Protein Supplements and Proteinuria
Protein supplements do not appear to cause proteinuria in individuals with normal kidney function, but should be avoided in those with existing kidney disease.
Effects of Protein Supplements on Kidney Function
Normal Kidney Function
- Protein supplements do not appear to affect renal function in healthy individuals with normal kidney function 1
- A study of elite athletes found no significant differences in urinary protein levels between those who consumed protein supplements and those who did not 1
- There is no significant evidence for detrimental effects of high protein intakes on kidney function in healthy persons who have historically consumed high-protein Western diets 2
Existing Kidney Disease
- For people with chronic kidney disease (CKD), dietary protein intake should be limited to 0.8 g/kg body weight per day (the recommended daily allowance) 3
- Higher levels of dietary protein intake (>20% of daily calories from protein or >1.3 g/kg/day) have been associated with increased albuminuria, more rapid kidney function loss, and cardiovascular disease mortality in those with CKD 3
- Protein supplements should be avoided in patients with CKD due to potential risks and insufficient safety data 4
Mechanisms of Protein-Related Kidney Effects
- High dietary protein intake may promote hyperfiltration in the kidneys, which is a potential mechanism for renal damage in susceptible individuals 2, 5
- In animal studies, amino acid and keto acid supplements added to low-protein diets resulted in an increase of preexisting proteinuria in rats with reduced kidney function 5
- Protein degradation products from high dietary protein intake may contribute to kidney function decline, particularly in those with existing kidney disease 3
Special Populations and Considerations
Diabetic Kidney Disease
- For patients with diabetic kidney disease, a slightly higher protein range of 0.6-0.8 g/kg/day is recommended compared to non-diabetic CKD patients 3
- Despite this slightly higher target, patients with diabetes may experience greater hyperfiltration following protein consumption 3
- Medical nutrition therapy that favorably affects cardiovascular risk factors may also have a favorable effect on microvascular complications such as nephropathy 3
Children with CKD
- Protein supplements may be considered for children with CKD stages 2-5 and 5D who are unable to meet their protein requirements through food and fluids alone 3
- At least 50% of dietary protein intake should be of high biological value to protect body protein and minimize urea generation in children with CKD 3
Monitoring and Management
- Regular monitoring of kidney function is essential when introducing any new dietary supplement, especially in those with risk factors for kidney disease 4
- For individuals with CKD, monitoring should include albuminuria and estimated glomerular filtration rate (eGFR) to enable timely diagnosis of CKD progression 3
- CKD patients should seek medical or pharmacist advice before using over-the-counter medicines or nutritional supplements 4
Conclusion
For healthy individuals without kidney disease, protein supplements appear to be safe and do not cause proteinuria 1, 6. However, for those with existing kidney disease or risk factors for CKD, protein intake should be carefully monitored and limited according to clinical guidelines, and protein supplements should generally be avoided 3, 4.