Most important anti-estrogenic foods are the cruciferous vegetables such as broccoli, cauliflower, brussels sprouts, and cabbage. The estrogen-inhibiting and modulating effects of cruciferous indoles may explain why crucifers have been widely regarded as a cancer- preventing food.
The active ingredients in crucifers—indole 3 carbinol, DIM, and indole 3 acetate—have shown substantial capacity to shift estrogen metabolism to produce beneficial antioxidant and anti-cancerous metabolites. Cruciferous indoles work as a first defense against excess estrogen. Studies reveal that cruciferous indoles can increase the ratio of beneficial estrogen metabolites, (2-hydroxy estrogens) over harmful estrogen metabolites, (16-hydroxy estrogens). It has been established that a high ratio of the chemicals 2-hydroxy to 16-hydroxy estrogens is associated with a low risk for estrogen-related cancer.
Source : www.antiestrogenicdiet.com