PROTEIN AND KIDNEYS: DOES IT AFFECT KIDNEY FUNCTION?

By Flora Giatra, Biochemist

Modern scientific data in health and nutrition show that nutritional plans rich in nutrients and with sufficient amounts of protein seem to be the most effective in losing fat while maintaining muscle mass and metabolism.

The emphasis on protein is recommended not only for people who want to reduce their weight, but also for athletes, women in menopause, the elderly, people with limited time, and many other groups of people. In fact, many times when the needs are not met nutritionally, protein supplements are also recommended.

At this point, reasonable questions arise that mainly concern the safety of the protein and whether it affects kidney function.

WHAT IS KIDNEY FUNCTION AND HOW IS IT RELATED TO PROTEIN?

The kidneys are organs that filter waste compounds, excess nutrients, and fluids from the bloodstream by producing urine. One of their main functions is to clear protein metabolites from our body.

Chronic Kidney Disease (CKD) is a condition characterized by permanent kidney damage, with or without a decline in kidney function.

Risk factors for its appearance are:

• Hypertension
• Diabetes
• Dyslipidemia (increased cholesterol and triglycerides)
• Obesity
• Cardiovascular diseases
• Smoking

HOW MUCH PROTEIN DO I NEED?

Depending on our state of health, lifestyle, age, and physical activity, our protein needs differ.

People suffering from Chronic Kidney Disease or Acute Kidney Failure need a lower amount of protein, but this does not mean that they should completely limit their protein intake, as such an approach can lead to sugar imbalances and malnutrition.

• O.8-1 g. of protein/kg of body weight for healthy adults
• 1.2-1.4 g. of protein/kg of body weight in endurance sports
• 1.4-2 g. of protein/kg of body weight in speed sports

Chronic Kidney Disease and protein needs:

• Stages 1-2: 0.8-1.4 g. of protein/kg of body weight
• Stages 3-4: 0.6-0.8 g. of protein/kg of body weight

Acute Kidney Failure and protein needs:

• 0.8-1.2 g. of protein/kg of body weight
• 1.2-1.5 g. of protein/kg of body weight (for cleansing)

WHAT HAVE SCIENTIFIC STUDIES SHOWN?

A diet that is too high in protein (more than the daily requirement) can put the kidneys into overdrive to filter the blood. Over time, this increased workload could damage the kidneys or worsen kidney disease.

However, it is important to mention that while protein restriction may be appropriate for the treatment of existing kidney disease, no significant evidence has been found for the deleterious effect of high protein intake on kidney function in healthy individuals.

According to the American Kidney Fund, a study involving more than 1,600 adults over 6 years showed a protective role of plant-based proteins in a kidney-friendly meal plan. This means that plant-based proteins offer more protection for the kidneys than whey proteins. The reason is the sodium and saturated fat that red and processed meat contain, which are strongly associated with kidney disease risk.

Furthermore, it is important to clarify that the risk for kidney stones is not attributed to protein supplements alone, but to an overall over-intake of protein from various dietary sources.

Therefore, we conclude that in the healthy population protein intake from dietary sources or from high-quality plant-based supplements, in the context of a balanced diet, does not threaten kidney health. It is important to focus on the risk factors for kidney dysfunctions, to lead an active lifestyle, and to eat according to the standards of the Mediterranean Diet, maintaining a healthy body weight.

SOURCES

António, J., Ellerbroek, A., Silver, T., Vargas, L., Tamayo, A., Buehn, R., & Peacock, C. A. (2016). A high protein diet has no harmful effects: A One-Year crossover study in Resistance-Trained males. Journal of Nutrition and Metabolism, 2016, 1–5. https://doi.org/10.1155/2016/9104792

Gannon, M. C., & Nuttall, F. Q. (2004). Effect of a High-Protein, Low-Carbohydrate diet on blood glucose control in people with type 2 diabetes. Diabetes, 53(9), 2375–2382. https://doi.org/10.2337/diabetes.53.9.2375

Key benefits of plant proteins in your kidney-friendly food plan. (2023, November 10). American Kidney Fund. https://www.kidneyfund.org/article/key-benefits-plant-proteins-your-kidney-friendly-food-plan

Knight, E. L., Stampfer, M. J., Hankinson, S. E., Spiegelman, D., & Curhan, G. C. (2003). The Impact of Protein Intake on Renal Function Decline in Women with Normal Renal Function or Mild Renal Insufficiency. Annals of Internal Medicine, 138(6), 460. https://doi.org/10.7326/0003-4819-138-6-200303180-00009

Levey, A. S., Adler, S. G., Caggiula, A. W., England, B. K., Greene, T., Hunsicker, L. G., Kusek, J. W., Rogers, N. L., & Teschan, P. E. (1996). Effects of dietary protein restriction on the progression of advanced renal disease in the modification of diet in renal disease study. American Journal of Kidney Diseases, 27(5), 652–663. https://doi.org/10.1016/s0272-6386(96)90099-2