Knowing Your Lipids Intake (Part 3)
Use of Fatty Acids As Fuel
From triglycerides to fatty acids
Depending on whether you are in the fasted state or just consumed a heavy meal, most of the blood’s triglycerides are present either as VLDL or chylomicrons. The action of lipoprotein lipase bound to the wall of capillaries in the heart, skeletal muscle, and fat tissue results in the conversion of triglycerides within VLDL and chylomicrons into fatty acids.
The fatty acids subsequently enter the tissues to be used as fuel (muscle, heart) or to be stored as triglycerides (fat tissue). Insulin stimulates lipoprotein lipase activity in fat tissue and goes up after a meal to ensure efficient storage of consumed fat.
From fatty acid to energy
Once taken up into cells, most of the fatty acids burn to yield energy in the form of ATP. The breakdown of fatty acids to generate ATP resembles the breakdown of glucose to ATP.
- In the first step, the fatty acid progressively shortens to yield Acetyl-CoA. This step is called beta-oxidation.
- In the second step, Acetyl-CoA further oxidizes via the tricarboxylic acid (TCA) cycle or citric acid cycle.
The energy liberated during beta-oxidation, and the TCA cycle is temporarily stored in NADH (or FADH2 to be exact). Thus, NADH donates its power to a set of proteins that together comprise the electron transport chain, which ultimately converts the energy into ATP.
In addition to serving as fuel, fatty acids are also important signaling molecules that regulate various processes in the cell. For instance, fatty acids can turn on genes by binding to particular receptors called PPARs.
Storage of fatty acids
The fatty acids are taken up into cells store as triglycerides in lipid droplets that are not needed to produce energy. Fat cells consist of one large lipid droplets. Muscle cells and many other cell types contain many small lipid droplets. Excess fat storage in many cell types can wreak havoc on the normal functioning of cells.
Cholesterol has several functions in the body.
- First, cholesterol is needed to make bile acids required for the efficient digestion of dietary fats.
- Second, cholesterol is used to make several (steroid) hormones, such as male and female sex hormones.
- Third, cholesterol is a component of cell membranes.
It is essential to realize that cholesterol is not a nutrient because our cells can make cholesterol. Only approximately one-third of the cholesterol in our bodies comes from our diet. The rest synthesize in the body. For this reason, we can subsist on a diet that is entirely devoid of cholesterol.
The cholesterol in the diet and the cholesterol produced in our body together comprise the cholesterol input. Cholesterol leaves the body in the feces that excrete as part of bile or bile acids. Disturbances in bile acid metabolism can influence cholesterol metabolism and vice versa.
Introduction to Lipids and Health
Image source: bipartisanpolicy.org
Now let’s talk about the health effects of lipids. Dietary lipids mainly connect to heart/cardiovascular disease. So we must take a closer look at it. What is it, and how does it develop? What are the significant risk factors for heart disease?
On the other hand, do you know what atherosclerosis is? It is the process that is based on heart disease.
You probably know that one of the risk factors for heart disease is the cholesterol level in your blood. It exists in your blood in two forms:
Thus, it would help if you were especially concerned about your LDL cholesterol level. And that is because having a high LDL cholesterol increases your risk of heart disease.
Now, what is interesting about LDL is that you can change its levels by altering your diet. Have you ever wondered about the consumption of saturated and unsaturated fat?
Some people are promoting the idea that saturated fat isn’t bad after all, so how should we look at that? We will also look at trans fat known as killer fats, abundant in frying oil, pastries, fast food, certain margarine, and many other processed foods.
Another hot topic is omega-3 fatty acids. Numerous claims have been made about these types of fatty acids, particularly about heart disease.
Finally, we have also covered the specific recommendations for dietary fat intake. So together, these lipid articles will teach you a lot about how dietary fatty acids and lipids may influence health and disease, particularly heart disease.
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