Cruciferous Vegetables Have Variable Effects on Biomarkers of Systemic Inflammation in a Randomized Controlled Trial in Healthy Young Adults

Abstract

Background:Isothiocyanates in cruciferous vegetables modulate signaling pathways critical to carcinogenesis, including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), a central regulator of inflammation. Glutathione S-transferase (GST) M1 and GSTT1 metabolize isothiocyanates; genetic variants may result in differences in biologic response. Objective:The objective of this study was to test whether consumption of cruciferous or cruciferous plus apiaceous vegetables altered serum concentrations of interleukin (IL)-6, IL-8, C-reactive protein (CRP), tumor necrosis factor (TNF) α, and soluble TNF receptor (sTNFR) I and II, and whether this response was GSTM1/GSTT1 genotype dependent. Methods:In a randomized crossover trial, healthy men (n = 32) and women (n = 31) aged 20–40 y consumed 4 14-d controlled diets: basal (vegetable-free), single-dose cruciferous (1xC) [7 g vegetables/kg body weight (BW)], double-dose cruciferous (2xC) (14 g/kg BW), and cruciferous plus apiaceous (carrot family) (1xC+A) vegetables (7 and 4 g/kg BW, respectively), with a 21-d washout period between each intervention. Urinary isothiocyanate excretion was also evaluated as a marker of systemic isothiocyanate exposure. Fasting morning blood and urine samples were collected on days 0 and 14 and analyzed. Results:IL-6 concentrations were significantly lower on day 14 of the 2xC and 1xC+A diets than with the basal diet [−19% (95% CI: −30%, −0.1%) and −20% (95% CI: −31%, -0.7%), respectively]. IL-8 concentrations were higher after the 1xC+A diet (+16%; 95% CI: 4.2%, 35.2%) than after the basal diet. There were no effects of diet on CRP, TNF-α, or sTNFRI or II. There were significant differences between GSTM1-null/GSTT1+ individuals for several biomarkers in response to 1xC+A compared with basal diets (CRP: −37.8%; 95% CI: −58.0%, −7.4%; IL-6: −48.6%; 95% CI: −49.6%, −12.0%; IL-8: 16.3%; 95% CI: 6.7%, 57.7%) and with the 2xC diet compared with the basal diet (IL-8: −33.2%; 95% CI: −43.0%, −1.4%; sTNFRI: −7.5%; 95% CI: −12.7%, −2.3%). There were no significant reductions in biomarker concentrations in response to diet among GSTM1+/GSTT1+ or GSTM1-null/GSTT1-null individuals. Twenty-four-hour urinary isothiocyanate excretion was not associated with any of the inflammation markers overall; however, IL-6 was inversely associated with total isothiocyanate excretion in GSTM1-null/GSTT1-null individuals (β = −0.12; 95% CI: −0.19, −0.05). Conclusions:In this young, healthy population, consumption of cruciferous and apiaceous vegetables reduced circulating IL-6; however, results for other biomarkers of inflammation were not consistent.