Human Nutrition - An Evolutionary Perspective

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Human Nutrition - An Evolutionary Perspective JoAnn Guest May 15, 2005 10:20

PDT

 

 

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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