NOVEMBER 2009

Adiet designed to fight high blood pressure may also help prevent painful kidney stones, according to an analysis of three large studies totaling more than 240,000 men and women. People whose diets most closely matched the Dietary Approaches to Stop Hypertension (DASH) eating plan were 40% to 45% less likely to develop kidney stones than those whose diets were most at odds with DASH. The benefit was seen even after excluding hypertension patients and regardless of intake of calcium (involved in the formation of calcium oxalate kidney stones, the most common type).

Eric Taylor, MD, of Brigham and Women’s Hospital and colleagues analyzed data on 45,821 men in the Health Professionals Follow-up Study, 94,108 older women in the Nurses’ Health Study I and 101,837 younger women in the Nurses’ Health Study II. The studies followed participants for 14-18 years. Overall, researchers documented 5,645 cases of symptomatic kidney stones.

Participants were assigned a DASH score calculated from eight dietary components:
• High intake of fruits, vegetables, nuts and legumes, low-fat dairy products and whole grains
• Low intake of sodium, sweetened beverages, and red and processed meats.

(For an in-depth look at the DASH plan and how it compares to other dietary guidelines, see our October 2009 Special Report.)

Comparing the highest one-fifth in matching the DASH plan to the lowest onefifth, Dr. Taylor and colleagues found that men with the highest DASH score had a 45% lower risk of developing kidney stones. Older women in the top DASH group were at 42% lower risk, and young women, 40%.

The findings may also overturn some common dietary advice for preventing kidney stones. Dr. Taylor noted, “Although we think it reasonable for calcium oxalate stone formers with high levels of urinary oxalate to avoid intake of some individual foods very high in oxalate (such as spinach and almonds), our data do not support the common practice of dietary oxalate restriction in calcium stone formers, particularly if such advice results in lower intake of fruits, vegetables and whole grains.” The DASH plan, after all, emphasizes consumption of those very dietary components.

The researchers pointed out that eating fruits and vegetables—despite their oxalate content—also increases urinary citrate production, which inhibits the formation of calcium- containing kidney stones. Previous research has also associated reduced risk of stone formation with diets low in animal protein and sodium, and higher risk with high fat intake and low dietary calcium.

The findings, Dr. Taylor and colleagues concluded, make a case for further research in the form of a randomized clinical trial or dietary intervention.

TO LEARN MORE: Journal of the American Society of Nephrology, online ahead of print; abstract at dx.doi.org/10.1681/ASN.2009030276. Healthy Eating with DASH www.nhlbi.nih.gov/hbp/ prevent/h_eating/h_eating.htm.