“…in which they found estrogen increasing effects of grapefruit juice, but later publications found that that wasn't accurate. I think they were using the typically under-ripened grapefruit that has some irritating properties, but good ripe grapefruits are very sweet, and like orange juice, they have a protective pro-oxidative, pro-thyroid effect. When your thyroid is working right, your estrogen is kept minimal except during the one or two days around ovulation. It's safe for the estrogen to surge, but otherwise the thyroid should trim the estrogen down to a minimum.”