Proteins are essential macronutrients required by the body for growth, repair, and maintenance of tissues, muscles, and organs.

Adequate protein consumption is especially important for athletes, bodybuilders, and fitness enthusiasts to sustain muscle mass and promote muscle growth. Despite its importance, there are numerous myths circulating about protein, including that it’s harmful to the kidneys. But is there any truth in this? Let’s separate fact from fiction.

What Are Proteins?

Proteins are complex molecules composed of amino acids. There are 20 different types of amino acids, nine of which are essential, meaning the body cannot produce them and must acquire them through dietary sources.

Proteins serve various functions in the body, including:.

Providing structure and support to tissues, cells, and organs
Regulating various metabolic processes
Aiding in the transportation of molecules throughout the body
Assisting in the body’s immune response
Acting as enzymes, hormones, and neurotransmitters

Protein and Kidney Function

The kidneys are responsible for maintaining a balance of fluids and electrolytes in the body and filtering waste products from the blood. Some studies suggest that a high protein diet may increase the workload on the kidneys, leading to harmful effects.

However, the evidence is inconclusive and varies depending on factors such as an individual’s kidney function, age, and overall health.

A review of several studies by the American Journal of Clinical Nutrition found that in healthy individuals, a high protein diet did not adversely affect kidney function.

The review did acknowledge that in individuals with pre-existing kidney disease, a high protein diet may exacerbate the condition. However, it’s essential to note that pre-existing kidney disease is not prevalent in the general population.

Another study published in the Journal of Renal Nutrition found that high protein diets did not negatively impact kidney function in resistance-trained individuals.

In fact, the study found that a high protein intake improved markers of kidney function in this population. The study concluded that high protein diets may even be beneficial for those with normal kidney function.

What About People with Poor Kidney Function?

Individuals with pre-existing kidney disease or poor kidney function should exercise caution when consuming high-protein diets.

In these instances, the kidneys may have difficulty processing and eliminating waste products from the blood, leading to an accumulation of toxins in the body. These individuals should consult with a medical professional or registered dietitian before making any significant dietary changes.

Does Excess Protein Turn into Fat?

Another prevalent myth surrounding protein intake is that excess protein consumption will turn into fat. While it’s true that a caloric surplus, from any macronutrient, can lead to weight gain, excess protein does not magically turn into fat.

Protein must first be broken down into amino acids, which are then used for various functions in the body. Any excess amino acids are excreted in the urine and not stored as fat.

How Much Protein Do You Need?

The amount of protein an individual needs varies depending on several factors, including age, sex, weight, activity level, and overall health.

The Recommended Dietary Allowance (RDA) for protein is 0.8 grams per kilogram of body weight for sedentary individuals. However, individuals engaged in regular exercise, particularly strength training, may require higher amounts of protein to support muscle growth and repair.

The American College of Sports Medicine recommends 1.2-2.0 grams of protein per kilogram of body weight for active individuals.

Choosing High-Quality Protein Sources

It’s not just about the quantity of protein but also the quality. Different sources of protein contain varying amounts of essential amino acids and can vary in their digestibility.

High-quality protein sources provide all nine essential amino acids in significant amounts and have excellent digestibility. Examples of high-quality protein sources include:.

Lean meats, such as chicken, turkey, and lean cuts of beef and pork
Fish and seafood
Eggs and egg whites
Milk, cheese, and yogurt
Plant-based sources, such as quinoa, soy, and spirulina. These sources can be less bioavailable, however, and may not contain all nine essential amino acids in significant amounts

The Bottom Line

While the idea that protein is harmful to the kidneys is a pervasive myth, the evidence does not support this claim.

Except for individuals with pre-existing kidney disease, high protein diets are not harmful to kidney function and may even have positive implications. As with any nutrient, it’s essential to choose high-quality sources and consume an appropriate amount for your individual needs.

Consulting with a registered dietitian can help determine your specific protein needs and any dietary changes necessary for optimal health.