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Building muscle with one kidney: pro tips for protein and gains

One of the most frequent questions I get from people concerned with their kidney health revolves around protein—like how much they should eat and when's the best time to consume it. Today, let's dive into the science behind bulking up with only one kidney. We'll explore protein distribution and timing—including how much protein to have after a workout—to keep both your muscles and kidney happy.


Coach Anna flexing (photo: FotosGallegos)

What we mean by "protein distribution"


As a writer, you are taught not to define a word or phrase with the word or phrase itself. But in this case, I would say it is a valid answer.


"Protein distribution" means just that: distributing your protein intake throughout the day. The idea is grounded in research that shows spreading out your protein helps maximize muscle growth and repair, as well as improves physical performance.


Here's the science behind why protein distribution works:


  • Improves muscle repair and growth: By spacing out your protein intake, you give your muscles a steady supply of amino acids—our muscles' building blocks. A 2020 review in the journal Nutrients reiterated that optimizing protein intake, including amount, type, source, and timing, promotes positive muscle growth over time.

  • Maximizes muscle protein synthesis: A 2014 study in the Journal of Nutrition shows that consuming moderate amounts of protein at each meal stimulates 24-hour muscle protein synthesis (MPS) more effectively than concentrating protein intake toward the evening meal. (Muscle protein synthesis drives exercise adaptations.) By how much did it work better? The researchers found that spreading out protein intake evenly throughout the day resulted in a 25% greater increase in muscle growth over a 24-hour period than saving it all for dinner.

  • Prevents muscle breakdown: Distributing your protein may also help prevent your body from breaking down muscle tissue for energy. By keeping a constant supply of protein in your system, you can maintain a positive protein balance and preserve muscle. A 2013 study published in the Journal of Physiology found that protein distribution not only helps with peak muscle gain but also with maintaining your muscle mass.


Is there one way to approach protein distribution?


Short answer: No. While some strategies like the Protein Pacing Diet focus on consuming a specific number of grams across four to six meals, research suggests what matters more is maintaining consistency rather than hitting a set amount every time. A 2022 Clinical Nutrition study found that increasing protein intake at breakfast and lunch—without decreasing your intake at dinner—is the most efficient way to maximize the overall anabolic response to protein over 24 hours. (Anabolic response, by the way, is the net gain in protein balance—or the difference between protein synthesis and protein breakdown—after consuming protein alone or in a meal.)


Additionally, recent science challenges the notion that your body can only use so much protein at once to build muscle. According to a 2023 study published in Cell Medicine Reports, consuming 100 grams of protein in one sitting can also lead to sustained muscle protein synthesis, which would eliminate the need for frequent protein-rich meals. In other words, eating all your protein in one go will have the same effect as eating 100 grams divided over four smaller noshes.


Except for when it doesn't. Researchers behind the Cell Medicine Reports study admit that they conducted their experiment on "healthy, young men" who are active. They also admit that their findings may not apply to those with clinical compromises (e.g., reduced kidney function or having a solitary kidney). People with special considerations, therefore, may indeed have an upper limit to protein consumption in one meal.


tl;dr: Experts need to continue to investigate the science behind protein distribution. But based on current studies, eating protein consistently throughout the day—whether over three meals or six—seems to have the most benefit for muscle gain, recovery, and preservation. In fact, the International Society of Sports Nutrition (ISSN) recommends daily protein intake be "evenly distributed, every 3 to 4 hours across the day."


How does this apply to building muscle with one kidney?


As a personal trainer and nutrition coach, I emphasize protein distribution and timing as essential nutrition strategies for my clients. Even though each of us has just one kidney, our kidney function differs from person to person. And despite working out at similar intensities, we can't all consume the same amount of protein. Some of us may intake 160 grams daily, while others can only have 90. Plus, our diets vary: while I can manage six meals a day, some clients can only fit in three.


First, we start with timing


Conventional wisdom dictates that the muscle-building effect of exercise fades quickly, and the best time to improve muscle growth and recovery is within 30-60 minutes after a workout (otherwise known as the "anabolic window"). Turns out, this is more fiction than fact. Studies show the anabolic effect—that is, when muscle protein synthesis is elevated—depends on the intensity of your training: a particularly grueling workout may leave the window open for 36 hours, while light exercise might keep it open for up to 24 hours. You may even have a few hours after your workout to get your protein in, especially if you had a meal before hitting the gym. This means consuming enough protein overall may matter more for your muscle gains than when you eat said protein. Still, the anabolic effect of exercise does decrease gradually over time, and studies show eating right after a workout might help experienced lifters with short-term performance, muscle growth, and recovery.


Given this information, here are two timing strategies I recommend to my clients (who are often advanced in their training):


  • Consume at least 25 grams of protein (whether vegan or whey) 2 to 3 hours before starting your workout. Research published in Frontiers in Nutrition found that consuming protein before training can boost muscle protein synthesis. Similarly, a double-blind, crossover study published in Nutrients revealed that eating 25 grams of whey (re: animal) protein before a workout led to greater overall muscle growth compared to those who took a placebo.

  • After your workout, aim to eat at least 20 grams of protein within 3 hours. To be honest, "within 3 hours" is somewhat of an arbitrary rule. After all, we know that our anabolic window is not as fleeting as once believed. But research suggests that up to 6 hours post-workout is the optimal time to capitalize on this effect. So, 3 hours is just splitting the difference. As for the amount of protein: a 2009 American Journal of Clinical Nutrition clinical trial found that eating 20 grams of complete protein is enough to fully stimulate muscle protein synthesis post-weightlifting. Twenty grams, though, is the minimum; one 2016 study found that, in young, experienced lifters, eating 40 grams of whey protein after strength training caused a bigger increase in muscle protein synthesis compared to 20 grams.


Timing your protein intake around exercise can be crucial for building muscle. Although research isn't definitive, it's clear that consuming protein before and after workouts can provide the necessary building blocks for muscle repair and growth. This can help prevent muscle breakdown and support faster recovery, ultimately leading to better results in building strength. If you have one kidney and eat a more modest amount of protein, implementing timing strategies may make all the difference for maximizing your gains.


Then, we look at distribution


Once my client and I establish the amount of protein they'll consume before and after workouts, we subtract this total from their daily protein intake. Then, we'll discuss whether they will spread the rest of their protein over three meals or over six. For more advanced lifters, I recommend eating five to six meals a day. Not because eating more frequently increases your overall metabolic rate or how many calories you burn in a day—as a 2023 systematic review found, neither is true. Consuming three 700-calorie meals results in the same thermic effect as consuming six 350-calorie meals. That being said, my clients in a bulking or maintenance phase tend to eat a lot of calories, and chowing down on a 1000-calorie meal three times a day can leave someone uncomfortably full. Eating more frequently, then, may feel better on the body. Either way, I will distribute the remaining amount of protein as evenly as possible over the rest of their meals—however many there may be.


By the way, any nutritional advice I offer a client, I apply to my own training. Said in cliche: I practice what I preach.


But how much protein should people with one kidney eat?


Listen, we know a lot about how protein affects people with kidney problems. But most studies focus on those with two kidneys who live sedentary lifestyles. Surprisingly, there's very little research on how protein affects people who have one kidney and exercise regularly. So, the findings from existing studies might not even apply to us.


This is even true for how we measure kidney function—the current modeling to define chronic kidney disease (CKD) only applies to someone with two kidneys. A solitary kidney, even if otherwise healthy, might lead to slightly higher levels of creatinine (and we know elevated creatinine could result from a variety of non-kidney-related factors). Yet, long-term data from living kidney donors who have had one kidney removed show no ongoing decline in kidney function over many decades, according to a 2022 Mayo Clinic Proceeding report.


Of course, it's entirely possible for a person with one kidney to have kidney disease. If that's the case, they might need to tweak their diet to help slow down the progress of the condition. But more often than not, a person with one kidney may be erroneously diagnosed with CKD only because their creatinine level is high, indicating a lower eGFR (or estimated glomerular filtration rate). In fact, overuse and misdiagnosis of kidney disease has been a pervasive and controversial issue since 2002, when the National Kidney Foundation introduced a new way to classify it. The new classification framework for chronic kidney disease depends entirely on whether a person's estimated glomerular filtration rate (eGFR) is below 60 milliliters per minute per 1.73 square meters of body surface area (eGFR<60 mL/min/1.73m²).


In other words, many people with only one kidney are being told by their doctors to stop lifting heavy weights and cut back on protein—by a lot. But since there isn't much guidance specifically for us, we're left following our doctors' advice and feeling frustrated with our slow progress.


To be fair, I'm not qualified to determine the exact amount of protein my clients should consume daily; it's beyond my expertise. But I do understand, based on what we know from current and emerging research, that their doctors might underestimate just how much protein my clients actually need. So, I suggest a protein range after looking at their lifestyle, medical history, recent lab results, and the latest nutritional science, and ask that they consult with a doctor they trust. To inform my suggestions, I follow guidelines established by the International Society of Sports Nutrition, which recommends a daily intake of 1.4 to 2.0 grams of protein per bodyweight kilogram for people with active lifestyles.


What's the bottom line?


When you're trying to build muscle with just one kidney, knowing how to handle protein can make a big difference. Even though there's still a lot we don't understand about how protein affects people with only one kidney, we can use what we do know to create a plan that works for us.


Strategies like making sure you get enough protein before and after your workouts and spreading out your protein intake throughout the day can help your muscles grow, recover, and stay healthy. But it's essential to listen to your body and maybe talk with your doctor to figure out what's best for you.


In the end, building muscle with one kidney is about finding what works for you. It might take some trial and error, but with the right approach and a bit of patience, you can reach your fitness goals while keeping your kidney health in check.


 


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