From the Guidelines
Increased protein intake enhances glomerular filtration through several interconnected mechanisms, primarily by stimulating the release of glucagon and growth hormone, which cause afferent arteriolar vasodilation, increasing renal plasma flow and intraglomerular pressure, and directly elevating the glomerular filtration rate (GFR) 1.
Mechanism of Action
The mechanism by which increased protein intake increases GFR involves:
- Increased renal plasma flow and intraglomerular pressure, directly elevating GFR
- Stimulation of glucagon and growth hormone release, causing afferent arteriolar vasodilation while maintaining efferent arteriolar tone
- Generation of nitrogenous waste products like urea, requiring elimination and triggering adaptive increases in filtration capacity
- Alteration of tubuloglomerular feedback mechanisms by amino acids from protein digestion, normally regulating GFR
Clinical Implications
These effects explain why high-protein diets consistently lead to hyperfiltration, a phenomenon that may be physiologically appropriate in the short term but potentially concerning in individuals with compromised kidney function, as chronic hyperfiltration might accelerate kidney damage in vulnerable populations 1.
Recommendations
For people with stages 3–5 non–dialysis-dependent CKD, dietary protein intake should be 0.8 g/kg body weight per day, as 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 CVD mortality, and should be avoided 1.
Key Considerations
- Restriction of dietary sodium (to <2,300 mg/day) may be useful to manage blood pressure and reduce cardiovascular risk
- Individualization of dietary potassium may be necessary to manage serum potassium concentrations
- Recommendations for dietary sodium and potassium intake should be individualized based on comorbid conditions, medication use, blood pressure, and laboratory data 1