Apparently what I took for fact has been invalidated — the idea that you need to combine certain “complementary” vegetables to get a “complete” protein. The classic example being beans and rice.
Now that I think about it, my belief originated the same place it did for a lot of people: in the seminal 1971 book Diet for a Small Planet, which I perused during a brief stint of vegetarianism back in the day. The protein combining concept has since been discredited. Science wins again! ;)
Even if you’re not planning out a vegetarian diet, but instead substituting for meat as much as possible, it’s useful information to have.