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Fact checked by Andrew Lenau, ISSA CPT & Sports NutritionistFACT CHECKED
Updated On: June 20, 2023
It seems like every effective supplement must always deal with a group of negative Nancy's that swear it will cause some sort of catastrophic health problem. We mean, creatine is basically a steroid, yea? For any of our readers too young (this was prevalent in the 90’s), that idea was actually thrown around back in the day. Creatine is not a steroid (thanks for the compliment though!), but we’re not talking about that here. In this article, we want to discuss protein and if consuming too much will shut down your kidneys, what is the maximum amount of protein (if any) that you should eat each day, and what is ideal for building muscle?
Let’s find out if eating too much protein will make your kidneys explode.
Our daily protein intake is determined by using a nitrogen balance technique that involves calculating the total amount of dietary protein entering the body and the total amount of the excreted nitrogen. Basically, protein is made up of amino acids which contain the molecule nitrogen. In fact, “amino” refers to a compound containing NH2 (Nitrogen & 2 Hydrogen). This is important because out of the 3 macronutrients, only protein contains nitrogen making it unique.
Therefore, studies can look at the amount of protein that’s consumed and compare it with the amount of nitrogen excreted to determine the status of someone’s protein consumption. This leaves 3 possibilities:
Now, let’s look at how much protein the professionals say you should eat daily. This number is going to vary widely depending on who you ask. So let’s first start with what the RDA says, as this is the number usually thrown around to “prove” you’re eating too much.
The RDA stands for the Recommended Dietary Allowances, which is set by the Food and Nutrition Board of the Institute of Medicine. It’s defined as:
“The daily dietary intake level of a nutrient considered sufficient to meet the requirements of 97.5% of healthy individuals in each life-stage and sex group.”
Basically, this is the minimum amount of protein that 97.5% of the world’s population needs to live a healthy, functional life. However, this number is also set for the sedentary population. So basically, 0.8g/kg is how much protein you need to support basic life functions if you live a sedentary life.
And this is the issue. These numbers are calculated by using the nitrogen test above, yet they do not consider the role of exercise. As mentioned, the RDA is set to address the nutritional needs of the large majority of the population to maintain healthy life functions. IT IS NOT an individualistic diet plan. Athletes have very different nutritional needs compared to sedentary populations who never train, which will affect the optimal amount of protein.
Still, what’s interesting to think about is that this also implies that 0.8g/kg of protein would cause a deficiency in 2.5% of the population. It also means that if the other 97.5% ate less than this, they too would be in a deficit. So why are so many nutritionists recommending the minimal threshold? Seems as if they like living dangerously…
We need to also realize that there is a difference between an amount that’s sufficient for healthy life function and an amount that’s optimal for improved performance. It’s like saying a Natural Ice and a nice microbrew are the same because they’re both “sufficient” to get you drunk. However, one tastes like piss and leaves you with an awful hangover with a splitting headache and the other is a nice microbrew. To be clear, this is not a criticism of the RDA as its purpose is not to suggest protein intake for weight lifters.
So now, let’s talk about how much protein bodybuilders and weightlifters should eat for optimal performance.
When it comes to studies looking at the optimal amount of protein athletes and weightlifters should eat, research is pretty clear that their needs far surpass the RDA numbers.
The Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine release their stand on nutritional needs for athletes on a regular basis. Concerning protein, they recommend consuming 1.2–2.0 g/kg per day1. Still, they even suggest higher intakes of protein could be necessary during specific times, such as when losing weight or cutting.
The International Society For Sports Nutrition (ISSN) promotes a protein intake of 1.4 – 2.0 g/kg and, again, suggests that some circumstances could justify even higher amounts2.
American College Of Sports Medicine recommends a protein intake of 1.2-1.7g/kg daily3.
We could go on and on with citations as the vast amount of sports researchers recommend a protein intake much higher than the RDA with doses in the range of 1.4-2.2g/kg a day. This population needs the extra protein per day due to the extreme levels of stress they place on the body, as well as simply to gain muscle.
Still, this isn’t even the most amount of protein that you “could” eat per day. The amounts given above are determined to be the upper limits of where noticeable benefits stop occurring. In other words, there seems to be a dose-response (the more you eat = more benefits) up until these upper numbers, and then the benefits level off. So what’s the most you can eat without experiencing health issues? Likely higher...much higher.
We can start by looking at a protein intake, a review put out by The International Journal Of Sport Nutrition And Metabolism. They state that a healthy individuals’ daily protein intake of 2.5g/kg a day would be suitable for healthy individuals and present no health risks4. Hmmm 2.5g is more than 0.8g…3x actually.
Before we go down this road any further, the real issue with trying to answer “what’s the most” protein you can eat is simply the fact that studies haven’t really examined that specifically; at least what we’re aware of. We’re talking about a study that keeps feeding participants more and more protein until their kidneys bleed (if at all possible).
However, what we can answer from a different angle and answer “What's the most protein we know of that can be consumed with no kidney damage?”
The major criticism of a high protein intake is that it can be harmful to the kidneys. When we hear this, we like to retort with a logical scenario to help illustrate the problem.
And that’s basically the protein and kidney argument. While protein does add stress to your kidneys; literally everything you eat “causes stress” to the kidneys as that’s its job. For any wisecracks who suggest excessive jogging can cause foot fracture, we need to consider that there have been no studies showing that high protein diets can cause issues. However, if you already do have problems with your kidneys, a high protein diet can exacerbate the issue. If you’re healthy there really shouldn’t be an issue. But, if you do have kidney issues, you should seek a medical professional or dietician who deals with this area.
This same conclusion was made in another study published by the International Journal Of Sport Nutrition And Exercise Metabolism, which used glomerular filtration rate to test the function and stress on kidneys in athletes. They used up 2.8g/kg of protein per day and saw no influx in the filtration rate, indicating no added stress5.
Dr. Jose Antonio of ISSN has conducted a study using very high intakes of protein to measure its effect on the kidney as well as body comp. One study used protein diets up to 3.3g/kg per day for a year and saw no decrease in kidney or liver function6.
To be clear, we are not suggesting you eat this amount of protein and still suggest a 1.6-2.2g/kg range for most people. That being said, as long as you are a healthy individual with normal kidney function, the amount of protein you eat should not be a concern. Of course, considering you’re not eating 10g/kg as we’re sure there’s a threshold somewhere.
In relation to the above question of how much protein can you eat, Dr. Jose Antonio’s research using 3.3g/kg a day is the highest amount we know of in a study that monitored kidney damage (Dr. Jose Anotnio had another study using 4g/kg a day but they only measured body composition).
Instead of asking; “what’s the most protein can you eat?”; The better question is; “what’s the most protein you should eat?”. Reason being is that looking at all of the available studies, it seems that you can safely eat a lot more protein than most people would ever need to.
Therefore, if we were going to look at the upper-upper limits, we would suggest 2.2-2.5g/kg a day. Again, we suggest most people consume 1.6-2.2g/kg, but those higher numbers are the most we’ve recommended by professionals.
Again, going back to Dr. Jose Antonio, a very pro-high-protein diet researcher; he suggests that athletes eat at least 2.2g/kg per day7. Dr. Antonio is a professional and a leader in sports nutrition, so we’re going to go with that!
Be aware that everyone handles protein differently. Even if you don’t have kidney issues, you may experience stomach distress when eating so much. Or maybe it makes you feel sluggish. The point being is to be mindful of how you feel. If you experience discomfort, you may need to lower the dose or switch protein powders (there’s many great lactose-free protein powders on the market if you are lactose intolerant!). Find what works for you and work it!
Now you know how much protein to eat per day, check out how much protein you should eat each serving! And once you've got that down, you can dig even further and determine the best timing for taking protein shakes.
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