This is a question often asked of vegans, people who eat no animal products — no meat, no milk, no eggs, no cheese, no ice cream, no butter, no lard, no fish, no chicken, no pork, no honey. Generally, they don’t even wear leather, feathers, fur, or any product made from a dead animal.
In US culture, protein is considered the gold standard of nutrition. We hear about how eggs are “high quality” protein or “perfect” protein, as if any other source of protein can’t be quite as good. Actually, eggs, and all animal-based foods, contain cholesterol and fat our bodies don’t need. They actually aren’t health-producing in a human body, especially in the quantities typical of the Standard American Diet.
Protein comes in the form of amino acids. Most of the amino acids humans need are produced in the body from the materials consumed in the diet. However, there are eight amino acids that are termed “essential” that human bodies don’t know how to synthesize. Wikipedia provides a table listing the essential amino acids and their relative daily requirement for adult humans according to the World Health Organization:
|Amino acid(s)||mg per kg body weight||mg per 70 kg||mg per 100 kg|
|M Methionine+ C Cysteine||10.4 + 4.1 (15 total)||1050||1500|
|F Phenylalanine+ Y Tyrosine||25 (total)||1750||2500|
(Methionine and Cysteine can be interconverted from one to the other, so the diet only has to include a pool of one or the other, although it may include both. The same holds true for Phenylalanine and Tyrosine. See the Wikipedia page linked above for more details.)
Eggs happen to contain these amino acids in amounts very close to these proportions. That’s why they are considered a “high quality” or “perfect” or “highly digestible” protein source. Plant foods also contain plenty of these amino acids. They aren’t necessarily in the same proportions in plant foods but they’re all there. It’s not necessary that the amino acids be present in the proportions in which the body uses them, just that the diet provide enough of the least prevalent amino acid.
As it turns out, if a person eats enough calories, it’s almost impossible for them to be deficient in any of the amino acids, no matter which foods they choose to eat. Here’s what the Wikipedia entry says, with references:
Although it is possible to induce deficiency of one or more of the individual essential amino acids in a laboratory setting by providing an elemental diet or a diet based on gelatin (the only “incomplete” protein that is commonly found in human diets), it would be highly unusual for such a deficiency to occur in a community setting. It is practically impossible to design a diet based on unrefined starches and vegetables that would fail to provide enough protein, including sufficient amounts of all of the essential amino acids, to support human health. Nor is it necessary to combine “complementary” plant sources to provide complete protein.
So, where do vegans get their protein? The same place everyone does, from their food. They just happen to make different food choices, which provide all the protein they need.
Let me ask another question. Where do wild elephants get their protein? Here’s Wikipedia on elephant diets:
Elephants are herbivores, and spend up to 16 hours a day eating plants. Their diets are highly variable, both seasonally and across habitats and regions. Elephants are primarily browsers, feeding on the leaves, bark, and fruits of trees and shrubs, but they may also eat considerable grasses and herbs. As is true for other nonruminant unglulates, elephants only digest approximately 40% of what they eat. They make up for their digestive systems’ lack of efficiency in volume. An adult elephant consumes 140–270 kg (300–600 lb) of food a day.
They digest less than half of what they eat, they don’t eat the same thing all the time, clearly their diets are not carefully planned or thought out, yet they get enough protein from what they eat to build a huge, strong, robust body. Cattle of all kinds, horses, and giraffes are other examples of large animals who get all their protein from plant sources. Clearly, plants must contain plenty of protein if such large bodies can be built entirely from plant-based nutrition.
Or how about our nearest genetic relative, the chimpanzee? According to the Honolulu Zoo’s website, chimp diets are largely vegetarian with only 5% of their diet coming from hunted meat (mostly juvenile red colobus monkeys). Although The Predatory Behavior and Ecology of Wild Chimpanzees emphasizes chimpanzee hunting behavior, it says that only 3% of their calories come from hunting. The vast majority of chimps’ calories, 95% – 97%, and therefore most of their protein, come from plant foods. On average, Americans get around 25% of their calories from animal sources in their indoctrinated fear of protein deficiency. Yet the typical chimpanzee has five to seven times the muscular strength of the strongest human. If the animal foods were providing so much more or higher quality protein, why aren’t we stronger than the chimps?
The bottom line is that plants provide all the protein humans need, without any special planning or care given to combining or sequencing foods. That’s where vegans get their protein.