How much protein should I eat? - and when, and what kinds? - have been questions on athletes' minds since the discovery of protein itself. With bodybuilders and strength athletes in mind, here's what the relevent research has to tell us...
The maximum safe daily protein intake is about 1.62 g/lb/day for people unaccustomed to high protein levels. For people adapted to higher protein intakes, this may go up to as high as 2.07 g/lb/day. Anything beyond that and the liver will not be able to deaminate the amino acids entering the bloodstream and the person will almost surely begin to experience signs of hyperammonemia.
The most anabolic rate of amino acids entering the bloodstream is about 0.0471-0.0546 grams of protein per pound of lean body mass per hour. For a 180-lb trainee at 15% body fat (153 lbs of lean body mass) that comes to 7.21-8.35 g/hour. That would be 173-200 grams of protein, or 1.13-1.31 g/lb-LBM/day, assuming he didn't sleep and stayed up all night eating or ate 58-67 grams of a very slow digesting protein before bed and the rest spread out over the day.
However, we must sleep, so removing the bedtime pig-out from the equation gives 0.75-0.87 grams/lb-LBM/day or roughly 1.66-1.92 g/kg-LBM (1.41-1.63 g/kg of body weight in this case). That puts it in range of the 1.6-1.8 g/kg (0.726-0.816 g/lb) of body weight amount that Peter Lemon found as the "ideal" amount for maximum nitrogen retention. Adding back in 14-32 grams of protein before bed would bump this 180-lb trainee to the upper limits of Lemon's findings.
In other words, the data sources seem to support each other to a fair degree. 0.0471-0.0546 grams of protein per pound of lean body mass per hour seems to be the maximally anabolic amount per hour, and a total of about 0.96-1.31 g/lb-LBM/day seems to be the most "anabolic" daily amount. In terms of total body weight, that comes to about 0.82-1.11 g/lb for a person who's 15% body fat.
How do you get 0.0471-0.0546 grams of protein per pound of lean body mass per hour? You have choices. You can eat slow-digesting proteins that are absorbed at about the right rate (such as casein), or you can eat smaller amounts of faster-digesting proteins more often. Here's a table of the rates of absorption of some common protein sources...
- Protein source, absorption rate (g/h) for a 147-lb man
- Egg protein raw, 1.3
- Pea flour, 2.4
- Egg protein cooked, 2.8
- Pea flour proteins, 3.4
- Milk protein (complete), 3.5
- Soy protein isolate, 3.9
- Free amino acids, 4.3
- Casein isolate, 6.1
- Free amino acids with casein profile, 7-7.5
- Whey protein isolate, 8-10
So, how would you use this? First of all it's a good idea to scale the absorption rates to your body weight. The values in the table were taken for a 147-lb man. If you weighed 180 lbs you'd therefore scale all the numbers up by multiplying by 1.22 (i.e. 180/147). So for you, the approximate absorption rate of casein, for example, would be 1.22 x 6.1 = 7.4 grams per hour.
To set up an example diet, let's say you're 180 lbs @ 15% body fat. In that case your lean body mass would be 153 lbs and the optimum amount of protein for you to consume would be 0.0471-0.0546 x 153 = 7.2-8.4 grams per hour. From the above we can see that an ideal protein for you would be casein isolate because, as we've seen, you'd digest it at a rate of about 7.4 grams per hour. In that case, you could consume 30 grams of casein and be good for 4 hours, as that's how long it would take you to digest it naturally.
Or, looking at whey protein isolate, we see that you'd likely digest that at a rate of about 1.22 x 8-10 = 9.8-12.2 g/h. That's a little too fast for the optimum range of 7.2-8.4 grams per hour we calculated for a guy with 153 lbs of lean body mass, so we'd have to slow it down by only eating 8.4 grams of whey isolate an hour... and best to spread that out over two or three feedings during the course of the hour (or merely sips in this case).
At this rate of 0.0471-0.0546 x 153 = 7.2-8.4 grams per hour you'd have eaten 115 to 134 grams of protein over the course of the day. You're optimum daily intake, however, is in the 0.96-1.31 g/lb-LBM/day range. At 153 lbs of lean body mass that's 0.96-1.31 x 153 = 147 to 200 grams of protein per day. You'd add in something in the range of 13-85 grams of a very slow-digesting protein just before bed to make up the rest. However, if you slept for 8 hours and went for the top of the range of 85 grams of protein at bedtime (worst case assuming you ate 115 grams during the day and were shooting for the maximum of 1.31 g/lb-LBM/day) that would be 10.6 g/h ...too fast. In this case, your max should be in the range of 7.2-8.4 g/h, or something in the range of 58 to 67 grams of protein spread out over the whole 8-hour sleeping period. Again, a good choice would be casein. At a digestion rate of 7.4 g/h for you, that would be 59 grams of casein at bedtime. That could mean a casein protein shake or a big chunk of cheese, or a combination of the two. Is it really practical to consume that much protein before bed? That's for you to decide.
At the lower end of the overnight scale you could consume just 13-34 grams of protein before bed and still be in Lemon's ideal range of 0.96 g/lb-LBM/day (depending on how much protein you ate over the course of the day). That's certainly a more practical range for most people to load their stomachs' down with before going to sleep. In that case you'd still want to choose a protein that would last the whole night. At a digestion rate of 3.5 g/h, 28 grams of milk protein could do the trick. Or at 2.8 g/h you could take in 22.4 grams of protein from cooked eggs (about four hard-boiled eggs). These absorption rates are lower than the optimally anabolic rate we calculated at 7.2-8.4 g/h for a man with 153 lbs of lean body mass, but they will keep him out of catabolism overnight and, quite frankly, no one knows whether the body will "make up" for it or not in the morning by entering a more anabolic state when you start taking in 7.2-8.4 g/h again.