By Jeff Novick, M.S., R.D.
following was written in 2003 and appeared in Health Science (the membership
magazine of the National Health Association) and in Healthy Times (the newsletter
of Dr Fuhrman).
Recently, I was teaching a nutrition class and describing the adequacy of
plant-based diets to meet human nutritional needs. A woman raised her hand
and stated, “I’ve read that because plant foods don’t
contain all the essential amino acids that humans need, to be healthy we
must either eat animal protein or combine certain plant foods with others
in order to ensure that we get complete proteins.”
I was a little surprised to hear this, since this is one of the oldest myths
related to vegetarianism and was disproved long ago. When I pointed this
out, the woman identified herself as a medical resident and stated that
her current textbook in human physiology states this and that in her classes,
her professors have emphasized this point.
I was shocked. If myths like this not only abound in the general population,
but also in the medical community, how can anyone ever learn how to eat
healthfully? It is important to correct this misinformation because many
people are afraid to follow healthful, plant-based, and/or total vegetarian
(vegan) diets because they worry about “incomplete proteins”
from plant sources.
How did this “incomplete protein” myth become so widespread?
No Small Misconception
“incomplete protein” myth was inadvertently promoted and popularized
in the 1971 book, Diet for a Small Planet, by Frances Moore Lappe. In it,
the author stated that plant foods are deficient in some of the essential
amino acids so in order to be a healthy vegetarian, you needed to eat a
combination of certain plant foods at the same time in order to get all
of the essential amino acids in the right amounts. It was called the theory
of “protein complementing.”
Frances Moore Lappe certainly meant no harm, and her mistake was somewhat
understandable. She was not a nutritionist, physiologist, or medical doctor.
She was a sociologist trying to end world hunger. She realized that there
was a lot of waste in converting vegetable protein into animal protein,
and she calculated that if people just ate the plant protein, many more
people could be fed. In a later edition of her book (1991), she retracted
her statement and basically said that in trying to end one myth—the
unsolvable inevitability of world hunger, she created a second one—the
myth of the need for “protein complementing.”
In these later editions, she corrects her earlier mistake and clearly states
that all plant foods typically consumed as sources of protein contain all
the essential amino acids, and that humans are virtually certain of getting
enough protein from plant sources if they consume sufficient calories.
Amino Acid Requirements
did the concept of “essential amino acids” come from? In 1952,
William Rose and his colleagues completed research that determined the human
requirements for the eight essential amino acids. They set the “minimum
amino acid requirement” by making it equal to the greatest amount
required by any single person in their study. To set the “recommended
amino acid requirement,” they simply doubled the minimum requirements.
This “recommended amino acid requirement” was considered a “definitely
Today, if you calculate the amount of each essential amino acid provided
by unprocessed plant foods and compare these values with those determined
by Rose, you will find that any single one, or combination, of these whole
natural plant foods provides all of the essential amino acids. Furthermore,
these whole natural plant foods provide not just the “minimum requirements”
but provide amounts far greater than the “recommended requirements.”
Modern researchers know that it is virtually impossible to design a calorie-sufficient
diet based on unprocessed whole natural plant foods that is deficient in
any of the amino acids. (The only possible exception could be a diet based
solely on fruit.)
Pride and Prejudice
the “incomplete protein” myth seems unwilling to die. In an
October 2001 article in the medical journal Circulation on the hazards of
high-protein diets, the Nutrition Committee of the American Heart Association
wrote, “Although plant proteins form a large part of the human diet,
most are deficient in one or more essential amino acids and are therefore
regarded as incomplete proteins.”1 Oops!
Medical doctor and writer John McDougall wrote to the editor pointing out
the mistake. But in a stunning example of avoiding science for convenience,
instead of acknowledging their mistake, Barbara Howard, Ph.D., head of the
Nutrition Committee, replied on June 25, 2002 to Dr. McDougall’s letter
and stated (without a single scientific reference) that the committee was
right and “most (plant foods) are deficient in one or more essential
amino acids.” Clearly, the committee did not want to be confused by
Maybe you are not surprised by this misconception in the medical community.
But what about the vegetarian community?
Behind the Times
it or not, an article in the September 2002 issue of Vegetarian Times made
the same mistake. In a story titled “Amazing Aminos,” author
Susan Belsinger incorrectly stated, “Incomplete proteins, which contain
some but not all of the EAAs [essential amino acids], can be found in beans,
legumes, grains, nuts and green leafy vegetables.... But because these foods
do not contain all of the EAAs, vegetarians have to be smart about what
they eat, consuming a combination of foods from the different food groups.
This is called food combining.”
A Dangerous Myth
wrongly suggest people need to eat animal protein for nutrients will encourage
them to add foods that are known to contribute to the incidence of heart
disease, diabetes, obesity, and many forms of cancer, to name just a few
1. Circulation 2001;104: 1869-74.