Abstract B45: A preliminary study of cruciferous vegetable consumption and urinary isothiocyanate levels in African Americans and Caucasians in the eastern United States.

Cruciferous vegetable consumption is associated with decreased cancer risk for bladder, breast, cervical, colorectal, liver, lung and prostate cancer. Unique to cruciferous vegetables are glucosinolates, phytochemicals that upon contact with myrosinase are converted to isothiocyanates (ITCs). ITCs have been shown to prevent cancer by inducing apoptosis, inhibiting cell cycle progression and histone deacytelase while inducing histone hyperacetylation, and both inhibiting and inducing phase I biotransformation enzymes. Numerous cohort studies examine the association between cruciferous vegetable consumption as reported in food frequency questionnaires and cancer risk, while the Shangai and the Multi-Ethnic Cohort studies examined the association between urinary ITC levels and cancer risk. To validate the use of food frequency questionnaires as measures of cruciferous vegetable consumption in an eastern US population, we examined the correlation between self-reported cruciferous vegetable intake and urinary ITC levels in African American and Caucasian smokers from New York and Wilmington, DE. ITCs can be measured in the urine samples after cyclocondensation with 1,2-benzenedithiole to form 1,3-benzodithiole-2-thione (1,3-BDT). We developed a streamlined method for urinary ITC detection with a limit of detection of 0.1 μM, a limit of quantitation of 0.2 μM, and precision of 1.29 (%RSD) for standards and 1.99 for samples. Standard curves for 1,3-BDT detection is linear in the range of 0.2-200 μM with r2>0.99. The assay has less than 15% variation between trials. In samples of 119 smokers in NY, our findings indicate that African Americans consume on average of twice as much total cruciferous vegetables as Caucasians. In another sample of 91 mostly smokers, we observed detectable levels of ITC in the urine of 33% of the participants compared to 20% detection rate for the NY study. There was no statistical difference in urinary ITC levels between African Americans and Caucasians in either study. The Wilmington study did show a slight difference, with higher frequency of detection in African Americans as compared to Caucasians. Neither study show a correlation between cruciferous vegetable consumption as reported by food frequency questionnaires and urinary ITC levels. In addition, the Wilmington study did not show a correlation between urinary ITC levels and 24 hour recall of cruciferous vegetable consumption. A larger sample size may give more accurate data, but based on these preliminary findings, food frequency questionnaires may not be the best measure of exposure to cruciferous vegetables in the eastern US. Urinary ITC measures have been used to study cancer risk in mostly Asian populations. In an American population, these foods appear to be consumed too infrequently to provide reliable measures of intake. The short half-life of ITCs may also limit its validity as a biomarker in American populations. Citation Format: Anna K. Hull, Odinaka Anyanwu, Nikoia Fredericksen, Titilope Idowu, Ambata Poe, Joshua E. Muscat, John P. Richie, Derrick J. Swinton. A preliminary study of cruciferous vegetable consumption and urinary isothiocyanate levels in African Americans and Caucasians in the eastern United States. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr B45.