Plant-Rich Diets Boost Kidney and Heart Health by Lowering the Body’s Acidity
Four extra servings (roughly 2 cups) per day of fruits and vegetables may slow chronic kidney disease and significantly improve blood pressure and other risk factors for heart attack and stroke, a new study found.
The findings from the new five-year study highlight the need to prioritize changes in diet that focus on fruits and vegetables to manage high blood pressure, a risk factor for kidney and heart disease. Often, doctors don’t automatically recommend changes in diet to people with high blood pressure unless medications fail, according to the authors.
But these findings show that the script should be flipped, says the lead investigator, Donald E. Wesson, MD, a professor of internal medicine at the Dell Medical School of the University of Texas in Austin.
“Fruits and vegetables should be foundational in the management of hypertension, with medications added as needed. In our study, participants given fruits and vegetables had lower blood pressure, better kidney health, and better heart health while taking lower doses of blood pressure medications than those participants not given fruits and vegetables,” says Dr. Wesson.
Why Can Acidity Harm the Body?
The study aimed to find out if making participants’ bodies less acidic improved markers of kidney disease.
The process of digesting animal products like meat makes the body more acidic, Wesson explains, while the process of digesting most fruits and vegetables makes the body more basic (alkaline). Things that are basic neutralize acidity.
To keep the body in balance, the kidneys must remove excess acid from the blood and expel it from the body in urine.
The study was designed to see if more plants and fewer animal products in the diet would “lighten the load” for the kidneys, and thereby improve kidney health and overall health.
How Did the Trial Work?
Subjects in the trial had high blood pressure (but not diabetes) and very high levels of macroalbuminuria, a marker of severe chronic kidney disease.
Researchers randomly divided participants into one of three groups:
- Those instructed to add 2 to 4 cups of fruits and vegetables to their regular diet.
- Those prescribed twice-daily sodium bicarbonate, also known as baking soda, as an antacid to neutralize acidity.
- People who received standard medical care from primary care doctors.
Participants filled out food diaries before, during, and at the end of the study. Those in the fruit and vegetable group reported eating about 2 extra cups per day.
Both the fruit and vegetable group and the sodium bicarbonate group had better kidney health at the end of the study, which researchers attributed to reduced acidity. But the fruit and vegetable eaters also had improvements in risk factors related to heart health: They lowered their cholesterol, saw their average BMI (body mass index) drop from 28.2 to 27 (for the average American, that would translate to a weight loss of about 6 pounds), and reduced their blood pressure while taking less medication than the other groups.
These Simple Dietary Changes Can Be Sustained for Years
The study findings provide further support for a standard recommendation given to people with kidney disease, which is to eat more plant foods, says Christopher Gardner, PhD, a professor of medicine and the director of nutrition studies at the Stanford Prevention Research Center at Stanford University in Palo Alto, California.
It makes sense that lowering acid by consuming either plant foods or sodium bicarbonate would benefit kidney health, Dr. Gardner says. He suggests that subjects who ate more produce probably also benefited their heart health because they were getting more fiber and less saturated fat.
Although a healthier diet isn’t a new strategy for treating heart or kidney disease, this study provides new evidence that people can make changes and stick to them, says Gardner, who was not involved in the research.
“What is really impressive about this study is that the follow-up was for five years, and not simply five weeks or five months. These were long-term dietary changes that were made and maintained, with long-term health benefits,” he says.
Gardner adds that nutrition is a topic that gets very little attention in medical school, and many physicians feel inadequately prepared to counsel patients on lifestyle behavior changes like nutrition.
“However, this is not a complicated strategy — eat more plants — and hopefully study findings like these will encourage more physicians to take advantage of this strategy and combine it with the other tools they use to treat and prevent disease,” he says.
A Healthy Diet Starts When Certain Foods Are Added — Not Eliminated
“My dietitian colleagues have taught me over the years that it is best to make recommendations on what to eat, rather than what not to eat, and I think this is the approach we should take,” says Wesson.
Case in point: For this study, people were told to add 2 to 4 cups of fruits and vegetables without any recommendations on foods to cut out or reduce.
“Our dietary surveys done before and after the study showed that they substituted the provided fruits and vegetables for the most expensive elements of their previous diets, which were often processed meats. This taught us that when we focus on telling patients what we want them to eat, they will typically substitute these foods for the foods that we do not want them to eat,” he says.
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