More plant-based protein may slow kidney function decline in women older than 70 years
Older white women who consumed higher quantities of plant-based proteins had a slower yearly decline in eGFR, according to a study conducted in Australia.
These results are similar to an Iranian study that Healio Nephrology recently reported on, which showed substituting red meat with plant-based proteins significantly reduced the risk for developing chronic kidney disease (that study, however, also found an association between meat consumption and incident CKD, whereas this one did not reveal an association between animal protein and eGFR decline).
“Population studies of individuals without risk factors for renal impairment have identified a progressive reduction in renal function with age, and older women developing CKD face an increased burden of comorbidities,” primary investigator Amélie Bernier-Jean, MD, of the Centre for Kidney Research, Children’s Hospital at Westmead, and the University of Sydney in Australia, and colleagues wrote. “Thus, population-based interventions aimed at reducing the loss of kidney function in this population are attractive.”
Noting that protein restriction may play an important role in slowing kidney function decline — with the current Kidney Disease: Improving Global Outcomes guidelines recommending against protein intake of more than 1.3 g/kg/day for patients with CKD — the researchers contended that “evidence suggests that the origin of protein may be an influential factor for kidney function.”
According to Bernier-Jean and colleagues, this could be due to the fact that while plant-based proteins reduce acidosis, animal proteins contribute to the acid-load which may cause hyperfiltration and proteinuria.
“The evidence for this effect in the general population is mostly theoretical and observational studies are often limited to a baseline assessment of diet even though diet and kidney function are dynamic processes that are better evaluated longitudinally across repeated measurements,” they added.
To elucidate on the effect of plant-based protein compared with animal-based protein on renal function, the researchers administered a food frequency questionnaire to 1,374 white women who had a mean age of 75 years and a mean eGFR of 65.6 mL/min/1.73m2 at baseline (33% with CKD stage 3 or higher).
The questionnaire, which measured participants’ usual eating and drinking habits during the previous 12 months, was completed at baseline and again at 5 and 10 years (eGFR was also measured at these times).
The mean total protein intake throughout the study was 75.2 g/day (1.15 g/kg of weight/day), with the researchers noting that at baseline, 18% of participants consumed less than the 57 g of protein/day recommended for women aged 70 years or older with a normal kidney function (34% had a high protein intake at baseline).
For all three assessments, the mean animal protein intake was 51.4 g/day (0.75 g/kg/day) and the mean plant protein intake was 28.9 g/day (0.40 g/kg/day).
Observing an average decline in eGFR of 0.64 mL/min/1.73 m2 per year, the researchers found higher intakes of plant-sourced protein were associated with slower declines in eGFR. Specifically, each 10 g of plant protein led to a reduction of 0.12 mL/min/1.73m2 in yearly eGFR decline. This reduction in eGFR decline was primarily associated with fruit-, vegetable- and nut-derived proteins.
According to the researchers, these results demonstrate a beneficial association between plant-based protein and eGFR.
“A patient-centered approach to dietary advice with a focus on the promotion of plant sources of dietary protein rather than restriction may be considered,” they wrote. “Importantly, from a public health point of view, encouraging high intake of fruits, vegetables and nuts may prevent or slow renal deterioration in older women in addition to their benefit on other organ systems.”