The protein combining myth

All nutrients come from the sun or the soil. Vitamin D, the “sunshine vitamin,” is created when skin is exposed to sunlight. Everything else comes from the ground. Minerals originate from the earth, and vitamins from the plants and micro-organisms that grow from it.

The calcium in a cow’s milk (and her 200-pound skeleton) came from all the plants she ate, which drew it up from the soil. We can cut out the middle-moo, though, and get calcium from the plants directly.

Where do you get your protein? Protein contains essential amino acids, meaning our bodies can’t make them; and so, they are essential to get from our diet. But other animals don’t make them either. All essential amino acids originate from plants (and microbes), and all plant proteins have all essential amino acids. The only truly “incomplete” protein in the food supply is gelatin, which is missing the amino acid tryptophan. So, the only protein source that you couldn’t live on is Jell-O.

As I covered previously, those eating plant-based diets average about twice the estimated average daily protein requirement. Those who don’t know where to get protein on a plant-based diet don’t know beans! Get it? That’s protein quantity, though, but what about protein quality?

The concept that plant protein was inferior to animal protein arose from studies performed on rodents more than a century ago. Scientists found that infant rats don’t grow as well on plants. But infant rats don’t grow as well on human breast milk either; so, does that mean we shouldn’t breastfeed our babies? Ridiculous! They’re rats. Rat milk has ten times more protein than human milk, because rats grow about ten times faster than human infants.

It is true that some plant proteins are relatively low in certain essential amino acids. So, about 40 years ago, the myth of “protein combining” came into vogue—literally, the February ‘75 issue of Vogue magazine. The concept was that we needed to eat “complementary proteins” together, for example, rice and beans, to make up for their relative shortfalls. This fallacy was refuted decades ago. The myth that plant proteins are incomplete, that plant proteins aren’t as good, that one has to combine proteins at meals—these have all been dismissed by the nutrition community as myths decades ago, but many in medicine evidently didn’t get the memo. Dr. John McDougall called out the American Heart Association for a 2001 publication that questioned the completeness of plant proteins. Thankfully though, they’ve changed and acknowledged that, “Plant proteins can provide all the essential amino acids, no need to combine complementary proteins.”

It turns out our body maintains pools of free amino acids that it can use to do all the complementing for us, not to mention the massive protein recycling program our body has. Some 90 grams of protein are dumped into the digestive tract every day from our own body to get broken back down and reassembled, and so our body can mix and match amino acids to whatever proportions we need, whatever we eat, making it practically impossible to even design a diet of whole plant foods that’s sufficient in calories, but deficient in protein. Thus, plant-based consumers do not need to be at all concerned about amino acid imbalances from the plant proteins that make up our usual diets.

This article has been reprinted from the NutritionFacts.org website with permission from the NutritionFacts team. This article has been exclusively first published on NutritionFacts.org – a strictly non-commercial, science-based public service providing free updates on the latest in nutrition research.

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