Flax Oil and Estrogenic Compounds: Should Men Avoid Flax Oil?

Over the years I have read on several ‘net forums and other places, that flax oil contains estrogenic compounds and men should avoid flax oil. It’s often written as fact. Is it true? Let’s see…

man boobs picture

Will eating flax cause moobs?!

For one, it’s actually a moot issue if you are talking about flax oil. The main flaxseed lignan is secoisolariciresinol diglucoside (SDG), which is found in the hull but which occurs in the oil in very small quantities. I don’t generally recommend large amounts of ground flax seed to men per se, but it’s also a far more complicated issue than people – in particular self proclaimed experts found on the ‘net – realize, and no simple flax lignan = estrogenic effects should be made.

The term “phyto estrogen” is not automatically a negative per se, as it may act as an anti estrogen depending on the tissue in question and other variables.

For example, flax lignans were found to reduce mammary carcinogenesis, which means it’s acting as an anti estrogen in those tissues. According to one review on the topic:

…phytoestrogens, like certain selective estrogen receptor modulators, have an antiproliferative effect on the breast, and positive effects on the lipoprotein profile and bone density. They might also improve some of the climacteric symptoms.” (1)

The bottom line here is, it’s WAY more complicated than you think. Should men run out and eat large amounts of ground flax seed in hopes of getting an anti estrogenic effect?

No, as large amounts of weak estrogens in the male system can still have a net negative effect depending on many physiological variables, but the effects, dose needed, etc, etc are far from clear at this time.

Should men worry about the tiny amounts of lignans found in flax oil? No. As mentioned in other places and articles, I have known and or trained some high level men using up to 7tbl spoons per day of flax oil, with no negative impact on them that I could see, and one mentioned a reduction in gyno, which he attributed to the addition of the flax oil, but of course that’s an n =1 observation and not objective science by any means.

Studies in animals, again, suggest interesting effects on hormone levels, at least in animals given large amounts of flaxseeds. (2). A study called “Dose, timing, and duration of flaxseed exposure affect reproductive indices and sex hormone levels in rats” done at the Department of Nutritional Sciences, University of Toronto, Ontario, Canada found:

In male rats, lifetime 10% flaxseed exposure raised serum testosterone and estradiol levels and produced higher relative sex organ weights and prostate cell proliferation. In contrast, lifetime exposure to 5% flaxseed reduced adult relative prostate weight and cell proliferation, suggesting potential protection against prostatic disease, although sex hormone levels were unaffected. In conclusion, flaxseed can potentially alter reproduction, depending on the dose and timing of exposure.

So, at very high amounts for their entire life span, flax seeds increased both testosterone and estradiol and even at 5% of their diets for their entire life, no effects on hormones were found. Conclusion, people recommending men avoid flax oil “because it contains estrogens” don’t have a clue what they are talking about…

(1) Brzezinski A & Debi A, Eur J Obstet Gynecol Reprod Biol, 85(1): 47, 1999)

(2) Tou JC, Chen J, Thompson LU.J Toxicol Environ Health A. 1999 Apr 23;56(Cool:555-70.

  1. Luke 15 years ago

    Great article, thank you , I use Flax myself, this has been very helpful.

    • frank 13 years ago

      thank you…………… I read this site all the time and will be ordering your books………….

  2. Author
    Will Brink 15 years ago

    Glad to be of assistance Luke!

    • Andrzej 12 years ago

      About flaxseed and cyanide and cancer Check this out http://www.cancure.org/budwig_diet.htm .
      it makes a lot of sense and woman was nominated for nobel prize seweral times

      • Andrzej 12 years ago

        Of course try to read more history about Dr Budwig as that link is just short explanation of the diet.But who is interested in cancer will be interested in great achievements she had…

  3. Ryan 15 years ago

    I have used Bartlens (could be wrong spelling easy) which is a cold pressed version of flax seed oil not pill form. Is it a better product in the cold pressed form where you drink 2 Tbsp. every morning? The only thing I did notice is it seemed to regulate my body weight where it seemed to say the same while using it. My biggest question does it make a big difference in it being cold pressed verses pill form?
    Thanks Ryan

  4. Muryal Braun 15 years ago

    As one who has been engaged in nutritional research for over 40 years, I am always pleased to read an article that is written in a straight forward style with just the facts. Thanks for getting this information about flax out. It is sad that anyone might avoid such a wholesome nutrient because of questionable side effects. Thanks for the good work about flax!

  5. Gus Gilbert 15 years ago

    Besides the weak estrogen question, the flax plant has a built-in “binary insecticide.” Farmers don’t have to use insecticides on flax because the flax seed naurally has two compounds that mix together when eaten and form a “cyanide” compound that is something to consider. Cyanide has been measured in the fecal material of people who eat flax. In the absence of long term people or even animal studies, it would be prudent to use it in moderation and go heavier on “tested” oils like high quality fish oils and nuts like walnuts-especially if you’re a non-swat team insect, LOL.

  6. Author
    Will Brink 15 years ago

    Ryan, “cold pressed” is a process and has nothing to do with pill form or oil. All correctly made flax oil products are cold pressed. It takes 12-14 caps to = 1tbs of flax oil, and 1-3 tbs of flax oil per day is generally recommended, thus caps are a a waste of your $$$.
    Muryal , Glad you enjoyed the article. BTW, I was the person who introduced flax oil to the bodybuilding/fitness world by writing the first articles on the topic “back in the day” in the muscle mags.
    Gus, again, are we talking about the oil or the seed? Before or after processing? At what dose? Lots of foods we eat have potentially negative and positive/health promoting compounds in them. The long and the short of is is: The issue is away risk to benefit, and in my opinion data supports the benefits far out weigh the risks regarding flax, seed or oil. I agree however in that moderation is always the key to good health long term

  7. David 15 years ago

    I’m an elite masters athlete that supplemented with flax oil for years. I switched to a quality fish oil with lots of olive oil and didn’t notice much difference in terms of recovery etc. I’ll stick with fish oil.

  8. Gus Gilbert 15 years ago

    Okay, the hydrogen cyanide is in the flax seed but I think would carry over into “cold pressed” flax oil. Since hydrogen cyanide boils out at about 80 deg F., it might be better to go with heat processed flax oil.
    I use a little flax myself but only along with my high end fish oil and walnuts. Everything in “moderation.”

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  11. LeeHayward 14 years ago

    Cool, interesting read. Thanks for posting!

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  13. Phlipkat 12 years ago

    This link was sent to me in regards to a conversation where I had recommended not using flax. This is an interesting article, but the information and references are far too out of date, as well the article seems to be more of a personal opinion “I have known and or trained some high level men using up to 7tbl spoons per day of flax oil, with no negative impact on them that I could see” . I am not saying Will is wrong, but to have followed this statement with an actual test would be much more accurate.
    Your body is the greatest investment you will ever have, so I would suggest looking at current and thorough information, and then cross reference it as well. Good living to all !

    • Bill 12 years ago

      Do you happen to have more current sources that you’re willing to share? I think we all would be interested.

  14. DougM 12 years ago

    Hi Will,
    You are my guru when it comes to EFA’s. Never paid any attention to them before, and since starting with flax, and moving on to concentrated fish oils, and even algae oil (courtesy of Monica), I’ve enjoyed a huge drop in blood pressure. I hope my huge fat loss is also due to my increase in EFA’s. But I suspect you’ll agree, that depends upon several other things. I certainly have no fear of estroenic effects, so thanks for nailing that here. Some time, when it hits you right, I’d like to hear the best dope on flax vs. fish oil, or other EFA sources. Seems to be the total rage these days, and to the benefit of us all. Rock on Will. You’re the best!
    – Doug

  15. Moses 11 years ago

    Hello! I know this is an old post, but do you know if high-lignan flaxseed oil changes the game any? To be clear, I’m using Barlean’s. Thanks!

    • Author
      Will Brink 11 years ago

      Nothing as changed from my general conclusions in the right up as I have not seen new research that would alter the position.

  16. Elton 10 years ago

    This was estremely helpful. Thank you,

  17. vamsi 10 years ago

    Very nice article.
    after all these now i am in doubt…….
    As i am a man who is using 20 grams of flax seed powder per day for my well being, what should i do now whether i need to continue or stop the thing. kindly advice me..

  18. Joe 8 years ago

    You may want to contact Livestrong website as they are reporting that the lignans found in Flax oil promote estrogenic activity. many other sites claim that it is negative for testosterone production in males.

  19. Foued 6 years ago

    Thank you for the clarifications .. It is so confusing subject, was watching another video claiming to totally avoid flax seeds , nuts and many of the things i like , don’t know if it is legitimate claims .. (

  20. Jim 5 years ago

    thanks. This was the best article I’ve read on the subject so far. The studies are so unhelpful in this. All the ones showing a decrease also had cancer and low fat in them. I take about 6 tblspoons a day of ground flaxseed. It’s a craving at the moment as my body is recovering from an extended period of heavy stress. I haven’t found any ill effects from it, though I don’t go to doctors, so I have no idea of my actual T levels. However, it all seems to work well enough for me. I’m going to go with not worrying about it and just keep on doing what my body asks me to do. It craves them, so that’s what I give it.

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