While a healthy-plant based diet is tied to a lower risk of kidney disease, people who fill their plates with starchy, sugary vegetarian fare may actually increase their risk of kidney damage, a new study suggests. Researchers examined data on eating habits and kidney function for 14,686 middle-aged adults, following half of them for at least 24 years. Overall, 4,343 participants developed chronic kidney disease.
People who most closely adhered to a diet of healthy plant-based foods were 14 percent less likely to develop kidney disease than individuals who rarely ate these foods, the study found.
At the same time, participants who consumed the greatest amount of unhealthy vegetarian foods were 11 percent more likely to develop kidney disease than people who ate the smallest amounts of these foods.
“Relatively higher intakes of healthful plant foods and relatively lower intakes of less healthful plant foods and animal foods are associated with favorable kidney outcomes,” said senior study author Casey Rebholz of the Johns Hopkins Bloomberg School of Public Health in Baltimore.
“We believe that healthful plant foods played an important role because higher consumption of healthful plant foods were associated with a lower risk of kidney disease and slower decline in kidney function when the consumption of less healthful plant foods and animal foods were held constant,” Rebholz said by email.
A healthy plant-based diet includes whole grain foods; fruits like apples, pears, and oranges; veggies like dark, leafy greens, sweet potatoes, and broccoli; nuts and natural peanut butter; and legumes like string beans and lentils.
Study participants who had the healthiest plant-based diets consumed an average of nine to ten servings a day of these foods. These individuals were more likely to be women, white, older, high school graduates, and physically active.
An unhealthy plant-based diet may limit meat but load up on potatoes. This type of diet might also include juice instead of whole fruit, sodas and sugary drinks, and lots of candy, cake and chocolate.
Participants who had the least healthy plant-based diets consumed an average of seven servings a day of these foods. They were more likely to be men, younger, sedentary, and drink more alcohol.
The association between plant-based diets and chronic kidney risk was especially pronounced for people with a normal weight at the start of the study, researchers report in the Clinical Journal of the American Society of Nephrology.
The study wasn’t a controlled experiment designed to prove that certain eating patterns directly contribute to kidney disease.
One limitation of the study is that researchers relied on participants to accurately recall what they ate and drank, which can lead to measurement errors, the study authors note. Researchers also may not have had a complete picture of long-term eating habits.
Still, it’s possible eating more fruits and vegetables may make it easier for the kidneys to rid the body of toxins, said Dr. Michal Melamed of Albert Einstein College of Medicine and Montefiore Medical Center in Bronx, New York. Fruits and vegetables have less acid, putting less demand on the kidneys than meats which have a lot of acid.
“It could also be that the people who eat more fruits and vegetables also do other things, such as exercise more, get more sleep, or in general have a healthier lifestyle and that is the reason why this association is seen,” Melamed, who wasn’t involved in the study, said by email. “In general, multiple studies have shown that eating a lot of processed meats and red meats is probably not good for people, not just for their kidney health but also for the heart.”