Diet and supplements: What's good and bad for kidney disease patients

Two studies presented during the American Society of Nephrology's Annual Kidney Week provide new information on dietary benefits and dangers in kidney disease patients.

Lilach Shema, PhD (Western Galilee Medical Center in Israel) and colleagues investigated the long-term effects of drinking pomegranate juice on heart disease risk factors -- such as high cholesterol and blood pressure -- in kidney disease patients. Pomegranate juice is rich in antioxidants and has been touted as having a variety of health benefits.

The researchers randomized 101 dialysis patients to receive about three-and-a-half ounces of pomegranate juice or placebo, three times a week. After one year, the number of blood pressure drugs patients took decreased in 22% of patients drinking pomegranate juice compared to 7.7% in the placebo group, while an increase was documented in 12.2% of patients drinking pomegranate juice compared to 34.6% in the placebo group. Patients who drank pomegranate juice also had healthier blood pressure and cholesterol levels and less plaque build-up in their arteries. These results suggest that drinking pomegranate juice might decrease the high rates of illness and death among kidney disease patients.

Another team led by Vanessa Grubbs, MD (University of California, San Francisco) looked at the use of dietary supplements among patients with chronic kidney disease (CKD). The National Kidney Foundation identifies 39 herbs that may be harmful to CKD patients, but no one knows how many of these patients take them.

Using data from the 1999 to 2008 annual National Health and Nutrition Examination Survey (NHANES), a program of studies designed to assess the health and nutritional status of adults and children in the United State, the investigators examined the reported use of dietary supplements in the past 30 days among 21,169 adults. While an estimated 52.4% of participants reported taking any dietary supplement, the supplement was potentially harmful among 15.3%. Use of supplements was not statistically different by CKD severity.

Because many CKD patients use potentially harmful supplements, they may be unaware of their risks. "Although people tend to think of dietary supplements as healthy, many contain ingredients that can actually be harmful to the kidneys," said Dr. Grubbs. Healthcare providers, too, may be unaware that some supplements are potentially harmful and that patients with CKD are taking them. Further research and education are warranted.