BMI is associated with increased plasma and urine appearance of glucosinolate metabolites after consumption of cooked broccoli

Authors: Charron, Craig; Vinyard, Bryan; JEFFERY, ELIZABETH - University Of Illinois; ROSS, SHARON - National Cancer Institute (NCI, NIH); SEIFRIED, HAROLD - National Cancer Institute (NCI, NIH); Novotny, Janet

Submitted to: Frontiers in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2020
Publication Date: 9/24/2020
Citation: Charron, C.S., Vinyard, B.T., Jeffery, E., Ross, S., Seifried, H., Novotny, J.A. 2020. BMI is associated with increased plasma and urine appearance of glucosinolate metabolites after consumption of cooked broccoli. Frontiers in Nutrition. https://doi.org/10.3389/fnut.2020.575092.
DOI: https://doi.org/10.3389/fnut.2020.575092

Interpretive Summary: Many studies show that consumption of brassica vegetables such as broccoli decreases cancer risk. However, there are other studies that do not show a protective role of brassica vegetables. This discrepancy may arise from variation among individuals’ abilities to absorb the brassica metabolites that are thought to be protective. These metabolites arise from natural compounds in brassicas called glucosinolates in combination with the enzyme myrosinase. We reported previously that glucosinolate metabolite absorption after consuming cooked broccoli plus raw daikon radish (as a source of plant myrosinase) was decreased in subjects with BMI (body mass index) >26 kg/m2 (HiBMI) if preceded by 16 days of daily broccoli/radish intake. Our objective in this current study was to determine whether a similar response occurs using cooked broccoli without a source of plant myrosinase. In a randomized, crossover study, 18 subjects consumed no broccoli or the same diet with cooked broccoli daily for 16 days. On day 17, all subjects consumed cooked broccoli. Glucosinolate metabolites were measured in plasma and urine of the participants. There was no effect of diet alone or interaction of diet with BMI. However, various measures of absorption doubled in HiBMI subjects (AUC 219%, plasma metabolites 202% compared to values for LoBMI, BMI<26 kg/m2), and the time to reach the maximum plasma metabolites and 24-h urinary metabolites also increased, to 127% and 177% of LoBMI values, respectively. BMI impacts absorption and metabolism of glucosinolates from broccoli and should be considered an important factor in future clinical trials.

Technical Abstract: Preclinical studies suggest that brassica vegetable diets decrease cancer risk, but epidemiological studies show varied effects, resulting in uncertainty about any health impact of brassicas. Factors controlling absorption of glucosinolate metabolites may relate to inconsistent results. We reported previously that subjects with BMI > 26 kg/m2 (HiBMI), given cooked broccoli plus raw daikon radish (as a source of plant myrosinase) daily for 17 days, had lower glucosinolate metabolite absorption than subjects given a single broccoli meal. This difference was not seen in subjects with BMI < 26 kg/m2 (LoBMI). Our objective in this current study was to determine whether a similar response occurred when cooked broccoli was consumed without a source of plant myrosinase. In a randomized crossover study (n = 18), subjects consumed no broccoli for 16 days or the same diet with 200 g of cooked broccoli daily for 15 days and 100 g of broccoli on day 16. On day 17, all subjects consumed 200 g of cooked broccoli. Plasma and urine were collected for 24 h and analyzed for glucosinolate metabolites by LC-MS. There was no effect of diet alone or interaction of diet with BMI. However, absorption doubled in HiBMI subjects (AUC 219%, plasma mass of metabolites 202% compared to values for LoBMI subjects) and time to peak plasma metabolite values and 24-h urinary metabolites also increased, to 127 and 177% of LoBMI values, respectively. BMI impacts absorption and metabolism of glucosinolates from cooked broccoli, and this association must be further elucidated for more efficacious dietary recommendations.