Thursday, September 19, 2013

Where does Trans fatty acids come from?

What are Trans fatty acids (TFA)? Trans fatty acids (TFA) are unsaturated fats with at least a double bond in Trans configuration. TFA is geometrical isomers of monounsaturated and polyunsaturated fatty acids having non-conjugated, interrupted by at least one methylene group, carbon–carbon double bonds in the Trans configuration (Codex Alimentarius, 1985). It has been present in the diet in small quantities ever since humans began consuming food from animal origin.

      Cis Vs. Trans Fat

      How to generate Trans fatty acids (TFA)? TFA in foods originate from three main sources: 

  1.     Bacterial transformation of unsaturated fatty acids in the stomach of ruminants (e.g. cattle, sheep, goats): Lower levels of TFA, produced by bacterial hydrogenation of unsaturated fatty acids in the rumen of ruminants. Therefore, TFA can present naturally in milk, cheese, butter, meat/meat products of ruminant
  2.     Industrial hydrogenation (used to produce semi-solid and solid fats) and deodorisation (a necessary step in refining) of vegetable oils high in polyunsaturated fatty acids (PUFA)Industrial TFA is used widely in the food industry for its low cost compared with other fats, its ability to prolong the shelf-life of products, and its desirable characteristics imparted to the food. Foods containing industrial TFA are baked products (e.g. cakes, biscuits, pies, bread), snacks (e.g. deep fried food, candy), salad dressings, margarines/shortenings. TFA can also be produced from heating oils above 180 0C and deodorisation of oils.
  3.       During heating and frying of oils at extreme high temperature

      Health concerns of TFA

Diets high in total TFA are associated with increased risk of coronary heart disease (atherosclerosis, heart attack) through increases in serum LDL cholesterol and decreases in HDL cholesterol. TFA can increase the risk of CHD by not only raising the level of low density lipoprotein (LDL) cholesterol (the harmful cholesterol), but also reducing the high density lipoprotein (HDL) cholesterol (the beneficial cholesterol). Recent studies showed that increased total TFA intake, ranging from 2.8 to 10 g per day, is associated with a 22% increase in risk of CHD events with a similar increased risk of fatal CHD.

TFA isomers differ between the industrial (I-TFA) and ruminant TFA (R-TFA. Elaidic acid (t9-C18:1) predominant in I-TFA and vaccenic acid (t11-C18:1) predominant in R-TFA. Studies comparing the health effects of I-TFA and R-TFA are limited. I-TFA has consistently been associated with increased risk markers for CHD whereas R-TFA intake does not appear to affect CHD risk. The lack of effect of R-TFA may be due to;
  • The relatively low levels of intake or
  • May be related to endogenous conversion of vaccenic acid to conjugated linoleic acid (CLA) which may have positive health benefits
How to avoid TFA health risk?

     Processes have been developed to produce oils that are both low in TFA and also saturated fatty acids and are based on use of blends of oils, including palm oil and liquid seed oils such as sunflower seed oil or rapeseed oil, with processes including combinations of fractionation (crystallisation of solid fat molecules and separation from liquid molecules), interesterification (rearrangement of the structure of the fat molecules to make the fat more solid) and full hydrogenation of liquid oils. In addition the public is advised to:

Ø  Choose foods based on their overall nutrient profile, including the amounts of TFA and SFA (Saturated fatty acids)
Ø  Make reference to the information in the food label (including the ingredient list and nutrition label) and the available food composition databases to make healthier food choices
Ø  Consume foods containing high TFA infrequently, such as foods with puff pastry
Ø  Reduce the use of oils/fats when preparing foods. If necessary, use liquid vegetable oils rather than animal fats. Use margarines and butter sparingly
Ø  Avoid re-use of oil, especially utilized for deep fat fry
Ø  Use saturated fat for deep fat fry – Eg; Coconut oil



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