Flaxseed – Antioxidants for Health (Part 1)

By Kelley Fitzpatrick

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The Institute of Medicine (IOM) recommends that diets contain antioxidants. New foods are appearing in the grocery aisles touting their antioxidant content. In addition to its high level of omega 3, protein and fibre, flaxseed contains a wealth of antioxidant compounds. Why are antioxidants important? 

Everyday life is tough on our cells. They are under constant attack from molecules known as reactive oxygen species (ROS). ROS occur as a result of processes necessary to sustain life, including breathing which generates approximately 90% of cellular ROS (1). When there is an imbalance between the levels of ROS and antioxidants, oxidative stress can cause damage to cells. Research has shown that oxidative stress plays a role in the development of chronic disease, including cancer, cardiovascular disease, and even neurological impairment (1).

The IOM defines an antioxidant as a substance in food that significantly decreases the adverse effects of reactive species on normal physiological functions in humans (2). Antioxidants are can “neutralize” ROS before they are able to damage cellular components. The body does have complex defense mechanisms that are supported by the consumption of antioxidant-containing foods. As humans age the body’s antioxidant levels decline which can result in oxidative damage. We need dietary antioxidants to maintain the body’s defense systems (1).

Phytochemicals are naturally occurring substances in plants, many of which possess antioxidant activity. Some studies have shown that supplements of individual nutrients may not offer the same beneficial effects as diets rich in fruits, vegetables, seeds and whole grains. The health benefits of whole foods are likely due to the interactions of many phytochemicals working together.

Flaxseed – Rich in Antioxidants

Flaxseed contains a number of antioxidants that can benefit health and reduce disease. They play an important role in many of positive effects of flaxseed for wellness.

Lignans

Flaxseed is one of the richest sources of lignans providing 75-800 times higher levels than other plant sources. Depending on the method used for measuring lignans in foods, flaxseed contains 0.82-10.55 mg SDG/g of flaxseed. Whole seed and ground flaxseed typically contain between 0.7 and 1.9% SDG which is equivalent to approximately 77-209 mg SDG/tbsp of whole seed or 56-152 mg SDG/tbsp of ground flaxseed (3).  Secoisolariciresinol diglycoside (SDG) is the main lignan in flaxseed. Other lignans present in small amounts in flaxseed include matairesinol, pinoresinol and isolariciresinol (3).

Lignans have been reported to be effective antioxidants against DNA damage and lipid peroxidation. These unique compounds show antioxidant efficacy against free radical promoters 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,20-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-initiated peroxyl radical plasmid DNA damage and phosphatidylcholine liposome lipid peroxidation (4).

The antioxidant properties of flaxseed play an important role in reducing the risk of many diseases. SDG has been shown in a number of studies by Prasad and co-workers to be effective in retarding the development of type 2 diabetes (5). Thompson and co-workers have attributed anti-cancer effects of flaxseed to ne due in part to its lignan content (6).

Phenolic acids

Phenolics are also antioxidants found in flaxseed. They consist of a wide variety of subgroups, including phenolic acids, flavonoids, stilbenes, coumarins, and tannins. Flaxseed contains about 8 to 10 g of total phenolic acids per kilogram (kg) (7). Phenolic acids show significant protection against oxidation.

Ferulic acid is a phenolic phytochemical that possesses high antioxidant activity, and has anti-inflammatory and tumour inhibition properties (8). Diets rich in phenolic compounds are associated with reduced risk of cardiovascular disease and some cancers (9).

Flavonoids

Flavonoids bind certain metals, interact with enzymes and have anti-oxidant actions. Flaxseed contains about 35-70 milligrams (mg) of flavonoids/100g (10).

Vitamin E

The tocopherol (Vitamin E) content of flaxseed is affected by the variety, maturity of the seed, growing region, growing conditions and method of extraction. The gamma-tocopherol content can range from 150 mg/kg to 800 mg/kg flaxseed (11).

Oxidative modification of LDL-cholesterol promotes blockages in coronary arteries that may lead to atherosclerosis and heart attacks. Vitamin E may help prevent or delay coronary heart disease by limiting the oxidation of LDL-cholesterol.

Observational studies have associated lower rates of heart disease with higher vitamin E intake. A study of approximately 90,000 nurses suggested that the incidence of heart disease was 30% to 40% lower among nurses with the highest intake of vitamin E from diet and supplements. The range of intakes from both diet and supplements in this group was 21.6 to 1,000 IU (32 to 1,500 mg), with the median intake being 208 IU (139 mg) (10). Antioxidants such as vitamin E help protect against the damaging effects of free radicals, which may contribute to the development of cancer (11).

The numerous antioxidants and phytochemicals in flaxseed contribute to the many health benefits being reported for this incredible seed. Check out my next blog for the role that antioxidants in flaxseed play in food stability.

References

  1. Goszcz K, Deakin SJ, Duthie GG, Stewart D, Leslie SJ, Megson IL. Front Cardiovasc Med. 2015;2:29.
  2. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Institute of Medicine. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000. pp. 35-57, 364.
  3. Thompson, LU, Beatrice A. Boucher, BA, Zhen Liu, Z et al. 2006. Nutr. Cancer, 54(2):184–201.
  4. Hu C, Yuan YV, Kitts, DD. 2007. Food and Chemical Toxicology 45:2219–2227.
  5. Prasad K and Dhar A. 2016. Current Pharmaceutical Design. 22, 141-144.
  6. Mason JK, Thompson LU. 2014. Appl Physiol Nutr Metab. 39(6):663-78.
  7. Velioglu YS, Mazza G, Gao C, and Oomah BD. 1998. J. Agric. Food Chem. 46, 4113-4117.
  8. Herrera E, Jimenez R, Aruoma OI, Hercberg S, Sanchez-Garcia I, Fraga C. 2009. Nutr Rev. 67 Suppl 1:S140-14.
  9. Andersson AA, Lampi AM, Nystrom L, et al. 2008. J. Agric. Food Chem. 56(21):9767-9776.
  10. Oomah BD, Mazza G. 1998. Functional Foods: Biochemical & Processing Aspects, ed Mazza G, Technomic Publishing, Lancaster, PA, pp. 91-138.
  11. Daun JK, Przybylski R. 2000. Proc. Flaxseed Inst. 58: 80-91.
  12. Stampfer MJ, Hennekens CH, Manson JE, et al. 1993. N Engl J Med 328:1444-9.
  13. Waters DD, Alderman EL, Hsia J, et al. 2002. J Am Med Assoc. 288:2432-40.