I’ve been eating a lot of tuna lately, as it’s a protein-packed, filling meal on my lower calorie days. Since it’s not the tastiest meal around, I’m always on the lookout for ways to make it a bit more palatable. My go-to technique for years has been to mix three cans of tuna with one tablespoon each of mayo and flaxseed oil.
I also used to add two tablespoons of milled flaxseeds to my protein shakes for added fiber.
Turns out that both habits were counter-productive, to say the least.
Ground flaxseeds are quite high in lignans.1 That’s bad news, because lignans are one of the principal classes of phytoestrogens.2 Phytoestrogens are plant compounds similar to estrogen. Many phytoestrogens are endocrine disruptors3 that interfere with testosterone.
Researchers at the University of Texas found in 2001 and 2008 that consumption of 30 grams of flaxseeds daily for one month reduced total testosterone levels in men between 10 and 15 percent.4, 5
So, ground flaxseeds are out. Be wary of flaxseed oil as well. While the majority of flaxseed oil brands contain lignans, some do not. If you’re deadset on flaxseed consumption for your daily intake of fats, check the label before picking up a bottle.
Still, better safe than sorry. As a general rule, we recommend men avoid flaxseeds because of their potential for lowering testosterone.
Now for a little caveat that may be a kick in — or near — the groin.
Flaxseed consumption may actually benefit men under certain situations. A 2004 meta-analysis of cancer research found that the lignans in flaxseed can actually reduce the number and size of tumors. This may be of particular interest for men battling prostate cancer.6
If you’re healthy now, you’re probably not faced with the lose-lose choice between your prostate and your sex drive. But if you’re at risk of developing prostate cancer, you might want to speak with your doctor about the potential benefits of flaxseed.
As for me, I’ll renew my search for flavor-enhancing tuna mixers.
What about you? Do you mix your tuna with something else, or just eat it plain?
1. Thompson, L.U., Robb, P., Serraino, M., Cheung, F. (1991). Mammalian lignan production from various foods. Nutr Cancer, 16(1), 43-52. [URL]
2. Brooks, J.D., Ward, W., Lewis, J., Hilditch, J., Nickell, L., Wong, E., Thompson, L. (2004). Supplementation with flaxseed alters estrogen metabolism in postmenopausal women to a greater extent than does supplementation with an equal amount of soy. Am J Clin Nutr, 79(2), 318-325. [URL]
3. Patisaul, H.B., Jefferson, W. (2010). The pros and cons of phytoestrogens. Front Neuroendocrinol, 31(4), 400-419. [URL]
4. Demark-Wahnefried, W., Price, D.T., Polascik, T.J., Robertson, C.N., Anderson, E.E., Paulson, D.F., Walther, P.J., Gannon, M., Vollmer, R.T. (2001). Pilot study of dietary fat restriction and flaxseed supplementation in men with prostate cancer before surgery: exploring the effects on hormonal levels, prostate-specific antigen, and histopathologic features. Urology, 58(1), 47-52. [URL]
5. Demark-Wahnefried, W., Polascik, T.J., George, S.L., Switzer, B.R., Madden, J.F., Ruffin, M.T. 4th, Snyder, D.C., Owzar, K., Hars, V., Albala, D.M., Walther, P.J., Robertson, C.N., Moul, J.W., Dunn, B.K., Brenner, D., Minasian, L., Stella, P., Vollmer, R.T. (2008). Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. Cancer Epidemiol Biomarkers Prev, 17(12), 3577-87. [URL]
6. Donaldson, M.S. (2004). Nutrition and cancer: A review of the evidence for an anti-cancer diet. Nutrition Journal, 3(19). [URL]