Nutritional Benefits

With our North American love of all that is flax, it is important to note that there is some research out there that identifies that there are some risks with consuming it. By educating yourself about all of the information, you can make a more informed decision about if you consume it and how much of it you choose to eat. So here are some facts (along with the sources of research) that I discovered in my review:

• 40% of the world’s flaxseed is grown in Canada: so it is heavily promoted as a North American crop.
• Flaxseeds and flaxseed oil can spoil if they are not kept refrigerated. It should be protected from light, heat, air, and moisture.1
• Flaxseed has less dietary fibre (27% vs. 33%), and can hold less water (approx. 6 times its weight) than Chia although it has more soluble fibre (ratio insoluble: soluble = 2:1, vs. 8:1).
• Flaxseed contains 60% less calcium, but has more magnesium and potassium.
• The ORAC value of flaxseed is unknown. Chia’s ORAC = 840 units per 12 grams.
• Per 12 gram flaxseed contains 2.7g omega-3, Chia® 2.3 g omega-3. Omega-6 content is equal.
• Ratio omega-6: omega-3 is 1:4 (flaxseed), 1:3 (Chia). Researchers speculate that the optimal omega-6: omega-3 ratio is between 4:1 2 and 1:1 3,4. To balance the extreme omega-6 intake in the North-American diet, it is necessary to decrease omega-6 intake, and increase omega-3 intake. 4
• Flaxseed has to be milled to be able to absorb its nutrients.

Cyanogenic glycosides
• Flaxseed contains the cyanogenic glycosides which defend flaxseed against micro-organisms and herbivores. In humans they lead to the build up of poison as they are converted into thiocyanate in the intestinal tract. Our body can detoxify cyanide to up to 50 g flaxseed/day (6 tbsp). 5 High blood levels of thiocyanate for prolonged time may have adverse affects on the thyroid function.6

Vitamin B6 antagonistic factors
• Linatine is a vitamin B6 antagonist in flaxseed. Low vitamin B6 status has been associated with increased homocystein levels 7, and plaque formation, which increase the risk for heart disease 8.

Lignans
• Lignans are present in many plant foods; including seeds, whole grains, flaxseed, sesame seed, beans, fruits, and some vegetables. Flaxseed is by far the highest source of lignans found in nature, with 100- 800 times more lignans than other foods. Flaxseed oil does not provide any lignans. 9,10
• Median total intake of lignans in the US is less than 1mg/day. 11
• In addition to diet, circulating levels of lignans in the body are influenced by intestinal microflora, smoking, antibiotics, constipation, and obesity. 12
• Lignan glycosides from food are converted into enterodiol and enterolactone by bacteria in the colon. 13 These lignans have been found to bind to proteins called estrogen receptors, and to exert either estrogen-like or anti estrogen-like effects. It is suggested that if there is little estrogen in the body, e.g. after menopause, lignans may act like weak estrogens. When estrogen is abundant in the body, they reduce estrogen’s effects by displacing it from cells. 14 Other mechanisms have been suggested which interfere with normal estrogen functioning in the human body. 15,16,17
• Interference with estrogen functioning may either prevent or promote cancers, such as breast cancer, that depend on estrogen to start and develop.
• Since dietary habits, lifestyle factors, and genotype are unknown in most studies, investigating the association of enterolactone and cancer risk, makes it difficult to interpret results.
• Studies on the safety of lignans in animals, humans have shown inconsistent results.10,12,17,18
• Since safety in pregnant and lactating women has not been established, consumption of lignan supplements or substantial amounts of flaxseeds on a regular basis should be avoided by pregnant women, lactating women or women trying to become pregnant. In healthy people, eating moderate amounts of flax products should present no problem. 19
• Since phytoestrogen supplements have been shown to cause growth of breast tissue in animals and healthy women, and lignans are a type of phytoestrogens, use of lignan supplements for a long time could increase breast cancer risk. Most physicians do not recommend that patients with estrogen sensitive cancers (breast/prostate cancer) take phytoestrogens/ lignans, for fear of causing a recurrence.19

Cadmium
• Since cadmium is a heavy metal that can bind to estrogen receptors, it is speculated that tumor growth induced by flaxseed, may be due to its high cadmium content. Cadmium from flaxseed was found to significantly accumulate in the liver and kidney of rats. 20 It was previously shown that cadmium doses higher than 7ug/kg/weight activate estrogen receptors, induce early puberty onset, and alter breast development, predicting increased breast cancer risk.21,22

Other side effects
• Flaxseed oil should not be used with other laxatives or stool softeners. People who have inflammatory disease or narrowing of the intestine, esophagus, or stomach should avoid flaxseed. Flaxseed is also not recommended by some doctors for people with diabetes. Some medicines and supplements may not be absorbed properly if they are taken at the same time as flaxseed. For this reason, some doctors recommend taking medications 1 or 2 hours before or after flaxseed. A few severe allergic reactions to flaxseed have been reported. 1

Constipation
• Flaxseed was found to cause diarrhea and mild abdominal distension when doses of 40g/day were tested in women. 23

Diabetes
• Most studies on the effect of flaxseed on blood glucose levels and insulin resistance have shown no effect. 24, 25,26,27 Results on HbA1c levels are inconsistent.24
• Cunnane et al. found that bread with 25% flaxseed lowered blood glucose by 28%, whereas 21% of Chia added to white bread lowered glucose by approx. 45%!28
• One study found that flaxseed improved insulin sensitivity in adults with elevated lipid levels.29

Cardio Vascular Disease
• The effect of flaxseed and flaxseed oil on blood lipid values, inflammation (lower CRP), and blood pressure levels has been found in several studies, although results are inconsistent.29,30,31,32,33
• One study showed decreased protein thiol groups at week 3 after the flaxseed treatment than after the control, suggesting increased oxidation. 31

Hypertension
• Studies on the effect of flaxseed on blood pressure found inconsistent results. 34,35

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References:
1. American Cancer Society. www.cancer.org
2. Yehuda, S. Omega-6/Omega-3 Essential Fatty Acid Ratio: The Scientific Evidence. World Rev Nutr Diet. Basel, Karger. 2003; vol 92, pp 37-56.
3. http://articles.mercola.com/sites/articles/archive/2002/03/23/omega3-part-two.aspx
4. Ho, D. Discover The Optimal Ratio of Omega-3 to Omega-6 Oils. Enzineartciles. com. August 6, 2008
5. Cunnane, SC, Ganguli, S, Menard, C, et al. High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans.Br J Nutr. 1993 Mar: 69(2): 443-53.
6. Dorea, JG. Maternal Thiocyanate and Thyroid Status during Breast-Feeding. J Am Coll Nutr. 2004. Vol. 23, No. 2, 97–101.
7. Selhub, J, Jacques, PF, Wilson, PW, et al. Vitamin status and intake as primary determinants of homocysteinemia in an elderly population. JAMA. 1993 Dec; 270 (22): 2693-8.
8. Selhub, J, Jacques, PF, Bostom, AG, et al. Relations between plasma homocysteine and vitamin status in the Framingham study population. Impact of folic acid fortification. Public health Rev. 2000; 28(1-4): 117-45.
9. Milder, IE, Arts, IC, van de Putte, B, et al. Lignan contents of Dutch plant foods: a database including lariciresinol, pinoresinol, secolariciresinol, and matairesinol. Br J Nutr. 2005 Mar; 93(3): 393-402.
10. Tou, JCL, Chen, J, Thompson, LU. Flaxseed and its lignin precursor, secoisolariciresinol diglycoside, affect pregnancy outcome and reproductive development in rats. J. Nutr. 1998; 128: 1861-1868.
11.Daniells, S. Lignans may protect against prostate cancer. Nutraingredients.com. Mar 8, 2006.
12. Adlercreutz, H. Lignans and human health. Critical reviews in Clinical Laboratory Sciences. 2007; 44: 483-501.
13. Borriello, S. P., Setchell, K.D.R., Axelson, M. &. Lawson, A. M. Production and metabolism of lignans by human faecal flora. J. Appi. Bacteriol. 1985; 58: 37-43.
14. Whitten PL & Naftolin F. Dietary estrogens – A biologically active background for estrogen action. In New Biology of Steroid Hormones, Hochberg RB & Naftolin F eds, pp 155-167, Raven Press: New York 1991.
15. Adlercreutz, H, Mousavi, Y, Clark, J, et al. Dietary phytoestrogens and cancer: in vitro and in vivo studies. J Steroid Biochem Mol Biol 1992; 41: 331-7.
16. Adlercreutz, H, Bannwart, K, Wahala, T, et al. Inhibition of human aromatase by mammalian lignans and isoflavonoid phytoestrogens. J Steroid Biochem Mol Biol 1993; 44: 147-53.
17. Velentzis, LS. Do phytoestrogens reduce the risk of breast cancer and breast cancer recurrence? What clinicians need to know. Eur J Cancer. 2008 Jul 7.
18. Thompson, LU, Chen, JM, Li, T, et al. Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Clin Cancer Res 2005; 11(10): 3828-35.
19. healthlibrary.epnet.com
20. Khan, G, Penttinen, P, Cabanes, A, et al. Maternal flaxseed diet during pregnancy or lactation increases female rat offsrping’s susceptibility to carcinogen-induced mammary tumorigenesis. Reproductive Toxicology. 2007; 23: 397-406.
21. Johnson, MD, Kenney, N, Stoica, A, et al. Cadmium mimics the in vivo effects of estrogen in the uterus and mammary gland. Nat med. 2003;9: 1081-4.
22. Stoica, A, Katzenellenbogen, BS, Martin, MB. Activation of estrogen receptor-alpha by the heavy metal cadmium. Mol Endocrinol. 2000; 14: 545-53.
23. Pruthi, S, Thompson, SL, Novotny, PJ, et al. Pilot evaluation of flaxseed for the management of hot flashes.J Soc Integr Oncol. 2007 Summer;5(3):106-12.
24. Pan, A, Sun, J, Chen, Y, et al. Effects of flaxseed derived lignan supplement in type 2 diabetic patients: a randomized, double-blind, cross-over trial. Plos One 2007 nov; 2(11): e1148.
25. Barre, DE, Mizier- Barre, KA, Griscti, O, et al. High dose flaxseed oil supplementation may affect fasting blood serum glucose management in human type 2 diabetics. J Oleo Sci. 2008;57(5):269-7.
26. Mc Manus, Clandinin, Jumpson, J, et al. A comparison of the effects of n-3 fatty acids from linseed oil and fish oil in well-controlled type 2 diabetes. Diabetes Care 1996; 19, 463-467.
27. Goh, Y, Jumpson, J, Ryan, R. Effect of n-3 fatty acids on plasma lipids, cholesterol, and fatty acid content in NIDDM patients. Diabetologica 1997; 40: 45-52.
28.Cunnane, SC, Ganguli, S, Menard, C, et al. High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans. Br J Nutr. 1993; 69: 443-453.
29. Bloedon LT, Balikai S, Chittams J, et al. Flaxseed and cardiovascular risk factors: results from a double blind, randomized, controlled clinical trial. J Am Coll Nutr. 2008 Feb;27(1):65-74.
30. Hallund J, Tetens I, Bügel S. The effect of a lignan complex isolated from flaxseed on inflammation markers in healthy postmenopausal women. Nutr Metab Cardiovasc Dis. 2008 Sep;18(7):497-502.
31. Jenkins, DA, Kendall, WC, Vidgen E, et al. Health aspects of partially defatted flaxseed, including effects on serum lipids, oxidative measures, and ex vivo androgen and progestin activity: a controlled crossover trial. Am J Clin Nutr 1999;69: 395-402.
32. Zhang, W, Wang, X, Liu, Y, et al. Dietary flaxseed lignin extract lowers plasma cholesterol and glucose concentrations in hypercholesterolemic subjects. Br J Clin Nutr.2008; 99: 1301-1309.
33. Dodin, S, lemay, A, Jacques, H, et al. The effects of flaxseed dietary supplement on lipid profile, bone mineral density, and symptoms in menopausal women: a randomized, double-blind, wheat germ placebo-controlled clinical trial. J Clin Endocrinol Metab 2005; 90: 1390-1397.
34. Stuglin C, Prasad K. Effect of flaxseed consumption on blood pressure, serum lipids, hemopoietic system and liver and kidney enzymes in healthy humans. J Cardiovasc Pharmacol Ther. 2005 Mar;10(1):23-7.
35. Paschos, GK, Magkos, F, Panagiotakos, DB, et al. Dietary supplementation with flaxseed oil lowers blood pressure in dyslipidemic patients. Eur J Clin Nutr. 2007; 61: 1201-1206.