30 THE CHINA STUDYThis process of disassembling and reassembling the amino acids of
proteins is like someone giving us a multicolored string of beads to re-
place an old string of beads that we lost. However, the colored beads on
the string given to us are not in the same order as the string we lost. $0,
we break the string and collect its beads. Then, we reconstruct our new
string so that the colored beads are in the same order as our lost string.
But if we are short of blue beads, for example, making our new string is
going to be slowed down or stopped until we get more blue beads. This
is the same concept as in making new tissue proteins to match our old
worn out proteins.
About eight amino acids ("colored beads") that are needed for mak-
ing our tissue proteins must be provided by the food we eat. They are
called "essential" because our bodies cannot make them. If, like our
string of beads, our food protein lacks enough of even one of these
eight "essential" amino acids, then the synthesis of the new proteins
will be slowed down or stopped. This is where the idea of protein qual-
ity comes into play. Food proteins of the highest quality are, very sim-
ply, those that provide, upon digestion, the right kinds and amounts of
amino acids needed to efficiently synthesize our new tissue proteins.
This is what that word "quality" really means: it is the ability of food
proteins to provide the right kinds and amounts of amino acids to make
our new proteins.
Can you guess what food we might eat to most efficiently provide
the building blocks for our replacement proteins? The answer is human
flesh. Its protein has just the right amount of the needed amino acids.
But while our fellow men and women are not for dinner, we do get
the next "best" protein by eating other animals. The proteins of other
animals are very similar to our proteins because they mostly have the
right amounts of each of the needed amino acids. These proteins can be
used very efficiently and therefore are called "high quality." Among ani-
mal foods, the proteins of milk and eggs represent the best amino acid
matches for our proteins, and thus are considered the highest quality.
While the "lower quality" plant proteins may be lacking in one or more
of the essential amino acids, as a group they do contain all of them.
The concept of quality really means the efficiency with which food
proteins are used to promote growth. This would be well and good if the
greatest efficiency equaled the greatest health, but it doesn't, and that's
why the terms efficiency and quality are misleading. In fact, to give you
a taste of what's to come, there is a mountain of compelling research