Greater consumption of the flavonoid quercetin may reduce the risk of renal cell cancer among male smokers, according to data obtained from a study of men in southwestern Finland. Increased intake of Baltic herring, however, was associated with an increased risk.

Compared with participants whose intake of quercetin was 4.8 mg/day or less, those who consumed more than 9.1 mg/day had a 40% reduced risk of renal cell cancer after adjusting for numerous potential confounders, according to a report in the American Journal of Epidemiology (2009; published online ahead of print).

Other flavonoids examined in the study showed no association with renal cell cancer risk. In addition, compared with men who ate 2.1 g/day or less of Baltic herring, those who ate more than 12.2 g/day had a twofold increased risk of renal cell cancer. These risks appeared to be higher among individuals with both high fish intake and high BMI.

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The study, which was conducted by Robin Taylor Wilson, PhD, of Pennsylvania State University College of Medicine in Hershey, included 27,111 male smokers who participated in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study and had dietary information available. Subjects had a mean and median follow-up of 15.2 years, during which 228 renal cell cancer cases were diagnosed.

The original objective of the study was to determine the efficacy of alpha-tocopherol, beta-carotene, or both in preventing lung cancer.

As to how higher intake of Baltic herring might increase the risk of renal cell cancer, the authors noted that fish consumption is positively correlated with blood levels of polychlorinated biphenyls, dioxin, cadmium, lead, and mercury. Cadmium, lead, and mercury are nephrotoxic.

They induce oxidative stress and damage to the proximal renal tubule, which is where nearly all renal cancer cancers arise, the researchers observed.

The investigators found no association between renal cell cancer and total fish consumption or consumption of fresh, frozen, or canned or salted fish, although there was some suggestion of elevated risk associated with greater fish intake among individuals living in the urban Baltic coast region. Further biomarker follow-up studies are needed, the authors noted.