Composition and Sources of Trans Fat
Director, Nutrition Research Program
Child and Family Research Institute
Composition and Sources of Trans Fats in the Canadian Diet Trans fatty acids from two sources are present in the diet: those from the industrial, partial hydrogenation of cis unsaturated fats and oils and those from the natural, bacterial hydrogenation of unsaturated fatty acids in the rumen. Both the amount and types of trans fatty acids differ between foods containing industrially prepared partially hydrogenated oils and the milk and tissue fats of ruminants. Typically, ruminant fats contain only about 2-5% trans fatty acids, while trans fatty acids can represent as much as 60% of the fatty acids in partially hydrogenated oils. The major trans fatty acid formed in the rumen is trans vaccenic acid (11-trans 18:1), which represents about 60% of the trans fatty acids in milk and butterfat. Small amounts of conjugated linoleic acid (CLA) —which are 18 carbon-chain fatty acids with two double bonds occurring on adjacent carbon atoms — are also present. The major trans fatty acid in partially hydrogenated oils is elaidic acid (9-trans 18:1), although a large number of isomers are present, including vaccenic acid. Whereas margarines and shortenings containing partially hydrogenated fats and oils contain high amounts of trans fatty acids, their direct consumption accounts for less than 15% of Canadians’ average total intake of trans fatty acids. Rather, it is fats and oils used by industry in the preparation of processed and staple foods that makes up most of the trans fatty acids consumed by Canadian adults. Available estimates suggest that the intake of trans fatty acids has decreased in Canada from an average of about 8 grams per day to 4-5 grams per day, although this varies widely depending on food choices. Prior to 2003, about 50% of dietary trans fatty acids were derived from baked goods, including breads, cakes, pastries and cookies, while meats and dairy products contributed about 10%. However, industry has been responding to the new labelling regulations and the forthcoming regulations on industrially created trans fatty acids in Canadian foods by removing trans fatty acids from many breads and snack foods.
Sources
- Elias SL, Innis SM. 2002. Bakery foods are the major source of trans-fatty acids among pregnant women with diets providing 30 percent energy from fat. J Am Diet Assoc 102:46-51.
- The Danish Nutrition Council. 2003. The influence of trans fatty acids on health. Fourth edition. Eds. Stender S, Dyerberg J.
- Katan MB, Zock Pl, Mensink RP. 1995. Trans fatty acids and their effects on lipoproteins in humans. Ann Rev Nutr 15:473-493.
- WHO/FAO. 2003. Report on diet, nutrition and the prevention of chronic diseases, 2003.
- National Academy of Sciences. DRI Report on Macronutrients, 2002.
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