Broccoli, cabbage and a variant gene

A class of nutrients, isothiocyanates, found only in cruciferous vegetables - broccoli, cauliflower, cabbage, watercress, bok choy, among others - was protective against lung cancer in the study of a sample of 18,244 males, 45-64 years old, in Shanghai, China. The study also showed a unique gene-diet interaction. Subjects genetically deficient in an enzyme (GSTM1) that quickly eliminates isothiocyanates (ITCs) from the body got the most benefit from cruciferous vegetables, presumably because ITCs stayed around longer to confer their protective effect.

Among all subjects, those with detectable levels of isothiocyanates in the urine had a 40% decrease risk of lung cancer. Among those lacking the metabolism enzyme, a 64% decrease was noted.

Precursors of ITCs, a class of naturally occurring chemicals, are released when cruciferous vegetables are chewed and the anticarcinogenic isothiocyanates are formed.

The study appearing in the journal Lancet (Vol. 355) was a collaboration by scientists at the National Institute of Environmental Health Sciences, Research Triangle Park, N.C.; University of Southern California, Los Angeles; American Health Foundation, Valhalla, N.Y.; and Shanghai Cancer Institute, China. The study was funded through grants by NIEHS and the National Cancer Institute, agencies of the National Institutes of Health.

Both blood and urine samples were collected from study participants. The urine test for total ITC levels was developed by the researchers specifically for epidemiological research. Stephanie London, NIEHS, a co-lead-author, said, "We are aware of no prior data linking a biologic marker of ITC intake to the risk of any cancer." The authors noted that the benefits of ITCs may vary between individuals and across populations based on genetic variation in metabolism.

Subjects in the study were followed up through annual contacts with all surviving cohort mem
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Contact: Tom Hawkins
hawkins@niehs.nih.gov
919-541-7860
NIH/National Institute of Environmental Health Sciences
17-Sep-2000