trans fats

Examples of trans fats in the following topics:

• Lipid Molecules

  • If hydrogens are present in the same plane, it is referred to as a cis fat; if the hydrogen atoms are on two different planes, it is referred to as a trans fat.
  • Margarine, some types of peanut butter, and shortening are examples of artificially-hydrogenated trans fats.
  • Many fast food restaurants have recently banned the use of trans fats, and food labels are required to display the trans fat content.
  • Each double bond may be in a cis or trans configuration.
  • In the trans configuration, the hydrogens are on opposite sides.

• Organic Isomers

  • In triglycerides (fats and oils), long carbon chains known as fatty acids may contain double bonds, which can be in either the cis or trans configuration .
  • Fats with at least one double bond between carbon atoms are unsaturated fats.
  • On the other hand, triglycerides with trans double bonds (popularly called trans fats), have relatively linear fatty acids that are able to pack tightly together at room temperature and form solid fats.
  • In the human diet, trans fats are linked to an increased risk of cardiovascular disease, so many food manufacturers have reduced or eliminated their use in recent years.
  • These space-filling models show a cis (oleic acid) and a trans (eliadic acid) fatty acid.

• Fats & Oils

  • The triesters of fatty acids with glycerol (1,2,3-trihydroxypropane) compose the class of lipids known as fats and oils.
  • Some of the remaining double bonds are isomerized (to trans) in this operation.
  • These saturated and trans-fatty acid glycerides in the diet have been linked to long-term health issues such as atherosclerosis.
  • The catalysts used to effect the addition of hydrogen isomerize the remaining double bonds to their trans configuration.
  • These unnatural trans-fats appear to to be associated with increased heart disease, cancer, diabetes and obesity, as well as immune response and reproductive problems.

• Lipids: Sources, Uses in the Body, and Dietary Requirements

  • Fats store energy, facilitate absorption of fat-soluble vitamins, aid brain growth and development, and protect against many diseases.
  • Most of the fats found in food are triglycerides, cholesterol, and phospholipids.
  • Some dietary fat is necessary for the absorption of fat-soluble vitamins (A, D, E, and K) and carotenoids.
  • In contrast, the consumption of trans fats, such as those present in partially hydrogenated vegetable oils, are now known to be a risk factor for cardiovascular disease.
  • Several studies have suggested that total dietary fat intake is linked to obesity and diabetes.

• Nutrition and Health

  • The body gets energy from macronutrients—the fats, carbohydrates, and proteins in the food we eat.
  • If excess caloric energy is consumed, beyond what is needed to maintain body functioning, it is stored in adipose (fat) tissue.
  • Macronutrients include carbohydrates, proteins, and fats.
  • Fats, or lipids, are combinations of fatty acids.
  • Omega-3 and omega-6 fatty acids are particularly important in maintaining health, while trans fatty acids have been found to harm body function.

• Fatty Acids

  • The trans-double bond isomer of oleic acid, known as elaidic acid, has a linear shape and a melting point of 45 ºC (32 ºC higher than its cis isomer).

• Hydrogenation

  • The degree of saturation of fats changes important physical properties such as the melting range of the oils; an example of this is how liquid vegetable oils become semi-solid at various temperatures.
  • Incomplete hydrogenation of the double bonds has health implications; some double bonds can isomerize from the cis to the trans state.
  • This isomerization occurs because the trans configuration has lower energy than the cis configuration.
  • The trans isomers have been implicated in contributing to pathological blood circulatory system conditions (i.e.

• Alkene Isomerization

  • Both cis and trans-stilbene undergo π → π* electron excitation by absorption of uv light.
  • Both the initial S1 states formed from the cis and trans ground states are slightly twisted (the cis by 25º & the trans by 13º) with the C=C double bond being lengthened by about 4.5%.
  • A small proportion (6%) of the trans-S1 state fluoresces back to the trans-isomer, but there is less than 0.1% fluorescence from the cis-S1 state.
  • The initial cis and trans triplets undergo fast, and in the case of trans reversible, conversion to a lower energy twisted triplet, which then decays to cis and trans-stilbene at rates that favor cis by a factor of 1.5.
  • First, the efficiency of energy transfer to cis-stilbene diminishes and the trans isomer is selectively activated, resulting in a greater [cis]/[trans] photostationary state.

• Electrocyclic Reactions

  • In the first case, trans,cis,trans-2,4,6-octatriene undergoes thermal ring closure to cis-5,6-dimethyl-1,3-cyclohexadiene.
  • The sterospecificity of this reaction is demonstrated by closure of the isomeric trans,cis,cis-triene to trans-5,6-dimethyl-1,3-cyclohexadiene, as noted in the second example.

• Bile

  • Bile acts as a surfactant, helping to emulsify the fats in the food, in the same way in which soap emulsifies fat.
  • When exposed to water mixed with fat, like in the small intestine, the bile salts congregate around a fat droplet, with their hydrophobic side pointing towards the fat and their hydrophillic side pointing towards the water .
  • This increases the surface area of the fat, allowing greater access by the pancreatic enzymes that break down fats.
  • Since bile increases the absorption of fats, it is an important part of the absorption of the fat-soluble vitamins, such as the vitamins D, E, K, and A.
  • Bile salts congregate around fat, separating them into small droplets called micelles.