Plants and Protein
As the war between animal and plant protein rages on, remember, if you go far enough back everything you eat is just processed sunshine. Plants have the unique capacity to turn sunshine, air, and water into starches and sugar. Their roots reach down into the soil for nitrogen, and after bacteria within convert it to nitrates, the plant has everything it needs to produce protein. Plants are autotrophic, meaning they make their own food from water and light. Animals are heterotrophic, meaning they have to eat outside substances to live; simply put, plants are the producers and animals are the consumers. But given the way we look at animal protein, it can still be surprising to learn that plants and bacteria, not animals, are the chief producers of almost every amino acid deemed essential in the diets of humans.1 In fact, the nitrogen content of every protein in your body can be traced back to plants,2 with few exceptions.
And as for us heterotrophic humans, we need to consume our protein, we can't just produce it like those awesome plants. Specifically, we need nine essential amino acids in our diet; our body can, however, produce the other twelve. This is where animal protein gets the edge. Animals have similar amino acid profiles to our own right from the start, they have the nine essential amino acids in the estimated proper proportions,4 their protein is absorbed well by our GI tract,5 and you've probably heard the tagline a thousand times; animal protein is complete and plant protein is incomplete. But this begs the question, how did an animal create complete protein when animals, like us, can't produce many of their own amino acids? Simply put, the animal ate plants. Or it ate some other animal that ate plants. Plants are almost invariably the origin. Remember, if you go far enough back, everything you eat is just processed sunshine.
Plants are essentially closed systems (they’re autotrophs, remember?), so they need to be able to produce the full complement of amino acids needed to sustain themselves.3 In other words, plants have a much wider-ranging enzymatic capacity for amino acid production than animals. Yet plant protein is frequently disregarded. Why is that?
The trouble for plant protein began with the 1971 book, Diet for a Small Planet, from a forward-thinking sociologist named Frances Moore Lappé.6 She introduced the idea of avoiding meat, and choosing plants, as a way of saving the environment and feeding the world; all the way back in 1971. With this book she also popularized the idea of protein combining in order to ease the minds of uneasy meat-eaters that were unconvinced a plant-based diet could meet their protein needs. This concept included combining incomplete proteins; taking a plant that was lacking in one essential amino acid then combining it with another plant with an abundance of that amino acid to produce complete amino acid profiles. Examples include combining beans with rice, pita with hummus, or soy with millet. The early conceptualization of this emphasized that this should be done at each meal. This made vegetarian protein sourcing something of a nightmare, people were afraid that they weren’t getting the necessary protein from their plant-based diet, and it was a huge bar to entry to would be vegetarians who feared the constant, conscious effort that would go into planning each meal, favoring the simplicity of their meat-heavy diet. In 1981 Lappé recanted her complimentary protein model, stating that, “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.”7 and that with a few exceptions, like purely junk food diets and those that include only fruit or tubers, “if people are getting enough calories, they are virtually certain of getting enough protein.”7
But the damage was already done, and to this day current or prospective vegetarians and vegans often fear the nature of plant-protein and protein combining. What has changed, however, is the voice of the scientific community. The Academy of Nutrition and Dietetics published a paper in 2009 stating that complementary proteins are unnecessary at the same meal, and that an assortment of plant-foods throughout the day supplies all the protein and amino acids that healthy adults need.8 The American Heart Association states that, “5 to 6 servings of whole grains and 5 or more servings of vegetables and fruit would, in fact, supply all of the amino acids necessary for health.”9 and the USDA has even recommended a shift from meat, poultry, and eggs, to nuts, seeds, and beans as sources of protein in the 2016-2020 Dietary Guidelines for Americans.10
Some dietitians and doctors even contend that solitary plant-protein sources are in fact complete, and in line with actual human requirements, claiming that if a person ate any single, whole, plant food for 100% of their calories, their protein and amino acid needs would be met.11
Conscious protein combining is heavily outdated; a varied plant-based diet supplies the complete amino acid profile needed for health without conscious effort.
My personal staples include: black beans, raw almonds, chia and hemp seeds, peanut butter, brown rice, and, of course, all of the brilliant, colorful veggies. But by all means, feel free to include a powdered protein supplement to aid you as you transition to a plant-based diet. A supplement like this will help you ease your worries while you embrace the benefits of the plant-based world.
See you next week,
Thomas Larsen, D. Lee Taylor, Mary Beth Leigh and Diane M. O'Brien Ecology Vol. 90, No. 12 (December 2009), pp. 3526-3535
Kimball, John W. Biology. Wm. C. Brown, 1994.
Baldwin, T. & Lapointe, M. (2003). The Chemistry of Amino Acids. The Biology Project [Online], Available: http://www.biology.arizona.edu/biochemistry/
Eliot F. Beach, Bertha Munks, and Abner Robinson, THE AMINO ACID COMPOSITION OF ANIMAL TISSUE PROTEIN J. Biol. Chem. 1943 148: 431.
"protein, reference." A Dictionary of Food and Nutrition. . Encyclopedia.com. 11 Aug. 2017
Frances Moore Lappé, Diet for a Small Planet, 1971.
Frances Moore Lappé, Diet for a Small Planet, Tenth Anniversary Edition, 1981
Craig, W J, and Mangels, A R. “Position of the American Dietetic Association: Vegetarian Diets.” Journal of the American Dietetic Association, vol. 109, no. 7, 2009, pp. 1266–1282., doi:10.1016/j.jada.2009.05.027
https://doi.org/10.1161/01.CIR.0000018905.97677.1F Circulation. 2002;105:e197 Originally published June 25, 2002
U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015.
RD, Jeff Novick MS. “The Myth of Complementary Protein.” Forks Over Knives, 13 Apr. 2016, www.forksoverknives.com/the-myth-of-complementary-protein/#gs.AF9aBIU.