Consuming sufficient protein is key for a high-functioning body.
Getting enough protein provides an adequate amino acid supply so that our muscles, tendons, etc., can recover completely and even grow in size if provided with the right stimulus. Without protein, you can't build muscle, which seems to be the No.1 concern of many athletes and gym-goers.
However, there's still a lot of misinformation out there regarding protein. Much of this misguided advice centers around questions like:
- How much protein is lost in our body per day?
- How much protein can we use per day?
- How much protein can we use per meal?
Daily protein turnover scales around 1-2% per day. This is classified as a high turnover rate, so it makes sense to think we need continuous restoration of body proteins to preserve or even grow new muscle cells and other sources of supportive tissue. But as I noted earlier, specific hormones regulate just how much dietary protein we can actually utilize for these tasks at a given time.
Of all the macronutrients, protein seems to have the strongest effect on determining short-term fullness (satiation), which is basically how we determine when we're going to put down the fork and end our meal. Although we might feel the need to stuff ourselves with protein every second of every day, hormones like CCK, PPY, Leptin and others do a pretty good for job of telling us when enough is enough.
But for those who attempt to ignore these natural signals and stuff themselves full of protein in pursuit of "extra gains," the harsh reality is that our body can only use a limited number of grams to build muscle per day. That exact limit may vary a bit depending on your physique and biology, but not by a drastic amount.
As you can see in the figures below, protein digestion rates are rather "slow" overall. In a best-case scenario, 10 grams of protein can be digested per hour.
Protein Absorption Rate (g/hour)
- Raw Egg Protein* 1.4
- Cooked Egg Protein* 2.9
- Pea Protein 3.5
- Milk Protein 3.5
- Soy Protein Isolate 3.9
- Casein Isolate 6.1
- Whey Isolate 8-10
- Tenderloin Pork Steak* 10.0
*Measurements marked with an asterisk should be considered fairly rough estimates, as these studies used indirect measurements of protein digestion. These numbers come from this 2018 Journal of the International Society of Sports Nutrition review
So monstrous amounts of protein aren't going to turn you into The Incredible Hulk overnight. With that, what percentage of our daily calories should come from protein each day?
This number depends largely on your biology and your goals. Ever since I can remember, recommendations for protein intake for those interested in building muscle have seemed to scale around 1.5-2.5 g/kg of body weight per day. However, the above 2018 review recommends a minimum of 1.6 g/kg a day and a maximum of 2.2 g/kg a day for those with the "goal of maximizing resistance training-induced gains in muscle mass and strength." For a 180-pound man, the former equals about 131 grams of protein a day, while the latter equals about 180 grams of protein a day. Some may see little to no gain by going with the 2.2 g/kg a day over the 1.6, while others may receive significant benefit. It just depends on the individual.
But what happens when someone significantly exceeds these recommendations?
Although you may have heard that you simply excrete the excess protein out via bodily function, the truth is that it is still absorbed by the body. The next step just happens to usually be it being converted into glucose and then stored as fat rather than used to build muscle. From Healthline: "Excess protein is usually stored as fat while the surplus of amino acids is excreted. This can lead to weight gain over time, especially if you consume too many calories while trying to increase your protein intake."
Consuming too much protein can also take a toll on the body in the form of excessive nitrogen accumulation. The human liver has a governor for digesting nitrogen. If 30% or more of your daily caloric intake is coming directly from protein, your liver cannot digest that much nitrogen. This causes it to accumulate inside the body, which can be toxic for the liver. Our body will work to flush out this excess nitrogen with fluids and water, but this in turn often leads to dehydration. So more protein is certainly not always better.
Lastly, recent research has been able to narrow down even how much protein can be utilized from a given meal! From the aforementioned 2018 JISSN Review: "Based on the current evidence, we conclude that to maximize anabolism one should consume protein at a target intake of 0.4 g/kg/meal across a minimum of four meals to reach a minimum of 1.6 g/kg/day. Using the upper daily intake of 2.2 g/kg/day reported in the literature spread out over the same four meals would necessitate a maximum of 0.55 g/kg/meal."
As for the absolute minimum amount of protein you need to live healthily, the Recommended Dietary Allowance is 0.8 g/kg of body weight per day. Less than that, and you're likely to get sick. For a 180-pound man, that's just 65 grams of protein per day.
So there are the facts as they stand today. All of this ridiculous talk about an elite bodybuilder or weightlifting enthusiast who manages to somehow routinely eat 500-1,000 grams of protein per day should not be taken seriously, and it certainly should not be emulated. Most Americans have zero problem getting enough protein, but if you're curious about where you stand, log your typical diet for a few days and calculate your protein intake.
- 10 Athlete-Approved High-Protein Cereals
- 9 Foods You Didn't Know Have as Much Protein as Peanut Butter
- 5 Side Effects of a Low-Protein Diet for Athletes