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Kelp has anti-estrogenic effect

Kelp, or bladderwrack seaweed scientific name Fucus vesiculosus may have an anti-estrogenic effect. Substances found in kelp delay the manufacture of estradiol in the body and sabotage the working of the estradiol receptor.

Researchers at the University of California at Berkeley stumbled upon the anti-estrogenic effect of kelp when they tested an alternative theory on why very few Japanese women have breast, womb or ovarian cancer. These types of cancer are caused by estradiol. The conventional theory is that high consumption of soya, a food with an anti-estrogenic effect, protects Japanese women against estradiol-related cancers.

The researchers, however, had a different theory. The Japanese eat between 3 and 13 g of seaweed every day. That led the Americans to wonder whether seaweed also has anti-estrogenic effect. They did a simple experiment in which female rats received 175 or 350 mg of seaweed per kg of bodyweight each day. The highest dose was the most effective and reduced the concentration of estradiol in the rats by almost 40 percent. [Human equivalent of the high dose: 3000-5000 mg/day.] The graph below shows this.

Kelp has anti-estrogenic effect

Because the researchers wanted to understand the mechanism by which kelp reduces estradiol levels, they exposed human ovary cells technically speaking luteinized granulosa cells to different concentrations of kelp. The cells produce small amounts of testosterone, estradiol and progesterone. The higher the concentration of kelp, the less estradiol the cells made, the Americans discovered. The production of progesterone rose slightly.

The researchers wanted to know more about how the process works so they did another experiment. In test tubes they tested whether certain substances in kelp were capable of sabotaging the receptors for estradiol and progesterone. And yes, they managed to do so, see here below.

Kelp has anti-estrogenic effect

Kelp contains many polyphenols and sulfated sugar chains, fucoidans. Exactly which of the components is responsible for the anti-estrogen effect the researchers do not know.

Supplements that also have an anti-estrogen effect are Ginkgo biloba, green tea and gamma-linoleic acid. According to researchers at the US Department of Agriculture, mushrooms also have an anti-estrogenic effect.

J Nutr. 2005 Feb;135(2):296-300.