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 in 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 directly from the plants.
Where do you get your protein? Protein contains essential amino acids, meaning our bodies can’t make them so they’re 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 of the 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 you couldn’t live on is Jell-O.
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—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. However, infant rats don’t grow as well on human breast milk either. 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, in the February ’75 issue of Vogue magazine, as I discuss in my video The Protein Combining Myth. The concept was that we needed to eat so-called complementary proteins together (for example, rice and beans) to make up for their relative shortfalls. However, this fallacy was refuted decades ago. The myths that plant proteins are incomplete, aren’t as good as animal proteins, or need to be combined with other proteins at meals have all been dismissed by the nutrition community 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, they’ve changed and now that “[p]lant proteins can provide enough of the essential and non-essential amino acids” and that we “don’t need to consciously combine…complementary proteins…”
It turns out our body is not stupid.
Our body maintains pools of free amino acids that can be used to do all of the complementing for us, not to mention our body’s massive protein recycling program. Some 90 grams of protein are dumped into the digestive tract every day from our own body to get broken back down and reassembled, so our body can mix and match amino acids to whatever proportions we need, regardless of what 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-food proteins that make up our usual diets.”
How did all of these myths surrounding protein come to be? Learn about The Great Protein Fiasco.
I cover protein quantity in my Do Vegetarians Get Enough Protein? video.
For more detail on the benefits of protein from plants, see:
Plant protein also doesn’t have the same effect on the cancer-promoting growth hormone IGF-1 that I discuss in the cancer section of my Food as Medicine presentation. Meat-heavy maternal diets may even affect the obesity rates and stress responses of their children, as I explore in my videos Animal Protein, Pregnancy, & Childhood Obesity and Maternal Diet May Affect Stress Responses in Children.
Michael Greger, M.D.
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