Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

Women’s Health

Today on the NutritionFacts Podcast, we look at the latest research on endometriosis, the potential cancer-fueling estrogenic effects from eggs and processed meat, and the effect of soy on uterine fibroids. This episode features audio from How to Treat Endometriosis with Seaweed, Oxidized Cholesterol 27HC May Explain 3 Breast Cancer Mysteries, and Should Women with Fibroids Avoid Soy?. Visit the video pages for all sources and doctor’s notes related to this podcast.


You know the feeling you get – when you learn something new about a health problem you’ve been trying to reverse – maybe high blood pressure, diabetes, or heart disease. Well – there’s nothing I like better than bringing you the information that will help you do just that. Welcome to the NutritionFacts podcast. I’m your host – Dr. Michael Greger.

There are a variety of unique health issues that women face that affect their quality of life. And today, we start with one way to treat one of the most debilitating diseases that women face: endometriosis.

“Endometriosis is a major cause of disability and compromised quality of life among women.” It is “a chronic disease which is under-diagnosed, under-reported, and under-researched.” For patients, it “can be a nightmare of misinformation, myths, taboos, lack of diagnosis, and problematic hit-and-miss treatments overlaid by a painful, chronic, stubborn disease.” Pain is what best characterizes the disease: pain, painful intercourse, heavy irregular periods, and infertility. About one in a dozen young women suffer, and it accounts for about half the cases of pelvic pain and infertility. It’s caused by what’s called “retrograde menstruation.” Instead of the blood going down, it goes up into the abdominal cavity, where bleeding tissue of the uterine lining can implant onto other organs.

You can have the lesions surgically removed, but the recurrence rate within five years is as high as 50%. Now, “[e]ndometriosis is an estrogen-dependent disease.” So, might the anti-estrogenic effects of the phytoestrogens in flax seeds and soy foods help—as they appear to in breast cancer? I couldn’t find studies on flax, but soy food consumption “may [indeed] reduce the risk of endometriosis.” But, I couldn’t find any studies on treating the disease with soy. There’s another food, though, associated with decreased breast cancer risk—seaweed.

Seaweeds have special types of fiber and phytonutrients not found among land plants. So, it’s not like choosing to get your beta-carotene from carrots versus a sweet potato. If you want these unique seaweed components, some of which may have anticancer properties, we need to find a way to incorporate sea vegetables into our diet.

Anticancer properties, such as anti-estrogen effects. Japanese women have among “the lowest rates of breast, endometrial, and ovarian cancers.” They have longer menstrual cycles, and lower estrogen levels circulating in their blood. And, that may help account for their low risk of estrogen-dependent cancers. We assumed this was their soy intake, but the seaweed might be helping as well.

You can drip seaweed broth on human ovary cells that make estrogen, and see estrogen levels drop, because it’s either inhibiting production or facilitating breakdown of estrogen—and may even block estrogen receptors, lowering the activity of the estrogen you do produce. This is in a petri dish, though, but it happens in women, as well.

They estimate that an effective estrogen-lowering dose of seaweed for an average American woman might be around five grams a day. But, no one has apparently tried testing it on cancer patients yet. But, it has been tried on endometriosis. Three women with abnormal cycles—two of which with endometriosis—volunteered to add a tiny amount of “dried, powdered bladderwrack,” a common seaweed, to their daily diet. It effectively lengthened their cycles, and reduced the duration of their periods—and, not just by a little.

Check out subject #1. A 30-year history of irregular periods averaging every 16 days, but, having just a teaspoon, a quarter-teaspoon, of this seaweed powder a day added ten days onto her cycle, up to 26 days. And, a half-teaspoon a day brought her up to 31—nearly doubling the length of her cycle. And, they all experienced marked reductions in blood flow, and a decreased duration of menstruation. Poor subject #1 was having periods every 16 days that lasted nine days long—can you imagine? After 30 years of this kind of craziness, just a half-teaspoon of seaweed a day, and she was having periods just once a month, and only lasting about four days. And, most importantly, in the two women suffering from endometriosis, they reported substantial alleviation of their pain. How is that possible? A 75% drop after just a quarter-teaspoon of seaweed powder a day; 85% after a half-teaspoon. 

Now, obviously, with just a couple women, no control group, we have to do bigger, better studies. But, look when this study was published—more than a decade ago, and not a single such study has been published since. Does the research world just not care about women? Millions of women are suffering with these conditions. Who’s going to fund it, though? That much seaweed costs less than five pennies; so, a larger study may never be done. But, with no downsides, I would suggest endometriosis sufferers give it a try.

In our next story, we look at how the oxidized cholesterol from eggs, processed meat, and parmesan cheese) can have cancer-fueling estrogenic effects on human breast cancer.

In 1908, the presence of cholesterol crystals was noted “in the proliferating areas of cancers,” suggesting that perhaps cholesterol, in some way, was “associated with the regulation of [cancer] proliferation.” A century later, we now recognize “the accumulation of cholesterol [as] a general feature of cancer tissue, and recent evidence suggests that cholesterol [may indeed play] critical roles in the progression of cancers, including breast, prostate, and colorectal cancers.”

Perhaps that could explain why “egg consumption was associated with increased breast cancer risk.” And, indeed, a systematic review of the evidence suggests that “dietary cholesterol intake increases risk of breast cancer,” and the more cholesterol you eat, the higher the risk appears to go. But, why?

One thought is that the “[p]rolonged ingestion of a cholesterol-enriched diet induces chronic, auto-inflammatory response,” and we know that “chronic…inflammation can lead to the initiation, promotion, and progression of tumor development.” It’s true that sprinkling some cholesterol on white blood cells in a test tube can trigger the release of inflammatory compounds, and LDL cholesterol can induce breast cancer proliferation and invasion. But again, that’s in vitro, where you can show that like breast cancer cells can migrate nearly twice as far within a day in a petri dish in the presence of LDL cholesterol. But what about in people?

Well, the level of LDL cholesterol in the blood of women diagnosed with breast cancer does appear to be “a predictive factor of breast tumor progression.” About two years after surgery/chemo/radiation, not one of the women in the lowest third of LDL cholesterol levels had a cancer recurrence. The same could not be said for women with higher cholesterol. We know cholesterol can cause inflammation in our artery walls; maybe it’s also playing an effect on breast cancer initiation and progression? They speculate that the high cholesterol levels may have a “cancer-fueling effect.” And indeed, women with breast cancer who happen to be taking cholesterol-lowering statin drugs appear to live about 40 percent longer before the cancer comes back. But the data isn’t good enough to ensure the drug benefits outweigh the risks, though lowering cholesterol with diet, one may be able to get the best of both worlds. But what does this have to do with dietary cholesterol?

Sure, animal studies show that if you feed mice cholesterol, you can accelerate their cancers, “but extrapolation to humans is difficult as dietary cholesterol has limited effects on blood cholesterol levels in humans.” Thus, “dietary cholesterol might [just] be indicative of a lifestyle prone to health-related problems, including cancer.” Maybe people are just more likely to chase bacon and eggs down with a cigarette, compared to oatmeal? It’s hard to imagine how dietary cholesterol alone could promote cancer development. But that all changed recently, with the discovery that 27-Hydroxycholesterol, a metabolite of cholesterol, “can function as an estrogen and increase the proliferation” of most breast cancer cells.

Ah, so it’s not the cholesterol itself, but what it turns into in the body. “Scientists have long struggled to understand why women with heart disease risk factors are more likely to develop breast cancer.” Now, perhaps we know. “The discovery that the most abundant oxidized cholesterol metabolite” in our bloodstream can have estrogenic effects may explain the link between high cholesterol and the development and progression of breast cancer and prostate cancer. Yes, 27-Hydroxycholesterol also stimulates the proliferation of prostate cancer cells, boosting growth by about 50 percent.

I’ve explored before the role oxycholesterols may play in mediating pro-oxidative and pro-inflammatory processes in degenerative diseases, such as Alzheimer’s and heart disease, but now it looks like oxidized cholesterol can play a role in all three stages of tumor development as well: initiation, promotion, and then the progression of the cancer. Not just promoting the growth of breast cancer cells, but also inducing their invasion and migration—potentially facilitating breast cancer metastasis through suppressing anti-cancer immunity, and then inducing angiogenesis, helping breast tumors hook up their blood supply.

This is all supported by “several lines of evidence [that point to] a pathologic role” for this cholesterol metabolite. Yeah, you can feed mice cholesterol; their oxysterol levels go up and their tumors accelerate. It “also appears to dramatically hasten the spread, or metastasis, of breast tumors to other organs.” But turning to human breast tissue samples, they found that more aggressive tumors have higher levels of the enzyme that converts cholesterol into 27-HC. In breast cancer patients with estrogen receptor-positive tumors, the 27-Hydroxycholesterol content in their breast tissue is increased overall, and especially within the tumor itself—so much so that circulating oxysterol levels in the blood may one day be used as a prognostic factor. And “breast cancer patients with low tumor levels of [the enzyme] that breaks down 27-HC did not live as long” as women who can detoxify it better. “The bottom line…is that some estrogen-driven breast tumors may rely on 27-HC to grow when estrogen isn’t available.” And that may explain a second breast cancer mystery.

Over 80 percent of breast cancers start out responding to estrogen, and so what we do is use hormone blockers—either aromatase inhibitors to stop the formation of estrogen in the first place, or tamoxifen to block its action. Despite the efficacy of these drugs, many patients relapse with resistant tumors. And that’s where oxidized cholesterol can come in. 27-HC can fuel breast cancer growth without estrogen, which could explain why sometimes these estrogen blockers don’t work.

And finally, 27-HC may explain why breast cancer patients with higher vitamin D levels appear to live longer. Vitamin D supplementation decreases 27-HC levels in the blood. The best way, though, may be to just lower overall cholesterol. Lower cholesterol, and you lower oxidized cholesterol. So, discovering this role of cholesterol is actually really good news, since “cholesterol is a highly amenable risk factor, either by lifestyle, dietary, or pharmacologic interventions.” The implications of these findings, according to the principal investigator, is that “lowering cholesterol with dietary changes or [drugs] could reduce a women’s breast cancer risk or slow tumor growth.”

Finally, when it comes to uterine fibroids, is soy helpful, harmful, or harmless?

About one in four women will eventually suffer from fibroids, most commonly manifesting as excessively heavy periods and pain or pressure. Why might you feel pressure? Because you may be carrying around 26 pounds of tumors in your uterus. Fibroids are the most common reason women get hysterectomies—having their uterus removed completely, a major surgery associated with disability and death. But, all surgery carries risk. The chances of dying within a month of surgery may only be about one in 1,200, which makes it among our safest surgeries—safer than getting your gallbladder removed, for example. But, of course, you lose the ability to bear children, and these surgeries cost billions of dollars a year. Yet, “[d]espite the high prevalence, significant [pain and suffering], and huge economic…impact…, relatively little is understood” about the cause and disease process that lead to fibroid tumors.

Avoiding atomic bomb blasts whenever you can is probably a good idea in terms of decreasing fibroids risk. But, what about more easily modifiable risk factors? Well, alcohol consumption is associated with increased risk—particularly beer. And, whenever you hear that, whenever you hear beer specifically, you think of the hormonal effects specific to beer—specifically the powerful phytoestrogen found in hops. Well, if that phytoestrogen is increasing fibroids risk, what about the phytoestrogens in soy?

Well, this was looked at in the Black Women’s Health Study. Fibroids are two to three times more prevalent among African-American women. So, they thought maybe dairy intake might be “contribut[ing] to the disparity,” given their higher levels of lactose intolerance. And, indeed, dairy consumption was associated with reduced risk. They figured it was the calcium content, or maybe the vitamin D. But perhaps the women were drinking soy milk instead, and that was increasing their risk? No. “Soy intake was [found to be] unrelated.” Same finding in a group of predominantly white women, though they did note a protective association with the amount of lignans flowing through their bodies. Lignans are another class of phytoestrogens found predominantly in flax seeds, but also throughout the plant kingdom. Hard to make any generalizations about the soy phytoestrogens, though, as soy consumption was rather low across the board. This research was done in Washington state.

If you go to Japan, where they have the highest per capita soy consumption in the world, you could get a bigger spread of intakes. The researchers had “previously found that soy…intake was inversely associated with the risk of hysterectomy”—meaning women who ate more soy had lower hysterectomy rates, suggesting a potentially protective effect of soy against uterine fibroids, since that’s the main reason women have their uterus removed. This would be consistent with in vitro studies that found that the main soy phytoestrogen seemed to inhibit fibroid tissue proliferation in a petri dish. But, when they specifically looked, “[t]here was no evidence of” a link to soy at all, protective or otherwise. The same was found in one study out of China. Fruit and vegetable intake was associated with significantly lower risk of fibroids, but soy food consumption was not.

But, a second study out of China, published the same year, found a significant association between soy milk intake and fibroids. That’s consistent with the three alarming case reports of women with symptomatic fibroids reporting “an unusually high intake of soy milk,” or “regularly consuming excessive amounts of soy,” or “extremely high intake[s] of soy…everyday” for decades. It’s hard to take these cases seriously when nowhere do they actually say how much they were consuming. The only quantitative mention was 40 grams of isoflavones, which roughly translates to 400 gallons of soy milk every day. That would be excessive, but also impossible.

The only way to know for sure is to put it to the test. Not just a population study or anecdotal reports, but randomize women to two years of soy phytoestrogens—the amount found in three to five cups of soy milk a day—and “no significant” effect on the frequency or growth of fibroids was found.

We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to nutritionfacts.org/testimonials. We may share it on our social media to help inspire others.  To see any graphs, charts, graphics, images, or studies mentioned here, please go to the NutritionFacts podcast landing page. There, you’ll find all the detailed information you need, plus links to all of the sources we cite for each of these topics. 

My last two books are “How to Survive a Pandemic” and the “How Not to Diet Cookbook.” Stay tuned for Dec 5, 2023 for the launch of my one “How Not to Age.” And – of course – all the proceeds I receive from the sales of all my books go to charity. 

NutritionFacts.org is a non-profit, science-based public service where you can sign up for free daily updates – or the latest in nutrition research via bite-sized videos and articles. Everything on the website is free. There are no ads, no corporate sponsorship, no kickbacks. It’s strictly non-commercial. I’m not selling anything. I just put it up as a public service, as a labor of love, as a tribute to my grandmother, whose own life was saved with evidence-based nutrition.

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