Protein combining is the outdated theory that vegetarians, particularly vegans, must eat certain complementary foods like bean

Bean

Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....

s and rice

Rice

Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 together in the same meal, so that plant foods with incomplete essential amino acid

Essential amino acid

An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism , and therefore must be supplied in the diet.-Essentiality vs. conditional essentiality in humans:...

 content combine to form a complete protein

Complete protein

A complete protein is a source of protein that contains an adequate proportion of all nine of the essential amino acids necessary for the dietary needs of humans or other animals...

, meeting all amino acid requirements for human growth and maintenance.

The theory was initially promoted in Frances Moore Lappé

Frances Moore Lappé

Frances Moore Lappé is the author of 18 books including the three-million copy Diet for a Small Planet. She is the co-founder of three national organizations that explore the roots of hunger, poverty and environmental crises, as well as solutions now emerging worldwide through what she calls...

's 1971 bestseller Diet for a Small Planet

Diet for a Small Planet

Diet for a Small Planet is a 1971 bestselling book by Frances Moore Lappé, the first major book to critique grain-fed meat production as wasteful and a contributor to global food scarcity...

. The American National Research Council

United States National Research Council

The National Research Council of the USA is the working arm of the United States National Academies, carrying out most of the studies done in their names.The National Academies include:* National Academy of Sciences...

 and the American Dietetic Association

American Dietetic Association

The American Dietetic Association is the United States' largest organization of food and nutrition professionals, with nearly 72,000 members. The American Dietetic Association is officially changing its name to the Academy of Nutrition and Dietetics. The announcement was made Saturday, September...

 (ADA) soon picked it up, cautioning vegetarians to be sure to combine their proteins. Later, the ADA reversed itself in its 1988 position paper on vegetarianism. Suzanne Havala, the primary author of the paper, recalls the research process:

There was no basis for [protein combining] that I could see.... I began calling around and talking to people and asking them what the justification was for saying that you had to complement proteins, and there was none. And what I got instead was some interesting insight from people who were knowledgeable and actually felt that there was probably no need to complement proteins. So we went ahead and made that change in the paper. [Note: The paper was approved by peer review and by a delegation vote before becoming official.] And it was a couple of years after that that Vernon Young and Peter Pellet published their paper that became the definitive contemporary guide to protein metabolism in humans. And it also confirmed that complementing proteins at meals was totally unnecessary.

Other nutrition experts and medical professionals who now agree that this theory is outdated include Dennis Gordon and Jeff Novick (registered dietitians), and John A. McDougall

John A. McDougall

John A. McDougall, M.D., is an American physician and author whose philosophy is that degenerative disease can be prevented and treated with a plant-based diet of whole, unprocessed, low-fat foods, especially starches such as potatoes, rice, and beans, and which excludes all animal foods and added...

, Andrew Weil

Andrew Weil

Andrew Thomas Weil is an American author and physician, who established the field of integrative medicine which attempts to integrate alternative and conventional medicine. Weil is the author of several best-selling books and operates a website and monthly newsletter promoting general health and...

, and Charles Attwood (medical doctors).

In fact, the original source of the theory, Frances Moore Lappé, changed her position on protein combining. In the 1981 edition of Diet for a Small Planet, she wrote:

"In 1971 I stressed protein complementarity because I assumed that the only way to get enough protein ... was to create a protein as usable by the body as animal protein. In combating the myth that meat is the only way to get high-quality protein, I reinforced another myth. I gave the impression that in order to get enough protein without meat, considerable care was needed in choosing foods. Actually, it is much easier than I thought.

"With three important exceptions, there is little danger of protein deficiency in a plant food diet. The exceptions are diets very heavily dependent on [1] fruit or on [2] some tubers, such as sweet potatoes or cassava

Cassava

Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...

, or on [3] junk food (refined flours, sugars, and fat). Fortunately, relatively few people in the world try to survive on diets in which these foods are virtually the sole source of calories. In all other diets, if people are getting enough calories, they are virtually certain of getting enough protein."

Fruit and vegetable sources of protein are more often lower in one or more essential amino acids than animal sources, especially lysine

Lysine

Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....

, and to a lesser extent methionine

Methionine

Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...

 and threonine

Threonine

Threonine is an α-amino acid with the chemical formula HO2CCHCHCH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar...

. Nonetheless, although cereal protein is particularly low in lysine compared to animal protein, even the lysine in cereals is adequate for adult needs. Adults can achieve adequate protein with any one of the legume, cereal, nut, seed, or fruit food groups, even though each of these groups is low (compared to animal protein) in certain essential amino acids.

External links

• When Your Friends Ask: "Where Do You Get Your Protein", McDougall Newsletter