Plant-Based Diets Help Reduce Kidney Disease Risk Long Term

A diet that favors plant-based foods, as well as a completely vegetarian diet, modestly reduces the long-term risk of chronic kidney disease (CKD) in the general population provided individuals are not overweight or obese to begin with, a new community-based cohort study indicates.

People who follow such a diet also have a slower annual rate of decline in kidney function, in terms of estimated glomerular filtration rate (eGFR), the work indicates.

"To the best of our knowledge, this is the first study to report associations between plant-based diets and prospective risk of eGFR decline and CKD in the general population," Hyunju Kim, PhD student, Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, and colleagues write.

"We found that a small but statistically significant percentage (4%) of CKD cases could have been avoided with higher adherence to plant-based diets," they note.

The study was published online April 25 in the Clinical Journal of the American Society of Nephrology.

Eat in Patterns

Asked by Medscape Medical News to comment on the findings, David Jacobs Jr, PhD, Mayo professor of public health, University of Minnesota, Minneapolis, observed that many of the diseases involving blood vessels and the heart have similar causes.

"What affects [the] heart and blood pressure, for example, is also likely to affect the kidney and its function," Jacobs said in an email.

Given that people tend to eat in patterns, preferring and consuming similar foods over long periods of their lives, "the associations of diet and vascular diseases also appear to be clearest when these joint features are considered," he added.

What the study by Kim and colleagues shows is that nutritionally rich plant foods eaten in typical patterns correlate with alterations in kidney function and competence over some 20 years of follow-up.

"The same types of foods have been shown to relate to other forms of cardiovascular disease," Jacobs noted.

"Thus, this study contributes to [our] confidence in guidelines such as the 2015-2020 Dietary Guidelines for Americans, which advocate eating nutritionally rich plant foods as a central part of a healthy lifestyle [and that] eating nutritionally poor processed plant foods is less advisable," he concluded.

First Look at Link Between Plant-Based Diets and Kidney Function

Kim and colleagues analyzed a sample of 14,686 middle-aged American adults who participated in the Atherosclerosis Risk in Communities (ARIC) study.

Participants were enrolled in the study between 1987 and 1989, and at both baseline and one of the study's follow-up visits, they were asked to answer a food frequency questionnaire.

"We constructed an overall plant-based diet index, a healthy plant-based diet index, a less healthy plant-based diet index, and a provegetarian diet index on the basis of responses on the food frequency questionnaire," the researchers note.

In general, a plant-based diet contains predominantly plant foods and a healthy plant-based diet excludes potatoes and refined grains — two food groups linked to high blood pressure and type 2 diabetes.

Investigators then scored the overall intake of plant-based foods and analyzed the effect that had on kidney health outcomes when adjusted for multiple confounding variables.

During a median follow-up of 24 years, 4343 incident CKD events occurred.

Depending on the variables included in the analysis, participants in the highest quintile consumption of a healthy, plant-based diet had a 14% lower risk of developing CKD compared with those who consumed the least healthy plant-based diet (P = .001).

Similarly, participants in the highest quintile of a provegetarian diet had a 10% lower risk of CKD compared with those in the lowest quintile (P = .03).

"In contrast, those in the highest quintile of [a] less healthy plant-based diet had an 11% higher risk of CKD (P = .04)," the study authors note.

A slower rate of annual eGFR decline was also documented for participants who reported consuming the highest levels of a plant-based diet compared with those who reported the lowest intake of a plant-based diet.

Annual eGFR Decline Based on Consumption of a Plant-Based Diet

	Decline in eGFR per year, mL/min/1.73 m²
Diet	Quintile 5	Quintile 1	P for trend
Overall plant-based diet	–1.54	–1.68	< .001
Healthy plant-based diet	–1.55	–1.62	.01

The way in which a healthy, plant-based diet may slow decline in kidney function and therefore lower the risk of CKD might be explained by two different mechanisms, say the study authors.

Firstly, participants who reported the highest intake of a healthy, plant-based diet would have had a lower dietary acid load, "which has been associated with a higher risk of CKD," Kim and colleagues note.

Secondly, the same individuals would have had a higher intake of fiber than those who consumed fewer plant-based foods, which might attenuate the risk of developing CKD by reducing risk factors for it, including high blood pressure and type 2 diabetes, the investigators propose.

The authors have reported no relevant financial relationships.

Clin J Am Soc Nephrol. Published online April 25, 2019. Full text

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