Flax: Science, Nutrition, and Functional Food Uses

Despite being cultivated by humans for thousands of years, flax (Linum usitatissimum) is still relatively new to the nutritional and functional ingredients arenas. But, with public awareness increasing for flax’s nutritional content and health benefits, the flax market is set for continued growth. Whether used as whole seeds or in its milled form, flax has huge potential.

Flax essentially contains three distinct groups of healthful compounds: polyunsaturated fatty acids (PUFAs) from the omega-3 family, soluble and insoluble dietary fiber, and lignans.¹ Flax is also a good source of digestible protein, with each seed comprising around 20% protein, but the health benefits of flax are often attributed to its omega-3 and fiber profiles.

Omega-3s

Flax contains two essential fatty acids (EFAs),  alpha-linolenic acid (ALA) and linoleic acid (LA), which provide omega-3 and omega-6 fatty acids, respectively. As one of the richest plant sources of ALA, flax may be seen as an alternative to fish-sourced omega-3s.

EFAs such as ALA are required by the body to help maintain the structure of cell membranes and the health of the skin.² The ALA in flaxseed also has other possible health benefits, including those associated with cardiovascular health.

Coronary heart disease is a leading cause of death in the United States and globally.³ A key factor in the prevention of the disease is lifestyle changes, especially those associated with nutritional modification, and omega-3s in particular are frequently triumphed as a powerful dietary method to help tackle coronary heart disease. Current dietary recommendations for adults suggest a daily adequate intake of around 1.6 g of ALA omega-3, based on a 2000-calorie diet.⁴ As such, healthy intakes of ALA are easily achieved by adding 1-2 tablespoons of milled flax to the daily diet.
In terms of very specific health benefits, flax’s ALA fraction offers antiatherogenic effects,⁵ meaning it can help prevent the formation of atheromas, fatty deposits in arteries which can restrict blood flow and lead to thrombosis, angina, and strokes. Evidence suggests that a strong anti-inflammatory action may be involved in this cardioprotective effect.⁶

A new cohort study from the Harvard School of Public Health directly attributes a reduction in mortality in older adults to an increased omega-3 intake.⁷ Analyzing 16 years of data from more than 2700 U.S. adults, ages 65 and older, who took part in the national, long-term Cardiovascular Health Study, researchers found that those who had the highest circulating levels of omega-3 had a significantly lower risk of mortality compared to those with lower levels. The reduction in mortality risk was as much as 27%, with a decrease of as much as 35% in mortality risk from coronary heart disease.

A recent double-blind, placebo-controlled study on the effects of flaxseed on blood pressure, conducted by Grant Pierce, PhD, executive director of research at St. Boniface Hospital (Manitoba, Canada), showed that adding milled flax to the diets of patients with peripheral arterial disease (PAD) produced large drops in blood pressure after six months of treatment.⁸ Although further research is needed to confirm the exact mechanism of action, the study presents promising news for consumers of dietary flaxseed.

Fiber and Lignans

In addition to potential cardioprotective function, flax also contributes to the transport of cholesterol, with several studies reporting that daily flax consumption reduces circulating total cholesterol by 6–11%, and LDL cholesterol by as much as 18%.⁹ These hypocholesterolemic effects are generally attributed to the dietary fiber and lignan content of flax.

Dietary fibers are linked to a reduced risk of diseases of the gastrointestinal tract. A good source of both insoluble and soluble fiber, flax provides 3 g of fiber per tablespoon. This means that one tablespoon of milled flax contains as much dietary fiber as one slice of whole wheat bread, one-half cup of cooked brown rice, or one-quarter cup of cooked oat bran.¹⁰ Insoluble fiber helps promote a healthy digestive tract, while soluble fiber is associated with lowering cholesterol and maintaining blood glucose levels and blood pressure. The main soluble fiber in flax is in the form of mucilage gum, making it easy to digest and useful as a nutritional or functional food ingredient.

Flaxseed fiber may also have beneficial effects on satiety and appetite suppression. In a recent single-blinded randomized crossover study on 44 adults, flax fiber significantly suppressed appetite and energy intake.¹¹ A similar study in 2011 found that flaxseed fiber reduced appetite in men and suppressed postprandial lipemia (excess lipids in the blood).¹²

Due to their phytoestrogen and antioxidant properties, flax lignans may possess chemo-protective or anti-carcinogenic benefits for consumers, too.¹³

Baking and Frying with Flax

It’s not just nutritional and health benefits that set flaxseed apart from other ingredients; flax also has potential for a variety of food formulations and applications. Recent breakthroughs in seed processing technologies have opened up the possibilities of using flaxseed as a cost-effective, functional ingredient. A clean-label alternative to using guar gum for moisture management in breads, flax-derived ingredients can also increase volume in fresh breads and baked goods. Trials on both whole wheat and white breads have shown consistent loaf-volume increases of as much as 15% with flax solutions.

Flax-derived ingredients can also help reduce fat absorption during frying. In studies using cake donuts, flax-derived functional ingredients reduced oil absorption by 10% compared to a control sample without the ingredient, resulting in an improvement in the nutrition facts label from 19 to 17 g of fat per serving. Similar levels of oil uptake reduction are evident in studies involving chicken batters and breadings, and cheese sticks.

With the simple addition of flax-based ingredients, baked goods manufacturers can also benefit from improved shelf life in frozen and ambient stored muffins, breads, cakes, biscuits, cinnamon rolls, and gluten-free products. Texture analysis has demonstrated a significant improvement in minimizing hardening and staling in bakery products at up to 21 days shelf life when flax ingredients are used.

Taking the nutritional and functional profiles into account, the benefits of flax are clear: flax helps create convenient products that fit consumer needs for healthy, tasty, and nutritious products. The flax story is only just beginning. 

References

1. AN Martinchik et al., “Nutritional value and functional properties of flaxseed,” [Article in Russian] Voprosy Pitaniia, vol. 81, no. 3 (2012): 4–10.
2. DH Morris et al., “Flax: a Health and Nutrition Primer,” Flax Council of Canada, 2007.
3. DR Leyva et al., “The cardiovascular effects of flaxseed and its omega-3 fatty acid, alpha-linolenic acid,” The Canadian Journal of Cardiology, vol. 26, no. 9 (November 2010): 489–496.
4. “The Food and Nutrition Information Center,” USDA National Agricultural Library, last modified May 30, 2013, http://fnic.nal.usda.gov.
5. CM Bassett et al., “Experimental and clinical research findings on the cardiovascular benefits of consuming flaxseed,” Applied Physiology, Nutrition, and Metabolism, vol. 34, no. 5 (October 2009): 965–974.
6. DR Leyva et al., “The cardiovascular effects of flaxseed and its omega-3 fatty acid, alpha-linolenic acid,” The Canadian Journal of Cardiology, vol. 26, no. 9 (November 2010): 489–496.
7. D Mozaffarian et al., “Plasma phospholipid long chain omega-3 fatty acids and total and cause-specific mortality in older adults: a cohort study,” Annals of Internal Medicine, vol. 158, no. 7 (April 2, 2013): 515–525.
8. DR Leyva et al., “The effect of dietary flaxseed on improving symptoms of cardiovascular disease in patients with peripheral artery disease; rational and design of the FLAX-PAD randomized controlled trial,” Contemporary Clinical Trials, vol. 32, no. 5 (September 2011): 724–730.
9. CM Bassett et al., “Experimental and clinical research findings on the cardiovascular benefits of consuming flaxseed,” Applied Physiology, Nutrition, and Metabolism, vol. 34, no. 5 (October 2009):965–974.
10. “A Focus on Fibre,” Flax Council of Canada, accessed May 30, 2013, http://www.flaxcouncil.ca.
11. S Ibrügger, “Flaxseed dietary fiber supplements for suppression of appetite and food intake,” Appetite, vol. 58, no. 2 (April 2012): 490–495.
12. M Kristensen et al., “Flaxseed dietary fibers suppress postprandial lipemia and appetite sensation in young men,” Nutrition, Metabolism, and Cardiovascular Diseases, vol. 23, no. 2 (February 2013): 136–143.
13. KK Singh et al., “Flaxseed: a potential source of food, feed, and fiber,” Critical Reviews in Food Science and Nutrition, vol. 51, no. 3 (March 2011): 210–222.