What Does Drinking Soy Milk Do to Hormone Levels?

The vast majority of breast cancers start out hormone-dependent, where estradiol, the primary human estrogen, “plays a crucial role in their breast cancer development and progression.” That’s one of the reasons why soy food consumption appears so protective against breast cancer: Soy phytoestrogens, like genistein, act as estrogen-blockers and block the binding of estrogens, such as estradiol, to breast cancer cells, as you can see at 0:24 in my video How to Block Breast Cancer’s Estrogen-Producing Enzymes.

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 that breast cancer tumors produce their own estrogen from scratch to fuel their own growth.

As you can see at 1:03 in my video, “estrogens may be formed in breast tumors by two pathways, namely the aromatase pathway and sulfatase pathway.” The breast cancer takes cholesterol and produces its own estrogen using either the aromatase enzyme or two hydroxysteroid dehydrogenase enzymes.

So, there are two ways to stop breast cancer. One is to use anti-estrogens—that is, 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 that 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? This occurred in breast cancer cells, too, and not only was aromatase activity suppressed, but that of the other estrogen-producing enzyme, as well. But this was in a petri dish. Does soy also suppress estrogen production in people?

Well, as you can see at 2:34 in my video, circulating estrogen levels appear significantly lower in Japanese women than Caucasian American women, and Japan does have the highest per-capita soy food consumption, but you can’t know it’s the soy until you put it to the test. Japanese women were randomized to add soy milk to their diet or not for a few months. Estrogen levels successfully dropped about a quarter in the soy milk supplemented group. Interestingly, as you can see at 3:04 in my video, when the researchers 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 who were already consuming soy in their baseline diet. So, the study was really just looking at higher versus lower soy intake. What happens if you give soy milk to women in Texas? As you can see at 3:29 in my video, circulating estrogen levels were cut in half. Since increased estrogen levels are “markers for high risk for breast cancer,” the effectiveness of soy in reducing estrogen levels may help explain why Chinese and Japanese women have such low rates of breast cancer. What’s truly remarkable is that estrogen levels stayed down for a month or two even after the subjects stopped drinking soy milk, which suggests you don’t have to consume soy every day to have the cancer protective benefit.

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 about 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:

 You may also be interested in:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

High Blood Pressure May Lead to Low Brain Volume

Having hypertension in midlife (ages 40 through 60) is associated with elevated risk of cognitive impairment and Alzheimer’s dementia later in life, even more so than having the so-called Alzheimer’s gene.

“It is clear that cerebral vascular disease”—that is, hardening of the arteries inside our brain—“and cognitive decline travel hand in hand,” something I’ve addressed before. “However, the independent association of AD [Alzheimer’s disease] with multiple AVD [atherosclerotic vascular disease] risk factors suggests that cholesterol is not the sole culprit in dementia.”

As I discuss in my video Higher Blood Pressure May Lead to Brain Shrinkage, one of the most consistent findings is that elevated levels of blood pressure in midlife, ages 40 through 60, is associated with elevated risk of cognitive impairment and Alzheimer’s dementia later in life—in fact, even more so than having the so-called Alzheimer’s gene.

“The normal arterial tree”—all the blood vessels in the brain—“is…designed as both a conduit and cushion.” But when the artery walls become stiffened, the pressure from the pulse every time our heart pumps blood up into our brain can damage small vessels in our brain. This can cause “microbleeds” in our brain, which are frequently found in people with high blood pressure, even if they were never diagnosed with a stroke.

These microbleeds may be “one of the important factors that cause cognitive impairments,” “perhaps not surprising[ly],” because on autopsy, “microbleeds may be associated with [brain] tissue necrosis,” meaning brain tissue death.

And speaking of tissue death, high blood pressure is also associated with so-called lacunar infarcts, from the Latin word lacuna, meaning hole. These holes in our brain appear when little arteries get clogged in the brain and result in the death of a little round region of the brain. Up to a quarter of the elderly have these little mini-strokes, and most don’t even know it, so-called silent infarcts. But “no black holes in the brain are benign.” As you can see at 2:12 in my video, it’s as though your brain has been hole-punched.

“Although silent infarcts, by definition, lack clinically overt stroke-like symptoms, they are associated with subtle deficits in physical and cognitive function that commonly go unnoticed.” What’s more, they can double the risk of dementia. That’s one of the ways high blood pressure is linked to dementia.

There’s so much damage that high blood pressure levels can “lead to brain volume reduction,” literally a shrinkage of our brain, “specifically in the hippocampus,” the memory center of the brain. This helps explain how high blood pressure can be involved in the development of Alzheimer’s disease.

As you can see at 3:02 in my video, we can actually visualize the little arteries in the back of our eyes using an ophthalmoscope, providing “a noninvasive window” to study the health of our intracranial arteries, the little vessels inside our head. Researchers “found a significant association” between visualized arterial disease and brain shrinkage on MRI. However, because that was a cross-sectional study, just a snapshot in time, you can’t prove cause and effect. What’s needed is a prospective study, following people over time. And that’s just what the researchers did. Over a ten-year period, those with visual signs of arterial disease were twice as likely to suffer a significant loss of brain tissue volume over time.

What can we do about high blood pressure? A lot! See, for example:

What else can we do to forestall cognitive decline or dementia? I referenced my video Alzheimer’s and Atherosclerosis of the Brain earlier, and here are other videos that offer information on treatment and prevention:


In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Are the BPA-Free Plastics Like Tritan Safe?

Do BPA-free plastics such as Tritan, have human hormone-disrupting effects? And what about BPS and BPF?

Recent human studies indicate that exposure to the plastics chemical BPA may be associated with infertility, miscarriage, premature delivery, reduced male sexual function, polycystic ovaries, altered thyroid and immune function, diabetes, heart disease, and more. Yet, “[a]s recently as March 2012, FDA stated that low levels of BPA in food are considered safe.” However, just months later, to its credit, the agency banned the use of BPA plastics in baby bottles and sippy cups. Regulators standing up to industry? Maybe I shouldn’t be so cynical! But, wait. The ban was at the behest of the plastics industry. It had already stopped using BPA in baby bottles so it was their idea to ban it.

The industry had switched from BPA to similar compounds like BPF and BPS. So, our diets now contain everything from BPA to BPZ, and the majority of us have these new chemicals in our bodies as well. Are they any safer?

As I discuss in my video Are the BPA-Free Alternatives Safe?, based on the similarities of their chemical structures, they are all predicted to affect testosterone production and estrogen receptor activity, as you can see at 1:40 in my video. However, they were only recently put to the test.

As you can see at 1:50 in my video, we’ve known BPA significantly suppresses testosterone production, and, from “the first report describing BPS and BPF adverse effects on physiologic function in humans,” we know those compounds do, too. Well, kind of. The experiments were performed on the testicles of aborted human fetuses. But, the bottom line is that BPS and BPF seem to have “antiandrogenic anti-male hormone effects that are similar to those of BPA.” So when you’re assured you shouldn’t worry because your sales slip is BPA-free, the thermal paper may just contain BPS instead. What’s more, BPS receipts may contain up to 40 percent more BPS than they would have contained BPA. So BPA-free could be even worse. In fact, all BPA-replacement products tested to date released “chemicals having reliably detectable EA,” estrogenic activity.

This includes Tritan, which is specifically marketed as being estrogen-activity-free. As you can see at 3:06 in my video, however, researchers dripped an extract of Tritan on human breast cancer cells in a petri dish, and it accelerated their growth. This estrogenic effect was successfully abolished by an estrogen blocker, reinforcing it was an estrogen effect. Now, the accelerated growth of the cancer cells from the Tritan extract occurred after the plastic was exposed to the stressed state of simulated sunlight. Only one out of three Tritan products showed estrogen activity in an unstressed state, for instance when they weren’t exposed to microwaving, heat, or UV rays. “Because there would be no value in trading one health hazard for another, we should urgently focus on the human health risk assessment of BPA substitutes.”

In the meanwhile, there are steps we can take to limit our exposure. We can reduce our use of polycarbonate plastics, which are usually labeled with recycle codes three or seven, and we can opt for fresh and frozen foods over canned goods, especially when it comes to tuna and condensed soups. Canned fruit consumption doesn’t seem to matter, but weekly canned vegetable consumption has been associated with increased BPA exposure. If you do use plastics, don’t microwave them, put them in the dishwasher, leave them in the sun or a hot car, or use once they’re scratched. But using glass, ceramic, or stainless steel containers is probably best.

For more on BPA, check out my videos:

Unfortunately, BPA isn’t the only plastics chemical that may have adverse health effects. See:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: