Protein Quality:
Some Protein ain’t Protein!
Most people know that any given “protein” is really composed of twenty or so
different amino acids—nine of which are essential for humans to get from food
because our bodies cannot make them from other things. The other amino acids are
still required in order to form various other compounds, but they are termed “non-essential”
because the body can make them from the essential nine—IF those essential nine are
present in sufficient quantities (note the big “IF”  ). Getting each of the twenty or so individual
amino acids in the right quantities is what the body wants, needs, and
will-wake-up-The-Beast-to-make-sure-it-gets.
But each type of “protein” (e.g. in beans, corn, milk, beef, etc.) has
completely different quantities of each amino acid. This means that using the word
“protein” is a very imprecise way to describe what your body is really trying to
get—enough of each needed amino acid.
Unfortunately, when scientists measure the amount of “protein” in foods, the
method typically used is to break the food down and measure how many grams of
nitrogen it contains. Then they multiply the grams of nitrogen by 6.25 to get the
grams of “protein” in the food. That’s the number you usually see in the food
charts which food processors are required to put on the food labels under Title 21,
Code of Federal Regulations (U.S.), Section 101.9(c)(7).
This method does measure the amount of crude protein in the food. But, by itself,
it gives no clue as to which amino acids are present in what quantities.
This means that (for example) some “protein” could (in theory) be
composed of nothing but the thirteen non-essential amino acids. In other words, it
could have no essential amino acids in it at all and still (theoretically) be counted
as “protein”. In this case, it would be such low quality protein that to The
Beast it would not be real protein at all—just another source of Calories. And as
always, The Beast would use the Calories and then make you hungry again for the real
protein you didn’t get but still need. In reality, low quantities of even one
essential amino acid (EAA) will make dietary “protein” nearly useless for tissue
maintenance and repair—which means it can only be used as energy.
When protein that is not used for tissue maintenance is used as energy, it
provides about four (4) Calories per gram—the same amount as carbohydrate.
Obviously, the ideal we shoot for is to provide exactly the amount of protein that
the body needs for tissue maintenance and have nothing left over for energy. This
ideal, of course, can rarely be achieved, so most authorities will point out that too
little protein is (eventually) dangerous to health while too much merely slows weight
loss. Therefore, as in most areas of life, we need to choose an appropriate balance
in order to get the results we want.
Nutrition science has long recognized that protein that is deficient in one or
more of the essential amino acids is greatly reduced in its usefulness as an
essential nutrient. Logically enough, nutritionists have coined another couple of
terms to refer to this fact. These terms are: “high-quality proteins” and “low-quality
proteins”.J High-quality proteins have all essential amino acids present in at
least sufficient, if not perfect, quantities. Low-quality proteins do not. Most
high-quality proteins are from animal sources. Most low-quality proteins are from
plant sources.
So if someone tells you that (e.g.) beans are a good source of protein, you can
tell them that crude bean protein has some, but not enough, of the essential amino
acids methionine and cystine. This means it’s a low-quality source of what The
Beast thinks is protein. The reference 70-kg (154 lb) male would have to eat about 4
cups (728 grams, with about 1000 Calories) of navy beans each day just to get his
official RDI (56g) of protein (using methionine as the “limiting” amino acid).
For sedentary people, this would be using up too many Calories to satisfy Protein
Factor requirements before even beginning to satisfy the other Vital Factors. And—as
we will see below—the official RDI for protein is not enough protein when you are
dieting.
On The Multi-Diet we simply avoid this issue entirely by using only “high-quality”
protein foods that have enough of all the amino acids.)
Since most vegetable proteins (like beans) are deficient in one or more of the
essential amino acids, they are—by themselves—not very useful for Multi-Diet
purposes. Therefore, for the rest of this discussion, whenever I mention protein or
amounts of protein, I am talking about high-quality proteins such as those listed in
Table 15: Protein & Calories in Foods.
Protein Quantity:
What’s Minimum? What’s Enough?
In dieting, the most important thing about protein is getting enough of the right
kind of it. The second most important thing is avoiding all the fat and other
Calories that tend to come mixed in with it. Further, if your body doesn’t actually
need all the real protein you eat at the time you eat it, it just treats the excess
as Calories (energy) instead of burning fat for energy. This is not exactly what we’re
trying to accomplish when dieting.J
You need enough protein or your body will wake up The Beast to make you go eat. If
you get too much, that means you are getting extra Calories that make losing weight
harder. So exactly how much is “enough-but-not-too-much?” On your own, that can
be a little tricky to decide. Fortunately, science and the food labeling system give
us some pretty good answers (though not perfect ones, as we shall see).
The U.S. Food and Nutrition Board says that 97.5% of Americans will get enough
dietary protein if they eat 0.8-grams of protein per kilogram of body weight per
day. (That’s about 0.4-grams per pound of body weight). Most other countries’
official RDIs are close to this. But for dieters there are some problems with using
this RDI.
Problem One: Body Structure
The Food and Nutrition Board’s protein RDA definitions are probably adequate for
people who are not trying to lose weight. But various weight-loss researchers have
realized that this definition is too simple for people who are trying to lose weight.
Here, in a somewhat exaggerated example, is one of the issues they confronted:
Consider the situation of a person who weighs (e.g.) 300 pounds (136 kg). If this guy
is a competitive weight lifter, he’s got a completely different body structure than
someone who just eats a lot of food. The lifter’s body is mostly muscle. The eater’s
body is mostly fat. Are they both going to need the same amount of protein? Hardly!
Why? Because the lifter’s body weight is mostly composed of muscle cells, which are
mostly protein, and need a constant supply of dietary protein for maintenance and
repair. The eater’s body weight is mostly composed of fat cells, which are mostly
fat (duhh!J), and need very little protein for maintenance and repair. Therefore,
these two 300 pound people do not have the same protein requirement—even though
they weigh the same amount.
There is also a second (and more important) reason to expect that the normal
protein RDI is not adequate for dieters.
Problem Two: The Protein-Energy Relationship
It has been well-established by nutrition research that when Calorie (energy)
intake is inadequate (as we want it to be when we’re trying to lose weight) then
some protein is diverted from tissue-building and repair into meeting the energy
needs of the body. This means that the need for protein in the diet is increased when
the amount of energy (Calories) in the diet is decreased. In at least some cases,
this can be a very significant effect. Kishi and associates, reported experiments
with young men in 1978 showing that decreasing energy from approximately 4000
Calories/day to approximately 3000 Calories/day would nearly double the protein
requirement (from 35 g/day to 72 g/day in a 70-kg (154 lb) person). The RDA for
protein at this weight is only 56 grams. Obviously, sedentary individuals and others—particularly
the elderly—require less energy than the above 3000 Calories just to maintain
weight—much less lose any. This inverse protein-energy relationship has significant
meaning for dieters. It lends further support to the observation made during VLCD
investigations that larger amounts of protein—in the range of 1.2 to 1.5 grams per
kilogram of ideal body weight—are required to prevent loss of muscle mass during
serious weight loss. There is also further confirming evidence of these amounts
from the field of sports medicine where experiments have shown that at least 1.2
grams of protein per kilogram of IBW (Ideal Body Weight) per day is required while
dieting to maintain physical exercise efficiency as measured by VO2 max. See ideal
body weight and more on… exercise.)
For reference, 1.2–1.5 grams per kg IBW would be 84-g to 105-g of protein per
day for the person with an IBW of 70-kg (154-lb). That 6-ounce can of tuna fish I
mentioned earlier has only 35–40 grams of protein. Of course, VLCDs tend to be
truly severe Calorie restriction diets and the Multi-Diet is not a VLCD. On the
Multi-Diet, you don’t restrict Calories to below 1200 Calories/day. Therefore, it
is possible that you may not strictly need quite this much protein. But dietary
protein is one area where getting too much is unequivocally better than getting too
little—until it pushes you over your daily Calorie limit.
So What’s The Ideal Amount, and How Do You Know?
VLCD and other researchers realized the importance of the above two issues and
decided that the best way to determine an individual’s protein needs was to begin
with the concept of Ideal Body Weight (IBW) rather than simple body weight. Ideal
Body Weight basically means the amount you would weigh if you had ideal (“normal”)
proportions of muscle and fat. How is this defined?
Most researchers have agreed that the best definition of Ideal Body Weight (ideal
proportions of muscle and fat) is the body weight that correlates with the lowest
death rates. This is an intuitively satisfying definition. After all, if you live the
longest possible time, that probably means you’re healthier than you would have
been otherwise, which means your body is as satisfied with your situation as is
possible. It also means you can do more of what you want for longer, and so are
probably happier with your life (other things being equal ).
As we discussed in more on… body weight & calories, the best measure of
weight related to life span remains the 1959 Desirable Body Weight Table produced by
the Metropolitan Life Insurance Company and based on the Build and Blood Pressure
Study of 1959. There have been various attempts over the years to create alternative
measures to this table. Some of the results of these attempts have been based on
science, others have merely been “well-intentioned” in one way or another. But
the Desirable Weight Table remains a standard (if not the standard) for those who
attempt to relate weight to life span and health. (For a more comprehensive view of
the issue of alternative measures, see Simopoulos 1995) This table was also the basis
of the measure used in the classic Framingham Heart Study. For convenience, the data
is restated below. (The values in Table 13 are identical to those in Table 3 and are
restated here for your convenience.)
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