The DASH diet was designed to help people reduce their blood pressure. People who eat nuts and legumes, low-fat dairy, fruits, vegetables and whole grains also tend to have an easier time losing abdominal fat than those who indulge in red and processed meat, sugar-sweetened beverages and sodium.
But new research conducted at Johns Hopkins Bloomberg School of Public Health suggests that the DASH diet — short for DASH for Dietary Approaches to Stop Hypertension — is also effective in preventing a series of other chronic illnesses, including cardiovascular disease. In fact, the findings, published in the American Journal of Kidney Diseases, show that people who follow a DASH diet significantly lower their risk of developing chronic kidney disease.
"The great thing about this finding is that we aren't talking about a fad diet. This is something that many physicians already recommend to help prevent chronic disease," says study leader Casey M. Rebholz, PhD, MPH, MS, an assistant professor in the Department of Epidemiology at the Bloomberg School.
Researchers estimate kidney disease affects 10% of the U.S. population — more than 20 million people. Fewer than one in five people who have it, however, are aware that they do.
The researchers began their work by examining records from the Atherosclerosis Risk in Communities (ARIC) study, which in 1987 began following a group of 15,792 middle-age adults from communities in Md., N.C., Minn. and Miss. for more than 20 years. At two early visits, participants filled out a 66-item food frequency questionnaire, which asked how often, on average, the participants consumed each food item in what portion size over the previous year.
The participants were not told what to eat. Instead, their adherence to a DASH-style diet was later categorized into a score based on low intake of red and processed meat, sweetened beverages and sodium; and high intake of fruits, vegetables, whole grains, nuts and legumes and low-fat dairy. The researchers then placed participants into categories based on their consumption of these food items. The DASH diet wasn't described and studied until the 1990s, while participants were enrolled in the ARIC study in the 1980s.
Meanwhile, over time, researchers determined whether a participant developed kidney disease by determining kidney function via blood tests of glomerular filtration rate, learning about a kidney disease–related hospitalization or death or finding out about end-stage kidney disease resulting in dialysis or transplant.
The researchers found that participants with the lowest DASH diet scores (those who ate few foods such as fruits, vegetables and nuts, and consumed more red meat and sodium) were 16% more likely to develop kidney disease than those with the highest DASH scores (those who ate more of the healthier foods and less of the unhealthy items).
Those who had the highest intake of red and processed meats were at a 22% higher risk of developing chronic kidney disease than those with the lowest intake of those foods. Those with the highest intake of nuts and legumes were at 9% lower risk of developing kidney disease than those with the lowest intake.
Rebholz says the reason that DASH-style diets appear to stave off kidney disease may be because hypertension has been linked to kidney disease — and since it was designed to lower blood pressure, then it follows it would help prevent kidney disease. She says that another possibility could be related to the "dietary acid load" in the foods people eat, or the overall acidity of the foods in a diet. High acid foods include meats and cheeses; low acid foods include fruits and vegetables. Several independent researchers have shown that high dietary acid may be linked to kidney disease.
The researchers also found that normal weight participants who followed a DASH diet were less likely to develop kidney disease than overweight or obese participants. "What this tells us is that we need to pay attention to diet before diseases develop. That is the right time to intervene," Rebholz says. "After disease develops, we may not be able to prevent the development of other chronic diseases. It may be too late."