This was the first ever study to analyse the effect of this dietary approach on delaying time to transplantation in patients scheduled for living-donor kidney transplantation, and the findings, although limited in their scope, were promising.
“Within the limits of a small number of cases, our study suggests that a supplemented low protein diet treatment can significantly delay the timing of pre-emptive kidney transplantation, by a median of 125 days,” wrote the researchers from the Kidney Research Centre at Chang Gung Memorial Hospital, Taiwan, in the journal Nutrients.
Significantly, the study also suggested that most severe post-transplant events such as mortality, cardiovascular disease and transplant failure requiring dialysis - were not increased in patients who had been on a supplemented diet prior to the transplant.
Protein and kidney disease
Protein restriction is a well known treatment option for advanced chronic kidney disease. This is because uremia (the condition of having high levels of urea in the blood as a result of kidney damage) is a state of protein intoxication. In addition, protein plays a major role in the functional changes that accompany advanced kidney disease.
In the 1970s, researchers first reported that a very low protein diet supplemented with keto-analogues of essential amino acids can safely delay the progression of chronic kidney disease. The advantage of keto acids is that they reduce nitrogenous waste products such as urea.
Since then, a number of studies have demonstrated the benefit of a supplemented low protein diet (sLPD) in slowing the progression of chronic kidney disease and in delaying the need to start dialysis. However, the question of whether it could also delay the need for kidney transplantation has not been explored.
Delaying the need for kidney transplantation is beneficial for several reasons: firstly because the lifespan of an organ transplant is limited, secondly because it delays exposure to immunodepressive drugs, which have associated risks and side effects, and thirdly because immunosuppressive treatments are improving all the time, so delaying a transplant may mean having access to better drugs.
Therefore, this study set out to investigate the effect of sLPDs in delaying the need for pre-emptive kidney transplantation and to evaluate whether such diets could have a detrimental long-term influence after transplantation.
In 1995, Taiwan launched the National Health Insurance (NHI) nationwide compulsory healthcare progamme, covering 99.8% of Taiwan’s population. Data collated from this population-wide scheme was used as the basis for this retrospective cohort study.
A total of 245 patients who received their first kidney transplantation between 2001 and 2017 were identified from the database. Of these, 62 had been on an sLPD whereas 182 had not.
Patients on the sLPD were significantly older than those without (47.5 vs 42.5 years mean age).
The main outcome the researchers analysed was the duration between the onset of advanced chronic kidney disease diagnosis and kidney transplantation. Secondary outcomes were adverse events after transplantation.
Low protein diet delayed transplant
The researchers found that there was a significantly longer time period between advanced chronic kidney disease diagnosis and kidney transplantation in the sLPD group - 345 days versus 220 in the non LPD group.
With regard to the secondary outcomes, no significant difference between the groups was found in terms of all-cause mortality, cardiac/cerebrovascular events, infection-related hospitalisation or death, newly diagnosed malignancy, new-onset diabetes mellitus, osteoporosis-related fracture or allograft failure requiring dialysis.
“The risk of post-transplantation adverse events did not differ between the two groups,” wrote the researchers.
Another point of interest, according to the researchers, was the age of the patients. On average it was 43.8 years – much lower than the average age of patients starting chronic dialysis.
“The study supports the interest of offering a supplemented LPD to young chronic kidney disease patients,” wrote the researchers.
They acknowledged that there were several limitations with the study design: the prevalence of preemptive kidney transplantation is lower in Taiwan than the global average, making for a small data pool; the results may not apply to other populations because of dietary and genetic differences; laboratory data were not available in the database; and it was not clear whether delaying access to transplantation would result in longer life expectancy or better quality of life.
Nevertheless, the study suggests that sLPDs have the potential to delay the timing of preemptive kidney transplantation, without increasing the risk of post-transplantation adverse events.
Yen. C-L., Fan. P-C., Kuo. G., Chen. C-Y., Cheng. Y-L., Hsu. H-H., Tian. Y-C., Chatrenet. A., Piccoli. G.B. and Chang. C-H
“Supplemented low-protein diet may delay the need for preemptive kidney transplantation: a nationwide population-based cohort study”