It is misleading to suggest, as Erica Weir and associates1 have done in a recent Public Health article, that nuts and seeds (other than flaxseed) are sources of omega-3 fatty acids. One hundred grams of the oil extracted from the most common nuts (peanut, coconut, almond, hazel, Brazil and cashew) would provide about 900 kcal of energy but no omega-3 fatty acids. Of the oils from these nuts, that of cashew has the highest omega-3 fatty acid content, at only 0.14 g/100 g.2 The only nuts that are good sources of omega-3 fatty acid are walnut (10.4% of the oil)2 and the almost-extinct butternut.
As a practical tip for Canadians, unhydrogenated canola oil is cheap and contains about 10% omega-3 fatty acid (α-linoleic acid) without an excessively high content of omega-6 fatty acid (linoleic acid).2 Similarly, flaxseed oil, at 55% omega-3 fatty acid, may be used as a supplement.2 Any oily fish contains the longer-chain omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid, which lower triglycerides and have other health benefits.3
Arguably, the most successful secondary prevention trial for heart disease was the Lyon Diet Heart Study,4 in which the only intervention was a daily dose of about 2 tablespoons (about 30 mL) of unhydrogenated canola oil in the form of a margarine. Omega-3 fatty acids are vitally important, and our new food labels should indeed help us to make informed choices.
Eddie Vos Sutton, Que.
References
- 1.Weir E, Traynor M, Levin W. Nutrition labelling tidbits. CMAJ 2004;170(10):1538-9. [DOI] [PMC free article] [PubMed]
- 2.Search the USDA National Nutrient Database for Standard Reference, release 16-1 [online]. [place unknown]: USDA Nutrient Data Laboratory; 2004. Available: www.nal.usda.gov/fnic/foodcomp/search/ (accessed 2004 Aug 17).
- 3.Harris WS, Connor WE, Illingworth DR, Rothrock DW, Foster DM. Effects of fish oil on VLDL triglyceride kinetics in humans. J Lipid Res 1990;31(9):1549-58. [PubMed]
- 4.Leaf A. Dietary prevention of coronary heart disease. The Lyon Diet Heart Study [editorial]. Circulation 1999;99:733-5. [DOI] [PubMed]