Healthy kidneys can efficiently process protein. However, over-consuming protein can add unnecessary strain on these organs. If you have risk factors for kidney disease, or have an undetected problem, the strain created by consuming too much protein could result in a serious acute or chronic kidney disorder.
What do the kidneys do with dietary protein?
Protein, along with 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 numerous other physiological processes. For Americans, the primary sources of dietary protein are animal (chicken and beef), followed by plant (yeast, bread products) and dairy (milk, cheese, yogurt). The kidneys filter out protein metabolites (tiny molecules) created when the body digests and metabolizes protein for assimilation. Many scientists agree that filtering out excess protein makes the kidneys work harder.
How much protein do I really need?
Making decisive statements about dietary protein intake and kidney health is a challenge for a few reasons:
Lack of Definitive Recommendations for Protein Intake. Unlike other nutrients that have established recommended minimum and/or maximum intake standards for good health, protein does not currently have Adequate Intake nor a Tolerable Upper Intake Level for the general population. Instead, there is an Acceptable Macronutrient Distribution Range: Protein should make up 10-35% of energy intake for adults age 19 and above. In that large group, there are widely varying health and lifestyle factors. Who should be at the upper limit? Who should be at the lower limit? How does intense physical training affect protein needs? The basic guideline is that adults need 0.8 – 0.85 g protein per kilogram of body weight (example: 150 lb person x .8g = 120g protein daily).
Limited Studies. With the popularity of high-protein diets, more research is needed to understand the stress a high protein diet places on kidney function in healthy people. The few studies that do exist are very small or focus on athletes with high fitness levels. Also, these studies are short-term when we know that changes in organ function due to dietary habits occur over time.
Kidney Disease and Protein Intake
If you have risk factors for or have a known kidney problem, The Kidney Disease Outcomes Quality Initiative Nutrition Guidelines recommend a low-protein diet (0.6 g protein/kg weight) for people who are not using dialysis. For people with chronic kidney disease, low protein intake (0.3–0.6 g/kg weight) has been shown to reduce renal death and delay the onset of dialysis.
Although there isn’t definitive research, eating less animal protein may decrease the stress placed on the kidneys. Also, consuming less animal protein is associated with many other positive health outcomes. It makes sense that this would extend to the health and function of the kidneys. To determine the best ratio of protein for your health goals and relative to any risk factors you may have for kidney disease, consult with a holistic physician.