Absorption and metabolism of isothiocyanates formed from broccoli glucosinolates: effects of body mass index and daily consumption

Authors: Charron, Craig; Vinyard, Bryan; ROSS, SHARON - National Institutes Of Health (NIH); SEIFRIED, HAROLD - National Institutes Of Health (NIH); JEFFREY, ELIZABETH - University Of Illinois; Novotny, Janet

Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2018
Publication Date: 12/28/2018
Citation: Charron, C.S., Vinyard, B.T., Ross, S., Seifried, H., Jeffrey, E., Novotny, J. 2018. Absorption and metabolism of isothiocyanates formed from broccoli glucosinolates: effects of body mass index and daily consumption. British Journal of Nutrition. 120:1370-1379. https://doi.org/10.1017/S0007114518002921.
DOI: https://doi.org/10.1017/S0007114518002921

Interpretive Summary: Broccoli consumption has been linked with reduced cancer risk. This protection depends on absorption of broccoli nutrients into the human body, which may be affected by how often broccoli is consumed. The objective of this study was to determine if eating broccoli every day alters the absorption and metabolism of the broccoli nutrients thought to confer protection against cancer. Eighteen subjects completed the study. For 16 days, subjects ate either a control diet with no broccoli (NB) or the same diet supplemented with cooked broccoli and raw daikon radish (DB) every day. On day 17, subjects in both groups consumed a broccoli and radish breakfast, and blood and urine samples were collected over 24 hours. The procedure was repeated a second time except that subjects switched groups (those who had been on the NB diet went on the DB diet, and those who had been on the DB diet went on the NB diet). Blood and urine were again collected over 24 hours on day 17. Broccoli nutrients in their original and altered forms were measured in the blood and urine. Subjects who were overweight or obese tended to absorb higher levels of nutrients when they had been on the control (NB) diet for 16 days, whereas lean subjects had higher levels of nutrients when they had been on the broccoli (DB) for 16 days. Also, women tended to have higher levels of nutrients when they had been on the NB diet. These results indicate that absorption and metabolism of broccoli nutrients is affected by body mass index, gender, and whether broccoli is eaten every day.

Technical Abstract: Sulphoraphane originates from glucoraphanin in broccoli and is associated with anti-cancer effects. A preclinical study suggested that daily consumption of broccoli may increase the production of sulphoraphane and sulphoraphane metabolites available for absorption. The objective of this study was to determine whether daily broccoli consumption alters the absorption and metabolism of isothiocyanates derived from broccoli glucosinolates. We conducted a randomised cross-over human study (n 18) balanced for BMI and glutathione S-transferase µ 1 (GSTM1) genotype in which subjects consumed a control diet with no broccoli (NB) for 16 d or the same diet with 200 g of cooked broccoli and 20 g of raw daikon radish daily for 15 d (daily broccoli, DB) and 100 g of broccoli and 10 g of daikon radish on day 16. On day 17, all subjects consumed a meal of 200 g of broccoli and 20 g of daikon radish. Plasma and urine were collected for 24 h and analysed for sulphoraphane and metabolites of sulphoraphane and erucin by triple quadrupole tandem MS. For subjects with BMI >26 kg/m2 (median), plasma AUC and urinary excretion rates of total metabolites were higher on the NB diet than on the DB diet, whereas for subjects with BMI <26 kg/m2, plasma AUC and urinary excretion rates were higher on the DB diet than on the NB diet. Daily consumption of broccoli interacted with BMI but not GSTM1 genotype to affect plasma concentrations and urinary excretion of glucosinolate-derived compounds believed to confer protection against cancer. This trial was registered as NCT02346812.