Low Density Lipoprotein (LDL) Explained
Let’s take a minute to talk to you about LDL or Low Density Lipoprotein. You may have heard it called LDL cholesterol. This is one of the biomarkers on your typical lipid profile. It’s important to understand because it has direct consequences on your health, especially cardiovascular disease.
Your body manages, stores and metabolizes fat through molecules collectively referred to as lipoproteins. Technically, there are 5 categories: chylomicrons, very low density lipoproteins (VLDL), intermediate density lipoproteins (ILDL), low density lipoproteins (LDL) and high density lipoproteins (HDL). Although technically different, chylomicrons, VLDL, ILDL and LDL all fall into the same general category of function. Physicians and medicine generally focus on LDL and that’s all I am going to discuss moving forward.
As the name lipoprotein suggests, they contain both lipids (i.e. fat) and proteins. This gives them both structure and function. Lipids normally don’t like water, that is to say they are hydrophobic, but attaching them to proteins makes them less hydrophobic. This allows us to move them around our body more effectively for various purposes. We are, after all, made up of about 60% water. So the purpose of lipoproteins is transportation of the things they contain.
Generally speaking, lipoproteins carry and transport varying amounts of 5 different molecular structures: Protein, triglycerides, phospholipids, cholesterol and cholesterol esters. LDL contains approximately 25% protein, 50% cholesterol, and 20% phospholipids. It has a lower density than HDL (hence the name) and the highest cholesterol content of any of the lipoproteins.
The purpose of LDL is to deliver it’s contents to various tissues throughout the body. You can think of it as a delivery truck for protein, cholesterol and phospholipids, although it has more cholesterol than anything else. Your body uses all of those molecules for many purposes including cellular structure and function, signaling between different cells, creation of hormones and steroids, synthesis of different proteins and many other various cellular and organ functions. LDL is not innately bad, and it’s important in our body for delivering it’s contents. However when in excess, LDL can contribute to disease.
One place that LDL can deliver cholesterol to is the arterial wall, where it is often intended to support the structure of the cell membrane. Unfortunately, the wall can be damaged or if there is too many LDL particles, excess cholesterol can be deposited in the arterial wall. A specific immune cell called a macrophage can then gobble up the excess cholesterol leading to plaque formation. Eventually, these plaques can lead to atherosclerosis, increasing your risk of heart attack and stroke. So although LDL is supposed to deliver some cholesterol to the cell wall for maintenance, when your body has too much, it can lead to plaque build up and atherosclerosis. It’s also worth noting that LDL also has inflammatory properties, can increase cytokine release and is significantly more destructive in the oxidized state.
Many studies have linked high LDL cholesterol to an increased risk of heart attack and stroke. There are many things that can cause you to have a high LDL. Smoking, obesity, being sedentary and low physical activity have all been associated with a high LDL. Some individuals or families have genetic dyslipidemias that, for one reason or another, do not allow them to utilize LDL appropriately
There are many ways in which you can attempt to improve your lipid profile overall, including lowering your LDL. These include quit smoking, losing weight and exercising more. Diet’s high in mono- and polyunsaturated fats and low in trans and saturated fats have been shown to improve LDL. Drinking alcohol in moderation has also been shown to have a positive impact on LDL cholesterol. There are also pharmaceutical options that you can talk to your doctor about.
Optimal LDL level is less than 100 mg/dL. High LDL is anything over 160 mg/DL. Between 100 and 160 you can be either sub-optimal (100-129) or borderline (130-159). The average for an adult american is 115 mg/dL. Target goals for LDL cholesterol can be modified by the presence of other diseases such as diabetes and other risk factors for heart attack or stroke.