What happens to hormone levels in women and men randomized to drink soy milk?
How to Block Breast Cancer’s Estrogen-Producing Enzymes
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.
The vast majority of breast cancers start out “hormone-dependent,” meaning the primary human estrogen, called “estradiol plays a crucial role in [breast cancer] development and progression.” That’s one of the reasons why soy food consumption appears so protective against breast cancer—because soy phytoestrogens, like genistein, act as estrogen-blockers. They block the binding of estrogens, like estradiol, to breast cancer cells.
But, wait a second. “The majority of breast cancers occur [after menopause], when the ovaries have [stopped producing estrogen].” What’s the point of eating estrogen blockers if there’s no estrogen to block? It turns out the breast cancer tumors themselves produce their own estrogen from scratch to fuel their own growth.
Estrogens may be formed in breast tumors by multiple pathways. The breast cancer takes cholesterol, and, using the aromatase enzyme, or two hydroxysteroid dehydrogenase enzymes, produces its own estrogen.
So, there’s two ways to stop breast cancer. One is to use “antiestrogens,” estrogen-blockers, like the soy phytoestrogens, or “the anti-estrogen [drug] tamoxifen…However, another way to block estradiol is by using anti-enzymes” to prevent the breast cancer from making all the estrogen in the first place.
And, indeed, there are a variety of anti-aromatase drugs in current use. In fact, inhibiting the estrogen production has been shown to be “more effective” than just trying to block the effects of the estrogen—”suggesting that the inhibition of estrogen synthesis is clinically very important for the treatment of estrogen-dependent breast cancer.” It turns out soy phytoestrogens can do both.
Using ovary cells taken from women undergoing in vitro fertilization, soy phytoestrogens were found to reduce the expression of the aromatase enzyme. What about in breast cancer cells, though? Breast cancer cells, too—not only suppressing aromatase activity, but the other estrogen-producing enzyme, too.
But, this is in a petri dish. Does soy suppress estrogen production in people too Well, circulating estrogen levels appear significantly lower in Japanese women than American white women. And, Japan does have the highest per capita soy food consumption. But, you don’t know it’s the soy until you put it to the test. Japanese women were randomized to add soymilk to their diet—or not—for a few months. Estrogen levels did seem to drop about a quarter in the soymilk-supplemented group. Interestingly, when they tried the same experiment in men, they got similar results: a significant drop in female hormone levels, with no change in testosterone levels.
These results, though, are in Japanese men and women that were already consuming soy in their baseline diet. So, it’s really just looking at “higher versus lower…soy intake.”
What happens if you give soymilk to women in Texas? Circulating estrogen levels cut in half. Since increased estrogen levels are a “[marker] for high risk for breast cancer,” the effectiveness of soy to reduce estrogen levels may help explain why Chinese and Japanese women have such low rates of breast cancer.
And, what was truly remarkable is that estrogen levels stayed down a month or two, even after they stopped drinking it. This suggests you don’t have to consume soy every day to have the cancer-protective benefit.
Please consider volunteering to help out on the site.
- Fioravanti L, Cappelletti V, Miodini P, Ronchi E, Brivio M, Di Fronzo G. Genistein in the control of breast cancer cell growth: insights into the mechanism of action in vitro. Cancer Lett. 1998 Aug 14;130(1-2):143-52.
- So FV, Guthrie N, Chambers AF, Carroll KK. Inhibition of proliferation of estrogen receptor-positive MCF-7 human breast cancer cells by flavonoids in the presence and absence of excess estrogen. Cancer Lett. 1997 Jan 30;112(2):127-33.
- Rice S, Mason HD, Whitehead SA. Phytoestrogens and their low dose combinations inhibit mRNA expression and activity of aromatase in human granulosa-luteal cells. J Steroid Biochem Mol Biol. 2006 Nov;101(4-5):216-25.
- Nakata T, Takashima S, Shiotsu Y, Murakata C, Ishida H, Akinaga S, Li PK, Sasano H, Suzuki T, Saeki T. Role of steroid sulfatase in local formation of estrogen in post-menopausal breast cancer patients. J Steroid Biochem Mol Biol. 2003 Sep;86(3-5):455-60.
- Pasqualini JR, Chetrite GS. Recent insight on the control of enzymes involved in estrogen formation and transformation in human breast cancer. J Steroid Biochem Mol Biol. 2005 Feb;93(2-5):221-36.
- Brooks JD, Thompson LU. Mammalian lignans and genistein decrease the activities of aromatase and 17beta-hydroxysteroid dehydrogenase in MCF-7 cells. J Steroid Biochem Mol Biol. 2005 Apr;94(5):461-7.
- Shimizu H, Ross RK, Bernstein L, Pike MC, Henderson BE. Serum oestrogen levels in postmenopausal women: comparison of American whites and Japanese in Japan. Br J Cancer. 1990 Sep;62(3):451-3.
- Nagata C, Takatsuka N, Shimizu H, Hayashi H, Akamatsu T, Murase K. Effect of soymilk consumption on serum estrogen and androgen concentrations in Japanese men. Cancer Epidemiol Biomarkers Prev. 2001 Mar;10(3):179-84.
- Nagata C, Takatsuka N, Inaba S, Kawakami N, Shimizu H. Effect of soymilk consumption on serum estrogen concentrations in premenopausal Japanese women. J Natl Cancer Inst. 1998 Dec 2;90(23):1830-5.
- Lu LJ, Anderson KE, Grady JJ, Nagamani M. Effects of soya consumption for one month on steroid hormones in premenopausal women: implications for breast cancer risk reduction. Cancer Epidemiol Biomarkers Prev. 1996 Jan;5(1):63-70.
- Key TJ. Endogenous oestrogens and breast cancer risk in premenopausal and postmenopausal women. Steroids. 2011 Jul;76(8):812-5.
- Labrie F. All sex steroids are made intracellularly in peripheral tissues by the mechanisms of intracrinology after menopause. J Steroid Biochem Mol Biol. 2015 Jan;145:133-8.
- Würtz AM, Tjønneland A, Christensen J, Dragsted LO, Aarestrup J, Kyrø C, Overvad K, Olsen A. Serum estrogen and SHBG levels and breast cancer incidence among users and never users of hormone replacement therapy. Cancer Causes Control. 2012 Oct;23(10):1711-20.
Image credit: Kristina DeMuth. Image has been modified.
Video credit: Tyler McReynolds, Teetotalin LLC.
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.
The vast majority of breast cancers start out “hormone-dependent,” meaning the primary human estrogen, called “estradiol plays a crucial role in [breast cancer] development and progression.” That’s one of the reasons why soy food consumption appears so protective against breast cancer—because soy phytoestrogens, like genistein, act as estrogen-blockers. They block the binding of estrogens, like estradiol, to breast cancer cells.
But, wait a second. “The majority of breast cancers occur [after menopause], when the ovaries have [stopped producing estrogen].” What’s the point of eating estrogen blockers if there’s no estrogen to block? It turns out the breast cancer tumors themselves produce their own estrogen from scratch to fuel their own growth.
Estrogens may be formed in breast tumors by multiple pathways. The breast cancer takes cholesterol, and, using the aromatase enzyme, or two hydroxysteroid dehydrogenase enzymes, produces its own estrogen.
So, there’s two ways to stop breast cancer. One is to use “antiestrogens,” estrogen-blockers, like the soy phytoestrogens, or “the anti-estrogen [drug] tamoxifen…However, another way to block estradiol is by using anti-enzymes” to prevent the breast cancer from making all the estrogen in the first place.
And, indeed, there are a variety of anti-aromatase drugs in current use. In fact, inhibiting the estrogen production has been shown to be “more effective” than just trying to block the effects of the estrogen—”suggesting that the inhibition of estrogen synthesis is clinically very important for the treatment of estrogen-dependent breast cancer.” It turns out soy phytoestrogens can do both.
Using ovary cells taken from women undergoing in vitro fertilization, soy phytoestrogens were found to reduce the expression of the aromatase enzyme. What about in breast cancer cells, though? Breast cancer cells, too—not only suppressing aromatase activity, but the other estrogen-producing enzyme, too.
But, this is in a petri dish. Does soy suppress estrogen production in people too Well, circulating estrogen levels appear significantly lower in Japanese women than American white women. And, Japan does have the highest per capita soy food consumption. But, you don’t know it’s the soy until you put it to the test. Japanese women were randomized to add soymilk to their diet—or not—for a few months. Estrogen levels did seem to drop about a quarter in the soymilk-supplemented group. Interestingly, when they tried the same experiment in men, they got similar results: a significant drop in female hormone levels, with no change in testosterone levels.
These results, though, are in Japanese men and women that were already consuming soy in their baseline diet. So, it’s really just looking at “higher versus lower…soy intake.”
What happens if you give soymilk to women in Texas? Circulating estrogen levels cut in half. Since increased estrogen levels are a “[marker] for high risk for breast cancer,” the effectiveness of soy to reduce estrogen levels may help explain why Chinese and Japanese women have such low rates of breast cancer.
And, what was truly remarkable is that estrogen levels stayed down a month or two, even after they stopped drinking it. This suggests you don’t have to consume soy every day to have the cancer-protective benefit.
Please consider volunteering to help out on the site.
- Fioravanti L, Cappelletti V, Miodini P, Ronchi E, Brivio M, Di Fronzo G. Genistein in the control of breast cancer cell growth: insights into the mechanism of action in vitro. Cancer Lett. 1998 Aug 14;130(1-2):143-52.
- So FV, Guthrie N, Chambers AF, Carroll KK. Inhibition of proliferation of estrogen receptor-positive MCF-7 human breast cancer cells by flavonoids in the presence and absence of excess estrogen. Cancer Lett. 1997 Jan 30;112(2):127-33.
- Rice S, Mason HD, Whitehead SA. Phytoestrogens and their low dose combinations inhibit mRNA expression and activity of aromatase in human granulosa-luteal cells. J Steroid Biochem Mol Biol. 2006 Nov;101(4-5):216-25.
- Nakata T, Takashima S, Shiotsu Y, Murakata C, Ishida H, Akinaga S, Li PK, Sasano H, Suzuki T, Saeki T. Role of steroid sulfatase in local formation of estrogen in post-menopausal breast cancer patients. J Steroid Biochem Mol Biol. 2003 Sep;86(3-5):455-60.
- Pasqualini JR, Chetrite GS. Recent insight on the control of enzymes involved in estrogen formation and transformation in human breast cancer. J Steroid Biochem Mol Biol. 2005 Feb;93(2-5):221-36.
- Brooks JD, Thompson LU. Mammalian lignans and genistein decrease the activities of aromatase and 17beta-hydroxysteroid dehydrogenase in MCF-7 cells. J Steroid Biochem Mol Biol. 2005 Apr;94(5):461-7.
- Shimizu H, Ross RK, Bernstein L, Pike MC, Henderson BE. Serum oestrogen levels in postmenopausal women: comparison of American whites and Japanese in Japan. Br J Cancer. 1990 Sep;62(3):451-3.
- Nagata C, Takatsuka N, Shimizu H, Hayashi H, Akamatsu T, Murase K. Effect of soymilk consumption on serum estrogen and androgen concentrations in Japanese men. Cancer Epidemiol Biomarkers Prev. 2001 Mar;10(3):179-84.
- Nagata C, Takatsuka N, Inaba S, Kawakami N, Shimizu H. Effect of soymilk consumption on serum estrogen concentrations in premenopausal Japanese women. J Natl Cancer Inst. 1998 Dec 2;90(23):1830-5.
- Lu LJ, Anderson KE, Grady JJ, Nagamani M. Effects of soya consumption for one month on steroid hormones in premenopausal women: implications for breast cancer risk reduction. Cancer Epidemiol Biomarkers Prev. 1996 Jan;5(1):63-70.
- Key TJ. Endogenous oestrogens and breast cancer risk in premenopausal and postmenopausal women. Steroids. 2011 Jul;76(8):812-5.
- Labrie F. All sex steroids are made intracellularly in peripheral tissues by the mechanisms of intracrinology after menopause. J Steroid Biochem Mol Biol. 2015 Jan;145:133-8.
- Würtz AM, Tjønneland A, Christensen J, Dragsted LO, Aarestrup J, Kyrø C, Overvad K, Olsen A. Serum estrogen and SHBG levels and breast cancer incidence among users and never users of hormone replacement therapy. Cancer Causes Control. 2012 Oct;23(10):1711-20.
Image credit: Kristina DeMuth. Image has been modified.
Video credit: Tyler McReynolds, Teetotalin LLC.
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How to Block Breast Cancer’s Estrogen-Producing Enzymes
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Content URLDoctor's Note
Wait, soy protects against breast cancer? Yes, in study after study after study—and even in women at high risk. Watch my video BRCA Breast Cancer Genes and Soy for the full story.
What if you already have breast cancer? In that case, see Is Soy Healthy for Breast Cancer Survivors?.
And what about GMO soy? Get the facts in GMO Soy and Breast Cancer.
Okay, then, Who Shouldn’t Eat Soy? Watch my video and find out.
What else can we do to decrease breast cancer risk? See:
- Broccoli vs. Breast Cancer Stem Cells
- Flaxseeds and Breast Cancer Prevention
- Breast Cancer vs. Mushrooms
- Preventing Breast Cancer by Any Greens Necessary
- Tree Nuts or Peanuts for Breast Cancer Prevention?
- Estrogenic Cooked-Meat Carcinogens
- Fiber vs. Breast Cancer
- Breast Cancer and Alcohol: How Much Is Safe?
- Breast Cancer Risk: Red Wine vs. White Wine
- Cholesterol Feeds Breast Cancer Cells
- Which Dietary Factors Affect Breast Cancer Most?
- Industry Response to Bovine Leukemia Virus in Breast Cancer
- The Role of Bovine Leukemia in Breast Cancer
You may also be interested in Soy Phytoestrogens for Menopause Hot Flashes.
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