by Donald G. Snyder, PhD
This article is sponsored
by Proper Nutrition, Inc., a proprietary company
Many of us lack a true understanding of the fundamental concepts
involved with protein nutrition, even though this major component
of our diets is so essential in nearly all aspects of cellular
metabolism. A good background in protein matters, we believe,
is especially important if we are to explore and understand
newer concepts in health and disease. Accordingly, it is fortuitous
that Dr. Donald Snyder has prepared a series of educational
articles on protein for our readers. The article that follows
on the concepts of the essential and limiting amino acids in
protein is the first in the series.
Dr. Snyder is well-equipped
to report on protein and the factors related to the utilization
of protein. After a classical education in biochemistry and
nutrition at Georgetown University, he became Director of a
large multi-disciplinary food-related research laboratory for
the US Department of the Interior. In addition, he was Interior's
representative on the US Government's Interdepartmental Committee
on Nutrition and a member of the Expert Protein Advisory Committee
for the UN. He also served as a foods and protein supplements
consultant to the Office of Agriculture Bureau of Technical
Assistance in the Agency for International Development.
As a member of a special committee
of the National Academy of Sciences, Washington, DC, he provided
counsel on international efforts to translate underutilized
ocean fish into a protein powder (Fish Protein Concentrate)
suitable for use as a dietary supplement in deficient diets
worldwide. At the time, a large US effort on fish protein concentrate
was underway at the research laboratory under Snyder's direction.
FDA approval of the use of whole fish as a raw material for
fish protein concentrate (FPC), a six-year effort involving
considerable research dollars and many government agencies,
was one of the accomplishments of the laboratory. Snyder then
became Director of Sciences for a large Food Trade Organization
in Washington and continued to consult for the World Bank, Food
and Agricultural Organization (FAG), United Nations Industrial
Development Organization (UNIDO), World Health Organization
(WHO), the US State Department, private organizations worldwide,
and foreign government agencies on world feeding matters with
emphasis on protein availability and utilization.
Dr. Snyder is currently associated
with Proper Nutrition Inc, a company that manufactures and sells
a dietary pre-digested protein supplement, SEACURE, from deep-ocean
white fish. SEACURE is one of the dietary supplements developed
under the aegis of the National Academy of Sciences' program
on world feeding.
We hope you'll enjoy this series
of articles on protein. Let us hear from you.
Essential and Limiting
It wasn't too long ago that the value of a food was judged solely
on the basis of the energy it provided. In time, however, scientists
observed that certain nitrogen compounds in our diets were also
vital for the normal functioning of our cells, Two pioneering
scientists, Osborne and Mendel, found out that not all of these
nitrogen compounds, subsequently called proteins, were equal
in value. For instance, observations revealed that growth and
performance of many animals improved when their diets contained
mostly animal proteins such as milk, beef, and fish; and growth
and performance declined when their diets included mostly vegetable
proteins such as corn, wheat, and soy.
Research later showed that all
proteins were formed from the union of small nitrogen-containing,
weak-acid compounds called amino acids, about 20 of them, strung
together in long chains. All protein, it seemed, contained some
of each of these amino acids.1 But if each of these amino acids
is present in all proteins, why then, as Osborne and Mendel
determined, did the value of various proteins differ?
Through the continuing imaginative
research of many dedicated scientists, the answer eventually
became clear: the nutritional value of protein depends on the
relative abundance of certain amino acids in the protein. Their
discoveries led to the concept we know today as essential amino
acids and then later to the concept of limiting amino acids.
Essential Amino Acids
Most of our knowledge about the indispensability of certain
amino acids in the diet came from the outstanding work of Rose
at the University of Illinois. He concluded that without the
presence of certain amino acids from protein in the diet, life
processes would cease. In other words, there are essential amino
acids that we must consume in our diets because they cannot
be manufactured by our bodies. About eight of these are essential
(critical) for adults and for optimal growth in infants and
children. About eight more amino acids are commonly found in
protein but are considered non-essential because the body can
synthesize or manufacture them from other dietary sources.2
I should emphasize here that an amino acid's being considered
non-essential does not mean that the animal does not need it,
but rather that the animal is able to manufacture it in the
body from other sources at a rate adequate to meet the demands
of growth and health. Interestingly enough, in critically ill
patients, in the management of certain pathological conditions,
and in serious injury, demands may vary. We'll discuss these
and similar issues in a future article in this series.
This concept of the indispensable
nature of certain amino acids eventually gave rise to a corollary
concept: that of limiting amino acids.
Limiting Amino Acids
The nutritional value of various proteins is often measured
by a unit of worth called biological value. Biological value
is a measure of the food nitrogen in protein that the body retains.
The more nitrogen from ingested protein that is actually retained
in the body, the better the quality of the protein is assumed
to be. It turns out that the biological value of beef protein
is 0.67, whereas the biological value of wheat protein is 0.42.
This is consistent with the original observations that animal
protein diets yielded better growth and performance than vegetable
protein diets. Remember, too, that scientists were curious to
know why the value of the proteins differed. Once they understood
that certain amino acids were essential, they began investigating
just how much of each was essential.
Investigation showed that if
vegetable proteins were supplemented with specific essential
amino acids, the overall biological value of that protein improved.
It also showed that small amounts of a particular amino acid
added to the overall diet of an animal on vegetable protein
resulted in small improvements, whereas larger amounts showed
greater improvement - but only up to a point. After that, no
matter how much more of that particular amino acid was added
to the diet, the biological value did not improve any further.
However, if another essential amino acid were added, biological
value might be improved still further. In other words, in every
native protein there is a particular essential amino acid that
limits that protein's value to the overall diet. Once that limitation
(minimum requirement) is met or exceeded, another amino acid
becomes limiting and so on until there is derived a theoretically
perfect balance of amino acids for optimal growth and performance.
Further supplementation will not improve the diet.
The concept of limiting essential
amino acids has been heavily applied in agriculture. Ideal diets
have been investigated for many animals. Indeed it's been said
that more is known about the nutritional requirements of a chicken
than any other animal, and application of the limiting amino
acid concept to the broiler chicken industry has yielded amazing
economic benefits. Let's examine how this knowledge is applied.
This information will give us insight into the value of the
concept of limiting amino acids.
We find that the poor biological
value of vegetable proteins is usually due to their low levels
of essential amino acids tryptophan, methionine, and lysine.
These are said to be their limiting amino acids. Corn, for instance,
is limiting in lysine, and soybean is limiting in methionine.
Because corn and soy make up the major source of protein in
formulated broiler chicken diets, additions of lysine and methionine
are required to optimize the growth of the chicken on a corn/soya
diet. Diet formulators, now armed with this information, search
for the least-expensive source of providing the additional nutrients.
For many years this source has been fish meal, which is high
in both lysine and methionine. It has also led to the development
of strains of high-lysine corn and methods of producing synthetic
methionine. Today, growers can consistently provide 4.2-pound
market-ready broilers in only six weeks after hatching. And,
incidentally, a pound of chicken can be produced with under
two pounds of feed.
The importance of understanding
protein values, essential amino acids, and limiting amino acids
is not limited to agriculture, of course. These fundamentals
take on great importance in problems associated with world hunger,
principally protein malnutrition.
Utilizing the concepts of essential and limiting amino acids,
the World Health Organization (WHO) of the United Nations has
modeled an idealized level of amino acids (see below) for humans.
Unfortunately, in much of the world this diet is only a distant
Protein malnutrition called
Kwashiorkor comes from eating too little protein or protein
of poor quality. Most places in the world survive on the poorer
quality starchy diets. This could easily be corrected as with
chickens, by adding supplemental levels of good-quality, high-value
animal protein like fish. And if we concentrate the raw protein
into an easily managed powder, we can change the level of protein
from 18% in the unprocessed fish to 80% in the powdered form.
Thus only a very little of the concentrate is needed as a supplement
to significantly increase the total protein in the diet and
to support those essential amino acids found to be limiting
in the traditional globally-deficient diets. This goal is the
objective of many world-feeding programs sponsored by various
organizations such as the United Nations. It was in pursuit
of this goal that SEACURE was developed.
Proper Nutrition Inc.'s SEACURE is a concentrate of pre-digested
protein from deep-ocean white fish. The concentrate was developed
years ago by a multi-disciplinary team of top-notch scientists
out of the University of Uruguay under the direction and counsel
of the US National Academy of Sciences. The purpose was to find
a satisfactory means of translating the vast stores of underutilized
ocean fish into concentrates that would serve as a protein supplement
to the diets of starving people, especially children, in third-world
nations. Although other efforts were underway, the Uruguayan
effort was the only one with a process derived from nature that
led to the pre-digestion of fish protein which not only maintained
the value of the native protein but actually enhanced it.
The value of the protein provided
by SEACURE is outstanding. Compare SEACURE to the model or ideal
balance suggested by the World Health Organization (WHO) of
the United Nations. Values are expressed in terms of milligrams
of amino acids per gram of protein. Values for soybean meal
and corn are provided for comparison reasons.
|Methionine & Cystine
|Phenylalanine & Tyrosine
As can be seen, the amino acid
balance of SEACURE exceeds that of the WHO model for every essential
Although the SEACURE concentrate
of fish protein was never used worldwide because of escalating
fish prices and loss of political interest in world-feeding,
the product was subsequently tested by medical personnel in
Uruguay for its wide range of therapeutic values on thousands
of sick babies and adults in clinics and hospitals. Outstanding
results were observed.
After a hiatus of a few years,
recognizing the potential benefits of SEACURE, Proper Nutrition,
Inc. secured SEACURE with the purpose of bringing benefits to
those seeking to attain and maintain good health. We are pleased
to relate that through reports from doctors and patients, Proper
Nutrition confirms daily the results earlier obtained. Feel
free to write to us for further information.
In our next article, we'll talk
about protein digestibility and factors that affect protein
digestibility and how it is measured.
Dr. Donald G. Snyder
Proper Nutrition, Inc.
P.O. Box 13905
Reading, Pennsylvania 19612 USA
Gelatin is an exception.
Adults require the
amino acids called lysine, methionine, phenylalanine, threonine,
tryptophan, and valine. Infants need these six plus arginine
and histidine. Cystine and tyrosine are substitutes in part
for methionine and phenylalanine, so they are considered
Values from Feedstuffs,
Annual References Issue 1996.