Here's the third part in the ongoing Nutrition Series! I realize there are a lot of links contained in each article, and these can help, but are not required, to further your understanding of the material. I encourage you to click on the links whenever slightly curious, they contain interesting and pertinent information relating to the information being presented. Enjoy!
THE BASICS - LIPIDS
Lipids include a variety of molecules that are either hydrophobic(water fearing - these molecules repel water) or amphiphilic(both water and lipid loving - these typically have both a hydrophilic side and a lipophilic side). Lipids include a broad range of molecules, but the groups that are most pertinent to the discussion of nutrition are triglycerides.
A triglyceride molecule is composed of three fatty acid chains connected to a glycerol molecule. Triglycerides make up the majority of animal fats as well as vegetable oils.
(A saturated fatty acid, myristic acid, notice the lack of double bonds)
(A monounsaturated fatty acid, oleic acid, notice the single double bond that creates the bent shape)
Fatty acids are characterized as either saturated or unsaturated, based on the presence of double bonds in their structure. If the molecule contains no double bonds it is said to be saturated, otherwise it is unsaturated to some degree. Double bonds reduce the number of hydrogens on each carbon. These different structures provide different chemical properties such as melting point, lipid peroxidation potential, etc. In general, the more double bonds(the more unsaturated) a fat has, the greater its tendency to oxidize and the lower its melting point.
Lipid peroxidation is the oxidative degradation of lipids, and results in a chain reaction that continues creating free fatty acid radicals until either two radicals meet, or the cycle is terminated by an anti-oxidant. Free fatty acid radicals can cause significant damage to cell membranes, as well as create end products that may be mutagenic and carcinogenic.
Saturated Fatty Acids(SFA) - These fatty acids contain no double bonds, and as such are fully saturated with hydrogen. Saturated fats have a relatively high melting point, and are resistant to oxidation, making them preferable for high-heat cooking. SFA’s include: Lauric acid, Myristic acid, Palmitic acid, Stearic acid, and Archidic acid. Saturated fats are solid at room temperature.
(above is shown the change that occurs during hydrogenation of a MUFA to a trans fat)
Trans-Fatty Acids(TFA) - These unsaturated fats with the characteristic “trans” configuration. Trans-fatty acids include both natural and artificial fatty acids. The two natural trans fats, found mostly in grass-fed beef and dairy, are Vaccenic acid and Conjugated Linoleic acids(CLA). These two fats are highly anti-carcinogenic(against cancer), in fact, CLA(specifically rumenic acid) is one of the most potent anti-cancer compounds known to man. Vaccenic acid is converted to rumenic acid by enzymes within the body. These two fats also have antiatherogenic(against atherosclerosis) effects, and positive effects on body composition. Artificial fatty acids, such as Elaidic acid are created by the process of partial hydrogenation, and have been associated with cancer, heart disease, and a myriad of other negative effects. Artificially created trans fats are solid, but malleable, at room temperature.
Monounsaturated Fatty Acids(MUFA) - these fats contain a single double bond, and have a higher melting point than polyunsaturated fats(PUFA), but a lower melting point than saturated fats. Likewise, they have a lipid peroxidation potential in between PUFA’s and SFA’s. Oleic acid is the most prominent MUFA found in olive oil and also in human adipose tissue. These fats are considered generally healthy. At room temperature, these fats are liquid, but they will solidify at refrigerator temperatures.
Polyunsaturated Fatty Acids(PUFA) are those that contain 2 or more double bonds. These fats have the lowest melting point, and are the most susceptible to lipid peroxidation. They are liquid even at below 0°C. The main types of PUFA are omega-3’s and omega-6’s, but there are also some PUFA’s in the Omega-9 fatty acid group. Both omega-3's and omega-6's are essential fats, and must be obtained in sufficient amounts through our diet. The omega-3 and omega-6 fatty acids in our diet influence the level of inflammation in our body by their effect in the production of eicosanoids. Eicosanoids are signaling molecules that are made from omega-3 and omega-6 fatty acids, and they play a large role in regulating inflammation and immunity.
Important Omega-3 fatty acids include: Alpha Linoleic acid(ALA), Eicosapentaenoic acid(EPA), and Docosahexaenoic acid(DHA). Omega-3 fatty acids tend to produce less inflammatory eicosanoids than omega-6’s do. It should be noted that EPA and DHA are the active forms in which our body uses omega-3’s, and conversion from ALA to EPA and DHA is very inefficient (~5% for EPA); EPA and DHA can interconvert. Some rich sources of these fatty acids include: flax seed oil(ALA), fatty fish(EPA/DHA), and algae(DHA). Below is a diagram of both omega-3 and omega-6 fatty acid structures.
Important Omega-6 fatty acids include: Linoleic acid (LA) and Arachidonic acid(AA), . Omega-6’s tend to produce more inflammatory eicosanoids than omega-3’s do. Some rich sources of these fatty acids include: Grains, seeds, nuts, grain-fed meat, and vegetable oils. However, Gamma Linolenic acid(GLA) and Dihomo-Gamma-Linolenic acid(DGLA) play a role in reducing inflammation. Borage oil, primrose oil, spirulina, and hemp seed oil are good sources of GLA.