Researchers: Fruits and vegetables lower blood pressure and protect kidneys

Despite advances in treating hypertension and its complications, chronic kidney disease associated with hypertension and its mortality related to heart disease are increasing. Heart disease is the leading cause of death in patients with chronic kidney disease. The results of a five-year follow-up study of patients with hypertension provide further evidence of the benefits of eating fruits and vegetables. Diets rich in fruits and vegetables have previously been shown to lower blood pressure, reduce the risk of cardiovascular disease, and improve kidney health through their alkalizing effects.

The DASH (Dietary Approaches to Stop Hypertension) diet, rich in fruits and vegetables, lowers blood pressure and is the recommended first-line treatment for essential hypertension. However, the diet is not prescribed often enough—and even when prescribed, patients do not always follow it. The DASH diet and other diets, generally rich in fruits and vegetables, are associated with lower blood pressure, lower risk and slower progression of chronic kidney disease, lower risk rates of cardiovascular disease, and lower cardiovascular mortality. “As a nephrologist (kidney specialist), I study in my lab the way the kidneys remove acids from the blood and excrete them in the urine. Our research has shown for years that the mechanisms used by the kidneys to remove acids from the blood can cause kidney damage if animals are chronically (long-term) exposed to an acidic diet. “Our studies in patients showed similar results: an acidifying diet (high in animal products, especially meat) was bad for the kidneys, whereas an alkaline diet (high in fruits and vegetables) was healthy for the kidneys. Other researchers have shown that a diet rich in fruits and vegetables is healthy for the heart. We hypothesized that one way that fruits and vegetables are healthy for both the kidneys and the heart is that they reduce the amount of acid in the diet and therefore the amount of acid that the kidneys have to remove from the body,” said lead author Donald E. Wesson, MD, of Dell Medical School, The University of Texas at Austin. To test this hypothesis, the study recruited people with high blood pressure but not diabetes who also had very high levels of albumin excretion in the urine (macroalbuminuria). Patients with macroalbuminuria have chronic kidney disease, a high risk of worsening kidney disease over time, and a high risk of developing cardiovascular disease later on. In a five-year study, researchers divided 153 hypertensive patients into three groups.

Participants in the first group, in addition to their regular diet, were given 2-4 cups of alkaline fruits and vegetables. The second group was given two daily doses of sodium bicarbonate (sodium bicarbonate, commonly known as baking soda) in two doses of 4-5 650-milligram tablets. The third group received standard medical care from their primary care physicians. As it turned out, both fruits and vegetables and sodium bicarbonate improved kidney health. Those given only fruits and vegetables (not sodium bicarbonate) had lower blood pressure and improved markers of cardiovascular disease risk. The results of the study were published in The American Journal of Medicine. Dr. Maninder Kahlon of Dell Medical School at the University of Texas at Austin, who also participated in the study, noted that fruits and vegetables “achieved these latter two benefits with lower doses of medications used to lower blood pressure and reduce cardiovascular disease risk.” This means you can get kidney health benefits from both fruits and vegetables and NaHCO3, but you lower blood pressure and reduce the risk of cardiovascular disease with fruits and vegetables, but not with NaHCO3.

“This supports our recommendation that fruits and vegetables should be a primary treatment for patients with hypertension, because we achieve all three goals (kidney health, lower blood pressure and reduced risk of cardiovascular disease) with fruits and vegetables, and we can do that with lower doses of medication,” Kahlon said. Many physicians start hypertension treatment with medication and then add dietary strategies if blood pressure is not adequately controlled. The research team emphasizes that the results support the opposite assumption: that treatment should start with fruits and vegetables and then medications can be added if needed. As Dr. Wesson concluded, “dietary interventions for the treatment of chronic diseases are often not recommended, and even less frequently performed, because of the many difficulties in getting patients to implement them. Nevertheless, they are effective, and in this case, they protect the kidneys and the cardiovascular system. We need to increase our efforts to include them in the treatment of patients and, more broadly, make healthy diets more accessible to populations at increased risk for kidney and cardiovascular disease.” The authors also advise patients with hypertension to ask their doctor to measure their urine albumin-to-creatinine ratio (UACR) to determine if they have kidney disease and an increased risk of later cardiovascular disease.