The Myth of Complementary Protein

(everyday I get a bit more convinced it’s totally okay to go all out vegetarian)
 
By Jeff Novick, M.S., R.D.   |   Posted on June 3, 2013
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 abound not only 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

The “incomplete protein” myth was inadvertently promoted and popularized in the 1971 book, Diet for a Small Planet,
by Frances Moore Lappé. 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.”

Lappé 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 converting vegetable protein into animal protein involved a lot of
waste, and she calculated that if people ate just the plant protein,
many more could be fed. In the tenth anniversary edition of her book
(1981), she retracted her statement and basically said that in trying to
end one myth—the inevitability of world hunger—she had created a second
one, the myth of the need for “protein complementing.”

In this and 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

Where did the concept of essential amino acids come from and how was
the minimum requirement for essential amino acids derived? In 1952,
William Rose and his colleagues completed research to determine the
human requirements for each of the eight essential amino acids. They set
the minimum amino acid requirement equal to the greatest amount required by any single person in their study. Then to arrive at the recommended
amino acid requirement, they simply doubled the minimum requirements.
This recommended amount was considered a definite safe intake.

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 whole natural plant
food, or any combination of them, if eaten as one’s sole source of
calories for a day, would provide all of the essential amino acids and
not just the minimum requirements but far more 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

Unfortunately, the “incomplete protein” myth seems unwilling to die.
In an October 2001 article on the hazards of high-protein diets in the
medical journal Circulation, 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 author John McDougall wrote to the editor pointing
out the mistake. But in a stunning example of avoiding science for
convenience, instead of acknowledging their error, Barbara Howard,
Ph.D., head of the Nutrition Committee, replied on June 25, 2002 to Dr.
McDougall’s letter, stating (without a single scientific reference) that
the committee was correct and that “most [plant foods] are deficient in
one or more essential amino acids.” Clearly, the committee did not want
to be confused by the facts.

Maybe you are not surprised by this misconception in the medical community, but what about the vegetarian community?

Behind the Times

Believe 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

To wrongly suggest that people need to eat animal protein for proper
nutrition encourages consumption of foods known to contribute to the
incidence of heart disease, diabetes, obesity, many forms of cancer, and
other common health problems.

This article was originally published on Jeff Novick’s website.