Let’s start with this high school biology review: There are 21 amino acids, the building blocks of protein; nine of them are “essential,” which means our bodies cannot produce them. They must come from food.

While it’s true that essential amino acids are generally found in lower percentages in plants than in animal foods, nearly all plant foods contain complete protein, and many (beans, lentils, certain whole grains, and seeds) have high concentrations. The complete suite of these compounds is widely distributed in our food choices. And, as you already know, generally speaking, not only you (your personal health) but we (our collective health) are better off eating more plants. More on that further down.

So, to the myth that you need animal products to get “complete” protein and therefore build muscle: Phooey.

On to the near-hysteria about getting enough protein, to which almost every person reading this — plus one of the writers of this piece — is at least occasionally susceptible: If you live in the United States, there’s almost no chance that, unless you’re in hospice or intensive care, you’re protein-deficient. Epidemiological research shows clearly that the average American is getting daily protein complete in amino acids and well in excess of requirements and recommendations for health. In fact, “getting enough protein” is highly effective meat and dairy industry marketing.

Not only are you virtually guaranteed of getting enough protein, but more isn’t better. (Devotees of T. Colin Campbell’s “The China Study” contend, not unreasonably, that even official recommendations are too high, and that the excess may be toxic.) The notions that protein fights obesity and diabetes, turns to muscle, and is low-glycemic, are all partly misguided. Yes, most foods delivering protein are satiating, but so are most foods delivering fiber, or for that matter wholesome foods you can eat a lot of, like fruits.

This one’s going to floor you: Excess calories from protein do not turn into muscle; they turn into fat. For protein to become muscle, it must be needed in response to physical demands on that muscle. Once the comparatively tiny carbohydrate reserve known as glycogen is full, and once the body “spills” calories as heat, it stores calories as fat and only fat. Eat too much protein, and you will gain fat. (If you’re into the keto diet — a mistake — we’ll get to that another time.)

It’s true that protein is low- or non-glycemic — that is, it doesn’t directly raise blood-sugar levels; it’s false that it does not trigger an insulin release. Both protein and carbohydrate in the blood do so after a meal, and the insulin response is greater to the combination of carbohydrate and protein than to either alone. Again: Yes, really. This is science.

Science also shows that even an exclusively vegan diet, if at all sensible and balanced, provides all of the amino acids you need, at or above the requisite levels. This message extends even into the realm of world-class athleticism (ask Kyrie Irving), including competitive bodybuilding.

Essential amino acids can be delivered separately and over time, and stored in the liver and muscle. Some can be used without others and some cannot, but — like the materials at a construction site — when they’re delivered relative to one another, with a latitude of several days, is unimportant, as long as they’re all there when they’re needed. In other words, fill the quotas for essential amino acids by eating a variety of foods over a few days, and the body’s work proceeds apace.

So, no: Complete protein from a single food is not required at every meal or even every day. You can even forget the peanut-butter-and-whole-wheat or brown-rice-and-beans mantra. Eat them separately. Eat them together. It just doesn’t matter.

The greatest muscles in the animal kingdom, on land at least, belong to herbivores. We’ve failed for millennia at alchemy, but nature can do it: Biology turns leaves into an elephant, and grass into a horse; it can turn lentils (or cheese) into you. Full-time herbivores must eat plants to grow themselves, as carnivores need meat. We are omnivores and have a choice.

Finally, and this is important: Most references to “high-quality protein” consider only the quality of protein in the food — the number, concentration, and digestibility of essential amino acids it contains. But they don’t consider the overall quality of the food itself. That’s problematic: wrong-headed, even. You can define quality protein based solely on biochemistry: that is, on the concentrations of essential amino acids. But you can also define it based on public health. Will eating this food help you get the protein you need and enhance your health?

The biochemical definition misleads people to all the wrong dietary priorities. The science on which the Dietary Guidelines for Americans is based clearly indicates benefit from more plant foods and fewer animal products, but the formal definition of protein quality points the other way. In addition, as you know, animal products are more detrimental to the planet’s health than plants, and that matters, too.

We eat foods, not nutrients, and the best foods are those that contribute to vitality and longevity. The highest quality is that which promotes the most health. The definition, therefore, should be updated to align references to “high-quality protein sources” with the foods that both deliver the protein we need, those that most reliably enhance the quality of our health, and protect that of the planet. As long as we get all the protein we need from them, plants are the foods to which “quality” should refer.

David and colleagues have made just that case in a recent peer-reviewed scientific paper and parlayed that into a petition for action by the federal authorities. We hope you will sign on, and thank you if you do.