Rapid and sustainable detoxication of airborne pollutants by broccoli sprout beverage: results of a randomized clinical trial in China

Abstract

Broccoli sprouts are a convenient and rich source of the glucosinolate, glucoraphanin, which can generate the chemopreventive agent, sulforaphane, an inducer of glutathione S-transferases (GST) and other cytoprotective enzymes. A broccoli sprout-derived beverage providing daily doses of 600 μmol glucoraphanin and 40 μmol sulforaphane was evaluated for magnitude and duration of pharmacodynamic action in a 12-week randomized clinical trial. Two hundred and ninety-one study participants were recruited from the rural He-He Township, Qidong, in the Yangtze River delta region of China, an area characterized by exposures to substantial levels of airborne pollutants. Exposure to air pollution has been associated with lung cancer and cardiopulmonary diseases. Urinary excretion of the mercapturic acids of the pollutants, benzene, acrolein, and crotonaldehyde, were measured before and during the intervention using liquid chromatography tandem mass spectrometry. Rapid and sustained, statistically significant (P ≤ 0.01) increases in the levels of excretion of the glutathione-derived conjugates of benzene (61%), acrolein (23%), but not crotonaldehyde, were found in those receiving broccoli sprout beverage compared with placebo. Excretion of the benzene-derived mercapturic acid was higher in participants who were GSTT1-positive than in the null genotype, irrespective of study arm assignment. Measures of sulforaphane metabolites in urine indicated that bioavailability did not decline over the 12-week daily dosing period. Thus, intervention with broccoli sprouts enhances the detoxication of some airborne pollutants and may provide a frugal means to attenuate their associated long-term health risks.

Figure 1

Intervention trial profile.

Figure 2

Geometric means for biomarker levels on days 0, 1, 7, 14, 28, 42, 56, 70, and 84 of the intervention. A. Daily average levels for PM₁₀ in Shanghai (black) and Qidong (red) during the study period. B. Urinary benzene mercapturic acid levels. C. Urinary acrolein and crotonaldehyde mercapturic acid levels. () Broccoli sprout beverage arm; (•), placebo beverage arm. The geometric means for benzene appropriately accounted for left-censoring using the flexible PROC NLMIXED command in SAS 9.2.

Figure 3

Effect of GSTM1 and GSTT1 genotypes on urinary excretion of benzene-mercapturic acid. Distributions of benzene-mercapturic acid levels (geometric means and 95% confidence intervals) in participants either null or positive for the GSTT1 gene (panel A) or the GSTM1 gene (panel B) by assignment group (placebo or treated and day of study). Bars highlighted in green indicate those receiving the broccoli beverage. Open symbols represent medians for the participants null for the genotype and solid symbols indicate the geometric means of those who were positive.

Figure 4

Urinary excretion of sulforaphane and its metabolites (sulforaphane-cysteine and sulforaphane-mercapturic acid) on days 1, 42, and 84 as measured by isotope dilution mass spectrometry in participants randomized to the broccoli sprout beverage arm.