Lipids, Fatty Acids and their roles

• Lipid is the chemical term for fat
• Lipids are organic molecules that mostly do not dissolve in water
• Lipids include fatty acids, triglycerides, phospholipids, and steroids
• Lipids provide texture, taste, flavor, and aroma to foods
• Fats and oils contain 9 calories per gram

Types of lipids in the body

• Fatty acids are used to synthesize triglycerides and phospholipids or catabolized to generate adenosine triphosphate (ATP)
• Triglycerides protect, insulate, and provide energy storage
• Phospholipids are major lipid components of cell membranes

Fatty Acids

• Fatty acids can be saturated or unsaturated
• Saturated fatty acids are strong and hard to break down inside the body
• Unsaturated fatty acids are more likely to have double carbon bonds

Essential Fatty Acid Deficiency

• If adequate amounts of essential fatty acids are not consumed, a deficiency can result
• Essential fatty acid deficiency symptoms include dry, scaly skin, and liver abnormalities
• Other symptoms include poor wound healing, growth failure in infants, and impaired vision and hearing

Linoleic Acid

• Linoleic acid is an omega-6 polyunsaturated fatty acid
• Linoleic acid is found in vegetable/nut oils

Linolenic Acid

• Linolenic acid is an omega-3 polyunsaturated fatty acid
• Linolenic acid helps with muscle recovery, especially when paired with protein after a workout
• Linolenic Acid is found in green leafy vegetables, flax, nuts, and seafood
• A daily diet should consist of 3-6 grams of essential fatty acids

Omega 3 Fatty Acids

• Omega-3 is a polyunsaturated fatty acid found in flax, canola & olive oils, and seafood
• EPA (eicosapentaenoic acid) is an example of omega-3 fatty acids
• DHA (docosahexaenoic acid) is an example of omega-3 fatty acids that helps with brain growth
• ALA (α- linolenic acid)is another type of omega-3 fatty acid
• Omega-3 fatty acids help decrease inflammation, increase muscle protein synthesis pathways, and increase oxygen delivery to the heart during exercise, and increase nerve conduction velocity
• Too much omega-6 can cause pro-inflammation
• Eicosanoids are made from omega-3 and omega-6 fatty acids, and help regulate blood clotting, blood pressure, and immune function

Trans Fatty Acids

• Trans fatty acids can be created by hydrogenation in unsaturated fatty acids
• Hydrogenation causes some double bonds to become saturated
• Hydrogenated fats can be found in margarines, vegetable shortening, and shelf-stable baked goods
• Trans fatty acids have been shown to raise blood cholesterol levels and increase the risk of heart disease
• Canada is the first country to ban trans fat

Cis vs Trans Fatty Acids

• Trans fatty acids have a higher melting point
• Trans fatty acids are prohibited as of 2018 in Canada

Fatty Acids in Food

• Ultra-processed food can lead to cancer
• Olive oil is the best oil

Triglycerides

• Triglycerides are the major form of lipid in food and in the body
• Triglycerides consist of 3 fatty acids attached to a glycerol molecule
• If only one fatty acid is attached to the glycerol it is called a monoglyceride
• Can be saturated or unsaturated
• When fatty acids combine with glycerol, they produce water molecules
• Fatty acids produce lots of ATP

Phospholipids

• Phospholipids are an important component of cell membranes, the phosphate molecule is attached

Types of Lipids in the Body

• Cholesterol is a minor component of all animal cell membranes, a precursor of bile salts, vitamin D, and steroid hormones
• Bile salts are needed for digestion and absorption of dietary lipids
• Vitamin D helps regulate calcium level in the body; needed for bone growth and repair
• Adrenocortical hormones help regulate metabolism, resistance to stress, and salt and water balance
• Sex hormones stimulate reproductive functions and sexual characteristics
• Eicosanoids have diverse effects on modifying responses to hormones, blood clotting, inflammation, immunity, stomach acid secretion, airway diameter, lipid breakdown, and smooth muscle contraction
• Carotenes are needed for the synthesis of vitamin A
• Vitamin E promotes wound healing, prevents tissue scarring, contributes to normal structure and function of the nervous system, and functions as antioxidants
• Vitamin K is required for the synthesis of blood-clotting proteins
• Lipoproteins transport lipids in the blood, carry triglycerides and cholesterol to tissues, and remove excess cholesterol from blood

Lipid Digestion

• Micelles are small molecules of digested fat that are coated with bile
• Chylomicrons are lipoproteins, a combination of triglycerides, cholesterol, phospholipids, and a small amount of protein
• Chylomicrons transport long-chain fatty acids into the lymphatic system and into the bloodstream without passing through the liver

Chylomicrons

• Chylomicrons are a combination of triglycerides, cholesterol, phospholipids, and a small amount of protein
• Chylomicrons transport long-chain fatty acids into the lymphatic system and into the blood stream without passing through the liver
• As chylomicrons circulate in the blood, lipoprotein lipase (enzyme) breaks triglycerides down
• Some of the triglycerides that get broken down can be re-synthesized and also enter the liver

Low-Density Lipoproteins

• The liver is the major lipid-producing organ in the body
• Triglycerides and cholesterol are produced in the liver and get incorporated into very-low-density lipoproteins (VLDLs)
• Lipoprotein lipase enzyme removes triglycerides from VLDLs, creating intermediate-density lipoproteins (IDLs)
• Approximately two-thirds of IDLs return to the liver; the remainder are transformed in the blood into low-density lipoproteins (LDLs)
• LDLs contain less triglycerides and more cholesterol than VLDLs
• LDLs deliver cholesterol to the cells
• If the amount of LDL cholesterol in the blood exceeds the amount that can be used by the cells, the result is a high level of LDLs
• High levels of serum LDLs are associated with an increased risk for heart disease

High-Density Lipoproteins

• Most cells cannot break down cholesterol
• Cholesterol is returned to the liver to be eliminated from the body via high-density lipoproteins (HDLs)
• This reverse cholesterol transport can be done by working out
• High levels of HDL in the blood help prevent cholesterol from depositing in the artery walls
• High levels of HDL are associated with a reduction in heart disease risk.

Lipid Mobilization

• Fatty acids must be mobilized from adipose tissue stores before they can be used for various processes
• Mobilization is highly regulated by hormone-sensitive lipase