Trans-unsaturated Fat

General Info | Animal Sources | Hydrogenated Fats | Health Impact | Recommendations

Trans-unsaturated fat

  • Geometrical isomers of unsaturated fatty acids that assume a saturated fatty acid-like configuration.
  • American diets contain between an average of 8-15 g/day
    • although wide variation between people

Animal Sources

  • Animal sources only provide 20% of trans fats
  • In form of conjugated linoleic acid and vaccenic acid
  • Naturally occurring amounts in meat and dairy products
  • 2-5% of total fat

Hydrogenated Fats

  • Processed foods and oils provide 80% of trans fats in diet
    • Most are supplied by products containing industrially hydrogenated vegetable oils
    • Examples
      • margarine (up to 15% trans fat by weight)
      • baking shortening (30% of trans fat)
      • partially hydrogenated and hydrogenated oil (up to 45% trans fat)
      • See Exchange List
    • Found in
      • fast foods and fried foods
      • Peanut butter (partially hydrogenated)
      • snack foods and many baked goods
        • replaces butter and lard
    • Example content
      • doughnut (medium): 3.2 g of TFA
      • French fries (large): 6.8 g of TFA
  • Created industrially through partial hydrogenation of plant oils
    • process developed in early 1900s
    • first commercialized as Crisco in 1911
  • US Nutrition fact labels are not required to list transfat if amount is less than 1 gram per serving
  • Benefits
    • extends shelf life and decreases refrigeration requirements
    • less expensive than semi-solid oils such as palm oil
    • can be reused longer in deep frying without going rancid
    • baked goods look better, browns more evenly
    • vegetarians can consume foods made from vegetable trans fats as opposed to butter and lard

Health Impact

Health Impact

  • Non-essential
  • Consumption increases risk of coronary heart disease (CHD)
    • Increased risk at 1 to 3 percent of total energy intake (Mozaffarian 2006)
    • Double risk in Cardiovascular Disease for every 2% in trans fat calories consumed (instead of carbohydrate calories) (Hu 1997)
    • An estimated 30,000 and 100,000 cardiac deaths per year in the United States are attributable to the consumption of trans fats (Mozaffarian 2006)
  • Cholesterol effects (Clevidence 1997)
    • Increases LDL (bad cholesterol)
    • Lowers HDL (good cholesterol)
  • Increases Lipoprotein (a), a particle more atherogenic than LDL (Clevidence 1997)


  • Trans fats be limited to less than 1% of overall energy intake (World Health Organization 2003, American Heart Association)
    • Example: consume less than 3 grams of trans fat on a 3000 Calorie diet

Also see Comparison of Dietary Fats


Clevidence BA, Judd JT, Schaefer EJ, Jenner JL, Lichtenstein AH, Muesing RA, Wittes J, Sunkin ME (1997). Plasma lipoprotein (a) levels in men and women consuming diets enriched in saturated, cis-, or trans-monounsaturated fatty acids. Arterioscler Thromb Vasc Biol. 17(9),1657-61.

Khosla P, Hayes KC (1996). Dietary trans-monounsaturated fatty acids negatively impact plasma lipids in humans: critical review of the evidence. J Am Coll Nutr. 15(4), 325-39.

Przybylski O, Aladedunye FA (2012). Formation of trans fats during food preparation. Can J Diet Pract Res. 73(2), 98-101.

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