Which Seaweed Is Most Protective Against Breast Cancer?

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Nori seaweed snacks may favorably alter estrogen metabolism by modulating women’s gut flora, resulting in decreased breast cancer risk.

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Unfortunately, as the traditional diets of East Asia Westernize, their breast cancer rates have risen, which some have linked to a quadrupling of animal product consumption.

This is the breast cancer rate of Japanese women living in Japan. If they emigrate to the United States, within ten years, they’re up to here. And, if they hang around long enough, here’s the risk of resident Japanese-Americans living in the United States. Note, though, that’s still somewhat lower than the U.S. national average. This may be because of some of the dietary habits may carry with them—soy consumption, green tea, maybe eating more mushrooms. But maybe, partly, it’s the seaweed.

We’ve known for over a decade that in vitro, in a petri dish, seaweed broth is effective at clearing cancer cells. Here’s three different types of human breast cancer, measuring cancer cell death. Here’s what a widely used chemotherapy drug can do, and here’s seaweed. Worked even better, and, unlike the chemo, didn’t hurt normal, noncancerous breast cells. But, what about outside of the test tube, in people?

Well, a population study comparing women with breast cancer, to women without, found that consuming a single sheet of nori a day may cut a woman’s odds of breast cancer in half. We think it’s because seaweed favorably alters estrogen metabolism—likely due to a modulation of the woman’s gut bacteria. It appears the more seaweed you eat, the less estrogen you have in your system, which may lower breast cancer risk.

This may be because of all the fiber in sea vegetables. Or, it may block the enzyme that undermines our body’s attempt to flush out excess hormones—or, even somehow interfere with estrogen binding to estrogen receptors. Either way, to effectively lower one’s estrogen levels, Asian women may be able to get away with maybe one sheet of nori a day. But, American women are so much bigger that it may take closer to two. There’s lots of yummy seaweed snacks out there to make it a tasty experience—just try to get some low-fat, low-sodium ones.

Wakame, the seaweed used fresh in seaweed salads, unfortunately did not appear to reduce breast cancer risk, though it has been found to rather dramatically lower blood pressure in hypertensives. Just two teaspoons of seaweed salad a day for a month dropped their blood pressure 14 points. And, after two months, was associated with up to a two-inch skinnier waistline.

As I’ve mentioned before, though, I’d recommend avoiding hijiki, which tends to have too much arsenic, and kelp, which tends to have too much iodine. In fact, too much seaweed of any type may actually increase one’s risk of thyroid cancer, because of the amount of iodine you’d be taking in.

But, there does not appear to be increased risk at the levels of consumption I’m talking about—like, you know, a sheet of nori every day. And, a study of seaweed eaters in California actually found decreased risk. But, again, we’re talking, you know, kind of modest levels of intake.

You know, I’ve frequently talked about the benefits of dietary diversity—eating different families of fruits and vegetables, eating different parts of individual plants; like beets, and beet greens. If we just stick to land plants, though, we’re missing out on all the plants from the other 70% of planet Earth. Sea vegetables have phytonutrients found nowhere else, types of fiber, and unique carotenoids, and polysaccharides, and various polyphenol defense compounds, each of which may have anticancer properties. So, I encourage everyone to try experimenting with sea vegetables until you find one you like, even if that means just sprinkling some powdered dulse on your food.

Please consider volunteering to help out on the site.

Images thanks to Emily Barney and jessica wilson {jek in the box} via flickr; and Agricultural Research Service, Alice Wiegand, and Lyzzy via Wikimedia. Thanks to Ellen Reid and Shane Barrett for their Keynote help.

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Unfortunately, as the traditional diets of East Asia Westernize, their breast cancer rates have risen, which some have linked to a quadrupling of animal product consumption.

This is the breast cancer rate of Japanese women living in Japan. If they emigrate to the United States, within ten years, they’re up to here. And, if they hang around long enough, here’s the risk of resident Japanese-Americans living in the United States. Note, though, that’s still somewhat lower than the U.S. national average. This may be because of some of the dietary habits may carry with them—soy consumption, green tea, maybe eating more mushrooms. But maybe, partly, it’s the seaweed.

We’ve known for over a decade that in vitro, in a petri dish, seaweed broth is effective at clearing cancer cells. Here’s three different types of human breast cancer, measuring cancer cell death. Here’s what a widely used chemotherapy drug can do, and here’s seaweed. Worked even better, and, unlike the chemo, didn’t hurt normal, noncancerous breast cells. But, what about outside of the test tube, in people?

Well, a population study comparing women with breast cancer, to women without, found that consuming a single sheet of nori a day may cut a woman’s odds of breast cancer in half. We think it’s because seaweed favorably alters estrogen metabolism—likely due to a modulation of the woman’s gut bacteria. It appears the more seaweed you eat, the less estrogen you have in your system, which may lower breast cancer risk.

This may be because of all the fiber in sea vegetables. Or, it may block the enzyme that undermines our body’s attempt to flush out excess hormones—or, even somehow interfere with estrogen binding to estrogen receptors. Either way, to effectively lower one’s estrogen levels, Asian women may be able to get away with maybe one sheet of nori a day. But, American women are so much bigger that it may take closer to two. There’s lots of yummy seaweed snacks out there to make it a tasty experience—just try to get some low-fat, low-sodium ones.

Wakame, the seaweed used fresh in seaweed salads, unfortunately did not appear to reduce breast cancer risk, though it has been found to rather dramatically lower blood pressure in hypertensives. Just two teaspoons of seaweed salad a day for a month dropped their blood pressure 14 points. And, after two months, was associated with up to a two-inch skinnier waistline.

As I’ve mentioned before, though, I’d recommend avoiding hijiki, which tends to have too much arsenic, and kelp, which tends to have too much iodine. In fact, too much seaweed of any type may actually increase one’s risk of thyroid cancer, because of the amount of iodine you’d be taking in.

But, there does not appear to be increased risk at the levels of consumption I’m talking about—like, you know, a sheet of nori every day. And, a study of seaweed eaters in California actually found decreased risk. But, again, we’re talking, you know, kind of modest levels of intake.

You know, I’ve frequently talked about the benefits of dietary diversity—eating different families of fruits and vegetables, eating different parts of individual plants; like beets, and beet greens. If we just stick to land plants, though, we’re missing out on all the plants from the other 70% of planet Earth. Sea vegetables have phytonutrients found nowhere else, types of fiber, and unique carotenoids, and polysaccharides, and various polyphenol defense compounds, each of which may have anticancer properties. So, I encourage everyone to try experimenting with sea vegetables until you find one you like, even if that means just sprinkling some powdered dulse on your food.

Please consider volunteering to help out on the site.

Images thanks to Emily Barney and jessica wilson {jek in the box} via flickr; and Agricultural Research Service, Alice Wiegand, and Lyzzy via Wikimedia. Thanks to Ellen Reid and Shane Barrett for their Keynote help.

Doctor's Note

Seaweed snacks are like kale chips—munchies made out of dark green leafy vegetables. Can’t beat that!

More on some of the other protective dietary components in the diets of Japanese women in Why Do Asian Women Have Less Breast Cancer? and Breast Cancer Survival & Soy.

If you dig anticancer comparison videos, make sure you also check out Which Fruit Fights Cancer Better?.

I’ve done a video on why kelp (Too Much Iodine Can Be as Bad as Too Little) are not the best choices.

If you’d rather stick to terrestrial plants, see Preventing Breast Cancer by Any Greens Necessary. And, for more on lowering breast cancer through diet:

And more on the importance of dietary diversity in Garden Variety Anti-Inflammation, Apples & Oranges: Dietary Diversity, and Constructing a Cognitive Portfolio.

For more context, check out my associated blog: Which Seaweed to Help Prevent Breast Cancer?

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