Every fitness enthusiast, serious athlete, or health-conscious person has heard about a high-protein diet. You may have even tried Paleo, Keto, Atkins or some other variety of a high-protein meal plan in an effort to lose weight, increase muscle mass, or address a health concern. Many people, for many different reasons, don’t achieve the results hoped to get by following a high-protein diet. More importantly, they don’t realize that too much protein can stress the kidneys, potentially leading to permanent damage to these organs. We’re going to cover several key issues about protein intake as it relates to the kidneys, overall health, and fitness or athletic performance.
- What is the function of kidneys in the body?
- What do the kidneys do with dietary protein?
- What are factors involved with identifying protein requirements?
- Why don’t people achieve the desired results on high-protein diets?
- What are the health risks that come with consuming too much protein?
The Job of the Kidneys in Your Body
The fact that the kidneys filter fluids and excrete waste through the urine is only one job that the kidneys have in your body. Filtering out waste, of course, is vital to many other functions in and the overall health of the body. Likewise, the following eight additional jobs performed by the kidneys are essential to many aspects of your health, including athletic performance:
- Regulation of the body’s fluid levels to maintain homeostasis especially in response to physical and emotional stressors.
- Regulation of fluid levels also effects blood pressure, and in turn, cardiovascular function.
- Reabsorbtion of nutrients where needed by organs, muscles, etc., to maintain homeostasis
- Releasing a hormone that regulates blood pressure
- Regulation of the electrolyte-water balance in the body, including sodium, potassium, magnesium and other minerals that are used by the heart, skeletal muscle, and organ systems.
- Maintaining acceptable body pH level
- Activation of vitamin D to maintain healthy bones
- Releasing a hormone that modulates production of red blood cells, which carry oxygen to the body
From this list, you can understand that if the kidneys are doing a poor job of filtering waste, regulating nutrient absorption, and maintaining fluid balance, many other organ functions are affected. Health and athletic performance will suffer. Let’s look at what the kidneys do with protein and why too much protein can affect health and performance.
What do the kidneys do with dietary protein?
If you aren’t familiar, protein, along with dietary fat and carbohydrate, is a macronutrient necessary for health. Protein is required for the growth and repair of tissues (muscles, organs), fluid balance, wound healing, and many other physiological processes.
The primary sources of dietary protein for are:
- animal (chicken and beef)
- plant (yeast, breads and rolls)
- dairy (milk)
The kidneys filter out protein metabolites (tiny molecules) created when the body digests and metabolizes protein for assimilation. Studies show that under certain conditions, the process of filtering out excess protein makes the kidneys work harder and less efficiently. And that is not good for health and fitness.
How much protein do I really need?
There are two key reasons why it’s tough to pin down exactly how much protein a person needs for general health, and beyond that for high-level athletic performance.
Limited Research on Protein Intake and Effects
When it comes to research on protein intake, most studies involve elite athletes whose dedication to demanding training routines look nothing like the needs of the average person or even a fitness enthusiast. Many of these studies are short-term: The studies typically look for
(1) an immediate effect of protein consumption in the form of a supplement (e.g., shake, bar, gel) on performance measures (speed, power, strength); or,
(2) the studies look at short-term effects of high-protein dietary consumption, such as a six-week diet and effect on performance.Performance effects are different from health effects.
(3) most studies involve men of college-age to early middle age
Few studies look at the high protein diets in relation to long-term impacts on kidney function. While there are case studies documenting problems that people, including athletes, have had with overconsuming protein, more diverse research is needed to understand the stress a high-protein diet places on kidney function in healthy people as well as athletes.
Lack of Definitive Guidelines for Protein Intake
For most dietary nutrients, guidelines have been established so health providers and consumers know what a healthy minimum and maximum range is based on age (in most cases). Protein does not currently have guidelines for Adequate Intake for men, women or children nor is there a Tolerable Upper Intake Level for general health or athletic purposes. Instead, there is an Acceptable Macronutrient Distribution Range:
Protein should make up 10-35% of energy intake for adults age 19 and above. Within this group–and that very large range, there is great variety in health and lifestyle factors (e.g., age, gender, exercise frequency, menstruating, pre-menopausal or post-menopausal, activity level, other health conditions). These factors affect a lot of nutrients, protein being among them. Who should be at the upper limit? Who should be at the lower limit?
The current basic guideline for protein intake indicates that a healthy adult (age 19+) requires .8 to .85g protein per kilogram of body weight.
And the question every physically active person asks: How does intense physical training affect protein need?
How Much Protein Does an Athletic Person Need?
If you are a serious athlete or fitness enthusiast who is training multiple days per week and/or more than once per day for well over an hour per day, then, yes, your protein requirement will be different. How different is going to depend on many factors, including (but not limited to)
- the sport
- your age
- your biological sex (hormone variables associated with this)
- menstruation status
- body weight
- body composition
- history of injuries
- other health-related issues unique to your medical history
Differences such as those listed can mean one athlete, or athletic person, needs 1 g of protein /kg of body weight, while another needs 1.2 g/ kg of body weight. These differences are subtle and important because too much protein for any athlete will stress the kidneys and impair athletic performance.
The best way to ascertain your daily protein requirement is to talk with a nutritionist or certified trainer who is well-versed in the position statement written by the American College of Sports Medicine on athletic performance and nutrition. This statement addresses protein requirement variations for athletes and athletic people are vigorously training in different sport and fitness activities, as each has unique energy demands: The powerlifter does not eat like the triathlete, and the triathlete does not eat like a baseball player. A Sports Nutritionist can guide you in varying your protein intake accordingly for training days, non-training days, and at different points in the seasonal athletic calendar.
Why Don’t People Achieve Their Goals on a High-Protein Diet
When someone embarks on a high-protein diet on their own, they usually increase the protein and decrease intake of foods from other nutrient groups. Those other nutrients, be it carbs, fats, etc., are essential for balancing body fluids, body weight, energy level, and kidney function among others. Also, if you increase protein in the diet but don’t drink enough fluids, that can be a problem. Lastly, if you increase dietary protein by using supplements (powders, bars), you could be feeding yourself a lot of junk such as artificial sweeteners and preservatives, sugars, or fats that do no support health or athletic performance. These are some of the reasons why people don’t achieve goals while on a high-protein diet.
What’s the Big Deal about Eating Too Much Protein?
Over-consuming protein can add an unnecessary stress to the kidneys, leading to kidney disease. If you already have risk factors for kidney disease (family history), then that stress on the kidneys is more likely to result in an acute or chronic kidney disorder. The thing is…most people don’t know they have kidney disease risk factors. And the kind of strain on the kidneys that comes from high-protein diets takes time to build-up in an otherwise healthy person. Usually, by the time kidney dysfunction is medically diagnosed, it is quite advanced.
If you follow a high-protein diet and you have symptoms such as those listed below, go see your doctor to assess if your dietary intake of protein is stressing your kidneys.
- Fatigue, weakness
- Difficult, painful urination or foamy urine
- Pink, dark urine (blood in urine)
- Increased thirst
- Increased need to urinate (especially at night)
- Puffy eyes; swollen face, hands, abdomen, ankles, feet, and shortness of breath
And remember, before you start any new diet, including a high-protein diet, check with your physician and consult with a nutritionist or personal fitness trainer who can help you determine what you need for your body and sport/fitness goals.
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Healthline.com “Is Too Much Protein Bad for Your Health?”