Flaxseed is a blue flowering crop, grown on the prairies of Canada for its oil-rich seeds. Flaxseed has been har¬vested since the beginnings of civilization and used in the human diet for thousands of years. The Babylonians cultivated flaxseed as early as 3000 B.C. In 650 B.C., Hippocrates used flaxseed for the relief of intestinal discomfort. In North America, the use of flax dates back to 1617 when Lois Hebert, the first farmer in Canada, brought it to New France. Today, many people consume flax for its many health rewards and its pleasant, nutty flavor.

Flaxseed is often referred to as a nutraceutical. It provides many essential nutrients, including protein, essential fatty acids, digestive enzymes, vitamins, and minerals. The seeds are tiny, flat, and smooth, with reddish-brown coloring. Flaxseed is available as an oil, a whole seed, or a milled seed. The oil is a rich source of omega-3 fatty acids.

To receive all the nutritional benefits of flaxseed, it is neces¬sary to consume the milled form, or crush the whole seeds just prior to consumption. Milled or crushed flaxseed also contains both soluble and insoluble dietary fiber, which help relieve constipation. In addition, milled or crushed flaxseed is a rich source of lignins, a type of phytoestrogen that may protect against breast cancer.

Studies have demonstrated that flaxseed may also help treat inflammatory disorders, reduce the risk of heart disease, and improve immune function and diabetic control (Schmidt EB, et al. In: Proceedings from the Scientific Conference on Omega-3 Fatty Acids in Nutrition, Vascular Biology, and Medicine. Dallas: Am Heart Assoc, 1994; Simopoulos AR Am J Clin Nutr 54:438¬463, 1991; Weksler BB. World Rev Nutr Diet 76:47-50, 1994; Kremer JM. Lipids 31 (Suppl):S243-S247, 1996).

Cornucopia of nutrients

Flaxseed offers a wealth of nutritional benefits. The major components of flaxseed are oil (41 percent) and protein (20 percent). The majority of the fat in flaxseed (more than 70 percent) is polyunsaturated fatty acids, namely omega-3 and omega-6 fatty acids, which are also referred to as “good fats.” Flaxseed is naturally very low in the saturated or “bad fats,” containing approximately nine percent (Flaxseed: A Smart Choice. Flax Council of Canada, 1996).

Essential fatty acids

Two types of essential fatty acids (EFAs) are required in the human diet: linoleic acid (LA), the parent fatty acid of the omega-6 family, and alpha-linolenic acid (LNA), the parent fatty acid of the omega-3 family. The omega-3 and -6 fatty acids are considered essential because the body cannot manufacture them from any other substance. Their presence in the body depends totally on dietary consumption.

These fatty acids are required for proper infant growth and development. They are also essential for maintaining the structure of cell membranes and permeability of the skin, and as precursors for prostaglandin synthesis (Food and Nutrition Board, Nat Res Council. In: Recom Dietary Allowances, 10th Ed, pp. 44-51. Washington, DC: National Academy Press, 1989). The role of prostaglandins in health will be discussed later in this article.

Linoleic acid (LA)

LA is plentiful in nature and is found in the seeds of most plants, except for coconut, cocoa, and palm. Some of the most commonly used supplemental forms are evening primrose, black currant, and borage oils. In addition to LA, these oils con¬tain a proportion of gamma-linoleic acid (GLA). GLA has demonstrated benefits in the treatment of diabetic nerve disease, inflammatory disorders, and symptoms associated with premenstrual syndrome (The gamma-linolenic acid multicentre trial group: treatment of diabetic neuropathy with GLA. Diabetes Care 16:8-15, 1993; Kunkel SL, et al: Suppression of chronic inflammation by evening primrose oil. Prog Lipid Res 20:885-888, 1981; Puolakka J, et al: Biochemical and clinical effects of the treatment of PMS with prostaglandin synthesis precursors. J Reprod Med 39[3]:149-153, 1985; Horrobin DF, et al: Abnormalities in plasma essential fatty acid levels in women with PMS and with non-malignant breast disease. J Nutr Med 259-264, 1991).

Alpha-Iinolenic acid (LNA)

LNA is found in green, leafy vegetables and in rapeseed, flaxseed, soybean seed, and walnuts. Canada is the world’s leader in the production and export of flaxseed. Northern Canadian flaxseed is a particularly rich source of EFAs, con¬taining approximately 60 percent omega-3 fatty acids. Recent research suggests that the omega-3 fatty acids in flaxseed reduce risk factors for coronary heart disease by reducing serum triglycerides and blood pressure. They also appear to protect against stroke by regulating blood clotting and platelet aggrega¬tion (Chan JK, et al. Am J Clin Nutr 53:1230-1234, 1991; Cunnane SC, et al. Am J Clin Nutr 61:62-68, 1994; Bierenbaum ML, et al. J Am Coll Nutr 12:501-504, 1993; Ascherio A, et al. Br Med J 313:84-90, 1996; Simon JA, et al. Stroke 26:778-782, 1995).

Omega-3 fatty acids have also been shown to protect against certain types of cancer, such as cancers of the breast and colon. Dr. L. Thompson, professor in the Department of Nutritional Sciences, University of Toronto, has been actively researching the benefits of flaxseed in cancer prevention. In animal studies, flaxseed was found to affect all three stages of cancer development: initiation, tumor development, and metastases (i.e., spread). According to Dr. Thompson, “Human clinical studies are needed to confirm these results, but flaxseed has tremendous potential to positively affect our health” (Kurzer MS, et al. In: Flaxseed in Human Nutrition, pp. 36-144; Serraino M, et al: The effect of flaxseed on early risk markers for mammary carcinogenesis. Cancer Letters 60:135-142, 1991; Serraino M, et al: Flaxseed supplementation and early markers of colon carcinogenesis. Cancer Letters 63:159-165, 1992; Rose DP, et al: Dietary fatty acids and breast cancer invasion and metastasis. Nutr Cancer 21:103-111, 1994).

Immune function

Two of the main components in flaxseed, LNA and lignins, have demonstrated a beneficial impact on the immune system. Both have been shown to affect immune cells and immune-response mediators, such as eicosanoids and cytokines. Through these mechanisms, flaxseed may play a beneficial role in the clinical management of autoimmune diseases (Blackburn GL. Proc Soc Exp Biol Med 200:183-188, 1992; Parbtani A, et al. In: Flaxseed in Human Nutrition. Cunnane SC, Thompson LU [eds]. Champaign: AOCS Press, 1995).

“Good” and “bad” prostaglandins

The processing and refinement of many of our plant oils—as well as changes in our dietary habits—has led to a decreased amount of omega-3 fatty acids in many foods, a deficiency of EFAs in our bodies, and an unbalanced ratio of omega¬6/omega-3 fatty acids in our diets. The balance of these fatty acids is important for proper prostaglandin (PG) metabolism. Prostaglandins are hormone-like substances that regulate many body processes, including inflammation and blood clotting. “Good” prostaglandins (PG1 and PG3) help reduce inflamma¬tion; regulate heart, lung, and kidney function; improve blood flow; and prevent platelets from sticking together. “Bad” prostaglandins (PG2), which have the opposite effect, lead to increased inflammation and platelet stickiness.

A diet rich in omega-3 fatty acids (flax, fish) leads to the production of the prostaglandin 3 series, which is beneficial. On the other hand, a diet high in omega-6 fatty acids can lead to the production of either prostaglandin 1 or 2 series. It is easy to see how dietary modifications can treat disease by altering prostaglandin metabolism.

Both kinds of fiber

Fiber is another essential but often deficient component of our diets. A diet high in fiber has been linked to a reduced risk of many chronic diseases, including heart disease and cer¬tain cancers (e.g., cancers of the colon and breast). Fiber also helps control weight and regulate blood sugar levels. Most health organizations, including the National Cancer Institute, recommend a minimum of 20 to 30 grams of fiber per day. The average North American consumes less than half this amount.

Milled flaxseed is a rich source of fiber, containing approx¬imately 20 grams of fiber per 50-gram serving. Flax contains a unique mix of both soluble and insoluble fibers. Most of the soluble fiber in flax is mucilage gum, which is a thick, sticky substance. Soluble fibers form a gel-like material that lowers cholesterol levels by blocking LDL absorption, helps balance blood glucose levels, and promotes bowel regularity.

Insoluble fiber also aids bowel regularity and helps prevent constipation. The insoluble fiber components in flax can hold water, thus helping to increase the bulk and soften the stool, allowing it to move through the colon more quickly.
Research has suggested that the constipation-relieving effects of flaxseed are quite significant. Flaxseed may increase the frequency of bowel movements by about 30 percent. Whole flaxseed, which is indigestible, is often consumed for this reason. Improved bowel regularity is associated with a reduced risk of colon cancer, because the quicker the waste is eliminated, the less time the colon is exposed to toxins and bacteria.

lignins

Lignins are widespread throughout the plant kingdom, but flax is one of the richest sources. According to research by Dr. L. Thompson at the University of Toronto, the lignin content of flaxseed is 75 to 800 times that of 66 other plant foods, includ¬ing soy, legumes, and cereals (Thompson LU. In: Flaxseed in Human Nutrition, pp. 219-236).

The potential value of flaxseed as a source of lignins has prompted a great deal of clinical research. It has been well-established that populations with high-fiber diets and high intakes of phytoestrogens such as lignins, tend to have lower rates of hormone-dependent cancers, such as breast, endome¬trial, and prostate cancers (Rose DP. Annu Publ Health 14:1-7, 1993). Lignins are believed to protect against these cancers by inhibiting certain enzymes involved in hormone metabolism, reducing the availability of estrogen, and interfering with tumor cell growth.

The main lignin precursor in flaxseed is secoisolariciresinol diglycoside, or SDG. Bacteria in the colon convert SDG to the primary lignins—namely enterodiol and enterolactone—found in humans and other animals. These phytoestrogens have demonstrated both estrogenic and anti-estrogenic activity (Adlercreutz H, et al. I Steroid Biochem 25:791-797, 1986).

While further study is needed, it has been suggested that the phytoestrogenic properties of lignins may also help alleviate menopausal symptoms (Cunnane S, Thompson LU). However, there have been few studies evaluating the effects of dietary flax on sex hormone levels in men. So far, it appears that flax con¬sumption has no effect.

Lignins have also been shown to possess other biological properties, including antimitotic (i.e., inhibiting the multi¬plication of cells), antifungal, and antioxidant activities. These properties may also contribute to the cancer-protective effects of flaxseed (Kurzer, M, et al. In: Flaxseed in Human Nutrition, pp. 136-144). It is important to note that most flaxseed lignins are removed during processing and thus are not found in appreciable amounts in the oil. Therefore, to obtain the valuable lignins from flaxseed, the whole seeds or milled flaxseed should be consumed.

Including flaxseed in your diet

As mentioned earlier, flaxseed is available in a variety of forms. Flaxseed oil provides a valuable source of the omega-3 fatty acids, and the whole seeds promote bowel regularity. However, to obtain the many other health benefits of flaxseed, it is best to consume the milled or crushed seeds.

When exposed to light and air, the EFAs in flaxseed easily become rancid. For this reason, it is important to store these products in air-tight containers in the refrigerator. In choosing a product, look for true, unadulterated flaxseed grown under organic conditions. Be aware of imitation products. Two genet¬ically altered derivatives of flaxseed, solan and linola, have appeared on the market. These products provide only trace amounts of omega-3 fatty acids.

The versatility of flaxseed makes it easy to incorporate into many foods. With its great taste and high nutritional value, flaxseed offers a healthy addition to our diets. Milled flaxseed can be sprinkled on yogurt or cereal, or used in baked goods and casseroles (see following page for recipes).

Sherry Torkos, B.Sc., Phm., graduated with honors from the Philadelphia College of Pharmacy and Science in 1992.Since that time, she has been practicing pharmacy and holistic health care at Professional Arts Pharmacy in Fort Erie, ON. With an emphasis on healthy lifestyle, nutrition,and supplementation,she integrates conventional and complementary therapies into her practice. Ms.Torkos serves on various medical advisory boards, and is the recent co-founder and director of the Pro Health Group, Inc. in Fort Erie, Ontario, Canada

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