November 1, 2004
Flax's health benefits have been written about since 650 B.C. However, the development of flax ingredients and the awareness of their health-promoting properties are relatively new. Research from the last 30 years has uncovered nutritional benefits of flaxseed related to its unique composition. Processing innovations in more-recent years have enhanced flaxseed's use as an ingredient, making it available in many forms with specific nutritional benefits for today's health-conscious consumer.
Just the flax
Flaxseed's composition is approximately 40% fat, 28% dietary fiber, 21% protein, 4% ash and 6% carbohydrate. The carbohydrate portion includes sugars, phenolic acids, lignans and hemicellulose. Its fat provides a healthy fatty-acid profile but also gives it some storage instability because its high level of unsaturates makes it susceptible to oxidation. The seed's oil contains about 73% polyunsaturated fats, 18% monounsaturated fats and 9% saturated fat. The polyunsaturated-fat portion contains approximately 16% omega-6 fatty acids, mainly linoleic acid, and 57% omega-3 fatty acids, mainly alpha-linolenic acid (ALA). Both linoleic acid and alpha-linolenic acid are essential fatty acids that ultimately affect important physiological functions like blood pressure, platelet aggregation, cell growth and division, inflammatory responses and more.
Flaxseed's gluten-free protein and fiber content also provides nutritional benefits, and its phenolic acids (about 8 to 10 mg per gram of flax) appear to have antioxidant, anticancer and antimicrobial activities. However, the components given almost as much attention as the fatty acids are the lignans. "Lignans are abundant in whole grains, fruits and vegetables, but flaxseed is the richest source of lignans, with 75 to 100 times more lignans than any other plant source," says Jocelyn Mathern, R.D., technical specialist, Acatris, Inc., Minneapolis. According to "North America Flax Facts," published by Ameriflax, Mandan, ND, lignans make up 0.7% to 1.5% of flaxseed's composition. They're also considered phytoestrogens, so they have an effect on hormone metabolism in humans. For example, they help balance hormone levels, such as estrogen, in the body. They've also been found to help reduce menopause symptoms, similar to soy phytoestrogens.
The whole seed's lack of digestibility can decrease the bioavailability of these components. "The human body cannot digest whole flaxseed, so most people grind it themselves to get the benefits of the lignans and the omega-3 fatty acids," says Doreen VandenTillaart, sales executive, flax ingredients, Natunola Health, Winchester, Ontario. "When the consumer grinds the flax, it releases the oil from the kernel. The flax oil is very unstable so the flax becomes rancid very quickly."
Flexing flax's ingredient muscles
Processing flaxseed into ingredients by separating the shell from the hull and the kernel to enhance the availability of the lignans, fatty acids and other components, while also maintaining the oil's oxidative stability, is a challenge where a few companies have been successful. "We purchase a 99.9%-pure whole flaxseed from eastern and western Canada, and we shell it by a patented mechanical process," says VandenTillaart. "We shell the brown flax, separating the shell from the kernel, without disrupting the fat in the kernel, so our products are very stable. We offer a flax ingredient with three different percentages of kernel -- 50, 70 and 90 -- with the remaining percentage as the hull." A higher percentage of kernel provides a higher percentage of omega-3 fatty acids. "According to Health Canada's recommendation for daily intake of omega-3 fatty acids, two teaspoons of kernel a day is the target serving size to get the recommended level of omega-3s. We also have a product that is almost entirely pure flax hull, where the flax lignans are found," she adds.
Currently, no Recommended Daily Intake for lignans exists. But, some guidelines exist. "One tablespoon of ground flax contains about 50 mg of lignans, a level that is found to be a health-promoting amount," says Mathern. "Our ingredient, LinumLife, made from the flax hull, is 10 to 30 times more concentrated than the lignan levels found in ground flax, so a formulator would not have to add as much of LinumLife. Our two main ingredients are a milled product called LinumLife complex and a LinumLife extract, which contains 20% SDG (secoisolariciresinol diglycoside) lignan, the main flax lignan, the highest level of lignan found in an ingredient," she adds. SDG is a phytoestrogen and a strong antioxidant, with health benefits for both men and women. It converts to the lignans enterodiol and enterolactone in the colon. They also offer protection against cancers of the breast, endometrium and prostate.
Flax in action
Users of flax ingredients focus on the health benefits they deliver, so it is important that no barriers exist for using flax in foods. Dr. Clifford Hall III, assistant professor, Cereal and Food Sciences, North Dakota State University, Fargo, focuses his research on flaxseed oil and lignan stability in processed foods. At this year's 60th Flax Institute of the United States conference, Hall reported that flaxseed extracts did not appear to have a significant impact on the fermentation process in yogurt. He also published in the Journal of Food Processing and Preservation (Vol. 28, 2004) that the addition of flaxseed into macaroni was oxidatively stable. "The work we have been doing shows that under the appropriate conditions, flaxseed is relatively stable," he says.
Research shows that flax nutrients ALA and SDG can hold up to baking temperatures. One study found that heating whole or ground flax at temperatures as high as 350°C for 60 minutes had little effect on fatty-acid composition or oxidation, and did not generate new trans forms of ALA or other undesirable fatty-acid byproducts.
Typical applications include cereals, breads, nutrition bars and dietary supplements. "Bread manufacturers are substituting a percentage of the flour with our fiber and getting up to four or five days shelf life versus the typical two- to three-day shelf life," says VandenTillaart. She adds that Natunola's kernel has a bright-yellow color, which adds visual appeal when used as a topping, and also adds a nutty flavor to any application.
Kimberlee J. Burrington is the whey applications program coordinator for the Wisconsin Center for Dairy Research in Madison, WI. She received her B.S. and M.S. in Food Chemistry from the University of Wisconsin-Madison. She has 18 years of product-development experience with an emphasis on bakery and dairy applications.
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