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Might flax seeds (ALA) increase prostate cancer risk?

There are a lot discussions and articles online about the supposed connection between flax seeds (ALA) and prostate cancer – suggesting that more flax consumed = increase chance of prostate cancer. I haven’t found this issue addressed on your website (sorry if I missed it). Can you comment? Thanks!

DSikes / Originally posted below Just the Flax, Ma’am

Answer:

The latest meta-analysis of prospective studies found that, if anything, alpha-linolenic acid (ALA, the omega-3 fat in flax) was protective against prostate cancer. Men consuming more than 1.5 g/day appeared to have significantly lower risk (the amount found in about a tablespoon of ground flax seeds).

One of the reasons there’s been so much conflicting data is that ALA is found in great foods (dark green leafies) and less than great foods (meat), and so ALA intake is not necessarily a marker of healthy eating. What you want is a randomized controlled study of men with prostate cancer. Give half of them flax and see what happens. And that was done! (full text here)

Researchers at the University of Texas Anderson Cancer Center took a bunch of men with prostate cancer about a month before they were to go into surgery. Half were put on a few tablespoons of ground flax a day and after surgery their cancerous prostates were examined. The proliferation rates of the cancer in the flax-eaters were only half that of the controls, confirming the test-tube studies done on prostate cancer cells suggesting that flax can indeed slow prostate tumor growth.

For more on the effect of flax nutrients see videos such as:

Image credit: AlishaV/ Flickr

Dr. Michael Greger

About Michael Greger M.D.

Michael Greger, M.D., is a physician, author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial. Currently Dr. Greger proudly serves as the Director of Public Health and Animal Agriculture at the Humane Society of the United States.

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  • Joe

    Table 11 of veganhealth.org’s Omega-3 article at http://www.veganhealth.org/articles/omega3
    says that the Nurse’s Health Study found that more than 1.25 – 1.5
    grams per day of ALA can possibly cause eye problems. One tablespoon of
    flaxseeds contains of 1.6 grams of ALA (see Table 8). So taking just
    one tablespoon of flaxseed a day could
    possibly be dangerous to your eyesight, unless flax is exempt from the
    Nurses Health Study findings. So is flax exempt from those findings?

    • Mela Rossa

      Flaxseed “oil”.

      Read up on lipid peroxidation. :)

  • Derrek

    I was wondering if anyone knew of anything to help with dandruff. I have a dry flaky scalp, and not sure if it is eczema, seborrhea dermatis or etc.

    I know people recommend that this suggests a lack of omega 3′s. I have trying to eat 2 tablespoons of flax seed a day and have also been taking two vegan omega 3 supplements. Do I need both EPA and DHA and how much should I be consuming per day?

    • barbarabrussels

      apparently a shampoo with selenium used to be very popular, I wonder if selenium itself has anything to do with the effectiveness. Just a thought…

    • Mela Rossa

      Omega 6 deficiency is the cause of dry skin.

      Omega 6 fatty acids from whole foods like nuts and seeds though.

      Avoid oxidized seed oils.

      • Toxins

        Omega 6 deficiency is essentially unknown. This population actually has trouble from getting too much omega 6.

        • Mela Rossa

          Omega 6 deficiency is known in families where extra virgin olive oil is consumed and where seed oils, nuts and seeds aren’t consumed. I grew up like this.

          Omega 6 fatty acids from whole foods are converted by intestinal bacteria into conjugated linoleic acids which promote the burning of fat as fuel.

          I get your point though. Its just that Omega 6 fatty acids are superior from whole foods and it is unfortunate that they are slandered just because most people consume them in oxidized form from them oils.

          I think his problem could be caused by gluten. I’ve noticed now that I haven’t had dandruff since I quit gluten.

          • Toxins

            Actually, Omega 6′s are converted to arachidonic acid once absorbed and competitive enzymes do the rest. Even a high olive oil diet provides more then enough omega 6. All foods are rich sources of omega 6, it isn’t possible, unless undernourished, to not get enough omega 6.

          • Mela Rossa

            Not all the Omega 6 fatty acids that are absorbed are converted right away into arachidonic acid. Excess linoleic acid is stored in adipose tissue and is known to lower cholesterol(lipoprotein) levels however most people consume oxidized lipids from seed oils which cause inflammation in the body. Read up on “Linoleic acid hydroperoxide”. Or they consume arachidonic acid directly from animal foods loaded with toxins that set off inflammation.

            Olive oil doesn’t provide sufficient quantities of quality Omega 6 fatty acids. The WHO recommendations are WAY underestimated because we have omega 6 alarmists that DON’T understand the science.

            http://en.wikipedia.org/wiki/Endocannabinoid_system
            http://en.wikipedia.org/wiki/Neurotrophin
            http://en.wikipedia.org/wiki/Prostaglandins
            http://www.sciencedirect.com/science/article/pii/S0014579304002467

            Omega 6 fatty acids from whole foods are required to increase cranial size and produce our own THC.

          • Toxins

            What you are arguing goes completely against public health concerns. Please research from reputable health resources. From the national academy of science.

            “Linoleic acid is the only n-6 polyunsaturated fatty acid that is an essential fatty acid; it serves as a precursor to eicosanoids. A lack of dietary n-6 polyunsaturated fatty acids is characterized by rough and scaly skin, dermatitis, and an elevated eicosatrienoic acid:arachidonic acid (triene:tetraene) ratio. The AI for linoleic acid is based on the median intake in the United States where an n-6 fatty acid deficiency is nonexistent in healthy individuals. The AI is 17 g/d for young men and 12 g/d for young women. While intake levels much lower than the AI occur in the United States without the presence of a deficiency, the AI can provide the beneficial
            health effects associated with the consumption of linoleic acid (see Chapter 11). There is insufficient evidence to set a UL for n-6 polyunsaturated fatty acids…Linoleic acid is the precursor to arachidonic acid, which is the substrate for eicosanoid production in tissues”

            As I have been saying with the conversion rates “Thus, high intakes of n-3 fatty acids or arachidonic and linoleic acids will reduce the efficiency of conversion of linoleic acid to arachidonic acid and α-linolenic acid to its products…n-6 Fatty acids are almost completely absorbed and are either incorporated into tissue lipids, utilized in eicosanoid synthesis, or oxidized to carbon dioxide and water.”
            http://www.nap.edu/openbook.php?record_id=10490&page=423

            You yourself have fallen into a false idea that omega 6 is rare and a deficiency is rampant. The opposite is true, lets not invent false health issues among Americans.

          • Mela Rossa

            This is what happens when nutritionists try to be biochemists. I am seeing the earth as a sphere and everyone is seeing the earth as flat.

            The ratio science doesn’t exist because it was done using oxidized seed oils. Therefore it is pure wishful thinking.

            The deficiency is rampant because the Omega 6′s found in oils have be oxidized during production and serve no purpose other than cause disease. Seed oils give me cystic acne on my forehead while consuming large amounts of nuts and seeds with leafy greens increase my mental processing.

          • Toxins

            Not all seed oils have gone rancid, and I am not talking about seed oils here. I am talking purely about whole foods.

            Where is your evidence that seed oil omega 6′s function differently in the body from omega 6′s in nuts and other foods? Please use scientific studies, not wikipedia or blog posts.

          • Mela Rossa

            Omega 6

            http://www.ncbi.nlm.nih.gov/pubmed/18293301

            Omega 3

            “It is further possible that a large part of the electrophysiological effects attributed to n-3 PUFAs may be dependent on their oxidation. An interesting study led by Sébastien Judé of Nutrition, Croissance et Cancer in France showed that the electrophysiological effects of DHA on the transient outward current in cardiomyocytes were only present when the DHA was oxidized with a small amount of hydrogen peroxide; DHA on its own was much less effective.10 This finding led the authors to speculate that perhaps it is oxidized derivatives of DHA that are responsible for many of the electrophysiological effects of DHA observed to date—primarily in culture dishes, where DHA is exposed to room air and thus likely to be oxidized.”
            http://www.the-scientist.com/?articles.view/articleNo/32901/title/Omega-3s–Fishing-for-a-Mechanism/

            http://www.ncbi.nlm.nih.gov/pubmed/12813005
            http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3118035/

          • Toxins

            These papers do nothing to address the question of “Where is your evidence that seed oil omega 6′s function differently in the body from omega 6′s in nuts and other foods?” Namely, where is your data that omega 6′s from oil depends on the omega6:3 ratio while omega 6 from nuts do not depend on the ratio? Yes oxidized oils are carcinogenic, this is not new information.

          • Mela Rossa

            Show me studies that used Omega 3′s and 6′s from WHOLE FOODS. Since the omega ratio studies used oxidized carcinogenic oils, they are automatically invalid. Flawed scientific studies don’t count.

            Whole foods also contain vitamins and minerals which play a major role in regulating everything regardless of the quantity of whole food consumed.

            http://www.ncbi.nlm.nih.gov/pubmed/2555646
            http://www.ncbi.nlm.nih.gov/pubmed/10189072

            Another reason why most people think that Omega 6 fatty acids are “inflammatory” is because the majority of people breath in air pollution and other airborne toxins like cigarette smoke that cause the inflammation in the first place.

            http://www.ncbi.nlm.nih.gov/pubmed/15513908
            http://www.atsjournals.org/doi/full/10.1165/rcmb.2008-0105OC#.UrcW_jzujAQ

          • Toxins

            It is not up to me to prove that a fat from a food extract functions the same as the fat from the food, you are the one with the outlandish claim. There is no evidence or reason to assume that omega 6 from oils does not metabolize to arachidonic acid. It is total nonsense. You clearly have a bias or have invested too much time reading a flawed blog post.

            To claim that “Since the omega ratio studies used oxidized carcinogenic oils, they are automatically invalid” is totally false. Arachidonic acid is inflammatory, DHA/EPA is anti inflammatory. These are facts, not invented opinions by “flawed scientific studies”. The ratio is still valid because it applies to non pre formed omega 6 and 3. Whether the oil becomes oxidized or not is not important when discussing the ratio. Again, present real EVIDENCE for your claims. Lets not invent reasons without a base.

          • Mela Rossa

            Of course it metabolizes to Arachidonic Acid BUT Arachidonic Acid is NOT inflammatory. You’ve been highly MISINFORMED and are obviously brainwashed.

            Educate yourself: http://www.youtube.com/watch?v=018PxnH702k

          • Toxins

            Your bases for believing omega 6 as anti inflammatory is based on a youtube video? Frankly I find that quite ridiculous. This is not how one should come to conclusions. I am not a paleolithic dieter, I am a whole foods plant based vegan. It is a sound fact the Arachidonic acid is a pro inflammatory and DHA/EPA is an anti inflammatory. They balance each other out, which is why the ratio is important to get a good amount of both.

            The biochemistry speaks for itself. “Arachidonic acid is a precursor to a number of eicsanoids (e.g.,thromboxane A2, prostacylcin, and leukotriene B4). These eicosanoids have been shown to have beneficial and adverse effects in the onset of platelet aggregation, hemodynamics, and coronary vascular tone. EPA has been shown to compete with the biosynthesis of n-6 eicosanoids and is the precursor of several n-3 eicosanoids (e.g., thromboxane A3, prostaglandin I3, and leukotriene B5), resulting in a less thrombotic and atherogenic state”
            http://www.nap.edu/openbook.php?record_id=10490&page=454

            As this conversation has gone on it has become more clear you are not interested in the science but have your own philosophy of how things work rather then how they actually do work. It is ok to examine the evidence and come to conclusions based on it rather then continue to debate this non issue that you simply cannot prove because no evidence exists supporting your claim.

          • Mela Rossa

            Correction: Arachidonic acid is a pro(promotes) inflammation and DHA/EPA is an less (promoting) of inflammation.

            “Arachidonic acid is a precursor to a number of eicosanoids (e.g.,thromboxane A2, prostacylcin, and leukotriene B4). These eicosanoids have been shown to have ***BENEFICIAL*** and adverse effects in the onset of platelet aggregation, hemodynamics, and coronary vascular tone. EPA has been shown to compete with the biosynthesis of n-6 eicosanoids and is the precursor of several n-3 eicosanoids (e.g., thromboxane A3, prostaglandin I3, and leukotriene B5), resulting in a less thrombotic and atherogenic state”

            When do the cells produce these eicosanoids?

            You are a blockhead and it is pointless trying to explain to you science that is clearly over your head.

            You can remain brainwashed by the Paleo pseudoscience because that is where the omega ratio myth originated.

          • Toxins

            Ah, I am the one who is the blockhead. This conversation has made that clear. Especially since the national academy of science are made up of paleo proponents. Yes I am the one who is misunderstanding basic concepts.

          • Toxins

            We should also note that because people get so much omega 6 in the diet, the 4:1 ratio of omega 6:3 is disrupted. too much omega 6 and you wont convert ALA to DHA and EPA. One should not strive to get MORE omega 6, one should try to lower omega 6 and raise omega 3. It is unfounded to do the opposite.

          • Mela Rossa

            This ratio nonsense only applies when consuming processed seed oils and animal products loaded with toxins. Both these types of foods initiate inflammation.

            The desaturase enzymes that convert ALA to EPA and DHA or LA to ARA and DGLA are regulated by Retinoic Acid(Vitamin A metabolite). We should strive to consume more leafy greens rich in Vitamin A and not worry about the consumption of Omega 6 fatty acids from whole foods.
            http://www.ncbi.nlm.nih.gov/pubmed/12538081

            Raising Omega 3 fatty acids and lowering Omega 6 fatty acids from whole foods will lead to a decrease in cranial size, depression, addiction, smaller penis size in male generations, and I can go on and on about how Omega 6 fatty acids from whole foods are extremely beneficial.

          • Toxins

            Again, what you are arguing is not true on a biochemical standpoint and is nonsense. Non preformed omega 6 is part of the ratio unless you bypass it by consuming pre formed arachidonic acid found primarily in eggs and other animal products. As I mentioned in the paper from the national academy of science, the ratio is not negligible and is an important player.

          • Mela Rossa

            The ratio doesn’t apply when consuming nuts and seeds because linoleic acid is also converted to various conjugated linoleic acids by intestinal bacteria and the various CLA’s play a major role in regulating where lipids are stored and promote the utilization of fat as fuel. When someone consumes seed oils, these seed oils cause inflammation in the intestine and kill the bacteria required for this bioconversion.

            http://en.wikipedia.org/wiki/Conjugated_linoleic_acid
            http://www.ncbi.nlm.nih.gov/pubmed/22079992

          • Toxins

            “There is limited evidence to suggest that the trans-10,cis-12 isomer reduces the uptake of lipids by the adipocyte, and that the cis-9,trans-11 isomer is active in inhibiting carcinogenesis. Similarly, there are limited data to show that cis-9,trans-11 and trans-10,cis-12 isomers inhibit atherogenesis”
            I would not call this role major, I would not even consider CLA as a major player in disease prevention.
            http://www.nap.edu/openbook.php?record_id=10490&page=428

            You are twisting the real issues at hand and inventing non issues.

          • Mela Rossa

            When did I say anything about disease prevention?

            I am pointing out that non-oxodized linoleic acid will be converted into various conjugated linoleic acids in a healthy intestine by intestinal bacteria and that CLA’s promote the storage of fats inside muscle tissue instead of adipose tissue. Hence the body works totally different on a whole foods diet.

  • smoothie77

    Hello, Dr. Greger. I posted a question on your YouTube site, but another viewer claimed that you were more inclined to answer questions here. I have researched high and low for an answer to whether the phytoestrogens in flax seed improve or worsen gynecomastia (in men obviously), but have not been able to find a conclusive answer. I would love to get the benefits from flax, but am afraid that I will just worsen the condition (aquired during adolecence) which I still have in my mid-30s. I’m asking you because you are so thorough in your research and therefore I trust your response. Please take a moment to detail your findings on this. Thank you.

    • http://www.DonForresterMD.com/ Don Forrester MD

      I would not worry about the phytoestrogens. I have never seen any studies associating the two and based on current understanding of human metabolism can see no credible hypothesis. The condition has many causes as I’m sure you are well aware. Given the length of time you have had the condition I’m sure the appropriate tests have been done and medication causes have been excluded. I would suggest maintaining ideal body weight which will lower your estrogen production by your fat cells. Of course it might make your condition a bit more prominent. Plant based diets generally increase the amount of steroid binding protein in the blood so there is less free estrogen and testosterone in the blood. I’m not aware of any long term studies on the course of gynecomastia acquired in adolescence. Sorry I couldn’t be of more help.

  • Ray

    Can Apple Cider Vinegar be used to combat dandruff?

  • david

    I’ve been consuming flax oil stored at room temperature with minimal light for a while now. I just realized that it might be getting oxidized, and the oxidized oil might be harmful. The flax oil that I buy is cold pressed, and nitrogen purged. From now on, I am going to store most of it in the freezer (the stuff that’s still nitrogen purged), and 1 open container in the frige.

    • Toxins

      Stick with the flax seeds, and avoid the oil. The benefits of flax are within the whole food.

  • foxfyr

    Not sure where the best place to post this question is…so here goes…
    Appreciating the value of adding ground flax seeds to one’s diet, one wonders regarding the benefits of sprouting flax seeds in the manner of broccoli seeds…

    I have read various articles that claim that sprouted flax seeds lack a factor that retards their ability to be digested (assuming they are ground), but the sources seem as much belief based as grounded in actual science.

    Has anyone conducted a reliable analysis of ground versus sprouted flax seeds?

    And would adding sprouted flax seeds to sprouted broccoli seeds to our daily regimen be productive as say the addition of broccoli sprouts?

    And as always, Thanks MUCH for your invaluable service and information!

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