It’s typically hard to define a single sitting, so I’m going to define it as less than 30 minutes. No more than a large meal.
I’ve seen estimates/some studies which suggest that 25 grams is the upper limit of protein that’s bio-available for muscle protein synthesis when eaten in a single sitting.
What is the reason for this? Do slow-digesting proteins legitimately make a difference?
Why would the body seemingly waste so much protein when surely pre-historical humans wouldn’t have had such steady access to 3-5 meals a day? When a pre-historic human finally got ahold of a good portion of meat and ate quickly in one sitting (say 60g of protein), the body just says “alright, bye 40g. We have no use for you?”
What is limiting our ability to absorb more protein in a single sitting?
Protein is used for a lot more than just muscle growth. It’s one of the building blocks of all of the cells in your body including bones, skin, hair and all of your organs. It helps build up your immune system, and is also used for hormone and enzyme production. Protein can also be used for energy.
That 30 minute window is only when you would get the absolute most benefit from protein for muscle building, and only really matters if you’re a serious body builder trying to maximize your gains. But your muscles really benefit from protein up to 24 hours after a good workout.