Breast Cancer Survival and Soy

In my Care2 posts last week, The Best Detox and Breast Cancer Stem Cells vs. Broccoli, I documented ways to boost our liver’s ability to clear carcinogens, make our DNA more resistant to any damaging agents that make it past our first line of defense, and then ramp up immune surveillance of any budding tumors—all in hopes of preventing cancer. But what about for those who already have it?

Though small consolation, one consequence of the fact that breast cancer is now the #1 cancer killer of young women is that breast cancer survival is a very active area of research. For example, a major study was recently published that followed 4,000 women with breast cancer for 7 years. Not all of them made it to the end. The researchers tried to figure out if there was anything about the diets of the non-survivors that may have played a role in their deaths. Two dietary components in particular were associated with an early death: saturated fat and trans fat.

Breast cancer survivors may decrease their risk of dying by 41% simply by avoiding saturated fat, found primarily in the American diet in cheese, chicken, and junk food (see my 3-minute video Breast Cancer Survival, Butterfat, and Chicken). And breast cancer survivors may improve their survival 78% by avoiding trans fat, found primarily in in junk food and animal products (see my 1-minute video Breast Cancer Survival and Trans Fat). Ideally everyone should try to minimize the intake of both, as explained in Trans Fat, Saturated Fat and Cholesterol: Tolerable Upper Intake of Zero.

On the other hand, the two foods expected to improve breast cancer survival are flax seeds and soy products. Breast cancer is initially so slow-growing that women may have tumors for years or even decades before they’re diagnosed (see my 1-minute video Cancer Prevention and Treatment May Be the Same Thing). So one might expect that the same dietary factors that helped grow the tumor in the first place would keep goading it on after diagnosis. This may not always be the case, though. Alcohol, for example, is strongly associated with breast cancer risk, but the data has been mixed as to whether once you already have a full-blown tumor, it makes a difference if you continue to drink or not. Still, in general, the diet that helps prevent breast cancer is the same diet that’s going to help prolong survival. And that certainly seems to be the case for the phytonutrients found in flax and soy.

Flax seeds are the most concentrated source of lignans, a class of cancer-fighting compounds that may cut breast cancer mortality risk in half (see my 3-minute video Breast Cancer Survival and Lignan Intake). Interestingly, there are no lignans actually found in the seeds, just precursors that the good bacteria in our gut turn into lignans. This may explain why women who have frequent urinary tract infections have higher breast cancer rates—the courses of antibiotics wipe out the gut flora critical to the production of these anti-cancer compounds (see my 2-minute Flax and Fecal Flora).

Soy foods appear to help prevent breast cancer and prolong survival more directly, though—the subject of today’s NutritionFacts.org video pick shown above.

In health,
Michael Greger, M.D.

image credit: imgdive / Flickr and MesserWoland / Wikimedia Commons

Related:
Dietary Sexual Dysfunction
Harvard’s Meat and Mortality Studies
Medical Establishment Resistance: The Tomato Effect

169 comments

Gary Loewenthal
Gary Loewenthal2 years ago

To correct some misinformation:
- It is easy to get enough protein on a moderately-balanced vegan diet. A diversity of champion athletes, including "the world's strongest man" and the American record-holder in the ultra-marathon, are vegan and have sky-high protein requirements. There are some websites that show the nutrient quantities in typical vegan meal plans, and you can see there is more than enough protein.

- The bulk of peer-reviewed studies show that soy helps protect against various cancers, and may have a modest beneficial effect on bone and heat health. For example, in a published study of 13,000 Seventh Day Adventist men, those who drank soymilk regularly instead of cow's milk had a 70% lower risk of prostate cancer. The American Cancer Society, hardly a bastion of animal rights, states that three servings of soy a day is safe for breast cancer patients. The Shanghai Breast Cancer Survival Study of 5042 breast cancer survivors over 7 years states that
“Soy food intake, as measured by either soy protein or soy isoflavone intake, was inversely associated with mortality and recurrence." And so on...

- There is a backlash against soy because its popularity as an alternative to meat threatens the powerful meat industry. The studies purporting to show dangers of soy tend to be un-replicated one-offs or notoriously contrived and unreliable animal studies.

Magdalen B.
Magdalenb B.2 years ago

"the two foods expected to improve breast cancer survival are flax seeds and soy products" Can you buy soya products that are not genetically buggered about with?

Gary Loewenthal
Gary Loewenthal2 years ago

Overwhelmingly, peer-reviewed studies show soy - fermented and unfermented - to reduce the risk, recurrence, and mortality of reproductive cancers. The Okinawan elders, often considered the healthiest, longest-lived people in the world, eat a lot of unfermented soy, such as tofu. 12 percent of their calories come from soy.

This article has more info, including links to peer-reviewed studies and meta-analyses: http://zenhabits.net/soy/

What *does* interfere with hormones is dairy. Because dairy cows today are forced to be almost constantly lactating, even while pregnant, their milk is flooded with real estrogens, not the phytoestrogens found in plant foods such as soy, which operate much differently and provide a hedge against the dangers of actual estrogens.

Vikki H.
Vikki H.3 years ago

My type of breast cancer is estrogen positive so I was encouraged to eat less soy. Itake an estrogen blocker everyday. Now I'm confused

Dale Overall

It would be nice if people expressing differing viewpoints could just discuss things pleasantly without bashing each other with two by fours.

Think that I will avoid soy for the most part because of GMO problems and stick to quinoa and yes meat in small portions, salad, fruit and veggies.

Elizabeth O.
.3 years ago

Thanks for posting.

Lynda H.
Lynda Hayles3 years ago

Jelka V, I think I can answer your question. Care2 pushes vegetarianism/animal rights (not welfare), and it is difficult to get enough protein on a vegetarian diet - especially a vegan one. Soy is very high in protein, and can be processed to imitate meat or dairy. Even if bona fide, real scientific studies prove how bad non-fermented soy products are for you, bogus, biased studies can be easily manufactured to refute them.

They’re still pushing the long debunked saturated fat and cholesterol warnings, for the same reason. http://www.cholesterol-and-health.com/Does-Cholesterol-Cause-Heart-Disease-Myth.html#17

This article was presented by Dr Michael Gregor, one of the vegan directors of the animal rights group HSUS. http://www.ncraoa.com/AR_AW_WhatYouShouldKnow.html

Lynda H.
Lynda Hayles3 years ago

Jelka V, I think I can answer your question. Care2 pushes vegetarianism/animal rights (not welfare), and it is difficult to get enough protein on a vegetarian diet - especially a vegan one. Soy is very high in protein, and can be processed to imitate meat or dairy. Even if bona fide, real scientific studies prove how bad non-fermented soy products are for you, bogus, biased studies can be easily manufactured to refute them.

They’re still pushing the long debunked saturated fat and cholesterol warnings, for the same reason. http://www.cholesterol-and-health.com/Does-Cholesterol-Cause-Heart-Disease-Myth.html#17

This article was presented by Dr Michael Gregor, one of the vegan directors of the animal rights group HSUS. http://www.ncraoa.com/AR_AW_WhatYouShouldKnow.html

Joe R.
Joe R.3 years ago

A bit confused here. Lots of conflicting opinions.

Bob P.
Bob P.3 years ago

thanks