Animal Protein: The Debate Over Vegan Diets Settled in the Knee

The animal protein debate settled in the knee

Lierre Keith could not bend her knees without agony. As soon as she added animal fat to her diet, the movement stopped hurting, according to a quote attributed to her and antiestéticatured in a Rambla Libre article. This anecdote has sparked an enduring debate: does humans require animal proteins and fats, or is this merely a myth of the carnivorous tribe?

The thesis, launched via Twitter, is blunt: humans are not vegetarian and need animal proteins and fats. From there, the argument unfolds across two distinct fronts—evolution and nutrients—neither yielding a unanimous answer.

From 300 grams to 1,500: the brain that ate meat

The star argument is encephalization. It is argued that hominid skulls grew from 300 grams to 1,500 over two million years, a leap made possible only by meat consumption. This implies larger cranial size relative to body mass among mammals and explains why human childbirth is painful. This reasoning has appeal but is presented as dogma when it is merely interpretation.

The counterargument trinc the same path. It criticizes the story’s frivolity: Homo sapiens sapiens remained the same species for tens of thousands of years before becoming an efficient hunter, and other human lineage species were fundamentally vegetarian, scavenging and practicing cannibalism occasionally. The timeline, they argue, does not fit the steakhouse epic.

B12, collagen, and the disputed nutrient list

The debate becomes technical regarding the list of compounds. Liposoluble vitamins, hormones, collagen, and formerly insulin are listed as animal-derived substances with no real substitute. Regarding collagen, it is absolutely claimed that plant-derived collagen does not exist. B12 appears as the ultimate proof: if a vegan must supplement, they argue, their diet is unnatural.

The counterreply lowers the tone. Some recall that taurine, creatine, carnitine, and carnosine are not essential amino acids—the human body synthesizes them—and that the balance between omega-3 and omega-6 or sufficient EPA and DHA are planning issues, not biological condemnation. The wry comparison launched is that farm animals eat industrial feed and also need supplements.

Those who don’t eat meat and still lift weights

The most uncomfortable argument is not theoretical, but physical. Testimonials from strict vegetarians of over ten years claim to move 200 kilos deadlift, perform seven squats with 150 kilos, and 130 in bench press. An extreme case: military press reps with 70 kilos and barely three days of shoulder training after a long break.

Their conclusion is that the body does not distinguish the label from the package. Against this, the opposing side does not dispute the specific performance but nuances: the healthy vegan is usually the one who watches what they eat, not the one who simply renounces meat. There is a difference between not eating animal products and doing it well.

Posturing and the hidden supplement

Part of the debate shifts to suspicion. It is claimed that many who declare themselves vegan publicly supplement their diet through the back door, and many have been discovered eating secretly. The phenomenon is described as an image issue rather than a health one: diet as an identity medal, with a flag raised at every event attended.

Others take the reproach to the cost terrain. Switching from animal to vegetable protein is not always a free choice: some argue that those who eat more vegetable than animal protein do so, in many cases, because they cannot afford anything else. The dilemma between choice and obligation creeps into an issue presented as sarracena.

What remains open

No one disputes that the human species is omnivorous; disagreement begins just after, when deciding whether this flexibility obliges us to eat meat or merely permits it. The initial claim—need, not can—never finishes being demonstrated with numbers.

After more than fifteen years of back-and-forth, according to one involved party’s count, the evidence closing the case has yet to appear. And a startling fact: only 14% of those who try the vegan diet maintain it. A very high abandonment rate, certainly, though not very different from any restrictive regime that becomes fashionable.