Flax Seeds & Breast Cancer Prevention

Flax Seeds & Breast Cancer Prevention
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Young women at high risk for breast cancer given just a teaspoon of ground flaxseeds a day showed fewer precancerous changes.

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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.

A quarter-century ago, a theory was put forth as to why those eating plant-based diets have lower cancer rates. Vegetarians appeared to have up to three times the level of lignans circulating within their bodies, thanks to the grains and other plant foods they were eating, these anticancer compounds.

Back in 1980, a new compound was described in human urine, a compound X—originally thought to be a new human hormone, but later identified to be from a large group of fiber-associated compounds, widely distributed in edible plants, known as lignans.

Population studies suggest that high intake reduces breast cancer risk. But, where’s it found? Seeds, whole grains, vegetables, fruits, berries. With that kind of list of healthy foods, why isn’t this just like the fiber story, where, you know, lignan intake is maybe just a surrogate marker for healthy plant food intake?

Well, in a petri dish, lignans do directly suppress the proliferation of breast cancer cells—but, only after the plant lignans are converted into human lignans by the bacteria in our gut. That’s why we want to use antibiotics judiciously, because a few days on antibiotics dramatically drops your body’s ability to make these anticancer compounds from the plants we eat. And, it can take weeks for our good bacteria to recover.

That’s why women with urinary tract infections may be at higher risk for breast cancer, because every time they took a course of antibiotics, they may be stymying their good bacteria’s ability to take full advantage of all the plants they were eating—though this remains little more than a hypothesis, or educated guess, at this point.

This is the National Cancer Institute study that provided the strongest evidence to date that there may indeed be something special about the lignan class of phytonutrients for breast cancer prevention. They took a bunch of young women at high risk for breast cancer—meaning they had a suspicious breast biopsy (showing either precancerous changes, or carcinoma in situ), or already had breast cancer in the other breast—and gave them a teaspoon of ground flaxseeds every day for a year, before getting repeat needle biopsies to see if there were any changes.

Yes, there are lignans in sesame seeds, nuts, whole grains, legumes, certain fruits, and veggies, but they’re most concentrated in flax seeds. They could have instead asked women to eat ten cups of strawberries a day for a year, but, they’d probably get better compliance with just their teaspoon of ground flax seeds.

So, what happened by the end of the year? The primary endpoint was the expression of a proliferation biomarker associated with cancer, called Ki-67. In 9 of the 45 women it went up (those in red), but in the other 80% of the women, it went down. And, overall, they found less cellular proliferation in their breast tissue, and fewer precancerous changes.

For those who don’t like the taste of flax seeds, sesame seeds may work just as well. Even though flax seeds have significantly more lignans than sesame, you appear to produce about the same amount of lignans from them—though this was comparing them whole. And, when you feed people whole flaxseeds, some may not get chewed up, and may pass right through you. So, ground flaxseed may be the best source, overall.

Please consider volunteering to help out on the site.

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.

A quarter-century ago, a theory was put forth as to why those eating plant-based diets have lower cancer rates. Vegetarians appeared to have up to three times the level of lignans circulating within their bodies, thanks to the grains and other plant foods they were eating, these anticancer compounds.

Back in 1980, a new compound was described in human urine, a compound X—originally thought to be a new human hormone, but later identified to be from a large group of fiber-associated compounds, widely distributed in edible plants, known as lignans.

Population studies suggest that high intake reduces breast cancer risk. But, where’s it found? Seeds, whole grains, vegetables, fruits, berries. With that kind of list of healthy foods, why isn’t this just like the fiber story, where, you know, lignan intake is maybe just a surrogate marker for healthy plant food intake?

Well, in a petri dish, lignans do directly suppress the proliferation of breast cancer cells—but, only after the plant lignans are converted into human lignans by the bacteria in our gut. That’s why we want to use antibiotics judiciously, because a few days on antibiotics dramatically drops your body’s ability to make these anticancer compounds from the plants we eat. And, it can take weeks for our good bacteria to recover.

That’s why women with urinary tract infections may be at higher risk for breast cancer, because every time they took a course of antibiotics, they may be stymying their good bacteria’s ability to take full advantage of all the plants they were eating—though this remains little more than a hypothesis, or educated guess, at this point.

This is the National Cancer Institute study that provided the strongest evidence to date that there may indeed be something special about the lignan class of phytonutrients for breast cancer prevention. They took a bunch of young women at high risk for breast cancer—meaning they had a suspicious breast biopsy (showing either precancerous changes, or carcinoma in situ), or already had breast cancer in the other breast—and gave them a teaspoon of ground flaxseeds every day for a year, before getting repeat needle biopsies to see if there were any changes.

Yes, there are lignans in sesame seeds, nuts, whole grains, legumes, certain fruits, and veggies, but they’re most concentrated in flax seeds. They could have instead asked women to eat ten cups of strawberries a day for a year, but, they’d probably get better compliance with just their teaspoon of ground flax seeds.

So, what happened by the end of the year? The primary endpoint was the expression of a proliferation biomarker associated with cancer, called Ki-67. In 9 of the 45 women it went up (those in red), but in the other 80% of the women, it went down. And, overall, they found less cellular proliferation in their breast tissue, and fewer precancerous changes.

For those who don’t like the taste of flax seeds, sesame seeds may work just as well. Even though flax seeds have significantly more lignans than sesame, you appear to produce about the same amount of lignans from them—though this was comparing them whole. And, when you feed people whole flaxseeds, some may not get chewed up, and may pass right through you. So, ground flaxseed may be the best source, overall.

Please consider volunteering to help out on the site.

Images thanks to mimitalks, married w/children via flickr

Doctor's Note

Today begins my three-part video series on the role flax seeds may play in the prevention and treatment of breast cancer. I covered their role in prostate cancer in Flax Seeds vs. Prostate Cancer, and Was It the Flax Seeds, Fat Restriction, or Both?. Then, I looked at their impact upon blood sugar control (Flax Seeds vs. Diabetes) and skin health (Flax Seeds for Sensitive Skin).

When I say “why isn’t it just like the fiber story,” I’m referring to my previous video, Fiber vs. Breast Cancer. The graph comparing the lignan contents of various foods is from my video, Breast Cancer Survival and Lignan Intake. Sorry if I covered the UTI-breast cancer connection a little fast—more background on the role our good bacteria play in Flax and Fecal Flora. As I note in the Flax Seeds for Sensitive Skin video, ground flax stays fresh, even at room temperature, for at least a month.

What if you or a loved one has already been diagnosed with breast cancer, though? I hope you’ll find my next two videos useful: Flax Seeds & Breast Cancer Survival: Epidemiological Evidence, and Flax Seeds & Breast Cancer Survival: Clinical Evidence.

For further context, also check out my associated blog posts: Treating Sensitive Skin From the Inside OutFlax and Breast Cancer Prevention; and Flax and Breast Cancer Survival.

If you haven’t yet, you can subscribe to my videos for free by clicking here.

44 responses to “Flax Seeds & Breast Cancer Prevention

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  1. Dr. Gregor,

    According to Jeff Novick, chia seeds are better utilized by the body as keeping flax seeds fresh is difficult. I had estrogen receptor positive Breast Ca in situ, stage 1 in 2009. Since then I use chia seeds in my morning smoothie. Are there sufficient lignans in chia seeds? I don’t grind them, should I?




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    1. Milled chia seeds are being marketed now, so I expect yes.

      I’d like Dr Greger to evaluate any further research on chia versus flax. So far, he’s favored flax versus chia, though including both in one’s diet is great for variety.

      Storing ground flax is not “difficult”. That sounds like marketing.




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      1. Whole seeds are stable for long long time against oxidation. Even Flax. Research shows that even ground flaxseed is stable for a month at room temperature. A cheap coffee grinder makes short work of a tablespoon of flaxseed. Grind daily if you are concerned. I dearly wish I could tolerate it myself! Good luck




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    2. Unlike flax (with its lignans) or soy (with its isoflavones), there’s no phytoestrogen modulating normal estrogen binding in chia.

      Some (eg. bodybuilders) prefer chia for this very reason.

      Chia fats are readily absorbed without milling, unlike flax.




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    1. MacSmiley: Funny you should say this. I found a website describing the difference between golden and brown and they said the brown ones are milder. :-)

      Perhaps the thing to do it for people to try the other type if they haven’t yet. Also, I think the easiest thing to do is mix it up in something where you won’t be tasting the flax seed at all. I don’t taste them in my chocolate oatmeal and others don’t taste them in their smoothies.

      How do you eat your flax seed?




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      1. To each his own.

        I eat one tablespoon a day of ground brown flaxseed. Half a tablespoon goes in my smoothie and half in my oatmeal. (Take old-fashioned rolled oats, add boiled water and flaxseed, and let it sit for 5 minutes.) I then pour a little of my smoothie into the oatmeal for flavor.




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          1. I’ve never liked cooked oatmeal but always loved granola and oatmeal cookies. So I was grateful to Dr. Esselstyn for pointing out in an interview that rolled oats are already cooked. The grain is steamed before it is rolled flat. It’s the only processed food I eat.




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            1. I do not like cooked rolled oatmeal either! I believe it is mostly a texture problem for me.

              A couple years ago, I discovered steel cut oatmeal. That was a big moment for me. All of sudden, I was liking oatmeal, at least the way I started preparing it.

              More recently, I modified an idea that I got from (I think) Dreena Burton: I take whole, raw (organic) groats (the whole grain oatmeal) and grind them up in my blender to pretty much a powder. Than each morning, I mix some fo that with: ground flax seed, alma powder pinch, cocoa powder, home-made date paste and almond milk. Microwave for 2 minutes. Stir. Then microwave for 1-2 more minutes. I then mound it up in the center of the bowl and poor in a moat of almond milk before eating. I love it. This idea works with other grains too such as wheatberries and millet.

              Just thought I would share some oatmeal ideas.




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  2. Aloha Dr. Greger,

    You cover in this video the adverse effect that antibiotics have on gut flora which raises a question for us as to other substances, foods, beverages etc. that could adversely affect gut flora. We are wondering specifically about alcoholic beverages generally and in particular red wine.

    Thank you




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  3. This is the real Mayo Clinic I think, saying some really cautionary stuff about flaxseed: http://www.mayoclinic.com/health/flaxseed/NS_patient-flaxseed/DSECTION=safety

    When you ignore the “balance” and tout the wonderfulness of something you are obviously sold on you put yourself on par with Dr. Oz (BARF!). Isn’t the Mayo some of the science that your read so we don’t have to?

    I love you, you save many lives …among them mine. This question sounds harsh on rereading…becasuse i have no tact. forgive me but I have been so sick for so long trying to get the goodness of flax. I blow up with major IBS flare up everytime I grind up a tablespoon of flaxseed into my porridge. No Flax = wonderful quality throne time.




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    1. Cambria wouldn’t you then just decide flax isn’t for you? Don’t eat it. We hear so much about the benefits of turmeric but it doesn’t like me. (Mad rush to the toilet) That doesn’t mean I wouldn’t still recommend someone with joint pain give it a try to see if they get relief. Better than a daily dose of NSAID.




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      1. I agree, just like wheat or certain whole grains may not be for someone who is gluten intolerant, and nuts may not be for someone who has nut allergies, it seems that flax seeds can be put in this category as well. Although, I do have to say that the Mayo web-site link did mention some interesting cautionary effects regarding flax seed safety, side effects, and warnings; some directly counter to what has been stated on this site. I’m not sure if the Mayo claims should be ignored, either.




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      2. You might have a iodine deficiency
        if you have pain. Pain often disappears with Iodine. Did you remove
        salt from your diet? I think the salt in snacks should have iodine.
        At the first sign of pain, have some iodine. Sea salt is the worst. Table salt is great. Perhaps Iodine is being rationed.




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    1. From studies on flax processing (most behind paywalls) the lignan content (and hence estrogen antagonist effect) seems uneffected by sterilizing heat, though broiler heat is higher. Recovery of flax α-linolenic acid (its anti-inflammatory omega-3 fat) goes down by about a quarter when flax is baked in goods.

      Sesame lignans can stand microwave roasting for 30 minutes losing only about 20%.

      There’s not a lot in the literature, but it seems toasting would reduce beneficial compounds somewhat, not kill them.




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  4. On the news this morning was an item about organic apples and pears being sprayed with antibiotics. As a result, antibiotic resistant bacteria are developing. Apparently there is a loophole for farmers to do this. I don’t want to give up these fruits. How safe is it to eat them and what can we do to protect ourselves, if we do? Thank you. –AliceJ




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    1. You are correct there are a lot of loopholes and beyond that some farmers and folks in the food processing industry break the rules. The best way to avoid chemicals in the environment is to avoid animal products… see http://nutritionfacts.org/video/presidents-cancer-panel-report-on-environmental-risk/ and see http://nutritionfacts.org/video/lowering-dietary-antibiotic-intake/. Going beyond that we can protect ourselves by washing our produce wash our produce and to buy organic and non GMO foods.




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  5. Whats about flaxseeds and cadmium and cyano glycoside and these study:

    Health aspects of partially defatted flaxseed, including effects on serum lipids, oxidative measures, and ex vivo androgen
    and progestin activity: a controlled crossover trial ? Thank you for an answer. By the way excuse my bad grammar because i´m from germany.




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  6. Dr. Greger,
    Thank you for making empirically based nutrition information so easily accessible! After watching your videos regarding nutrition and breast cancer prevention and survival I am wondering if there is any specific information regarding nutrition and premenopausal breast cancer associated with inherited mutations of the BRCA1 and BRCA2 genes? These women are at high risk (60-80% increased risk from what I’ve read); were they included in this study? If not, is there data on this anywhere? Thanks!




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  7. I don’t know if the beech tree is very common in the States, but here in Europe I often go beech nut gathering. It strikes me that linseed, which I’ve only recently been adding to my morning oatmeal, has a somewhat similar taste. Has the beech nut come up in any nutrional studies?
    Thanks for all the hard work doctor.




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  8. I have heard that flax has estrogenic effects & therefore, women should be cautious. I am a healthy middle-aged female & eat whole flax daily. Should I be concerned?




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    1. Holy hell! I’m eating 2 TABLESPOONS of the ground flax each day…so far, so good at age 57, just saying…ground flax is awesome from all perspectives I’ve researched!




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  9. My wife throws 2T flax in a vitamix with 3 dates and 2cups hot water and some cinnamon (can also add vanilla or vanilla bean)-and its a yummy warm shake-like drink to have as dessert or as a companion to some fresh veggie juice.




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  10. In the Ki-67 biomarker study, 9 individuals showed increase in this biomarker after eating flax. Doesn’t anyone find that scary? Weren’t some individuals responding to the lignans adversely? For 20percent of the women breast cancer risk increased right? I want to know more about this study. A sample of 45 is not that big. My mother died of estrogen driven breast cancer. I eat plant based but maybe I should avoid flax. It’s frustrating because I love flax and would eat it daily if I didn’t have doubts.




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    1. Yes! I noticed that, too, and am troubled by it. I’d like to think that eating flax seed isn’t a roll of the dice, but that statistic made me think that maybe it is. Great benefits for many people, but serious down sides for others, and there’s no way of knowing which group you’ll fall in.




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      1. I am one of those who is bothered by flax. I get breasts pains from flax. Also soy. Despite all the health claims, it’s a no no for me personally.




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  11. I have always read great things about flax seed and what it does for the body, especially related to breast cancer prevention. But I just read something that made me a little alarmed (because I’ve been eating the stuff daily for years now because of those recommendations!). According to this, the lignans are good and all, but it’s often grown in areas where it absorbs high levels of cadmium and copper, and both of those can lead to breast cancer growth, for different reasons. The recommendation was to limit yourself to no more than a teaspoon a day, or to consume ONLY flax seed growth in northern Canada. Not China or even the Dakotas or southern Canadian plains. ????




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    1. Well it is well past its posting time but just in case. The idea that we consume seeds that we haven’t a clue what has really happened in their processing astonishes me. Some are heated to ridiculous temperatures and x-rayed.
      When I grind flax, I get no hint of oil from the seeds at all, just dry powder. Now where has all that oil gone?
      As for purchasing any foodstuffs from China, especially the one’s marked organic, that is pure folly.




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  12. Interesting, but I’d have you look at the role of vitamin F of both flax and sesame seeds. F pushes the calcium to the tissues and raises iodine levels in the blood and tissues. That is possibly why you see the reaction in both seeds. Both calcium and iodine in the tissues reduce breast cancer.




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