Archibald said:"all plant foods contain all 8 essential human amino acids"
I'm going to play devil's advocate here - to what levels do they contain all of those amino acids? surely, they don't all have the same amount of each amino acid?
No they don't. Wheat for example is a bit short on Lycine, one of the essential amino acids. This doesn't mean you can't get your protein hit from wheat products, it just means you have to eat a bit more of it compared to eating eggs, meat or dairy.
Your daily protein requirement will be about 50-60gms. This is about the size of an egg. The moment you go over your protein requirement your body starts to break the redundant protein down. So most of that 300g steak is not building muscle, it's being flushed down the toilet.
A bowl of cereal with soy milk gives about 25g of protein. That's nearly half your daily protein needs over and done with at breakfast time and you still have several meals to go for the day. A very small handful of nuts has 5-6gms, a salad sandwich 15-20gms, a bowl of vegetable soup 10gms and you're basically done. Most of us would eat way more than this during a day so most of us are taking in way more protein than we need to without even trying. Well, after a bit of research that's my take on it anyway.