Busting the Myth of Incomplete Plant-Based Proteins

Getting ‘complete’ proteins from plants is easier than you think

Chana Davis, PhD
Published in
9 min readAug 17, 2018


Plants have got you covered

If you think that you need to eat copious amounts of rice and beans to get “complete” plant-based proteins, think again. Covering your essential amino acids from a plant-based diet is easier than you think.

The widely held belief that plant-based proteins are “incomplete” or “missing” amino acids traces back to a 1971 book, Diet for a Small Planet by Frances Moore Lappé, who trumpeted the lower environmental toll of a plant-based diet. Lappé recommended “protein complementing” — strategically pairing plant proteins at each meal, in order to achieve a certain balance of amino acids. While there was a kernel of truth at the root of her advice, she was way off the mark in terms of what it takes to cover one’s amino acid needs.

In the tenth anniversary of her book (1981), Lappé retracted her emphasis on strategic food pairings and clarified the very limited scope of this concern.

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

She hit the nail on the head, but the damage was done. The myth of incomplete plant-based proteins is incredibly sticky, and continues to thrive despite decades later, despite clear evidence to the contrary.

Indeed, it’s clear that something is amiss based purely on two basic tenets of biology:

  1. Plants use the same 20 amino acids as humans to build their proteins (the genetic code is universal).
  2. All animals ultimately get their protein from plants (or plant-like phytoplankton)— either directly or indirectly through the food chain.

To remove any lingering doubts, this article provides hard data on the levels of all nine essential amino acids across a range…



Chana Davis, PhD

Scientist (PhD Genetics @Stanford) * Mother * Passionate about science-based healthy choices * Lifelong learner * Founder: Fueled by Science