Flax Oil: Should Men Avoid It?

Will Brink, Brinkzone

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…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.Will Brink