Human Nutrition - An Evolutionary Perspective -Dr.Michael Murray, N.D.

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Human Nutrition - An Evolutionary Perspective JoAnn Guest

Apr 13, 2006 15:44 PDT

 

Human Nutrition - An Evolutionary Perspective

 

In order to answer the question - What is a healthy diet? - I think

that

it is important to first take a look at what our body is designed

for.

Basically, is the human body designed to eat plant foods, animal

foods,

or both? Respectively, are we herbivores, carnivores, or omnivores?

 

The answer is quite straightforward. While the human

gastrointestinal

tract is capable of digesting both animal and plant foods, there are

indications that it can accommodate plant foods much easier than the

harder to digest animal foods.

 

Specifically, our teeth are composed of twenty molars which are

perfect

for crushing and grinding plant foods along with eight front

incisors

which are well-suited for biting into fruits and vegetables. Only

our

front four canine teeth are designed for meat eating. Our jaws swing

both vertically to tear and laterally to crush, while carnivores'

jaws

only swings vertically.

 

Additional evidence to support the body's preference for plant foods

is

the long length of the human intestinal tract. Carnivores typically

have

a short bowel while herbivores have a bowel length proportionally

comparable to humans. Thus, the human bowel length favors plant

foods.

 

A look at our closest wild relatives

 

To answer the question what humans should eat, many researchers look

to

other primates, such as chimpanzees, monkeys, and gorillas. Non-

human

wild primates are also omnivores - or as often described herbivores

and

opportunistic carnivores.

They eat mainly fruits and vegetables but may also eat small

animals,

lizards, and eggs if given the opportunity. The gorilla and the

orangutan eat only 1 and 2%, respectively, animal foods as a

percentage

of total calories. The remainder of their diet is from plant foods.

 

Since humans are between the weight of the gorilla and orangutan, it

has

been suggested that humans are designed to eat around 1.5% of their

diet

as animal foods. Most Americans derive well over 50% of their

calories

from animal foods.

 

While most primates eat a considerable amount of fruit in their

diet, it

is critical to point out that the cultivated fruit in American

supermarkets is far different than the highly nutritious wild fruits

these animals rely on.

 

Wild fruits have a slightly higher protein content and a higher

content

of certain essential vitamins and minerals while cultivated fruits

tend

to be higher in sugars.

 

Cultivated fruits are therefore very tasty to humans, but because

they

have a higher sugar composition and also lack the fibrous pulp and

multiple seeds found in wild fruit that slow down sugar digestion

and

absorption of sugars, the cultivated fruits raise blood sugar levels

much more quickly than their wild counterpart.1

 

Wild primates not only fill up on fruit, but also other highly

nutritious plant foods. As a result, wild primates weighing 1/10 the

amount of a typical human ingest nearly 10 times the level of

vitamin C

and much higher amounts of many other vitamins and minerals.

 

There are other differences in the wild primate diet that are also

important to point out such as a higher ratio of alpha-linolenic

acid -

the essential omega-3 fatty acid - compared to linoleic acid - the

essential omega-6 fatty acid.

 

TABLE 1. Estimated mineral intakes of wild monkeys and humans

 

Mineral Total daily intake

7 kg adult monkey RDA for adult male

Calcium, mg 4571 800

Phosphorus, mg 728 800

Potassium, mg 6419 1600-2000

Sodium, mg 182 500

Magnesium, mg 1323 350

Iron, mg 38.5 10

Manganese, mg 18.2 2.0-5.0

Copper, mg 2.8 1.5-3.0

 

Hunter-gatherer diets

 

Determining what humans are best suited for may not be as simple as

looking at the diet of wild primates. Humans have some structural

and

physiological differences compared to apes. The key difference may

be a

larger, more metabolically active brain.

 

In fact, it has been theorized that a shift in dietary intake to

more

animal foods may have produced the stimulus for brain growth.

 

The shift itself was probably the result of limited food

availability

forcing early humans to hunt grazing mammals such as antelope and

gazelle.

 

Archeological data supports this association - brains of humans

started

to grow and be more developed at about the same time as there is

more

evidence of animal bones being butchered with stone tools at early

villages.

 

While improved dietary quality alone cannot fully explain why human

brains grew, it definitely appears to have played a critical role.

With

bigger brain, early humans were able to engage in more complex

social

behavior, which led to improved foraging and hunting tactics, which

in

turn led to even higher quality food intake fostering additional

brain

evolution.

 

Data from anthropologists looking at evidence from hunter-gatherer

cultures are providing much insight as to what humans are designed

to

eat.2 However, it is very important to point out that these groups

were

not entirely free to determine their diets.3 Instead their diets

were

molded as a result of what was available to them.

 

For example, the diet of the Inuit Eskimos is far different from the

Australian aborigines. It may not be appropriate to answer the

question

" What should humans eat? " simply by looking at these studies.

Nonetheless, here is something important to point out: whether a

hunter-gatherer community relied on animal or plant foods the rate

of

diseases of civilization such as heart disease and cancer is

extremely

low.

 

It should also be pointed out that the meat that our ancestors

consumed

was much different than the meat we find in the supermarkets today.

Domesticated animals have always had higher fat levels than their

wild

counterpart, but the desire for tender meat has led to the breeding

of

cattle which produce meat with a fat content of 25-30% or higher

compared to a fat content of lower than 4% for free-living animals

or

wild game.

 

In addition, the type of fat is considerably different. Domestic

beef

contains primarily saturated fats and virtually undetectable amounts

of

omega-3 fatty acids.

 

In contrast, the fat of wild animals contains over 5 times more

polyunsaturated fat per gram and has good amounts of beneficial

omega-3

fatty acids as well.

 

What does all this mean?

 

Basically it means that humans appear to be better suited to a diet

composed primarily of plant foods. That does not mean that everyone

should become a vegetarian, but rather we should stress plant-based

foods such as vegetables, fruits, grains, legumes, nuts, and seeds

over

animal foods in the diet.

 

This contention is supported by the tremendous amount of evidence

showing that deviating from a predominantly plant-based diet is a

major

factor in the development of heart disease, cancer, strokes,

arthritis,

and many other chronic degenerative disease. It is now the

recommendation of many health and medical organizations that the

human

diet should focus primarily on etc.

 

The Government and Nutrition Education

 

Throughout the years various governmental organizations have

published

dietary guidelines, but it has been the recommendations of the

United

States Department of Agriculture (USDA) which have become the most

widely known. In 1956, the USDA published " Food for Fitness - A

Daily

Food Guide. " This became popularly known as the Basic Four Food

Groups.

The Basic Four was composed of:

 

The Milk Group - milk, cheese, ice cream, and other milk-based

foods.

The Meat Group - meat, fish, poultry, eggs, with dried legumes and

nuts

as alternatives.

The Fruit and Vegetable Group.

The Breads and Cereals Group.

One of the major problems with the Basic Four Food Groups model is

that

it graphically suggests that the food groups are equal in health

value.

The result - over consumption of animal products, dietary fat,

refined

carbohydrates, and insufficient consumption of fiber-rich foods like

fruits, vegetables, and legumes. This in turn has resulted in diet

being

responsible for many premature deaths, chronic diseases, and

increased

health care costs.

 

As the Basic Four Food Groups became outdated, various other

governmental, as well as medical, organizations developed guidelines

of

their own designed to either reduce a specific chronic degenerative

disease like cancer and heart disease or reduce the risk for all

chronic

diseases.

 

In an attempt to create a new model in nutrition education, the

United

States Department of Agriculture first published the " Eating Right

Pyramid " in 1992. Since that time it has received harsh criticisms

from

numerous experts and other organizations. One big question consumers

may

want to ask' " Is it appropriate to have the USDA making these

recommendations? " After all, the USDA serves two somewhat

conflicting

roles: (1) it represents the food industry and (2) it is in charge

of

educating consumers about nutrition.

 

Many people believe that the pyramid was more weighted towards dairy

products, red meat, and breads due to influence of the dairy, beef,

and

grain farming and processing industries. In other words, the pyramid

was

not designed as a way to improve the health of Americans but rather

promote the USDA agenda of supporting multinational agra-foods

giants.

 

One of the main criticisms of the Eating Right Pyramid is that is

does

not stress strongly enough the importance of quality food choices.

For

example, the bottom of the pyramid represents the foods that the

USDA

thinks should make up the bulk of your diet: the Bread, Cereal,

Rice,

and Pasta Group.

 

At 6-11 servings a day from this group and you are supposedly on

your

way to a healthier life.

 

What the pyramid doesn't tell you, though, is that you are setting

yourself up for insulin resistance, obesity, and adult onset

diabetes if

you consistently make poor choices in this important category. The

Eating Right Pyramid does not take into consideration the glycemic

index

of foods.

 

The glycemic index tells us how quickly blood sugar levels will rise

after eating a certain type of food. If we take a quick look at the

glycemic indices of some of the foods that the pyramid is directing

Americans to eat more of it is easy to see the problem.

 

A New Food Pyramid

 

It is quite now that the USDA Food Pyramid is wrong. In fact, some

believe that it has been proven a dangerous and misleading dietary

guide

that has contributed greatly to the growing problems of obesity and

type

2 diabetes. Different medical organizations are offering their own

version, so I would like to do the same. With the help of Michael

Lyon,

M.D., I have created " The Optimal Health Food Pyramid. "

 

 

 

If you compare this pyramid to the USDA's you will notice some clear

differences. Our version incorporates the best from two of the most

healthful diets ever studied - the traditional Mediterranean diet

and

the traditional Asian diet.

 

These diets have also been shown to be protective against heart

disease

and cancer. Our pyramid also provides additional recommendations for

foundational supplement and lifestyle components. It graphically

illustrates " What is a healthy diet? " and represents the current

evidence on what humans are designed to eat for optimal health.

 

 

Key References:

 

Milton K. Nutritional characteristics of wild primate foods: do the

diets of our closest living relatives have lessons for us? Nutrition

1999;15:488-98.

Cordain L, Miller JB, Eaton SB, et al. Plant-animal subsistence

ratios

and macronutrient energy estimations in worldwide hunter-gatherer

diets.

Am J Clin Nutr 2000;71:682-92.

Milton K. Hunter-gatherer diets-a different perspective. Am J Clin

Nutr

2000;71:665-7.

 

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JoAnn Guest

mrsjo-

www.geocities.com/mrsjoguest/Diets