• A triglyceride is composed of 1 glycerol molecule connected with 3 fatty acid molecules.
• A fatty acid consists of a straight chain of an even number of carbon atoms (C), which each hold two hydrogen atoms (H). At one end, the chain has 3 H-atoms (methyl-end) and at the other end a carboxyl group (COOH). The carboxyl group makes it an acid.
• Fatty acids vary in carbon chain length and the number of double bonds in the chain.
• Chain length of fatty acids:
  • Short chain fatty acids: <6 C-atoms
  • Medium chain fatty acids: 6–12 C-atoms
  • Long chain fatty acids: >12 C-atoms
  • Long chain polyunsaturated fatty acids (LCPUFAs): >20 C-atoms
• Fatty acids can be saturated or unsaturated.
• Saturated fatty acids are straight chains, saturated with hydrogen (H). Each C-atom carries 2 H-atoms. These fatty acids have no double bond.
• Unsaturated fatty acids have one or more double bonds between the C-atoms (and in the place missing 2 H-atoms).
• The double bond in unsaturated fatty acids produces a kink or bend in the molecule. Bending causes the molecule to stay fluid at room temperature. These kinks in the structure make the body cell membrane (layer that covers the cell) flexible and permeable, allowing nutrients to enter the cell and waste products to leave.
• The number of double bonds classifies fatty acids as monounsaturated or polyunsaturated. The position of the first double bond classifies polyunsaturated fatty acids further.
  
  

Saturated fatty acids: no double bonds between the C-atoms

• Examples: butyric acid C4:0 (butter), lauric acid C12:0 (coconut oil) and stearic acid acid C18:0 (cocoa butter, meat).
• Consumption of saturated fat is associated with the risk of cardiovascular disease and reduced consumption is recommended.

Cis monounsaturated fatty acids: 1 double bond between the C-atoms

• Examples: palmitoleic acid C16:1 (cod liver oil, sardine oil) and oleic acid C18:1 (olive oil).

Cis polyunsaturated fatty acids: >1 double bond between the C-atoms.

• ω-3 (omega-3/n-3: position of double bond = 3) fatty acids: including ALA and DHA.
  • Examples: α-linolenic acid (ALA) C18:3 (vegetable oils), eicosapentaenoic acid (EPA) C20:5 (fish) and docosahexaenoic acid (DHA) C22:6 (salmon, herring, mackerel).
  • α-linolenic acid (ALA) is an essential fatty acid: it cannot be synthesised (produced) by the body; it needs to be supplied by food.
• ω-6 (omega-6/n-6: position of double bond = 6) fatty acids: including LA and ARA.
  • Examples: linoleic acid (LA) C18:2 (nuts, vegetable oils), gamma-linolenic acid (GLA) C18:3 (evening primrose oil) and arachidonic acid (ARA) C20:4 (meat, eggs).
  • Linoleic acid (LA) is an essential fatty acid: it cannot be synthesised by the body; it needs to be supplied by food.

• Animal fat has a higher melting point and is solid (hard) at room temperature. Animal products mainly contain saturated fatty acids. Examples include butter, milk and dairy products, and meat, but it is also ‘hidden’ in cookies, milk chocolate and snacks. Exception: fish oil and fatty fish (salmon, herring, mackerel) is rich in polyunsaturated fatty acids.
• Vegetable fat (oil) has a lower melting point and is liquid at room temperature. Plant products mainly contain unsaturated fatty acids. Examples: sunflower oil, corn oil and nuts. Exceptions: coconut oil, palm oil and palm kernel oil are rich in saturated fatty acids.

• See: Fatty acids ALA and LA & DHA and ARA.

• See: Fatty acids ALA and LA & DHA and ARA.

DRIs (Dietary Reference Intakes) have only been established for α-linolenic acid (ALA) and linoleic acid (LA).