Kelp can reduce level of hormone related to breast cancer risk

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Kelp can reduce level of hormone related to breast cancer risk

 

02/02/2005 - Kelp seaweed, the brown plant often found washed ashore

on beaches, could help to fight hormone-related cancers, suggests new

animal research.

 

Researchers at the University of California, Berkeley have found that

a diet containing kelp seaweed lowered levels of the most powerful

female sex hormone, oestradiol, in rats.

 

Their findings raise hopes that it might decrease the risk of

oestrogen-dependent diseases such as breast cancer in humans.

 

Breast cancer is the most common cancer among women across the

European Union. Britain has one of the highest breast cancer death

rates in the world, according to Breast Cancer Research, with one

woman in nine developing the disease during her lifetime.

 

" This study opens up a new avenue for research leading to cancer

preventive agents, " said Martyn Smith, UC Berkeley professor of

environmental health sciences and co-author of the study. " Kelp is a

little studied nutrient but there's good reason to look at it more

closely. "

 

Like soy, the researchers originally became interested in kelp because

of its high consumption in Japan and a potential link to the low rates

of breast cancer there. Prior studies have shown that Japanese women

have longer menstrual cycles and lower serum oestradiol levels than

their Western counterparts, which is thought to contribute to their

lower rates of breast, endometrial and ovarian cancers.

 

But scientists searching Asian diets for clues to the lower rates of

cancer have mostly focused their attention on soy. The Berkley team

say that their new results, published in the February issue of the

Journal of Nutrition (135, pp296-300), could demonstrate that soy is

not the only dietary component that protects against breast cancer.

 

" Brown kelp seaweed makes up more than 10 per cent of the Japanese

diet, " said Christine Skibola, lead author of the study. " Soy has

gotten most of the attention, but our study suggests that kelp may

also contribute to these reduced cancer rates among Japanese women. "

 

Skibola initially gained encouraging results from supplementing two

women with highly irregular menstrual cycles with 700mg of seaweed daily.

 

" It reduced much of the pain associated with endometriosis and

significantly lengthened the total number of days of their menstrual

cycles, " she said.

 

For the new study, the researchers randomly divided 24 female rats

into three groups. One group was fed a high daily dose of 70

milligrams of dried, powdered kelp for four weeks, while a second

group was fed a low daily dose of 35 milligrams. Both groups were

compared with a third control group of rats that did not receive kelp.

 

Researchers used bladderwrack seaweed (Fucus vesiculosus), the main

form of kelp sold in the US and closely related to wakame and kombu,

the brown seaweeds that are most commonly consumed in Japan. The doses

given to rats were roughly equivalent to the amount of seaweed eaten

by people in Japan.

 

The researchers report that the rats' menstrual cycles increased from

an average of 4.3 to 5.4 days for the low dose kelp group, and to 5.9

days for the high dose kelp group. Overall, dietary kelp resulted in a

37 per cent increase in the length of the rat oestrous cycle.

 

Studies in humans have linked longer menstrual cycle lengths to lower

risk of breast, ovarian and endometrial cancers.

 

" If you have longer cycles, you actually have fewer periods over a

lifetime, which means less time is spent overall in the phases where

hormone levels and breast and endometrial cell proliferation are at

their highest, " said Skibola.

 

During the early part of a woman's menstrual cycle, oestradiol levels

remain relatively constant. Almost halfway through the cycle,

oestradiol levels surge, peaking just before ovulation. These cyclic

periods of high oestrogen stimulate the division of breast cells that

already have DNA mutations, as well as increases the chances of

developing new mutations, factors that may increase risk of breast cancer.

 

The study also tested the impact of dietary kelp on oestradiol levels,

comparing them before supplementation and after. After just two weeks

of eating 35 milligrams a day, oestradiol levels were reduced from an

average of 48.9 nanograms per liter to 40.2 nanograms per liter. After

four weeks, oestradiol levels dropped further to 36.7 nanograms per liter.

 

In a separate test of human ovarian cell cultures, dosing with kelp

extract led to a 23 to 35 per cent decrease in oestradiol levels.

 

" One possibility is that the kelp may be acting as an oestrogen

antagonist by preventing estradiol from binding with its oestrogen

receptors, " said Skibola. " Our next step is to try to isolate the

active compound in kelp that is having this hormone-modulating effect. "

 

She noted that seaweed contains several complex compounds, including

polyphenols.

 

The researchers say they are working to isolate the active compounds

in kelp that affect oestradiol levels to avoid the possible toxicity

of the high levels of iodine and heavy metals in the plant.

 

" It's a study that points to the need for more studies, " said Smith.

" But this certainly suggests that there are other elements of the

Asian diet beyond soy that should be explored. "

 

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