• Carbs and Protein have 4 calories per 1 gram, Fats have 9 calories per 1 gram

The Structure

• Fatty acids are the building blocks of fats. They are comprised of long hydrocarbon chains. At one end of the hydrocarbon chain is a carboxyl group (COOH).

• Saturated fatty acids are only single bonds, but Unsaturated fatty acids have one or more double bonds too resulting in a bent shape

• Saturated fats, such as butter, are usually solid or semi-solid at room temperature. This is because of the single bonds.

• Unsaturated fatty acids are normally liquid at room temperature.

  • Monounsaturated Fats are an important part of a heart-healthy diet, such as with the Mediterranean diet, for example. Polyunsaturated fats are also a central part of a heart-healthy diet.

• Another fatty acid category is trans fat or trans-fatty acid. Trans fat is the resulting fat from taking an oil and forcing hydrogen into it so it becomes saturated—an example of hydrogenation.

• Trans Fat : An artificial fatty acid that occurs when hydrogen is added to liquid vegetable oils (unsaturated fat) to make them more solid (saturated fat) and have a more stable shelf life.

• A phospholipid is a compound lipid, meaning it is composed of at least two separate components. Phospholipids contain two fatty acids, a phosphate group and a glycerol molecule.

Dietary Fats

• Most dietary fat is comprised of triglycerides. The chemical structure of triglycerides is a glycerol backbone with three fatty acids

• In addition to triglycerides being the main chemical form for most fat in the food supply, it is also the main component of adipose tissue(body fat)in our bodies**.**

Main Ideas

• Prefixes.  Mono-, di-, tri- and poly- mean one, two, three or *many,*respectively. Therefore, when you see monounsaturated fatty acid, that means there is one fatty acid per glycerol. Triglycerides are three fatty acids per glycerol.

• Fat is hydrophobic.  Think phobic, which is defined as having an extreme fear or aversion to something. Fat has an aversion to water.

• There are compound lipids that contain hydrophobic (hates water) and hydrophilic (loves water) components. This is necessary to be able to get along with all compounds, such as fat-soluble and water-soluble vitamins, proteins, carbohydrates, and lipids when it comes to moving elements through the blood and into the cells.

• Visualise what happens when you mix oil and vinegar. They separate because oil does not want to mix with vinegar. When making salad dressing, an emulsifier, such as mustard, mayonnaise, egg yolks, or honey, is used to bind the oil and the vinegar.

• Saturated fat means there are the largest number of hydrogens per carbon and this makes the fat solid at room temperature. Think butter, cheese, or the fat around a piece of steak. Trans fat is taking oil and forcing hydrogen into it so it becomes saturated. Think shortening. Unsaturated fat means not every carbon has hydrogen. Think canola oil.

• Suffixes. Whenever you see -ase, that means it is an enzyme, like lipase. A word ending in -genesis means the formation of, like glucogenesis– the creation of glucose. One ending in -lysis means the breakdown of something, like hydrolysis.

• Lipoproteins are a lipid plus protein. Are you confused about what are the good lipoproteins and what are the bad ones? Try this. You want high HDLs. These remove cholesterol to the liver. Hello liver, goodbye cells. You want low LDLs.  These lipoproteins bring cholesterol to cells. Leave us alone, LDLs.

• How do you remember whether a food is low or high in a nutrient based on the percent DV? Give me five (5% or less) means a food is low in the nutrient. Think 20/20 vision for those foods that are high in a nutrient (20% or higher).

Function of Dietary Fats

• Fats as Major Source of Energy : While carbohydrates are the body’s preferred fuel source during physical activity, the body’s system turns to fat stored in the adipose tissue when carbohydrates are not available.

• Fats as Source of Essential Fatty Acids

• Fats Metabolise Fat-soluble Vitamins

Digestion and Absorption

Dietary fats must be broken down into their component parts through digestion and transported into the bloodstream through absorption. Then they are delivered to the cells to be used as energy or rebuilt into triglycerides and stored in adipocytes in the adipose tissue.

The Mouth and the Stomach

• The first step to digestion of triglycerides begins in the mouth when fats encounter saliva. The chewing of foods combined with phospholipids allows the digestive enzymes to work.

• The enzyme lingual lipase breaks down the triglycerides, separating fat from the water-soluble components of food, such as protein and carbohydrates.

• After swallowing, the fat moves to the stomach where gastric lipase begins breaking down triglycerides into diglycerides and free fatty acids.

• Note that minimal digestion of fat occurs in the mouth and stomach as compared to the small intestine.

The Small Intestine

• In the small intestine, a small amount of bile, an emulsifier, is released, which attracts fat molecules and holds onto them while being held by the water. Next, pancreatic lipases break down triglycerides into monoglycerides and free fatty acids.

• For absorption to occur, the bile salts surround the monoglycerides and free fatty acids to form micelles.  Inside of the micelle are products of lipid digestion and fat-soluble vitamins.

Transport of Lipids

• Once monoglycerides, fatty acids, and fat-soluble vitamins are released into the digestive tract lining of the small intestine, the monoglycerides and free fatty acids reassemble themselves into triglycerides.

  

• The function of LDL is to deliver cholesterol to the cells, where it can be used in cell membranes or to help in the synthesis of steroid hormones. On the other hand, HDL is responsible for retrieving excess cholesterol from the cells and bringing it back to the liver

Important Terms

• Enzymes : A protein molecule that acts as a catalyst to bring about a biochemical reaction, thus speeding up the process

• Emulsifier : A substance used to bind a hydrophobic and hydrophilic compound.

• Adipocytes : Cells specialized in the storage of fat that makes up adipose tissue.

• Bile : An alkaline fluid that aids in digestion. It is secreted by the liver and stored in the gall bladder.

• Micelle : A compound comprised of bile salts (water-loving) surrounding monoglycerides, free fatty acids, and fat-soluble vitamins (water phobic) in order for absorption to occur.

• Lymphatic System : An extensive network of vessels passing through almost all bodily tissues that produce and transport lymph (colorless fluid of white blood cells).

• Endothelium : ells that line the inner surface of blood vessels and other lymphatic tissue.

• Lipoprotein Lipase : An enzyme found in the endothelium of the cells which breaks down triglycerides into fatty acids and a glycerol for the cell to use.

Dietary Guidelines for Americans

• A variety of vegetables from all the subgroups—dark green, red and orange, legumes (beans and peas), starchy, and other

• Fruits, especially whole fruit

• Fat-free or low-fat dairy, including milk, yogurt, cheese, and/or fortified soy beverages

• A variety of protein foods, including seafood, lean meats and poultry, eggs, and legumes, and nuts, seeds, and soy products

• Monounsaturated and polyunsaturated oils

• Limiting saturated fats to 10% of total calories per day and avoiding trans fats

• The adequate intake (AI) for omega-3 fatty acid is 1.6 grams and 1.1 grams per day for males and females (ages 14 to 51+ years), respectively. For omega-6s, the AI is 17 grams for men and 12 grams for women.