notes/education/nutrition/Lipids.md

• Lipids are a class of nutrients that do not dissolve in water.
  • They will dissolve in organic solvents
• Oil is less dense than water, so it will rise to the top of a solution
• Major functions of lipids in the body include
  • Providing and storing energy
  • forming and maintaining cell membranes
  • producing steroid hormones
  • insulating the body
  • cushioning the body against bumps and blows
  • forming body contours
  • absorbing fat soluble vitamins and phytochemicals

Fatty Acids

A fatty acid is a hydrocarbon chain found in lipids; one end of the chain forms a carboxylic acid, and one end forms a methyl group.

• Short chain fatty acids have 2 to 4 carbons

• Medium chain fatty acids have 6 to 12 acids

• Long chan acids have 14 to 24 carbons

• Fatty acids are identified by:

  • The number of carbon atoms
  • The type of bond between carbon atoms

• An omega-3 fatty acid is a polyunsaturated fatty acid with its first double bond at the third carbon from the omega end of the chain.

• Saturated fatty acid (SFA) Every single carbon atom is filled with hydrogen atoms

• Unsaturated fatty acid is a fatty acid that is missing hydrogen atoms and has one or more double bonds within the carbon chain

  • Monounsaturated (MUFA)
    • Has one double bond within the carbon chain
    • Sources include:
      • Canola oil
      • Olive oil
      • Avocados
      • Nuts
      • Seeds
      • Peanut butter
  • Polyunsaturated (PUFA)
    • Fatty acid that has two or more bonds within the carbon chain
    • Sources include:
      • Soybean oil
      • Fatty fish
      • Flax seed
      • Walnuts
      • Corn oil
      • Sunflower oil

• Most naturally occurring fatty acids are cis fatty acids

  • Hydrogen atoms of the double bonded carbon are on the same side of the hydrocarbon atom

• Trans fats are unsaturated fatty acids that have a trans double bond.

  • Hydrogen atoms of the double bonded carbons are on the opposite side of the hydrocarbon chain
  • Hydrogenation is the food manufacturing process that adds hydrogen atoms to liquid vegetable oil, forming trans fats.
    • Can be stored for longer periods because they are less likely to undergo oxidation
    • Raise "bad" cholesterol levels in the blood
    • Increases risk of heart disease

• Essential fatty acids are fatty acids that must be supplied by the diet

  • Linoleic acid - 18 carbon omega-6 fatty acid found in vegetable oils
  • Alpha-linolenic acid - 18 carbon omega-3 unsaturated fatty acid, found in flaxseed, walnuts
    • Precursor for
    • Eicosapentaonoic acid (EPA) - 20 carbons
    • Docosahexaenoic acid (DHA): 22 carbons
      • Both acids are found mainly in fatty fish
  • Essential fatty acids are needed for growth and healthy cell membranes, especially in the brain.
    • Infants that have an essential fatty acid deficiency can experience developmental and nerve system issues.
    • Signs of essential fatty acid deficiency include:
      • Scaly skin
      • Hair loss
      • Poor wound healing

Triglycerides

A lipid that has three fatty acids attached to a three-carbon compound called glycerol

• Comprises 95% of lipids in food and body
• Glycerol is a three carbon alcohol that forms the backbone of fatty acids

Phospholipids

A phospholipid is a type of lipid needed for the flexibility, structure, and makeup of the cell membranes and for proper functioning of nerve cells.

• Partially water soluble
  • Hydrophilic
    • Part that attracts water
  • Hydrophobic
    • Part that repels water and attracts fat
• Can serve as an emulsifier
  • Helps water soluble and water insoluble compounds mix with each other

Sterols

Sterols are lipids that have a more chemically complex structure than a triglyceride or fatty acid

• -ol suffix: Attached to an alcohol Cholesterol is a lipid found in animal foods: precursor for steroid hormones, bile, and vitamin D.
• Found in:
  • Egg yolk
  • Liver
  • Meat
  • Poultry
  • Dairy products

Lipases

Lipases are enzymes that break down lipids

• Cholecystokinin is a hormone that stimulates the gallbladder to release bile and the pancreas to secrete digestive juices
  • Bile helps with the emulsification of and digestion of fat.
• Secretin is a hormone that stimulates the liver to produce bile and the pancreas to secrete bicarbonate rich pancreatic juice

Lipoproteins

Lipoproteins are water-soluble structures that transport lipids through the bloodstream. Lipoproteins are needed because fat is hydrophobic.

• Chylomicron mostly carries triglycerides
• High density lipoprotein (HDL) carries the most protein (45-50%), and roughly 30% phospholipids. HDL carries lipids away from tissues and to the liver, where they can be processed and eliminated. It's considered "good" cholesterol
• Low density lipoprotein (LDL) carries the most cholesterol, and it carries lipids from the liver out to other tissues in the body. It's considered "bad" cholesterol
• Very low density lipoprotein (VLDL) carries triglycerides from the liver into the bloodstream, where cells that line capillaries break down the triglycerides into fatty acids and glycerol
• Oxidized LDL is formed when chemically unstable substances damage LDL, transports cholesterol into the arterial lining