed as shortening or margarine and as foods containing
hydrogenated vegetable oils.
- The hydrogenation
process introduced a novel trans fatty acid (trans elaidic
acid) into the human diet, which elevates blood cholesterol concentrations
and leads to an increased risk of CVD.
Trans Fatty acids
in the US diet are now estimated toconstitute 7.4% of the total fatty acid
the present US diet, the percentage of total food energy derived from the
3 major macronutrients is as follows: carbohydrate (51.8%), fat (32.8%),
and protein (15.4%).
advice for reducing the risk of cardiovascular disease and other chronic
diseases is to limit fat intake to 30% of total energy, to maintain
protein at 15% of total energy, and to increase complex carbohydrates to
55–60% of total energy.
the current US macronutrient intakes and suggested healthful levels differ
considerably from average levels obtained from ethnographic and
quantitative studies of hunter gatherers in which dietary protein is
characteristically elevated (19–35% of energy) at the expense of
carbohydrate (22–40% of energy)
increasing body of evidence indicates that high-protein diets may improve
blood lipid profiles and thereby lessen the risk of CVD.
resulted in significant decreases in total, LDL, and VLDL cholesterol and
triacylglycerols and an increase in HDL cholesterol, beneficial blood
lipid changes in type 2 diabetic patients, improved metabolic control in patients with type 2 diabetes,
improved insulin sensitivity and prevention of muscle loss, whereas
hypocaloric, high-carbohydrate diets worsened insulin sensitivity and
caused reductions in fat-free mass.
populations have been shown to maintain lower plasma homocysteine
concentrations than non-meat eaters
protein has 3 times the thermic effect of either fat or carbohydrate and
because it has a greater satiety value than do fat or carbohydrate,
increased dietary protein may represent an effective weight-loss strategy
for the overweight or obese.
sugars are essentially devoid of any vitamin or minerals.
vegetable oils and refined sugars contribute 36.2% of the energy in a
typical US diet the widespread consumption of these substances, or foods
made with them, has considerable potential to influence the risk of
vitamin and mineral deficiencies.
B-6 prevents the accumulation of homocysteine in the bloodstream. Elevated
blood concentrations of homocysteine represent an independent risk factor
for the development of CVD, stroke, and deep vein thrombosis.
plant foods, known to be consumed by hunter-gatherers, generally maintain
higher micronutrient concentrations than do their domesticated
counterparts, as does the muscle meat of wild animals.
Neolithic introduction of dairy foods and cereal grains as staples would
have caused the average micronutrient content of the diet to decline. This
situation worsened as cereal-milling techniques developed in the Industrial
era allowed for the production of bread flour devoid of the more
nutrient-dense bran and germ.
displacement of more nutrient-dense foods (eg, fruit, vegetables, lean
meats, and seafood) by less-dense foods (refined sugars, grains, vegetable
oils, and dairy products) and the subsequent decline in dietary vitamin
and mineral density has far reaching health implications, consequences
that not only promote the development of vitamin- deficiency diseases, but
also numerous infectious and chronic diseases.
digestion, absorption, and metabolism, nearly all foods release either
acid or bicarbonate (base) into the systemic circulation.
Fish, meat, poultry, eggs, shellfish,
cheese, milk, and cereal grains are net acid producing, whereas fresh
fruit, vegetables, tubers, roots, and nuts are net base producing.
- Legumes yield near-zero mean acid values, which
reflects an overlapping distribution from slightly net acid producing to
slightly net base producing.
- Salt is net acid producing because of the chloride ion.
- The typical Western diet yields a net acid load
estimated to be 50 mEq/d. As a result, healthy adults consuming the
standard US diet sustain a chronic, low-grade pathogenic metabolic
acidosis that worsens with age as kidney function declines.
- Virtually all preagricultural diets were net base
yielding because of the absence of cereals and energy-dense, nutrient poor
foods…foods that were introduced during the Neolithic and Industrial Eras
and that displaced base-yielding fruit and vegetable.
- The known health benefits of a net base-yielding diet
include preventing and treating osteoporosis, age-related muscle wasting,
calcium kidney stones, hypertension, and exercise-induced asthma, and slow
the progression of age and disease-related chronic renal insufficiency.
- The average sodium content (3271 mg/d) of the typical
US diet is substantially higher than its potassium content (2620 mg/d)
- Three dietary factors are primarily responsible for the
dietary ratio of sodium to potassium.
1. First, 90% of the sodium in Western diets
comes from manufactured salt (sodium chloride); hence, the sodium content of
naturally occurring foods in the average US diet (330 mg) is quite low.
vegetable oils and refined sugars, which are essentially devoid of potassium,
constitute 36% of the total food energy. The inclusion of these 2 foods into
the diet displaces other foods with higher potassium concentrations and thereby
reduces the total dietary potassium content.
the displacement of vegetables and fruit by whole grains and milk products may
further reduce the potassium intake because potassium concentrations in
vegetables are 4 and 12 times those in milk and whole grains, respectively,
whereas in fruit the potassium concentration is 2 and 5 times that in milk and
- Taken together, the addition of manufactured salt to
the food supply and the displacement traditional potassium-rich foods by
foods introduced during the Neolithic and Industrial periods caused a 400%
decline in the potassium intake while simultaneously initiating a 400%
increase in sodium ingestion.
- The inversion of potassium and sodium concentrations in
hominin diets had no evolutionary precedent and now plays an integral role
in eliciting and contributing to numerous diseases of civilization.
- Diets low in potassium and high in sodium may partially
or directly underlie or exacerbate a variety of maladies and chronic
illnesses, including hypertension, stroke, kidney stones, osteoporosis,
gastrointestinal tract cancers, asthma, exercise-induced asthma, insomnia,
air sickness, high-altitude sickness, and Meniere’s Syndrome (ear ringing)
- The fiber content, (15.1 g/d), of the typical US diet
is considerably lower than recommended values (25–30 g).
- Refined sugars, vegetable oils, dairy products, and
alcohol are devoid of fiber and constitute an average of 48.2% of the
energy in the typical US diet.
- Fiber-depleted refined grains represent 85% of the
grains consumed in the United States.
- Fresh fruit typically contains twice the amount of
fiber in whole grains, and non-starchy vegetables contain almost 8 times
the amount of fiber in whole grains on an energy basis.
- Once again, the displacement of fiber-rich plant foods
by novel dietary staples, introduced during the Neolithic and Industrial
periods was instrumental in changing the diets that our species had
traditionally consumed, a diet that would have almost always been high in
- Diets low in dietary fiber may underlie or exacerbate
constipation, appendicitis, hemorrhoids, deep vein thrombosis, varicose
veins, diverticulitis, hiatal hernia, and gastroesophageal reflux.
In the United States and most Western countries,
diet-related chronic diseases represent the single largest cause of morbidity
and mortality. These diseases are epidemic in contemporary Westernized
populations and typically afflict 50–65% of the adult population, yet they are
rare or nonexistent in hunter-gatherers and other less Westernized people.
Although both scientists and lay people alike may frequently identify a single
dietary element as the cause of chronic disease (eg, saturated fat causes heart
disease and salt causes high blood pressure), evidence gleaned over the past 3
decades now indicates that virtually all so-called diseases of civilization
have multifactorial dietary elements that underlie their etiology, along with
other environmental agents and genetic susceptibility. Coronary heart disease,
for instance, does not arise simply from excessive saturated fat in the diet
but rather from a complex interaction of multiple nutritional factors directly
linked to the excessive consumption of novel Neolithic and Industrial era foods
(dairy products, cereals, refined cereals, refined sugars, refined vegetable
oils, fatty meats, salt, and combinations of these foods. These foods, in turn,
adversely influence proximate nutritional factors, which universally underlie
or exacerbate virtually all chronic diseases of civilization: 1)
glycemic load, 2) fatty acid composition, 3) macronutrient
density, 5) acid-base balance, 6) sodium-potassium ratio, and 7)
However, the ultimate factor underlying diseases
of civilization is the collision of our ancient genome with the new conditions
of life in affluent nations, including the nutritional qualities of recently