Greater consumption of fiber, fruits, and vegetables is associated with a decreased risk of developing kidney stones, according to a new study.
Mathew D. Sorensen, MD, of the University of Washington in Seattle, and colleagues analyzed data from 83,922 postmenopausal women who participated in the prospective Women’s Health Initiative Observational Study. The women had a mean age of 64 years, and 85% of them were Caucasian. Kidney stones developed in 2,937 women (3.5%) during a median follow-up of 8 years.
Among women with no history of kidney stones, multivariate analysis showed that those in the highest quintile of dietary fiber, fruit, and vegetable intake were 22%, 15%, and 22% less likely to report an incident stone event, respectively, compared with women in the lowest quintile, Dr. Sorensen’s group reported online ahead of print in The Journal of Urology. Women with a history of kidney stones prior to study participation did not demonstrate a significant relationship between fiber, fruit, and vegetable intake.
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The protective effects were independent of other known risk factors for kidney stones, including body mass index (BMI) and dietary intake of water, sodium, animal protein, and calcium, the investigators reported.
“Our findings suggest that there may be a fundamental difference between women who formed their first stone during this study and those who formed a recurrent stone during this study,” the authors wrote.
Only 3% of women with no history of stones had an occurrence compared with more than 15% of women with a history of stones, the researchers noted. Thus, women who have their first kidney stone sometime in their 60s might be phenotypically different from women with a history of stones earlier in life.
The study is not the first to show an association between a healthy diet and a reduced risk of kidney stones. For example, a team led by Eric N. Taylor, MD, of the Channing Laboratory in Boston, examined the effect of a DASH [Dietary Approaches to Stop Hypertension]-style diet on stone risk in three large prospective studies: the Health Professionals Follow-up Study (HPFS), which included 45,821 men aged 40 to 75 years and had 18 years of follow-up; the Nurses’ Health Study I (NHS I), which included 94,108 women aged 30-55 years at enrollment and had 18 years of follow-up; and the Nurses’ Health Study II (NHS II), which included 101,837 women aged 25-42 at enrollment and had 14 years of follow-up.
The investigators constructed a DASH score based on high intake of fruits, vegetables, nuts and legumes, low-fat dairy products, and whole grains, and low intake of sodium, sweetened beverages, and red and processed meats.
A total of 5,645 kidney stones occurred during a combined 50 years of follow-up. Subjects with higher DASH scores had higher intakes of calcium, potassium, magnesium, oxalate, and vitamin C and lower intakes of sodium.
Compared with HPFS subjects in the lowest quintile of DASH score, those in the highest quintile had a 45% reduced risk of kidney stones after adjusting for age, BMI, fluid intake, hypertension, diabetes and other potential confounders, according to a report in the Journal of the American Society of Nephrology (2009;20:2253-2259).
Among subjects in NHS I (older women) and NHS II (younger women), those in the highest quintile had a 42% and 40% reduced risk of kidney stones compared with those in the lowest quintile.
The DASH diet—which is encouraged by the National Heart, Lung, and Blood Institute—advises low sodium intake and consumption of fruits, vegetables, whole grains, low- and nonfat dairy products, fish, and poultry, and discourages consumption of red meat and sugar.
