Both indole-3-carbinol and dietary lignans have beneficial effects on estrogen metabolism and breast cancer risk. There is no published literature on the effects of a combination product. This study was designed to investigate the impact of a combination product on estrogen metabolism. The major trial objective was to determine whether a breast health supplement containing indole-3-carbinol and hydroxymatairesinol lignan would alter estrogen metabolism to favour C-2 hydroxylation and reduce C-16 hydroxylation. Higher concentrations of C-2 metabolites and lower concentrations of C-16 metabolites may reduce breast cancer risk and risk for other hormonally-related cancers.
Forty-seven pre-menopausal and forty-nine post-menopausal women were recruited for this study, and were divided by random allocation into treatment and placebo group. The treatment supplement contained HMR lignan, indole-3-carbinol, calcium glucarate, milk thistle, Schisandra chinesis and stinging nettle, and each woman consumed either treatment or placebo for 28 days. At day 0 and day 28, blood samples were analysed for serum enterolactone concentrations, and first morning random urine samples were assessed for estrogen metabolites. Repeated measures ANOVA statistical testing was performed.
In pre-menopausal women, treatment supplementation resulted in a significant increase (P < 0.05) in urinary 2-OHE concentrations and in the 2:16α-OHE ratio. In post-menopausal women, treatment supplementation resulted in a significant increase in urinary 2-OHE concentrations. In pre- and post-menopausal women combined, treatment supplementation produced a significant increase in urinary 2-OHE concentration and a trend (P = 0.074) toward an increased 2:16α-OHE ratio. There were no significant increases in serum enterolactone concentrations in the treatment or placebo groups.
Supplementation with a mixture of indole-3-carbinol and HMR lignan in women significantly increased estrogen C-2 hydroxylation. This may constitute a mechanism for the reduction of breast cancer risk as well as risk for other estrogen-related cancers. Further studies with higher numbers of subjects are indicated.
ClinicalTrials.gov registration #NCT01089049.