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Vegetarian protein combining: why sources matter, but myths are not realities

Updated on April 23, 2012

Protein is abundant in the vegetarian diet, with every plant cell in existence containing amino acids of some kind.  If you eat a balanced diet to start with and live in an abundant Western culture, it’s very difficult to be deficient in protein.  It’s amazing then, the misconceptions that continue to flourish, about protein and the vegetarian diet.

The main problem stems from a fundamental misunderstanding of the protein digestion process.  Science has evolved, but popular understanding still plays catch-up…  For decades it was thought that all eight essential amino acids (the protein constituents the body is unable to synthesise) had to be consumed in a single meal, in order for that meal to be complete and balanced and for the body’s protein needs to be met.  As a lot of animal protein sources (the myth inaccurately simplifies this application to ALL animal proteins incidentally) contain all of these essential amino acids, a meal containing meat was regarded as a ‘whole’ or proper balanced meal, not requiring anything else.  

Vegetarians, on the other hand, were advised that they should combine different protein sources in each meal, to ensure intake of all eight of the essential amino acids simultaneously.  Quite where this idea originated is unclear, but the traditional pairings of different vegetarian protein types in food cultures from many parts of the world were held as supporting evidence of this ‘natural law’ -  such as indigenous cuisines exist based on rice and beans, rice and tofu, hummus and bread.  This was taken as evidence that proteins must be combined on every plate and consumed together.  Such pairings have been described as ‘complementary proteins’, ie interpreted as having meaning beyond culinary preferment, to creating a balanced protein intake.

This all contributes to a continued and persistent perception of vegetarian foods as somehow incomplete or inferior – which is only relevant on a molecular level, given that beans are low in the essential acid lysine, despite being high in protein overall by volume, for example. It is when this gets scaled up to a general, social or meal-planning level that it becomes contradictory and irrelevant... It also reinforces the notion that a vegetarian diet is unnatural, complicated, and prone to failure without extensive planning and monitoring – instead of being the natural healthy normal diet of thousands of people around the world.

One significant factor the myth fails to take account of at all is that ‘complete proteins’ do exist in the plant kingdom, such as in the soy or soya bean - which contains all the 8essential amino acids. Soy is far from an uncontroversial health food admittedly, being highly allergenic,and packed full of estrogenic compounds that are potentially threatening to male reproductive cells and hormones – yet it remains a staple protein for generations of Asians in many countries (males and females), including many primarily vegetarian cultures/cuisines.

Quinoa on the other hand is a grain food that contains ALL twenty two of the amino acids found in the body (not just those essential to obtain from a dietary source), and is an amazingly healthy food… almost lost to the world during the European conquest of South America, when the conquistadores incinerated all the crops in an effort to obliterate the indigenous Inca culture, which regarded quinoa as sacred.  By forcing the locals to grow corn and other grains instead, this attempt at ethnic cleansing virtually eliminated one of the few “complete” vegetarian sources of complete protein on the planet!  Technically a grass rather than a grain, it cooks as easily as rice, has a delicious nutty taste, and is gluten free as well – truly the original superfood, mercifully restored to the world by a chance discovery in the early 80s.

But regarding protein combining, the real breakthrough came with improved understanding of exactly how the body uses the protein it ingests.  Not only can most amino acids be synthesised on demand to fit the widely-varying needs in each cell of the body, they can be used as an energy source directly(ie burned as fuel like glucose or fat), and also stored temporarily within the body.  This storage facility is known as the ‘labile protein reserve’, and is a short-term, easy-retrieval mechanism.  It helps the body respond to emergencies such as tissue trauma or overexertion…  And to smooth out the amino acid levels available between meals. 

The upshot for protein combining then is that there is simply NO NEED for proteins to be combined at every meal and on every plate, to ensure that adequate supplies of essential amino acids are available to the body.  Provided the very small daily amounts needed are taken in over the period of a day or so, no deficiencies will arise.

The American Dietetic Association reversed its official position on protein combining in 1988, clearly stating that there was no need to combine different sources of vegetarian protein in the same meal, and the WHO and other bodies also adopted this position decades ago.

Yet the pervasiveness of this myth is nothing short of astonishing, both in popular culture and usage, and also in culinary and health circles that really should know better!


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    • Kaye McCulloch profile image

      Kaye McCulloch 7 years ago from Australia

      Great information for vegetarians, thanks.