Dietary seaweed could reduce estrogen levels, lowering breast cancer risk.
By Serena Gordon
HealthDay Reporter
THURSDAY, Feb. 3 (HealthDay News) -- More than just a slimy nuisance that wraps
itself around your ankles while you walk the beach, seaweed may actually be a
powerful tool in the fight against breast cancer.
That's because a diet containing kelp seaweed may reduce the amounts of estrogen
circulating in the body, a new study claims. Lower estrogen levels mean there's
less fuel available for the development of estrogen-dependent cancers, such as
some forms of breast cancer, the researchers explain.
This study, which appears in the Feb. 2 issue of the Journal of Nutrition is the
latest to examine differences between the typical Asian diet and the typical
Western diet, looking at how those differences might contribute to the
development of breast cancer.
Japanese women, who have a significantly lower risk of breast cancer than women
in the United States, also have a much higher dietary intake of seaweed,
according to the study.
In Japan, seaweed is used in the preparation of sushi dishes, in Miso soup, in
stews, and as a thickening agent. In some Asian countries, seaweed is even eaten
as a snack, said study author Christine Skibola, an assistant research
toxicologist at the University of California at Berkeley School of Public
Health.
The current study, done in rats, developed out of several case studies Skibola
had conducted on women taking 700-milligram seaweed supplements daily to treat
extremely irregular menstrual cycles from disorders such as endometriosis.
Skibola noticed the women's menstrual cycles became longer and more regular, and
that their blood levels of estradiol -- a form of estrogen -- dropped
significantly.
"It was kind of amazing how much it helped their pain and how it altered their
menstrual cycles, and we saw a remarkable decrease in estradiol levels," said
Skibola, who stressed that while these case studies were remarkable, they were
conducted in just three women.
To further test the effects of seaweed, Skibola and her colleagues had rats
consume bladderwrack seaweed, which is closely related to two Japanese
favorites, wakame and kombu seaweed.
The study included 24 female rats, split into three different groups. One group
was given a high dose -- 70 milligrams -- of kelp, while another group was given
35 milligrams daily. These doses are about equivalent to the normal Japanese
diet, said Skibola.
The third group served as a control group and was given no kelp. To ensure that
the rats consumed the correct dose of dried kelp, it was sprinkled onto their
favorite food, apples.
After four weeks, the researchers found that consumption of kelp increased the
average length of the rodent's menstrual cycle by 37 percent. At the start of
the study, the average menstrual cycle was 4.3 days. After consuming kelp, the
low-dose group averaged 5.4 days, and the high-dose group increased to 5.9 days.
When the researchers tested blood levels of estradiol in rats from the low-dose
kelp group they found declines in the hormone from 48.9 nanograms per liter at
the start of the study to 36.7 nanograms per liter four weeks later.
According to Skibola, the researchers also tested human ovarian cells in culture
and found that the cells' estrogen levels fell when exposed to kelp extract.
Skibola explained that compounds in seaweed appear to compete with estrogen for
for spots on estrogen receptors in cells. The overall effect could be reductions
in circulating estrogen.
By increasing the length of the menstrual cycle and decreasing levels of
estrogen, the researchers suggest that seaweed could reduce the risk of
estrogen-dependent breast cancers because there would simply be less estrogen
available to fuel tumor growth.
Others aren't convinced, however.
"I think this is interesting, but it's another theory," said Dr. David Decker,
chief of hematology and oncology at William Beaumont Hospital in Royal Oak,
Mich. "They've shown that seaweed given to rats can change their estrogen
levels, but we don't know for sure if that applies to humans."
"Women shouldn't go out and start eating lots of seaweed," said Decker, who
added that it's probably more important for breast cancer prevention to eat an
overall healthy diet and to make sure you get screening mammograms beginning in
your 40s.
Skibola also hopes that no one consumes large quantities of seaweed, but says
that in moderation it can be a healthy addition to the diet. But, she cautioned,
seaweed does contain iodine and low levels of some heavy metals, so large
amounts, whether in dietary or supplement form, may not be good for some people.
"I don't think people should go out and self-medicate, but in the diet, seaweed
is generally a healthy thing to incorporate," she said.
Skibola said that the researchers are trying to isolate exactly which compounds
in seaweed effect estrogen levels, in hopes that they may one day be able to
develop a drug from those compounds to help prevent estrogen-dependent cancers.
Source :
http://www.principalhealthnews.com/article/hscoutn/103978721;jsessionid=IPW2NX0S0QQ0ECTYAEPENAQ