Dear Mark: Is Flax Bad?
Dear 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.)
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:
Modern Forager: The Vaunted Flax Seed
Subscribe to Mark’s Daily Apple feeds
Posted By: Mark Sisson
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.
I forgot to click notify me for followup comments
Ground flax seed cured my goiter.
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.
A new review study on this issue was published in the American Journal of Clinical Nutrition in 2009, authors Simon, Chen and Bent, link : http://www.ajcn.org/content/early/2009/03/25/ajcn.2009.26736E
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.
Hi there. I’m doing research on flax seed and its benefits when I came across your article.
Let me just state here: There is no clinical study up-to-date that proves flax seed consumption to cause prostate cancer or any cancer for that matter.
The research, done by Harvard showed that a diet high in ALA derived from ANIMAL sources was associated with a higher incidence of cancer.
As Flax seed is high in ALA an assumption was made that the consumption of flax seed would lead to a higher incidence in prostate cancer. It was not part of the experiment nor was it proven to be so. On the contrary there are studies that proves the opposite.
Have a look at this article.
http://www.healthy-oil-planet.com/flaxseed-oil-prostate-cancer.html
Barry Sears seems to be “the man” who kicked off the fish oil craze (Go Barry!) – and as a biochemist concerned with rancidity and mercury etc. possibily in some fish oils, I believe he obtains and sells the purest fish oil around.
I like the valuable info you provide in your articles. I will bookmark your weblog and check again here regularly. I’m quite sure I will learn many new stuff right here! Best of luck for the next!
DHA and EPA: One of the many proofs that humans need to eat primal meat in order to remain healthy.
DHA and EPA are the only forms of omega-3 that the body can use efficiently. These two forms are also found only in – MEAT. Plants have omega-3 but only in the ALA form, which the body cannot use well enough. Yes the body can convert ALA to EPA and DHA, but at too little amounts.
It is essential to have a 1:1 ratio of omega 3 to omega 6. Plant foods are high in omega 6 and high in the useless omega 3. So if someone is eating a plant based diet, this person is basically only getting omega 6 fatty acids, which is pro-inflammatory.
Humans are by nature, meat-eaters. Not herbivores, vegetarians or vegans.
DHA and EPA are synthesized by algae, not animals, and their dietary necessity compared to ALA is not at all clear, e.g.
http://www.ajcn.org/content/92/5/1040
“Substantial differences in intakes and in sources of Omega-3 polyunsaturated fatty acids existed between the dietary-habit groups, but the differences in status were smaller than expected, possibly because the precursor-product ratio was greater in non-fish-eaters than in fish-eaters, potentially indicating increased estimated conversion of ALA. If intervention studies were to confirm these findings, it could have implications for fish requirements.”
And more to the point, if any of this was significant, we would see increased mortality for vegans/vegetarians, which isn’t borne out by real-world experience.
http://nutritionfacts.org/blog/2012/01/07/ask-the-doctor-qa-with-michael-greger-m-d-week-15/
‘ asked on Just the Flax, Ma’am: 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!
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.’
My dad ate a lot of ground flax. HE was doing it to help his colon. He used it for about 3-4 years, then ended up with Prostate Cancer. Luckily They found it at the early stages. Who knows if it was from the Flax seed. My dad is convinced it is so he quit taking it.
My understanding of ground flaxseeds is that they contain lignan phytoestrogens, which are very different from phytoestrogens. On top of that, Flax Oil is very different from ground flax seeds in that it doesn’t have the lignan content that makes flax so beneficial.
there’s an article here from Cornell University about phytoestrogens (and flax) and breast cancer and prostate is mentioned towards the end.
http://envirocancer.cornell.edu/factsheet/diet/fs1.phyto.cfm
http://www.cancerforum.org.au/Issues/2011/July/Forum/Nutrition_and_prostate_cancer.htm
I’m still open to any new findings and would love to find a definitive answer as I finally just got my Dad to start on ground flax, so the last thing I want to do is put him at risk.