Background: Rates of estrogen-dependent cancers are among the highest in Western countries and lower in the East. These variations may be attributable to differences in dietary exposures such as higher seaweed consumption among Asian populations. The edible brown kelp, Fucus vesiculosus (bladderwrack), as well as other brown kelp species, lower plasma cholesterol levels. Since cholesterol is a precursor to sex hormone biosynthesis, kelp consumption may alter circulating sex hormone levels and menstrual cycling patterns. In particular, dietary kelp may be beneficial to women with or at high risk for estrogen-dependent diseases. To test this, bladderwrack was administered to three pre-menopausal women with abnormal menstrual cycling patterns and/or menstrual-related disease histories.

Case presentation: Intake of bladderwrack was associated with significant increases in menstrual cycle lengths, ranging from an increase of 5.5 to 14 days. In addition, hormone measurements ascertained for one woman revealed significant anti-estrogenic and progestagenic effects following kelp administration. Mean baseline 17beta-estradiol levels were reduced from 626 +/- 91 to 164 +/- 30 pg/ml (P = 0.04) following 700 mg/d, which decreased further to 92.5.0 +/- 3.5pg/ml (P = 0.03) with the 1.4 g/d dose. Mean baseline progesterone levels rose from 0.58 +/- 0.14 to 8.4 +/- 2.6 ng/ml with the 700 mg/d dose (P = 0.1), which increased further to 16.8 +/- 0.7 ng/ml with the 1.4 g/d dose (P = 0.002).

Conclusions: These pilot data suggest that dietary bladderwrack may prolong the length of the menstrual cycle and exert anti-estrogenic effects in pre-menopausal women. Further, these studies also suggest that seaweed may be another important dietary component apart from soy that is responsible for the reduced risk of estrogen-related cancers observed in Japanese populations. However, these studies will need to be performed in well-controlled clinical trials to confirm these preliminary findings.