Protein intake and risk of renal cell cancer.

BACKGROUND

Renal cell cancer, although still relatively uncommon, has been increasing in incidence in the United States and other countries around the world.

PURPOSE

Since previous studies have suggested an association with high intake of meat, we sought to further examine the role of diet in renal cell cancer risk.

METHODS

Patients with histologically confirmed renal cell cancer that had been diagnosed between July 1, 1988, and December 31, 1990, were identified through the Minnesota Cancer Surveillance System, a statewide cancer registry. The patients eligible for inclusion in this study were white residents of Minnesota between 20 and 79 years of age. Control subjects were selected from the general population of Minnesota residents; subjects under age 65 were selected by use of a random-digit-dialing method and those 65 years or older were sampled from the Health Care Financing Administration files. Population-based control subjects were frequency-matched to cases by sex and 5-year age groups. A total of 690 patients and 707 control subjects were interviewed. Patients and control subjects were similar in distribution by sex, age, and educational level. Usual adult dietary intakes were assessed by questionnaire, and odds ratios were calculated by logistic regression analyses.

RESULTS

Significantly increased risks of renal cell cancer were observed with increasing consumption of several food groups, including red meat (P for trend = .05), high-protein foods (P = .01), and staple (grains, breads, and potatoes) foods (P = .009). When examined by macronutrient status, risks increased monotonically with the amount of protein intake, from 1.2 (95% confidence interval [CI] = 0.7-1.9) to 1.4 (95% CI = 0.8-2.5) and 1.9 (95% CI = 1.0-3.6) (P for trend = .03) in the second, third, and fourth quartiles of intake, respectively, after adjustment for age, sex, caloric intake, body mass index, and cigarette smoking. No significant or consistent associations were detected with the intake of other dietary nutrients or beverages.

CONCLUSION

Although an independent effect of dietary protein has not been previously associated with renal cell cancer, high protein consumption has been related to development of other chronic renal conditions that may predispose an individual to this cancer.

IMPLICATION

These findings should prompt further study of dietary protein and its potential contribution to the origins of renal cell cancer.