Human Nutrition - An Evolutionary Perspective

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1:9:2003

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.

 

www.doctormurray.com

 

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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