Knowing what are lipids is just as important as understanding how these essential nutrients work inside of us. Lipids are a collective word for the fats and oils in our bodies.
They serve several functions in our body. These include storing highly-dense energy for cells, serving as a protective layer for our bodily organs, and acting as a vehicle for transportation of certain nutrients. Unlike the other energy nutrients - proteins and carbs - which contain 4 calories per gram, lipids contain over double that amount at 9 calories per gram.
This key factor about what are lipids is critical in food choices and a large part of the reason we have an issue with their overwhelming proportion of the modern diet.
As a part of the cell membrane, lipids help form the area that allows things to move in and out of our cells. They are a critical part of the hormones adrenaline and insulin, both of which play a key role in digesting food.
During common conversation, we use "fats" in reference to all lipids. There are several different types, however, all lipids share the inability to dissolve in water.
Have you ever had a lipid profile done after going to the doctor for a general well-visit? One type of lipid that gets tested for are triglycerides. These molecules are groups made up of three fatty acids attached together at one end by a glycerol molecule.
Saturated, Monounsaturated, and Polyunsaturated fatty acids, also generalized as "fats," are the three categories of fatty acids that have inundated our nutrition labels and conscious. Saturated fatty acids (SFAs) have taken the majority of the criticism for lifestyle diseases that are a growing epidemic. They are solid at room temperature and found typically in animals and their by-products.
The other two categories of fatty acids are both considered unsaturated and tend to be in a liquid form at room temperature.
Monounsaturated fatty acids (MUFAs) are sometimes referred to as Omega-9's and can be seen as oils derived from plants and nuts. One of the most common sources of Omega-9 fats is olive oil. Omega-6's and Omega-3's are two types of polyunsaturated fatty acids (PUFAs) both of which are found in vegetable and fish oils.
Each fatty acid is a chain of molecules and the degree of saturation refers to number of open sites where other molecules could potentially attach. Most triglycerides are a mixture of the different fatty acids and are classified by whichever is the most dominant.
For example, butter is composed mostly of saturated fatty acids, but also has smaller amounts of monounsaturated and polyunsaturated acids in its triglyceride composition.
The degree of saturation is a prime focus among nutritionists, food manufacturers and savvy consumers in determining healthy versus unhealthy food choices. This movement has really led to the demonization of SFAs and proliferation of PUFAs to be cornerstones of a healthy diet.
So that poses an interesting question in the conversation of what are lipids... Can Saturated Fatty Acids ever be healthy?
Triglyceride length is important because it determines how our body processes and uses the energy in these lipids. Long-chain triglycerides (LCTs) account for an overwhelming majority of our dietary fat. Conservative estimates are greater than 95% intake and are digested in a complex process that we will learn about in the following paragraphs and incorporate the other types of lipids, hormones, and various bodily organs to create usable energy.
On the other hand, medium-chain and short-chain triglycerides are able to skip the intricate digestion process and used almost immediately as energy similar to carbohydrates.
MCTs have gained some popularity as research continues on them and their potentially health benefits when included in the diet. There are virtually no food sources that are rich in SCTs but coconut an excellent source of MCTs.
It's time to learn about what are lipids and how they function inside our body. If fatty acids and trigylcerides are the core of dietary fat and food composition then phospholipids and sterols are a key part of the equation once we eat the food.
We learned earlier that lipids do not readily dissolve in water. This presents a problem during digestion because our bodies transport nutrients through the bloodstream, which is predominately water. Enter phospholipids. They are the middlemen that allow large lipids to be transported safely without interrupting the normal functions of blood.
How is this possible?
Look no further than your refrigerator and pull out a bottle of salad dressing. Creamy ones stay suspended like milk, but a vinegarette and you will see a distinct separation of fluids. Some molecules in the dressing act as emulsifiers. Phospholipids uses this same principle surrounding the lipid molecule while the other end attracts water acting as a bridge.
Sterols, on the other hand, have a unique edge over other lipids. Their interconnected ring structures act as building blocks for the sex hormones (estrogen and testosterone), vitamin D, and bile. Bile is a substance produced by the liver necessary to help break down and digest lipids. Cholesterol is the most infamous among this type of lipids.
Together, phospholipids and cholesterol help form lipoproteins. These are the vehicle for transporting long-chain lipids (LCTs) throughout the blood and delivering them to the areas of the body where they are needed.
As the name suggests, they are composed of protein and lipid molecules. Lipoproteins differ among each other but each is composed of a proportion of protein, cholesterol, phospholipid, and triglycerides. There are four major kinds but high-density lipoproteins (HDL) and low-density lipoproteins (LDL) are the ones we want to keep focus on. It is common to hear these lipoproteins referred to as "good" and "bad" cholesterol, respectively.
LDL, "bad cholesterol," are made up of about 80% lipid and 20% protein. Fat weighs less than protein which explains their name, low-density, meaning of less weight. These large-molecule lipoproteins deliver triglycerides and cholesterol where needed in our body's tissues.
HDL is about 50-50 split between protein and lipids. As a smaller and more dense molecule, their chief responsibility is to collect excess the cholesterol and phospholipids from the body for disposal.
When there aren't enough HDL to gather all the excess cholesterol for disposal, it begins to build up the walls of your arteries as plaque. Over time plaque hardens and can lead to blockages causing a variety of heart related problems. Coming full circle, this where a lipid profile is relevant. It measures the level of LDL, HDL, and triglycerides in your body to give an indicator of overall cardiovascular health and exposes potential risk factors for lifestyle diseases.
You now know the basics of what are lipids and their importance in your body. Learning about the healthy diet fats and oils and where to find them in foods will not only reduce your risks of degenerative disease, but also will give you another piece of the puzzle in creating your healthy diet plan!
Another step toward a piece of the puzzle.... Great job!
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What are Lipids?