Ah, the term "biological value" probably sounds abstract, but no that's the pedantic/scientific term for it. https://en.wikipedia.org/wiki/Biological_value htt

Ah, the term "biological value" probably sounds abstract, but no that's the pedantic/scientific term for it. https://en.wikipedia.org/wiki/Biological_value https://en.wikipedia.org/wiki/Biological_value The tl;dr is that it boils down to amino-acid profile. There are 9 Essential Amino Acid's (EAA's) that human body can't synthesize from other amino acids. A food's biological value is determined (primarily) by it's amino acid profile. It's also not just about the overall amount, but also the ratio, since the way that amino acid absorption works is on a first-come-first-serve basis and so the proportion matters almost as much as composition. There's a list of common foods and their biological value on that page if you're curious. > "When I looked in to this for myself, it seemed like it's very unlikely for vegetarians to have protein deficiencies as long as they ate enough calories to sustain themselves and ate a decent variety of food (which they should be doing anyway, to stave off other health issues)." Ah, yeah. For the average person, it doesn't matter. You can pretty much eat anything and be alright. The grand majority of people have god-awful diets and seem to function just fine. I recreationally bodybuild so my dietary requirements are kind of an edgecase scenario.