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Healthy Living March Issue
THE GREAT MEAT AND PROTEIN MYTH
Plant Versus Animal Sources of Protein
This brings us back to the basic question: do animal sources of nutrition provide
better "quality" protein than plant sources? If you look at the diet as a whole,
the answer is no. This is exactly what Hardinge and Stare found in their classic
research in the 1960s.11 They looked at the complete diets of three groups:
meat-eating Americans, pure vegetarians (those who excluded all animal products
from their diet), and lacto-ovo vegetarians (those who excluded all animal products
except for dairy products and eggs). The researchers measured the actual amount of
each amino acid consumed by each of these groups from their whole diets. They then
compared that intake with the ideal balance of amino acids needed by man according
to two standards: (1) the standard determined by Dr. Rose in the 1940s and 50s and
still used by the World Health Organization to this day, and (2) human breast milk.
The only food specifically designed to meet all the amino acid needs of a human is
human breast milk. Amazingly, the best quality protein among the three complete
diets was the pure vegetarian diet. The mix of amino acids in the total vegetarian
diet most closely resembled the mix in Rose’s recommendations and in human breast
milk, as illustrated in Figure 1: Total Vegetarian Diet Provides the Best Protein
Quality.
The message from this classic research is simple. If you look at a single food,
animal products have the upper hand in providing protein quality. However, when you
look at the entire diet, then the pure vegetarian diet emerges as superior in protein
quality. The non-vegetarian diet departs from both standards almost twice as far as
the pure vegetarian diet.
Comparisons of Protein in Milk of Different Species
The protein content of milk is an indication of the protein requirement of a new-born,
whether that new-born is human or animal. Let us examine the differences in amount of
protein in milk in the different mammalian species. They are tabulated in Figure 2:
Protein Comparisons in Milk of Different Species.12
This comparison demonstrates that humans actually need less protein than the animals o
n the list. Notice that the relative growth rate is greater in those that have greater
amounts of protein in the milk, as would be expected, because of the greater protein
requirement to build body tissue. If a human consumed a rat’s milk from birth, would
that baby be able to double its birth weight in days instead of months? The answer is
obviously no, since the rate of growth is largely genetically determined. The excess
protein would not be utilized and, as we will later see, could actually harm the
developing child.
Is the "Complementary" Theory Valid?
At this point some may counter: "what Hardinge and Stare did was unfair-you must eat
a perfect balance of amino acids at a given meal to utilize them properly."
This argument is based on an old theory that argued you must "complement" plant
proteins at a given meal to get the proper protein balance. This would require an
impractical task of weighing each serving that makes up a meal, calculating the amino
acid content of each, and then adding them up. Elaborate charts were drawn up that
listed what foods vegetarians needed to combine at a given meal to get the same
"quality" protein that a meat-eater was getting. This dogma went by the
wayside long ago. Historically, the American Dietetic Association (the professional
association for dietitians in the United States) has not been known for advocating a
vegetarian diet. However, in 1988, they came out solidly in support of vegetarian diets.
They stated: "It is the position of the American Dietetic Association that vegetarian
diets are healthful and nutritionally adequate when appropriately planned."13 They
addressed the issue of complementing proteins in their paper. "…it is not
necessary that complementation of amino acid profiles be precise and at exactly the same
meal, as the recently popular ‘combined proteins theory’ suggested."
The reality is that a vegetarian diet that contains fruits, grains, nuts, and
vegetables is fully adequate in protein.
Whether you are a total vegetarian or meat eater, you should "appropriately plan"
your diet beyond the narrow scope of amino acids. Other nutrients need to be included
in the planning. No one without some thought into his regular eating practices can
simply expect to be getting a nutritionally balanced diet-regardless of whether or not
meat is included in the fare. There is no evidence that vegetarians must be more
knowledgeable than meat eaters in order to be on a healthful diet. In fact, the evidence
leans solidly in the opposite direction. If you know nothing about nutrition, you will
likely be healthier by leaving meat out of your diet rather than including it.
The information in this chapter establishes that you can get all the essential amino
acids even with what may look like a very "unbalanced" vegetarian diet, as we will
see.
Can Plant Proteins Furnish All of the Essential Amino Acids?
Let us take some examples of the ultimate in "unbalanced" vegetarian
diets-namely, single plant foods-and see how they measure up to the amino
acid requirements. We have already made reference to Dr. Rose’s work in
determining amino acid requirements in humans. A number of other researchers have
each offered their own version of amino acid requirements not only for adult men,
but also for adult women, and for infants and children.14 Munro and Crim have
published a comparison of Rose’s requirements with those of two other experts.15
For the sake of assessing how plant products fare in their protein content, I have
chosen to compare them to the highest (most strict) adult daily requirement for each
of the essential amino acids as compiled by Munro and Crim.16 Since we are looking
at the wildly hypothetical example of a person eating only a single food all day long,
the comparisons must be based on a sufficient total daily caloric intake. I have
chosen to use a level of 2,500 calories, which is the basis of the Percent Daily
Values (as seen on the food label) for many American men and active women. I chose
eleven foods commonly eaten by non-vegetarians and vegetarians alike. The quantity
of each of the eight essential amino acids for these eleven foods is tabulated
in Figure 3: Eight Essential Amino Acid Contents of Common Plant Foods.
The essential amino acid color codes are shown on the extreme right of the figure. The
recommended daily amounts of these amino acids are represented by the cluster of short
bars on the lower right. The content of the amino acids in each of 11 plant foods is
represented by the taller bars in the main body of the figure. Note that these bars
are much taller for all 11 foods than the bars representing the recommended amounts,
signifying that plant foods supply much more protein than is needed. This is true
for every amino acid of every food. In fact, if you chose virtually any vegetable or
whole grain you would find that they have more than adequate quantities of all eight
essential amino acids. The recommended daily quantities are the strictest requirements
of Munro and Crim, (higher recommended quantities than others recommend) which are
similar to those of the World Health Organization.
Thus, there is no shortage of protein here. Any one of them alone furnishes more than
sufficient amounts of each of the eight essential amino acids. It follows that a diet
consisting of a variety of plant foods will have a greater content of all essential
amino acids than is needed.
Notice that there is no fruit on this list. Fruit contains a lower amount of protein,
and some varieties may not contain an adequate amount of each individual essential
amino acid when eaten alone. There may be other plant foods that are similar to fruit.
However, when you think about it, much of the world’s population for centuries has
survived primarily on plant proteins. They have been able to do this simply because
vegetable protein provides all the amino acids needed for good health.
Once when I was lecturing on the subject of protein, a woman raised her hand and said,
"For the first time I understand why our family survived the Great Depression."
I asked what she meant. She replied, "Our family was very poor at the time of the
Great Depression. My parents had many children and the only thing we had available
to eat during those years were potatoes. That was all. I never could understand how
all of us not only survived on such a diet, but also grew up healthy. Now I
understand how we did so well." She went on to say, "However, after the
Depression, I was so tired of potatoes that I did not have another one for
15 years." It may have been a monotonous diet, but it was nutritionally sound in
all the essential amino acids.
I do not recommend that you eat only one vegetable throughout the day and nothing else.
Such a diet would lack a balance of vitamins, minerals, and phytochemicals, even though
the protein intake would be adequate. Such a balance does come easily, however, by
eating a variety of vegetables, grains, nuts, and fruits.
We see that we do not need a college degree in nutrition to get "quality
protein" on a vegetarian diet. Remember, Drs. Hardinge and Stare found that
even pure vegetarians living in the 1960s without all the benefits of knowledge that
we have today were doing just fine regarding their intake of essential amino acids.
The data on amino acid content of foods helps us to appreciate why this was the case.
Perhaps one of the best summary statements on this whole topic is provided by a
respected nutrition scientist, Dr. Mark Messina. Dr. Messina holds a Ph.D. in Nutrition
Science from Michigan State University and has worked in the National Cancer
Institute’s Diet and Cancer Branch. After speaking in detail about the balance of
amino acids in plant products, he made the following summary statement: "…when
people eat several servings of grains, beans, and vegetables throughout the day, and
get enough calories, it is virtually impossible to be deficient in protein."17
Can We Get Too Much Protein?
Most Americans are well aware that it is possible to get too much fat in their diet.
They also know that eating too much sugar can be harmful. However, many do not
realize that there is much evidence that shows the serious consequences from eating too
much protein.
Why Does Meat in the Diet Cause Bone Loss?
What is it about meat eating and diets high in protein that causes bone loss and an
increase in osteoporosis risk? One explanation is that meat tends to be rich in
amino acids that contain sulfur, such as methionine. When consumed in excess, these
amino acids lead to a buildup of sulfur ions. Some believe that this increase in
sulfate alone may cause the kidneys to excrete more calcium in the urine.32 Others
provide a more complicated explanation for the relationship. They argue that the
excess sulfur makes the blood more acidic. The body then uses bone constituents to
neutralize this acid load, thus causing a loss of bone tissue. Increased calcium in
the urine then provides a telltale sign of this bone loss.33
Another explanation is still more complicated. It hinges on a well-known physiologic
fact: essential amino acids are needed in fairly precise amounts. When intake of
these essential amino acids exceeds the body’s needs, liver enzymes are turned on
to break down these amino acids. Some of the classic experiments in this regard were
done by Elwyn.34 He fed dogs excessive amounts of meat and traced the path traveled
by the amino acids. The protein was broken down in the stomach and intestines and then
the amino acids were taken up into the blood vessels surrounding the intestine. From
there, they were carried to the liver. At this point, because of the excessive amounts,
a large portion of the amino acids was immediately broken down when they passed through
the liver. Over half of them were converted to a breakdown product called urea, while
only 23 percent of the amino acids passed from the liver into the general circulation
where they could be used by other body tissues.
What happens to this excessive urea? It acts as a diuretic.35 A diuretic causes
elimination of water, but in the process it eliminates not only water, but also useful
minerals. A similar effect occurs when a person takes diuretic medications. That
individual often must take potassium because certain diuretics can eliminate potassium
along with water. Excess urea causes calcium loss with the water loss.
All of these mechanisms may be partial explanations. Whatever the case, it is well
established that a meat and high protein fare increases the risk of osteoporosis.
This line of evidence may prove very disconcerting to many readers. What are we to do
with the revered mineral, calcium? One of the most comprehensive studies on osteoporosis
helps to put the role of calcium in perspective. This study was not restricted to the
lone effect of calcium intake, but looked at many additional lifestyle factors in
relation to hip fractures. Four major research centers worked together to analyze the
risk of hip fracture in nearly 10,000 white women over 65.36 They found that a low
calcium intake-even below 400 mg per day - did not cause hip fractures in this extensive
study. This result agrees with the study shown previously in Figure 5: Relationship
Between Calcium Intake and Hip Fracture Rate. Beyond calcium, they found many other
factors that were damaging. They are listed in Figure 6: Lifestyle Factors and Hip
Fracture Risk.
Notice that those whose mothers had had hip fractures experienced double the risk of
hip fracture. Those who did not exercise regularly were at higher risk. Caffeine
consumption equivalent to 1-1/2 cups of coffee per day was also clearly associated
with an increased risk, as was taking anti-anxiety (benzodiazepines) or anti-seizure
medications. Numerous additional studies have shown that the higher the animal
protein intake, the lower the density of the body’s bones and the greater the risk
for hip fracture.37 Interestingly, higher consumption of vegetable protein does not
appear to be related to osteoporosis or bone fractures.38 Although calcium intake
and hip fractures are unrelated in many studies, some studies have shown that an
increase in calcium intake can prevent osteoporosis, particularly when the calcium
consumption is adequate and the protein intake is relatively low before the age of
30.39 Other known risk factors that additional studies have identified for
osteoporosis include inadequate sunlight (or low Vitamin D levels), alcohol consumption,
caffeine consumption, and lack of regular physical exercise.40 Many studies have shown
that thin post-menopausal women who are not taking estrogen supplements are also at
risk.41
A diet plentiful in calcium contained in plant foods is still recommended. Calcium is
not only essential for strong bones; it is beneficial in other important body functions.
For example, it may help to prevent high blood pressure. It also appears to assist the
heart in beating with greater vitality.42
A number of foods that have goodly amounts of calcium are listed in Figure 7: Calcium in
Common Foods.43
Soy beans and greens are a good natural source of calcium. Some green leafy
vegetables-like collards and lamb’s-quarters-have even more
calcium per serving than soybeans. Greens also have properties that help prevent
cancer. Indeed, we can obtain adequate calcium from plant sources. Furthermore,
these foods are lower in protein and therefore should not extract calcium from our
bones. If we avoid an excess level of protein intake and eat a good variety of plant
foods, our body calcium stores will likely be more than adequate.
Tables like that above fail to reveal one other important fact about calcium balance.
Namely, it is not only the quantity of calcium in a given food that is important, but
how well that calcium is absorbed. And calcium absorption is dependent to some degree
on the composition of the whole diet, not merely on the nutritional characteristics of
a given calcium-rich food.
Absorption of Calcium from Plant Foods vs. Milk
Although milk has a high calcium content, 60 to 80 percent of it is not absorbed
through the human intestine.44 Dr. C.M. Weaver and associates at Purdue University
have observed that, in general, humans absorb as much or more of the calcium in plant
products than they do from milk.45, 46 (The main exceptions are plant foods that
contain high concentrations of compounds that block calcium absorption. Examples
include spinach with its oxalic acid and wheat bran cereal with its liberal amounts
of phytic acid). Since it is now recognized that calcium can be assimilated as well
or better from vegetarian sources than from milk, we must simply become aware of the
rich sources of calcium in the vegetarian diet and choose to regularly consume these
items.
One possible reason for the very favorable absorption of calcium from plant products
like green leafy vegetables is their low phosphorus content. Dark green leaf
vegetables can have three to five times as much calcium as phosphorus. By way of
comparison, the typical U.S. diet is reversed: it has more than twice as much phosphorus
as calcium. And diets with a phosphorus-to-calcium ratio over two have been
linked to increased bone loss in animals.47 High levels of dietary phosphorus lead
to increased losses of calcium in the stool. It is recommended that at least as much
calcium as phosphorus is consumed in the diet if you want to optimize calcium
absorption.48 The balance of calcium and phosphorus in a variety of foods is shown
in Figure 8: Calcium/Phosphorus Ratio in Selected Foods.49
There is a problem with looking at ratios: they can be misleading. For example, some
may conclude that catfish is equal to potatoes because their ratios are equal.
Not so-the ratio and the total phosphorus are important. To keep your phosphorus load
down, you would favor the potato, which has only two-thirds as much as catfish; and
neither of them contribute much in the way of calcium.
Thus, in addition to looking at calcium-to-phosphorus ratios, we need to
consider the phosphorus content itself in common food groups. The average American
diet has been evaluated regarding the percentage of phosphorus in each of eight
major food groups that provide our total phosphorus intake. Two food groups
stand out with a high phosphorus content and they account for the major percentage
of our total intake. The percentage in each of the eight groups is shown in
Figure 9: Where do we get our Phosphorus?.
Note that two groups, meat and dairy products, account for 60 percent of our phosphorus
intake. To lower the intake, the best strategy would be to limit or stop our
consumption of foods in these two food groups.50
Other Advantages of Plant Protein
Other advantages of eating plant protein are just now surfacing in nutritional
research studies. A recent study of women suffering from severe hot flashes was
conducted. These uncomfortable episodes of intense heat sensation frequently accompany
the dropping estrogen levels in menopausal women. It was demonstrated that eating 20
grams of soy protein a day (equivalent to a half-cup or 4.5 ounces of tofu)
significantly reduced the severity of their hot flashes.80 The study’s lead researcher,
Dr. Gregory Burke from Wake Forest University and the Bowman Gray School of Medicine
in North Carolina, believes the improvement is due to plant estrogens in the soy
protein which "may have the same beneficial effects of estrogen, but may not have
some of the downside." These plant estrogens do not seem to increase the risk of
uterine cancer like their human and pill form counterparts. All of the women eating
the soy protein also experienced a beneficial "side effect" of a significant drop in
the total and LDL cholesterol (10 and 11 percent respectively) with no drop in their
good HDL cholesterol during the six week study.
Protein in Growth and Development
The average age of menarche, the age that girls begin to have menstrual periods, seems
to be connected with the amount or type of protein that is consumed in childhood. For
instance, several years ago when the Japanese were consuming a very low meat and animal
product diet, the average age of menarche was 17.81 This compares with the average age
of menarche in the U.S. of less than 12.8 years of age.82, 83 Many experts believe that
an early age of menarche is a significant risk factor for the later development of breast
and uterine cancer84 and may help explain why American women have over four times the
risk of breast cancer compared to Japanese women.85 The only study I know of that has
compared the growth of vegetarian children with meat-consuming children in the same
geographic area showed that the meat-eating children were slightly taller than the
vegetarians until age ten. However, when both groups had reached the age of 18, the
vegetarians had caught up with and then surpassed their meat eating counterparts, being
at least an inch taller as adults.86
U.S. Government Switches to Lower Protein Recommendation
Why did the American four food groups differ so much from those of the Chinese?
The USDA recommendations were not based on health so much as on American cultural
eating habits. It was not until very recently that our government undertook the
task of producing new recommendations that shifted emphasis from nutrient deficiencies
to chronic diseases. Their new recommendations reduced meat and diary consumption.
As expected, the dairy and meat industries were disturbed about this change and
pressured the government so heavily that the new food guide was withdrawn for months
while the special interest battle raged. In the end, the meat and dairy industries
succeeded in having the wording changed from "decrease consumption of meat" to
"have two or three (daily) servings [of meat]."87 Except for this unfortunate
alteration, the new food guide, which is in the form of a pyramid, is an improvement
over the older four-food groups. The chart is reproduced for you in Figure 23: USDA
Food Guide Pyramid.
The foods shown at the base of the pyramid are to be eaten with the greatest frequency.
This is based on health reasons, not cultural reasons. Grains are abundant in natural
foods. Most Western countries have adopted the practice of refining many of their grains.
However, we need to eat whole grain foods to receive the maximum benefits of fiber,
vitamins, and minerals. Fruits and vegetables are the next category. Today there are
numerous studies, many of which are presented in this book, that clearly indicate the
protective benefits of these foods. Those who eat the most fruits and vegetables have
the least amount of cancer and heart disease. Unfortunately, the average American has
failed to follow these practical recommendations. Latest surveys indicate that most
Americans eat an average of only 3.4 servings of fruits and vegetables per day, far
from the 5 to 9 the pyramid recommends.88
Meats, nuts, and eggs are now classified together in the protein group. However, we
have seen that vegetable proteins (including legumes) are by far the safest forms of
protein to consume. Dairy is also represented probably because of dairy association
pressure. But soy milk, which is a substitute for cows milk, is now commonly
available, and is cholesterol-free and low in fat; there are many flavors and varieties
to choose from. At the top of the pyramid, fats, oils, and sweets are listed. We
agree with the message of using these sparingly. In fact, the less the better.
What would be the result if Americans followed the full recommendations of the bottom
half of the food guide pyramid by eating 11 servings of grains, 5 servings of
vegetables, 4 servings of fruit, and 3 servings of nuts each day? Obviously, there
would not be much room left for the undesirable items listed at the top portion of
the pyramid. And that is precisely the point.
What would happen to the level of protein intake if we followed the pyramid
recommendations? It would drop dramatically to a safer level, because animal
products would have a smaller part in our diet. To consume a given amount of calories
each day by using a large amount of animal foods, a person would have a high intake of
protein. This is simply because the number of grams of protein in animal foods is high
in relation to the calories they contain. Conversely, consuming the same number of
calories by eating a large amount of plant foods would result in a lower protein intake,
because plant foods contain less grams of protein for a given number of calories.
A comparison of plant and animal foods in this regard is tabulated in Figure 24: Grams
of Protein Content per 100 Calories.89
We see that plant sources of food are generally much lower in protein for a given calorie
content than animal sources.
For those readers who desire to know the percent of calories from protein in the foods
listed, multiply the values by four.
Basic Four Diet Based on Information from this Chapter
If we were to construct our own recommended food groups based on the information
shared in this chapter, we could serve the cause of health well with a simple four
food group plan. This basic four plan is shown in Figure 25: Ideal Basic Four Diet
Plan.If we were to subsist wholly on these four food groups, we could prevent a whole
host of diseases, improve both our quality and quantity of life, and make a huge
difference in the health of the entire Western world.
Conclusion
It is high time we set aside the great meat and protein myth. Preoccupation with
meat and its protein, rather than improving health, has contributed to many
degenerative diseases such as heart disease, cancer, osteoporosis, kidney failure,
and kidney stones. Plant sources of nutrition are generally modest in protein and
reasonable in fat content; furthermore, they never contain any cholesterol. With our
growing understanding of protein physiology, a plant-ased diet has emerged as the
optimal way to eat for those interested in maximizing longevity and the quality of
living.
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