Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
8 Sep

Dear Mark: Is Flax Bad?

flax seedsDear Mark,

I’ve been researching flax and am ready to pull the plug on my dedicated flaxseed grinder. The kicker was seeing flaxseeds associated with prostate cancer. What’s your take?

Thanks to reader Clare for the thoughtful correspondence on flax. This is exactly why I love doing this blog. Research continues to unfold, and the conversation never fails to engage and inspire me.

As Apples know, I’ve been a flax supporter. Lately, I’ve been mulling that position. While I don’t think a single study’s results should rewrite the book on any issue, when a number of studies suggest that it may be linked to serious illness in some people, that’s enough to give me pause. And, well, it’s enough to incite me to do some digging – and pondering. Flax is one of those cases lately.

The deal is this. Flax seed is rich in a form of omega-3 fatty acids called ALA (alpha-linolenic acid). Omega-3 fatty acids as a whole (group) are especially vital for the development and ongoing well-being of the nervous system and for the health of the cardiovascular system. They improve lipid profiles, thin blood, and combat inflammation like nobody’s business. (You know how I feel about that one, eh?) They can also help curb insulin resistance.

Research time and again supports the role of omega-3s (again, as a group) in overall health; however, some studies and reviews over the last few years have linked high ALA intake (from both flax oil and milled seed) with higher incidence of prostate cancer. ALA blood levels are higher in response to flax oil intake than they are with milled seed intake. (Eating whole seeds isn’t recommended unless you’re looking for some serious abdominal havoc.)

I’ve always maintained that other animal-based forms of DHA and EPA offer more health-related bang for your buck, and I stand by that point. The preponderance of research supports the particular power of EPA and DHA in the omega-3 fatty acids. One study suggests that fish intake (rich in both DHA and EPA) actually reduces the risk for prostate cancer.

The bottom line is ALA doesn’t do much that DHA and/or EPA can’t do and probably do better. As avid Apples know, I suggest that everyone take a fish supplement. In the past I’ve seen ALA as a decent secondary choice for vegetarians and as a useful addition to a healthy Primal eating strategy (e.g. a bit of ground flax seed on some berries). The human body isn’t terribly effective at converting ALA to either DHA or EPA, hence the need for added dietary intake or supplementation. (An interesting side nugget: women’s bodies are a little better at this conversion. Research has shown that young women convert 21% of ALA to EPA (compared to 8% in men) and 9% to DHA (compared to 0-4% in men). The difference, apparently, is linked to estrogen levels.)

Fish Oil Capsules

So, what’s my current suggestion in light of the potential prostate cancer link? If you’re a woman, the obvious point of the research isn’t relevant. Nonetheless, the underlying role of phytoestrogens in flax is nonetheless an important one. I’d say that healthy women can consume low to moderate amounts of flax without concern. Sure, a large amount of research suggests the protective effect of phytoestrogens against breast cancer (in healthy women), and this research includes flax. Nonetheless, a lot of a seemingly good thing isn’t necessarily better or even safe. My advice would be to use fish oil as your primary omega-3 source and keep the ALA on the lower side.

If you’re a man? Particularly an older man? I’d definitely suggest you make fish oil your principal source of omega-3s. Is it time to chuck the flax grinder all together? Based on the research, I’d at least put it into semi-retirement. (I’d suggest forgoing flax oil entirely.) In the meantime, we’ll stay on top of this one and let you know about any new developments on this front.

As always, thanks for your questions and comments. Keep ‘em coming!

diglyesica, tellumo, spdrecrd Flickr Photos (CC)

Further Reading:

Omega 3 Fatty Acids Round Up:

Omega 3 to 6 Ratio

Omega 3 Daily Dose

Omega 3 Food Sources

Cooking Omegas

Modern Forager: The Vaunted Flax Seed

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I was told that flax was also estronogenic (sp?)
    As having breast cancer back in 1999 I was told by a nutritinist to stay away from it as the cancer I had was estrogen dependent.I just found your website ,Thank’s

    patty stone wrote on September 12th, 2008
  2. I take 1 1000 mg flax seed oil capsule twice a day. The only “benefit” I have noticed so far is gas of such proportions it makes my ribs hurt. Anyone have helpful advice that does not include sharp objects?

    Bill wrote on September 17th, 2008
    • I bought organic flax seed oil,, I have to admit i’m highly allergic to this oil,,my nose plugged up so bad I couldn’t breathe,,,my liver totaly refused this,,I’ve read if it can cause allergies and yes it can,,i’m not allergic to much;;wheat and milk that I know causes me symtoms just wanted to share

      mike wrote on July 25th, 2013
  3. These are some comments about flaxseed oil that I have read that are quite interesting:

    “Have you seen this paper on ALA to DHA and EPA conversion?

    They claim that ALA from flax seeds is as effective as fish oil, while some previous studies questioned it’s effectiveness. If you have an access to the full text of the paper, could you comment on that? Thanks,


    Just peeked at the full text. The abstract is really incomplete!

    First of all, they gave flax at doses up to 3X the fish oil. Despite that, after 12 weeks they saw no increase in total erythrocyte n-3 with flax, while they did with fish oil. The flax actually caused a decrease in erythrocyte DHA, while the fish oil caused an increase. The flax did cause an increase in EPA and DPA.

    Well that pretty much removes any reservations I had about trashing flax oil as a supplement.”

    Sue wrote on September 26th, 2008
  4. As I’m allergic to nearly every fish on the planet (including and especially the ones they use for fish oil supplements) I’ll stick with my Barlean’s Essential Woman capsules. :)

    Bonnie wrote on October 1st, 2008
  5. Here’s the way I look at this flax seed issue and herbivory more generally. Evolutionary thinking should lead us to look at things from the plant’s perspective. Specifically, does the plant want its foliage or seeds to be eaten or not? If the answer is yes, it wants to be eaten, then it’s unlikely that natural selection would favor plant genes that sequester toxins to repel or injure foragers like Grok and others. Such plants can probably be eaten by us in large quantity without concern for toxicity.

    In contrast, if the plant does *not* want to be eaten, then selection is likely to equip the plant with defense like spines, resins, and other phytotoxins to repel or injure foragers. It is this latter type of plant, the type that is by far in the majority among all plant species, that we should be concerned about. In fact, much of plant breeding has focused on breeding out these nasty wild type traits and replacing them with more benign (and tasty) qualities.

    Only through study of plant natural history and biochemistry can we determine which plants are safe to eat in quantity. But since such work is not always feasible then the safest policy is to only eat lesser-known plant varieties in moderation, if at all. As far as flax goes, why take the risk considering that there are other Omega-3 sources available that we are pretty certain do not poison us?

    MikeL wrote on December 15th, 2008
  6. I take as little PUFA as possible. They are way too vulnerable for radical oxygen damage. I take a tablespoon of cod liver oil in the morning for the fish oils and vit A+D and use coconut oil for mostly anything else (and some butter for the K2).

    Would paleolithic man have eaten flax? I don’t think so. He would have eaten fat fish.

    Just remember that flax oil goes rancid very quickly when you don’t keep it refridgerated. You wil need lots of vit E to keep it fresh in your body.

    My guess is that the walls of my bodycells will be more resistant to ROS (radical oxygen species) if they contain more staturated fat.

    Andre wrote on June 25th, 2009
  7. Worried about flax seed and cancer risks? Specific to this article, check out Cliff Beckwith details his experience with an existing prostate cancer, and how he addressed it with the use of flax seed and flax oil. Better yet, check out or preform a google search for “Johanna Budwig”. This 7 Time Nobel Prize Nominee was responsible for developing an alternative cancer therapy that is based largely around flax oil and cottage cheese consumption, most people include the seeds in their regimen for a good lignan source. PS, lignans are incredibly concentrated in flax seed and have AMAZING anticancerous benefits. My opinion, the study that site the “possible” increase in prostate cancer risks was poorly performed, poorly cited, and leaves much to be desired in order to carry any real weight. No question about it, EVERYONE should take fish oil daily! That said, flax has a whole host of benefits on it’s own (fiber, protein, lignans, EFA’s) and should be used daily as well!

    Jeff wrote on November 24th, 2009
  8. Flax seeds are an incredibly healthy food. In science, the burden of proof always lays with the person making the claim. For example, I can say that water is not beneficial, but the burden of proving that claim lays with me.

    Now there are two groups of people concerning flax, the large scientific and nutritional community that supports flax as a healthy food, and the newer studies suggesting that flax can increase the chances of cancer.

    Those who believe flax is healthy can easily prove their claim, there are basic nutritional standards flax meets and excels at. However, those suggesting flax can cause cancer have only the results of ambiguous studies on their side.

    Should this be an issue for further research, sure.

    Should someone stop eating flax, throw away their grinder, reach around and up, grab their prostrate and run away?

    I doubt it.

    jnewaz wrote on December 29th, 2009
  9. Any more news on this topic of Flax and cancer? My husband just started taking because his acupuncturist suggested it. I would never let him use it because of the controversy.

    Sheila wrote on January 3rd, 2010
  10. Likewise Shella. I’ve been taking Flax seed (Lindseed over here in the UK) for about a year now, putting them in my shakes in the morning & before training.

    matt wrote on January 8th, 2010
  11. was the study done with cold pressed flax oil? probably not, remember the bad rap on coconut oil? put those flax oil capsules you bought at wallyworld down the toilet and get only cold pressed/virgin for any oils you choose.after revisiting budwig/beckwith websites, there is no doubt in my mind that flax is hugely beneficial. Thanks jeff


    Eric wrote on January 12th, 2010
    • Please compost unwanted food and supplements, rather than putting it into the sewage system.

      Jeanmarie wrote on January 20th, 2010
      • sorry it was a matter of speach, I guess composting them might be good, but dont consume them, flax oil needs refridgeration

        Eric wrote on January 20th, 2010
  12. I think people should just use common sense on this one. Just think primal if anything. How many flaxseeds do you think you are going to be able find/pick in the wild?…probably not that many. I would just do a little in the morning or on a salad ground up. I personally have stopped using the oil many months ago because of the same reasons mark explained…DHA and EPA simply have more benefits per calories and dollar amount.

    kevin krautsack wrote on January 13th, 2010
  13. Some people (myself included) cannot tolerate fish oil. So, yes, I hear EVERYONE talking about the benefits of fish oil, but what can the rest of us do? I enjoy flax seeds in yogurt and smoothies (now started chia seeds), and enjoy flax oil on my salads.

    Peggy wrote on January 18th, 2010
  14. what about the budwig diet and use of flax?

    joe wrote on February 15th, 2010
  15. If you don’t want to use flax, use chia. It’s better for you anyway. Just shop around – as it gets trendy it’s also getting expensive. Costco sells the exact same brand as Shopper’s Drug Mart for exactly half the price. (Weber’s). Also don’t be fooled by the folks who tell you the white seeds are better for you than the dark ones. Not true.

    I use ground flax now and then to make a “muffin in a minute”, which has egg, oil (any kind) and baking powder and is great for sandwiches. bp may not be primal but on the rare occasions when I really want a big old ham and cheese with the trimmings, or chicken salad, it more than satisfies for practically no carbs.

    Sue wrote on April 22nd, 2010
  16. Indeed, let me add that at the link you provided, the only reference to “flax” is a link to another abstract, whose title is “Flaxseed Supplementation (Not Dietary Fat Restriction) Reduces Prostate Cancer Proliferation Rates in Men Presurgery.”

    Jared Israel wrote on April 30th, 2010
  17. I’m so confused now. It seems like the more I try to eat a healthier diet, the more I hear things like this that contradict what I originally thought. I eat 3/4 cup to 1 1/2 cups of flaxseed almost every day (as a pizza dough). Am I going overboard with the flaxseed? (I really hope not!)

    Trish wrote on May 14th, 2010
  18. Salam
    Based on my observations, flaxseed increases my libido and gives me acne, which in my opinion means increase in testerone and not the other way around

    Mohammed wrote on July 22nd, 2010
  19. When I started putting flax seeds in my diet, I knew that it was a replacement for the traditional role of cod liver oil in the diet – I just didn’t want to eat cod liver oil! FF a few years, and I became absolutely convinced I needed fermented CLO for other benefits, not just the omega 3’s, and went that way, letting go of the flax.

    I think the heavy push for flax comes from the vegan contingent, just like the push for agave (although clearly agave syrup is far more processed than flax seeds). Before considering a return to flax, I’d want to know whether they were consumed the way we’re told to now (via oil or fresh crushed seeds, in daily sizeable amounts) by any traditional society. If the answer is no, I don’t need to go any further. If yes, I’d then start looking for the body of research on the matter.

    I thin kthere’s probably a reason why I can think of many references to the usefulness of flax (for linen) & linseed oil in history, but cannot ever think of a mention of anyone consuming flax seeds or flax seed oil, just off the top of my head.

    MamaGrok wrote on July 22nd, 2010
    • Not a vegetarian, but regarding flax not being in history: as far as I know, that’s right. But chia, that someone recommended a few posts back? That was historically eaten all over Central and South America. Besides the Omega 3’s, it also has a decent amount of protein, and the fact that it turns gelatinous in the presence of water is why the various peoples would use it as a trail food. It holds the water in your system and gradually releases it, keeping you hydrated. The Aztecs used it for sure. The traditional method is to soak it in lemon or lime juice with a lot of water, and then stir the resulting gel into a glass of water and drink it. My own experience is that if I drink a large glass early in the day, several hours later I really have to go, but I don’t feel dehydrated in between.

      Tracey R wrote on September 18th, 2011
  20. I began using flax seed oil as an alternaive to fish oil. The main reason was to avoid MERCURY poisoning. Many cheaper fish oils can have traces of mercury, which btw, is cumulative in our bodies. There are some “mercury-free” fish oils. If making the switch back to fish oil, I would definitely recommend Mercury-free.

    Nick wrote on October 23rd, 2010
  21. I’m a vegetarian and I buy crushed flax seed from whole foods. I really will never believe that it has a connection to PC.

    In fact I read in a magazine that phytoestrogen does not make you into a woman. It does not give you man boobs. It has no feminizing effect at all.

    The phytoestrogens in soy was what they were talking about. The whole thing about soy giving you estrogen is a myth.

    “Phytoestrogen has no effect on estrogen levels or hormone levels or even testosterone.”

    Case in point: these scientists or researchers are making up things, and lying, in order to encourage a diet of flesh.

    Sounds gross right? Well just try to not dance to their tune. Be yourself and don’t be so easily influenced.

    Sid wrote on December 16th, 2010
  22. I appreciate the vegetarians and vegans who posted here. Here’s a little bit on the vile lying meat industry:

    “The meat industry spends hundreds of millions of dollars lying to the public about their product. But no amount of false propaganda can sanitize meat. The facts are absolutely clear: Eating meat is bad for human health, catastrophic for the environment, and a living nightmare for animals” – Chrissie Hynde from The Pretenders, in the PETA website

    “You can’t tear flesh by hand, you can’t tear hide by hand. Our anterior teeth are not suited for tearing flesh or hide. We don’t have large canine teeth, and we wouldn’t have been able to deal with food sources that require those large canines” – Dr. Richard Leakey

    “Nothing will benefit human health and increase chances for survival of life on Earth as much as the evolution to a vegetarian diet.” – Albert Einstein

    ” [A]lthough we think we are one and we act as if we are one, human beings are not natural carnivores. When we kill animals to eat them, they end up killing us because their flesh, which contains cholesterol and saturated fat, was never intended for human beings, who are natural herbivores.” – Dr. William C. Roberts, M.D., editor of the authoritative American Journal of Cardiology

    “Since I stopped eating meat, I have noticed that my digestion is better, my thoughts are better, and I run instead of walking. […] I eat vegetables and all kinds of vegetarian food. I am a vegetarian. I am not a meat-eater.” – Vaslav Nijinsky, The Diary of Vaslav Nijinsky

    Sid wrote on December 16th, 2010
    • good points when answering carnivores who say humans were meant to eat all foods including meat

      elliot davis wrote on January 10th, 2011
    • Chrissie Hynde: That’s why we buy grass-fed meat — great for the environment, happy animals. This meat is also absolutely superb for human health.

      Dr. Richard Leakey: Stone knives have been around long enough for us to evolve around them. Eating raw and cooked meat drove our evolution to acquire our big brains.

      Albert Einstein: Brilliant guy but he’s a physicist, not a biologist. Plus, what is his reasoning for that statement?

      Dr. William C Roberts: Where’s the evidence that we are “natural herbivores”? Is it our lack of a four-part stomach that would allow us to efficiently digest cellulose for energy as well as micro-nutrients? How about the very few molars we have? Indeed, why do we have canines at all? A small stomach like we have necessitates a calorically-dense diet, which plants don’t provide. Besides, the argument is that humans are *omnivores*, not carnivores. Cholesterol? Our liver makes much more than we eat. Eat less, the liver makes more. Eat more, the liver makes less. Homeostasis!

      Vaslav Nijinsky: Greatly depends on total diet before and after the change. It’s very unlikely that the only change made was to cut out meat, so there’s no way to say that the absence of meat was the cause. Post hoc, propter hoc.

      I eat meat as well as massive amounts of vegetables, and I have never felt better since re-introducing meat. I’m not bashing vegetarianism, but the biological evidence points to modest consumption of meat as very beneficial.

      Andrea Reina wrote on January 10th, 2011
  23. In regards to ground Flax Seed…I am an avid fan! I eat 3tbls daily. It’s helped me lose 40lbs in 3 years, I was a size 12 and now a size 4 and I firmly believe it’s due to Flax seed. I have a history of colon cancer in my family, my first colonoscopy was perfect.
    My husband has been battling Prostate Cancer for 3 years. After his diagnosis he began using ground flax until the “study” came out and he stopped and his PSA is rising again….he was doing better with the flax seed….I won’t stop using it.

    Linda Bilyeu wrote on March 5th, 2011
    • Linda you provide a way to test the claimed possible harmful effect of flaxseed through the study of PSAs for those men consuming flaxseed. BTW, nobody has pointed that zilch original research was carried out by the study that Mark cites. The authors of the study are just stating their opinion,

      Michael wrote on October 7th, 2012
  24. I forgot to click notify me for followup comments :)

    Linda Bilyeu wrote on March 5th, 2011
  25. Ground flax seed cured my goiter.

    rob wrote on March 5th, 2011
  26. I read an article today that says that whole flaxseeds are much better than the oil. Flax oil does not have fiber and it can actually cause cancer. Very interesting.

    flaxseedguy wrote on March 8th, 2011
  27. A new review study on this issue was published in the American Journal of Clinical Nutrition in 2009, authors Simon, Chen and Bent, link :

    The paper’s conclusions were complicated so I wont try to summarize them here.

    To the person who said they can’t tolerate fish oil, you might try krill oil.

    Rob wrote on April 1st, 2011

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