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Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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September 08, 2008

Dear Mark: Is Flax Bad?

By Mark Sisson
137 Comments

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

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137 Comments on "Dear Mark: Is Flax Bad?"

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Son of Grok
Son of Grok
8 years 18 days ago

This post is somewhat refreshing to me. I have never really been a fan of adding Flax to my diet. Not because I thought it bad for you but more because I have never enjoyed it and have always had difficult fitting it in time, place and taste wise with my diet. I still make sure i get plenty of omega-3’s though! Flax was looked at as almost a mecca back in my bodybuilding days but if more research shows this to be bad thing then I will be glad yet again that I ignored the mainstream hype.

nancy james
nancy james
4 years 1 month ago

The issue of flax is very complicated. I don’t see anything on the web that would preclude adding flax in moderate amounts to the diet.

nannyflute

steve s.
steve s.
2 years 6 months ago
I am 64 years old and I’ve heard all the arguments for and against flax. I take prostate supplements because I get difficulty in emptying the bladder sometimes. But the most relief I get from prostate problems is when I take 2 tablespoons of ground flax seeds every day. My prostate and bladder usually get back in good shape after doing this for a few days. So all the studies back and forth don’t mean anything to me. I know what gives me relief and better health. Don’t forget the famous cancer cure from Dr. Budwig which consists of flax… Read more »
steve s.
steve s.
2 years 6 months ago
Here is info from a flax seed study: “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… Read more »
Justin
Justin
5 months 8 days ago

I’m curious what’s the consensus here on rats compared to human physiology, in general.

One of the tenets of Chinese medicine is to test things on humans.

Raphanator
2 years 2 months ago
I am beginning to see that mainstream hype, is now geared towards blundering what is good for us. Each to their own as every human reacts differently to everything they put into their body’s. There’s never gonna be a quick fix for diets. Pure experimentation, and move on. Bottled water in a humid gym = chemical reactions with bottle = carcinogens. There’s no end to opposite opinions being mascaraed from a Chinese Whisper to what we call fact. The Internet confirms what we want to be true but may not be true in the end. I wasn’t aiming this at… Read more »
Chris - Zen to Fitness
8 years 18 days ago

I think flax is great but it must be used in the right way, the fact that when consumed as seeds (unground) they are a potent Estrogen metabolizes is something very interesting for men…I regularly add the seeds to yoghurt and shakes or even sprinkle some in burgers……I think its also best to mill your own batches of Flax and keep them in the fridge to ensure optimal freshness….

Phil
Phil
6 years 9 months ago

Just so I understand correctly..flax seeds can help men lower estrogen levels? (And thus reduce the effects of it?)

Or did I get this backwards?

chris
chris
3 years 3 months ago

no….Flax increases estrogen, it has a lot of estrogen in it along with Soy which is why its so toxic to men, also soy and flax leach the body of Zinc and zink prevents prostate cancers 🙂

Methuselah - Pay Now Live Later
Mark – thanks for this info. I have a couple of questions. 1. I have about 1000mg of flax seed oil per day – is this a relatively low amount in the context of this discussion? All this talk of flax grinders makes me think my consumption is probably on the low side, but it would be good to get your view. 2. I do get a lot of fish oil in my diet both via food and supplementation but had always understood that ALA offers something extra that is needed to complete the omega 3 picture. If this is… Read more »
Crystal
Crystal
8 years 18 days ago

I’m not a fan of flax. Interesting, people with certain endocrine disorders can not tolerate flax, including myself. I’d stick with the fish oil or grass-fed meat.

anna
anna
8 years 18 days ago

i cant see anything past september 6th?

Aaron
8 years 18 days ago

Thank you for the comment, Anna. We are working on a solution. I apologize for the inconvenience. In the meantime, Firefox seems to be displaying MDA just fine.

drcapt
drcapt
8 years 18 days ago

As we age, the enzyme (delta-6 desaturase) that converts Omega-3 to EPA/DHA, decreases in activity.

Thus with less anti-inflammatory EPA/DHA oils, the prostate, as well as other tissues, would become inflamed and dysfunctional.

I am willing to bet that with increased ALA in the diet, not only prostate cancer, but, other cancers would exist too.

new_me
new_me
8 years 17 days ago

How about the fibre content; is flax seed at least a valuable source of fibre? (Not that anyone following the PB diet needs to add fibre to the bountiful amount that veggies provide!)

I don’t understand why whole unground seeds pose a potential problem. Would not Grok have nibbled on a few pinches of flax seeds as he found them? Aren’t they whole, unprocessed, natural goodness?

I don’t know if my smoothies will ever be as good without the flax. 🙁

Brett
Brett
8 years 17 days ago

Hi Mark,

Can you let me know your thoughts on omega 3’s post workout? I had read somewhere that this is not optimal.

Thanks,

Sue
Sue
8 years 17 days ago

Crystal,you said that people with certain endocrine problems cannot handle flax. Is that someone who is hypothyroid?

Tony
Tony
8 years 17 days ago

There’s an inaccuracy in this article – there are vegan EPA and DHA supplements from algae.

http://www.water4.net/

Crystal
Crystal
8 years 17 days ago

Possibly Sue. There isn’t a lot of info. out there but it is common among hypoT./hypoA. people. It must have something to do with the conversion causing stress. Others think it’s a goitergen and should not be eaten.

Some people are intolerant to flax worsening a nervous/emotional disorder—but what is described is actually low cortisol IMO.

DC
DC
8 years 17 days ago

Hello Mark,

Any opinion on chia seeds as an omega source, flax alternative?

Thanks!

greg
8 years 17 days ago

I use a high-quality liquid fish oil as my main supplement to combat inflammation and have really cut back on the flaxseeds (ground) after talking with my natural doctor. He suggested trying hemp seeds.

I would also be interested in similar research (if it exists) on both chia and hemp seeds.

Aaron
8 years 17 days ago

Tony – The article doesn’t say there aren’t vegan sources; only that ALA is an option for vegetarians.

Thanks for the link.

trackback

[…] of flax, I saw this blog post discussing studies linking ALA intake (from both flax oil and milled seed) with higher incidence […]

Aaron
8 years 17 days ago

DC – Thanks for the question. I think we have a chia seeds post in the works. Check back!

Tony
Tony
8 years 17 days ago

Aaron, thanks for your response. Actually, Mark does say that there aren’t any vegan options for DHA and EPA:

“I’ve always maintained that other animal-based forms DHA and EPA offer more health-related bang for your buck, and I stand by that point.”

He says that DHA and EPA are “animal-based forms” of Omega-3s. This isn’t true and weakens his conclusion that fish oil is the best solution for those trying to get a healthy balance of Omega-3s.

Aaron
8 years 17 days ago

Tony – I’m still not sure how you get that Mark is saying vegan sources of DHA and EPA don’t exist. He is simply saying that he has always said that it is better to get Omega 3s via animals than flax. At least this is how I read it. Nevertheless I am pretty sure this is what was meant…

Tony
Tony
8 years 17 days ago
Hey Aaron. In the passage I quoted above Mark specifically says that EPA and DHA are animal-based. “He is simply saying that he has always said that it is better to get Omega 3s via animals than flax.” No, he isn’t simply saying that fish oil is better than flax – what he’s saying is that he recommends fish oil as the best source of a good balance of omega 3s (out of all options, not just compared to flax). Without any mention of plant-based EPA and DHA this conclusion seems hasty at best. I know people find it obnoxious… Read more »
Dana
Dana
4 years 8 months ago
Because someone might come along and read this later: I cannot go vegan unless I want to bleed out through my uterus. You can’t get real vitamin A from a vegan diet. I find that if I go low on vitamin A, my cycle gets all messed up. I am not the only one with this experience. A friend of mine on FB heard about my problem and tried vitamin A in her own health regimen and had the same results I did. And charity clinics in developing countries often use vitamin A to cure dysmenorrhea (sp?) in women of… Read more »
Mike
Mike
2 years 11 months ago
It’s true that with our hyper-sanitized food supply nowadays that vegans must supplement with B12. B12 of course, is a bacterium, not an animal product per se. Donald Watson, the gentleman who coined the term vegan, lived on a purely plant-based diet for over 55 years (most likely without B12 supplementation for all those years), and died at the ripe old age of 95. Not bad for someone subsisting on a diet that “results in malnutrition.” Omnivores must supplement with B12 as well, as they get older: “Many older adults, who do not have enough hydrochloric acid in their stomach… Read more »
mike
2 years 4 months ago

Want vitamin A on a vegan diet–just eat sweet potatoes or pumpkin
and you’ll get plenty.

Sue
Sue
8 years 16 days ago

The algae supplements come from Switzerland. Are they available in other countries?

I think its a lot easier to achieve optimal health on a diet that includes meat. It could possibly be achieved on a vegetarian diet but with a lot more thought and possibly a lot more supplements.

JC
JC
8 years 16 days ago

I stopped grinding flax a year or so ago based on the mixed research, some of it is pretty strong, same thing with soy, too much risk, there’s proof to suggest they are unsafe, that’s enough for me, other things like cod liver oil have down sides (pro oxidant, rancidity, heavy metals etc) but the research is more favourable, so i still consume it.

Tony
Tony
8 years 16 days ago
Hey Sue, I don’t really know of any other vegan DHA and EPA supplements, but I do remember reading about others in development a few years ago when V-Pure came out. Although they’re based in Switzerland I think they deliver to the states. Supposedly they’re also working on an algae-based b12 supplement, more good news for vegans. “I think its a lot easier to achieve optimal health on a diet that includes meat.” I think in general this is true – planning a vegan diet in our meat-obsessed culture can take some time. However, there are lots of health problems… Read more »
gloria
gloria
8 years 15 days ago

This may have been answered already but I can’t find it…I have never found a fish oil that doesn’t “repeat” on me. I have tried (& returned) virtually every one that anyone even suggested would agree with me. I even tried just a liquid which was mixed in with my daily protein smoothie. Yuck & ick! The only one even remotely palatable has been Coromega–but it seems pretty low dosage. Any suggestions? I currently take a 1000 mg “organic” flaxseed oil cap. daily. I’m 63 & take no medications.

Bridget
Bridget
3 years 10 months ago
I take Carlson’s Cod Liver Oil Professional Formula with light lemon flavour. I’m not saying it doesn’t ever “repeat” but I take it at night shortly before bed so it doesn’t bother me. I admit if I take it in the morning I can have an issue. Both of my 60 year-old parents take it in the morning, though, and never have a problem. I wouldn’t mix any CLO with food, even a smoothie– the taste always comes through. It doesn’t taste wonderful, but with a sip of water I down it like a pill and it’s not too fishy… Read more »
trackback
8 years 15 days ago

[…] rule, fish feeds the heart, first in a series on adaptive thermogenesis (metabolism), how flax oil affects the body (I long ago went to fish oil only), Pie Town opens in Charlotte, Leigh totally rips off […]

yipper
yipper
8 years 14 days ago

**OT, but can’t wait to read the chia post.

recently had a green bar w/chia..then started reading up on someone making chia drinks, etc. The fiber content is out of this world..

will check back soon.

Peter Sklar
8 years 14 days ago
Ground flax seeds do NOT cause any sort of cancer. This is another paranoid headline-grabbing phenomenon based on dubious science from a tiny study or handful of studies. Who sponsored the research? Think about it- who the heck would pay to study a link between flax seeds and prostate cancer? It wouldn’t surprise me if it was another scare tactic by the meat or pharmaceutical industry. Reminds me of the garbage about too much Vitamin E, too much soy, and most recently drinking too much water. There will always be research that supports or attacks anything ever studied. Intelligent people… Read more »
Sue
Sue
8 years 14 days ago

Peter, you said:
“Ground flax seeds do NOT cause any sort of cancer”

You can’t make such a statement, where is your proof that it doesn’t cause cancer. Flaxseeds contain phyto-oestrogens so it makes sense that there would be a study examining any links with cancer.

Peter Sklar
8 years 14 days ago
Susan- In science, one doesn’t normally seek to prove that a substance DOESN’T cause something, (such as cancer); one normally attempts to prove that it DOES. The scary word “phyto-estrogens” literally means plant estrogens. Virtually every healthy food we eat — most vegetables, most fruits, grains, beans, nuts, seeds, and roots — all contain phytoestrogens. Perhaps you didn’t realize that. The preponderance of independent research in fact indicates that phytoestrogens actually PROTECTS tissues from the cancer-causing effects of xenoestrogens and other hormonal pollutants. I repeat my suspicion as to why flax seeds were singled out for such a misleading headline.… Read more »
Michael
Michael
8 years 14 days ago

How come there’s no info on who did the study and what they did in the study? We need the proof before we can believe that this is true. To me it sounds like someone just made this up, why only flax and what about the other foods that have ALA in them? If it was the ALA that caused prostate cancer then why is flax the only food to be targeted?

Linda
Linda
8 years 14 days ago
It’s always a relief to see a note of reason, in present case, from Peter and Michael. I spend a lot of time finding valid info for consumers, and have seen good double-blind clinical studies [not funded by special interests] which have shown that flaxseed consumption is definitely beneficial in opposing prostate and other cancers. Anyone who has a cause to prove can always find something to back it, of course. The amount of irresponsibility so often seen re: quoting an isolated study [which as Peter and Michael have pointed out was not even identified] is sad. It is doubly… Read more »
Sue
Sue
8 years 14 days ago

The study is mentioned above. Just click on the link just after the picture of the flax bottle.

sl
sl
8 years 14 days ago

I would like to recieve your daily ‘informational’ updates, Thanks,

Peter Sklar
8 years 14 days ago

I reviewed the study. The final sentence from the authors’ own abstract says it all:

“It is quite uncertain at present whether the effect on prostate cancer is real.”

Case closed.

Thank you.

-P

Peter Sklar
8 years 14 days ago

O.k. One more point.

And this flimsy, non-conclusive, ambiguous conclusion inspired HEADLINES warning people against flax seeds.

Mark, with all due respect, how about a bit more homework next time before advising your readers to avoid an extremely healthy and essential nutrient source.

Thanks.

-P

FLOYD HOLMES
FLOYD HOLMES
8 years 14 days ago
Ok, I have read all of the pro’s and con’s and still have no idea whether I should continue having Flax seeds (3 tablespoons) with my cereal and my salads. I usually have one helping 3tbs per day. I am a male,76 years of age, in good health and take 1 each: 1000mg of Fish Oil Concentrate with Omega-3 Fatty Acids together with Vitamin B-6 (100mg); B-12(1000 mcg); Folic Acid (400 mcg); Vitamin D (1,000 IU); Magnesium (250 mg)and a Mature (Kirkland-same as Centrum Silver) Multi Vitamin daily. So, with all of the various discussions on this Blog, just where… Read more »
FLOYD HOLMES
FLOYD HOLMES
8 years 14 days ago

Addendum to Floyd Holmes comment: I also eat salmon (wild) twice a week and red meat once a week.

Peter Sklar
8 years 14 days ago
Uh…I thought it was pretty clear that flax seeds are a wonderful food. Let’s put it this way: I’m a 59-year-old male who researches nutrition daily, somewhat as a hobby and partly related to my work. I read at least a half-dozen health-related publications regularly. I reviewed the above study supposedly establishing a link between flax seeds and prostrate cancer. My conclusion? I am continuing to have crushed flax seeds almost daily with my meals. I read nothing whatsoever- except a sloppy interpretation of some research, and some paranoid gossip- that would make me concerned. Those of you who are… Read more »
MCM
MCM
8 years 14 days ago

I have been aware of this issue for many years now..that plain Flax seed oil is not beneficial to men and has phtoestrogen qualities and can cause issues with the prostate. BUT the kicker in this is “Plain” flax seed oil. “IF” the flax seed oil is with “Lignans” is has been stated to be okay for men. I believe that any flax seed oil taken should be organic and taken as oil “with Lignans for both men and women” always. The lignans help the nody remove excess estrogen.

MCM
MCM
8 years 14 days ago

Another great form of Omega 3s are from Chlorella. Chlorella, spirulina and algaes are all excellent sources and also provide numerous other health benefits. Definitely worth taking.

patty stone
patty stone
8 years 14 days ago

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

Bill
Bill
8 years 9 days ago

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?

mike
mike
3 years 2 months ago

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

trackback
8 years 8 days ago

[…] of day, etc. Better to get mostly straight DHA and EPA, just how they’re found in meat. read more: Flax Seed and Prostate Cancer Risk | Mark’s Daily Apple __________________ […]

Sue
Sue
7 years 11 months ago
These are some comments about flaxseed oil that I have read that are quite interesting: Comments: “Have you seen this paper on ALA to DHA and EPA conversion? http://www.ajcn.org/cgi/content/abstract/88/3/801 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, (Name) 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… Read more »
Bonnie
Bonnie
7 years 11 months ago

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. 🙂

trackback

[…] Dear Mark: Is Flax Bad? […]

MikeL
MikeL
7 years 9 months ago
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… Read more »
Andre
Andre
7 years 3 months ago
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… Read more »
trackback

[…] never in the raw state) – cereal grains and legumes – and question whether we should be eating certain seeds at all, I think I’m overdue for a celebration of (or a critical look at) all the other edible […]

trackback

[…] never in the raw state) – cereal grains and legumes – and question whether we should be eating certain seeds at all, I think I’m overdue for a celebration of (or a critical look at) all the other edible […]

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