WFPBD and kidney function

Whole Food, Plant-Based Diet and Chronic Kidney Disease:

 

Although there has been a great deal published regarding the positive effects of a whole-food, plant-based (WFPB) diet on the prevention and reversal of cardiovascular disease and cancer, there is much less written about the effects of WFPB diet on chronic kidney disease (CKD). A recent publication in the journal Nutrients [2020 Jul;12(7):1931], “Plant-Dominant Low-Protein Diet for Conservative Management of Chronic Kidney Disease” is a comprehensive, multi-author, and multi-institutional review. Here is a summary.

As noted by the authors, CKD affects over 10% of the population with approximately 120,000 in the US developing end-stage renal disease going on to dialysis with all its limitations, or kidney transplantation. Morbidity and mortality are exceptionally high with CKD patients on dialysis and the overall 5-year survival rate is under 50%. This places a great stress on these patients and on our health care system.

The average American consumes 1.2-1.4 g/kg/day of protein, despite the recommended 0.8 mg/kg/day by the US National Academy of Medicine. Most of this protein is consumed from animal sources. The popular trend toward ketogenic diets exacerbates this as they are high in protein, specifically animal protein. There is growing evidence that these diets adversely affect kidney function and 4 studies of high dietary protein over a period ranging from 41 months to 14 years demonstrate decline in eGFR (a calculation based on lab tests which is used to determine kidney function). From these studies it is hypothesized that those with kidney disease or at risk of kidney disease, such as diabetics or patients with solitary kidneys, may be adversely affected by a high protein diet.

Conversely, a low protein diet (.6-.8 g/kg/day) has been shown to be protective for long-term kidney function in both animal and human studies of CKD. This has been the conventional recommendation as it has been demonstrated that a low protein diet will slow the development of CKD requiring dialysis in those susceptible. Based on this it is the standard recommendation that a high protein diet (greater than 1 g/kg/day) be avoided in these patients.
The authors summarize many studies demonstrating the protective effect of a WFPB diet on kidney function. Laboratory studies have shown histological damage in kidneys exposed to high animal protein diets including 60-70% increase in renal and glomerular volumes, 55% more fibrosis, and 30% more glomerulosclerosis. They report on a recent comprehensive review of the literature which concluded that daily red meat consumption over the years may increase CKD risk, while a plant-dominant diet may slow CKD progression. Other studies cited included the 3348 women in the Nurses’ Health Study which demonstrated that those in the highest quartile of meat consumption had a 72% higher risk of microalbuminuria, an early marker for renal and general vascular disease. Several other long-term studies demonstrated the adverse effects of a high animal protein diet and the protective effects of a plant-based diet, including one showing reduced mortality in CKD patients on diets with higher plant sources of protein.

The main cause of high protein induced CKD has been shown to be due to glomerular hyperfiltration induced by changes in arteriolar resistance leading to glomerular hypertension, like that seen in diabetes. Eating a plant-based diet reduces this hyperfiltration by several known mechanisms. Several additional mechanisms for slowing the development of CKD have also been discovered: the reduction of ammonia and uremic toxin production, decreased acid load, reduced phosphorus burden, decreased risk of constipation which can contribute to hyperkalemia, and the higher intake of anti-inflammatory and antioxidant compounds. We also know that short chain fatty acids produced by favorable gut bacteria in patients eating WFPB diet leads to decreased production of trimethylamine (TMA) and TMA-N-oxide (TMAO), two compounds that lead to atherosclerosis, renal fibrosis, and increased risk of cardiovascular disease.

Although the above is complicated and can be difficult to understand (sorry, kidney function is complicated!) it is presented to demonstrate that there is clear understanding of how high protein diets adversely affect kidney function and those eating a WFPB diet do consume a lower amount of protein. In addition, the protein that they ingest has a protective effect on kidney function.

 

Author: Henri P. Lanctin MD, FACS