Epidemiological studies and, increasingly, clinical work support the beneficial effects of ALA in minimizing the risk of heart disease and for anti-inflammatory effects. ALA is the main, if not only, omega-3 in the diet of at least one billion vegetarians worldwide; despite not consuming fish, vegetarians do not have a higher prevalence of chronic diseases than nonvegetarians.
There is no doubt that EPA and DHA are beneficial, as these fatty acids have been the subjects of thousands of clinical trials. In Sept. 2004, FDA approved a qualified health claim for reduced risk of coronary heart disease on conventional foods that contain EPA and DHA. This claim, however, does not extend to ALA, because ALA was not a part of the petition process. The FDA has never assessed nor denied a qualified health claim for ALA.
Assessing intake
The current AI of ALA for men is 1.6 grams of ALA per day; for women who are not pregnant or breastfeeding, it is 1.1 grams of ALA per day. Of these amounts, about 10%—160 mg per day for men and 110 mg per day for women—can come from a combination of EPA plus DHA.2
Canadian children consume 1.2 grams of ALA and 92 mg of EPA plus DHA on average every day. Although their average omega-3 intake appears to be adequate, only 61% of the children met the AI for ALA and only 22% met the AI for EPA plus DHA.14
Some experts believe higher intakes of omega-3 fatty acids are needed for health: an intake of 2.2 grams per day for ALA; an EPA plus DHA intake of 500 mg per day to decrease the risk of coronary heart disease; and an EPA plus DHA intake of 1,000 mg (or 1 gram) per day for adults with diagnosed heart disease.15 Clinical studies suggest that 3.6 grams of ALA (found in less than 1.5 teaspoon of flax oil) can be converted by the body to 500 to 540 mg of long-chain omega-3s, bringing current intakes closer to that recommended for reducing the risk of heart disease.16,17
It is unfortunate that in the “omega-3 debate” there are those who choose to downplay the importance of ALA in the diet and simply ignore the omega-6 side of the metabolic equation. The typical North American diet is “deficient” in omega-3 fatty acids and overly rich in omega-6 fatty acids. The omega-6 to omega-3 ratio may be as high as 17:1 in some Western diets. In the Women’s Health Study, some women ate diets with a ratio of 33:1.18 The omega-6 to omega-3 ratio recommended by international nutrition agencies ranges from 4:1 to 10:1.19 The best route to improving one’s omega-6 to omega-3 ratio is by decreasing the intake of omega-6 fats and increasing the intake of the omega-3 fats ALA, EPA and DHA in whole foods, flax, fortified foods and supplements.
Kelley Fitzpatrick is the director of health and nutrition for Flax Canada 2015. She has a Master of Science in nutrition and close to 20 years of experience linking agriculture to the disciplines of food and health through research, marketing and promotion activities. She can be reached at
kelleyf@shaw.ca
. For more information about Flax Canada, log on to fc2015.ca or healthyflax.com.
References
1. Whitney E, Rolfes, SR. 2005. Understanding Nutrition. Belmont, CA: Wadsworth; p. 7.
2. Institute of Medicine. 2002. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids, National Academies Press, Washington, DC, pp. 7-1 to 7-69 (dietary fiber), 8-1 to 8-97 (fat and fatty acids).
3. Anderson GJ, Connor WE. 1989. On the demonstration of ω-3 essential-fatty-acid deficiency in humans. Am J Clin Nutr. 49:585-587.
4. Burdge GC, Calder PC. Conversion of α-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. 2005. Reprod. Nutr. Dev. 45:581-597.
5. Burdge GC, Wootton SA. 2002. Conversion of α-linolenic to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women. Br. J. Nutr. 88:411-420.
6. Liou YA, King DJ, Zibrik D, Innis SM. 2007. Decreasing linoleic acid with constant α-linolenic acid in dietary fats increases (n-3) eicosapentaenoic acid in plasma phospholipids in healthy men. J. Nutr. 137:945-952.
7. Goyens PLL, Spilker ME, Zock PL, et al. 2006. Conversion of α-linolenic acid in humans is influenced by the absolute amounts of α-linolenic acid and linoleic acid in the diet and not by their ratio. Am. J. Clin. Nutr. 84:44-53.
8. Caughey GE, Mantzioris E, Gibson RA, Cleland LG, James MJ. 1996. The effect on human tumor necrosis factor α and interleukin 1β production of diets enriched in n-3 fatty acids from vegetable oil or fish oil. Am. J. Clin. Nutr. 63:116-22.
9. Zhao G, Etherton TD, Martin KR, et al. 2007. Dietary alpha-linolenic acid inhibits proinflammatory cytokine production by peripheral blood mononuclear cells in hypercholesterolemic subjects. Am. J. Clin. Nutr. 85:385-91.
10. Ander BP, Weber AR, Rampersad PP, et al. 2004. Dietary flaxseed protects against ventricular fibrillation induced by ischemia-reperfusion in normal and hypercholesterolemic rabbits. J Nutr. 134:3250-3256.
11. Billman GE, Kang JX, Leaf A. 1999. Prevention of sudden cardiac death by dietary pure ω-3 polyunsaturated fatty acids in dogs. Circulation. 99:2452-2457.
12. Albert CM, Oh K, Whang W, et al. 2005. Dietary α-linolenic acid intake and risk of sudden cardiac death and coronary heart disease. Circulation. 112:3232-3238.
13. Christensen JH, Schmidt EB, Mølenberg D, Toft E. 2005. Alpha-linolenic acid and heart rate variability in women examined for coronary artery disease. Nutr Metab Cardiovasc Dis. 15:345-351.
14. Madden SMM, Garrioch CF, Holub BJ. 2009. Direct diet quantification indicates low intakes of (n-3) fatty acids in children 4 to 8 years old. J Nutr. 139:1-5.
15. Gebauer SK, Psota TL, Harris WS, Kris-Etherton PM. 2006. n-3 Fatty acid dietary recommendations and food sources to achieve essentiality and cardiovascular benefits. Am J Clin Nutr. 83(suppl):1526S-1535S.
16. Burdge GC, Jones AE, Wootton SA. 2002. Eicosapentaenoic and docosapentaenoic acids are the principal products of α-linolenic acid metabolism in young men. Br J Nutr. 88:355-363.
17. Emken EA, Adlof RO, Gulley RM. 1994. Dietary linoleic acid influences desaturation and acylation of deuterium-labeled linoleic and linolenic acids in young adult males. Biochim Biophys Acta. 1213:277-288.
18. Miljanović B, Trivedi KA, Dana MR, et al. 2005. Relation between dietary n-3 and n-6 fatty acids and clinically diagnosed dry eye syndrome in women. Am. J. Clin. Nutr. 82:887-893.
19. Gebauer SK, Psota, TL, Harris, WS, Kris-Etherton PM. 2006. n-3 Fatty acid dietary recommendations and food sources to achieve essentiality and cardiovascular benefits. Am. J. Clin. Nutr. 83:1526S-1535S.