Today's lesson is about the structure and functions of fat.
Fat is the substance in food that provides a rich texture and flavor. Animal products such as meat, dairy, and eggs contain the most fat. Cooking fats include olive oil, lard, canola oil, walnut oil, butter, margarine and shortening.
First a Little Chemistry
Fats and oils are made up of individual molecules called fatty acids. They're chains of carbon and hydrogen atoms that have a carboxyl group at one end and a methyl group at the other. Carboxyl groups contain one carbon atom, one hydrogen atoms and two oxygen atoms, and methyl groups include one carbon atom and three hydrogen atoms. The carbon atoms in the fatty acid molecules are linked by single or double bonds.
Fatty acids vary in length. Short chain fatty acids have two to four carbon atoms, medium chain fatty acids have six to 12 carbons atoms, long fatty acids have 14 to 18 carbon atoms. A have more than 20 carbon atoms chains.
Fatty acids are either saturated or unsaturated. Saturated fatty acids have no double bonds between any of the carbon atoms in the chain. Unsaturated fatty acids have one or more double bonds in the carbon chain.
Monounsaturated fatty acids have one double bond and polyunsaturated fatty acids have at least two double bonds. Unsaturated fatty acids are sometimes named by the position of the double bonds in the carbon chain. The names omega-3,-6 or -9 refer to the locations of the first double bond in the three different fatty acid molecules.
Unsaturated fatty acids can have two different configurations of the hydrogen atoms on either side of the double bonds. These are referred to as "cis" or "trans" configurations. Cis configurations have those hydrogen atoms both on the same side of the molecule. This causes the molecule to look like it's bent.
Trans configurations have those hydrogen atoms on opposite sides of the double bond. This gives the molecule a linear appearance, like saturated fats. Interestingly, it turns out that both saturated fats and trans fats are bad for your health.
Fats and cholesterol have a number of important functions, which include:
- Lubrication of body surfaces
- Components of cell membrane structures
- Formation of steroid hormones
- Energy storage
- Insulation from cold
- Carrying fat-soluble vitamins A, D, E, K
This waxy substance doesn't produce any energy like triglycerides, but it is important for many biochemical processes and hormone production. However, you can have too much of a good thing. Elevated cholesterol levels have been associated with an increased risk of cardiovascular disease.
The cholesterol in your body is mostly made in your liver. There are three different types: High Density Lipoproteins (HDL), Low Density Lipoproteins (LDL) and Very Low Density Lipoproteins (VLDL). Having higher HDL cholesterol levels can decrease your risk of cardiovascular disease, while elevated LDL cholesterol will increase that risk.
Dietary fats are called triglycerides. A triglyceride is made up of three fatty acid molecules attached to a glycerol molecule. Your body can use triglycerides as energy or store them as adipose tissue (body fat). The fatty acids determine the overall shape.
Fats that are composed of triglycerides with saturated fatty acids, like meat, are solid at room temperature. Fats that are composed of triglycerides with unsaturated and monounsaturated fatty acids, like vegetable oils and olive oil, are liquid at room temperature.
Saturated fats are mostly from animal sources, although saturated fats are also found in coconut oil, palm oil and palm kernel oil. Saturated fats can cholesterol levels in the body -- in fact, saturated fats will raise your cholesterol much more than eating dietary cholesterol does.
Eating a diet rich in red meat has been linked to an increased risk of cardiovascular disease and some cancers. Since red meat has the highest concentration of saturated fats, many experts suggest that you limit your consumption of red meat to only two or three small servings per week.