If you've ever been told that plant proteins are "incomplete" — that you need to combine rice with beans, or that brown rice protein can't build muscle like whey can — you've been told a story that the woman who originated it publicly retracted in 1981.
That retraction has been quietly ignored by an industry that benefits commercially from keeping the myth alive. So let's set the record straight, with citations, because this matters for anyone making an informed choice about what protein to put in their body.
Where the "Incomplete Protein" Myth Came From
The idea that plant proteins are incomplete, and that vegetarians must carefully combine foods at every meal to get all essential amino acids, was popularised by Frances Moore Lappé in her 1971 book Diet for a Small Planet. The book sold over 2.5 million copies and is widely credited with launching the modern vegetarian movement in the West.
Lappé was not a nutritionist, physiologist, or medical doctor. She was a sociologist trying to end world hunger, and her protein-combining theory was based on rat studies from over a century earlier — research that had arbitrarily labelled animal proteins as "first class" and plant proteins as "inferior" based on rat growth rates, not human nutritional needs.
To her credit, Lappé herself reviewed the science a decade later and retracted the claim. In the 10th anniversary edition of her book in 1981, 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 want to set the record straight."
She went further:
"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."
That was published 44 years ago. The myth has somehow outlived the retraction.
What Brown Rice Protein Actually Contains
Let's deal with the specifics, because this is where the marketing language gets slippery.
Every plant protein contains all nine essential amino acids. What varies is the proportion of each. Brown rice protein is lower in lysine compared to whey protein — a typical brown rice protein isolate contains around 3.5g of lysine per 100g of protein, versus whey at around 8.9g (Kalman, 2014, published in Foods journal).
Crucially, "lower in" does not mean "missing." The word "incomplete" — repeated endlessly in fitness marketing — is misleading. The accurate phrase is that some plant proteins have a lower proportion of certain amino acids than animal proteins. That is a meaningful distinction, but a very different one.
Does the Lysine Difference Actually Matter for Building Muscle?
This is the question that matters in practice, and it has been directly tested.
Joy et al. (2013), published in Nutrition Journal — a peer-reviewed study at the University of Tampa — gave young male athletes either 48g of rice protein or 48g of whey protein after resistance training, three times per week for eight weeks. The result:
"Body composition and performance improvements were similar between rice and whey protein supplementation."
The athletes on rice protein had comparable gains in lean body mass, strength, muscle thickness and power output to those on whey. The researchers concluded that, at adequate doses, rice protein performs equivalently to whey for body composition and strength outcomes (Joy et al., 2013, doi: 10.1186/1475-2891-12-86).
The "incomplete protein can't build muscle" claim, in other words, doesn't survive direct experimental testing.
What Do We Actually Need? The Lysine Numbers
The official daily requirement for lysine is set by the WHO/FAO/UNU Expert Consultation (2007), Technical Report Series 935, which is the global standard reference document for protein and amino acid requirements. The figure for adults is 30mg per kilogram of bodyweight per day.
For a 70kg adult, that's 2.1g of lysine per day.
A few things worth knowing about that number:
First, it's debated. A critique published in the British Journal of Nutrition by Professor D. Joe Millward of the University of Surrey (2012) reviewed the WHO methodology in detail. Millward concluded that the original nitrogen balance studies likely underestimated true requirements because they didn't account for miscellaneous nitrogen losses, and that revised values are appropriate. Other researchers have argued the opposite — that the breakpoint identified in the underlying studies sits between 20 and 30mg per kg, lower than the WHO figure.
Second, individual variation is significant. The WHO/FAO acknowledges this directly. Requirements vary with age, body composition, physical activity, illness, and pregnancy. The 30mg/kg figure is a population estimate with wide confidence intervals — it is not a precise individual target.
Third, and most practically: almost anyone eating a varied diet — vegan or omnivore — exceeds the lysine requirement comfortably, without thinking about it. Oats contain lysine. Beans contain lysine. Lentils, peas, quinoa, hemp, dairy, eggs, and any combination of these in a normal week will deliver several times the daily requirement.
What This Means in Practice
Three things follow from the actual evidence:
1. You do not need to combine proteins at every meal. Your body maintains a pool of amino acids across the day from everything you eat. The Academy of Nutrition and Dietetics, the British Dietetic Association and the NHS all confirm that varied plant-based diets meet protein needs comfortably without protein combining at each sitting.
2. Brown rice protein is not "incomplete." It contains all nine essential amino acids. It is somewhat lower in lysine than whey, but at the doses people actually use it, this is not a meaningful limitation — as the Joy et al. (2013) study demonstrated experimentally.
3. Blended plant proteins are stronger still. When brown rice protein is blended with other plant sources — oats, peas, hemp — the amino acid profile becomes effectively indistinguishable from whey for muscle protein synthesis. This is what we do in our protein porridges: brown rice protein blended with whole-grain oats, which raises the lysine contribution naturally.
Why the Myth Persists
It's worth asking why a claim retracted in 1981 by the person who created it still circulates in 2026.
The honest answer is that the whey protein industry has built a multi-billion-pound business on the premise of "complete" versus "incomplete" protein. Marketing departments are not in a hurry to retire a framing that sells product. Personal trainers and influencers pass the message on, often without checking the source. And the language sticks — "complete protein" sounds authoritative and definitive, even when the science behind it doesn't support the way it's used.
We are not saying whey is bad. For people who tolerate dairy and don't have digestive issues with it, whey is a perfectly good protein source. What we are saying is that brown rice protein is not the inferior cousin it's been painted as — and the people who have been told plant protein "doesn't work" deserve to know that the foundational claim behind that idea was withdrawn by its own author over four decades ago.
The Bottom Line
If someone tells you brown rice protein is incomplete or won't build muscle, you can now point them to:
- The 1981 retraction by Frances Moore Lappé
- The Joy et al. (2013) trial in Nutrition Journal
- The WHO/FAO/UNU (2007) Technical Report Series 935
- The Kalman (2014) amino acid analysis in Foods
- The position statements of the Academy of Nutrition and Dietetics and the British Dietetic Association
That's not opinion. That's the peer-reviewed evidence base, openly available to anyone who wants to check it.
At That Protein, we use organic brown rice protein because it works, because it's gentle on sensitive guts, and because the science behind it is far stronger than the marketing against it.
Key Sources
- Lappé, F. M. (1981). Diet for a Small Planet (10th Anniversary Edition). Ballantine Books.
- Joy, J. M., Lowery, R. P., Wilson, J. M., et al. (2013). The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance. Nutrition Journal, 12, 86. doi: 10.1186/1475-2891-12-86
- World Health Organization / Food and Agriculture Organization / United Nations University (2007). Protein and Amino Acid Requirements in Human Nutrition. WHO Technical Report Series 935.
- Kalman, D. S. (2014). Amino Acid Composition of an Organic Brown Rice Protein Concentrate and Isolate Compared to Soy and Whey Concentrates and Isolates. Foods, 3(3), 394-402.
- Millward, D. J. (2012). Identifying recommended dietary allowances for protein and amino acids: a critique of the 2007 WHO/FAO/UNU report. British Journal of Nutrition.
- Academy of Nutrition and Dietetics (2016). Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. Journal of the Academy of Nutrition and Dietetics, 116(12), 1970-1980.
This article is for general information only. Please consult a qualified healthcare professional for personal nutrition advice.