Cholesterol can’t dissolve in the blood. It must be transported through your bloodstream by carriers called lipoproteins, which got their name because they’re made of fat (lipid) and proteins.

The two types of lipoproteins that carry cholesterol to and from cells are low-density lipoprotein, or LDL, and high-density lipoprotein, or HDL. LDL cholesterol and HDL cholesterol, along with one fifth of your triglyceride level, make up your total cholesterol count, which can be determined through a blood test.

LDL (Bad) Cholesterol

LDL cholesterol is considered the “bad” cholesterol because it contributes to plaque, a thick, hard deposit that can clog arteries and make them less flexible. This condition is known as atherosclerosis. If a clot forms and blocks a narrowed artery, heart attack or stroke can result. Another condition called peripheral artery disease can develop when plaque buildup narrows an artery supplying blood to the legs.

HDL (Good) Cholesterol

HDL cholesterol is considered “good” cholesterol because it helps remove LDL cholesterol from the arteries. Experts believe HDL acts as a scavenger, carrying LDL cholesterol away from the arteries and back to the liver, where it is broken down and passed from the body. One-fourth to one-third of blood cholesterol is carried by HDL. A healthy level of HDL cholesterol may also protect against heart attack and stroke, while low levels of HDL cholesterol  have been shown to increase the risk of heart disease.

Triglycerides

Triglycerides are another type of fat, and they’re used to store excess energy from your diet. High levels of triglycerides in the blood are associated with atherosclerosis. Elevated triglycerides can be caused by overweight and obesity, physical inactivity, cigarette smoking, excess alcohol consumption and a diet very high in carbohydrates (more than 60 percent of total calories). Underlying diseases or genetic disorders are sometimes the cause of high triglycerides. People with high triglycerides often have a high total cholesterol level, including a high LDL cholesterol (bad) level and a low HDL cholesterol (good) level. Many people with heart disease or diabetes also have high triglyceride levels.

Lp(a) Cholesterol

Lp(a) is a genetic variation of LDL (bad) cholesterol. A high level of Lp(a) is a significant risk factor for the premature development of fatty deposits in arteries. Lp(a) isn’t fully understood, but it may interact with substances found in artery walls and contribute to the buildup of fatty deposits.

Cholesterol Limit Removed from 2015 Dietary Guidelines

On the up-side, the advisory panel has decided to eliminate warnings about dietary cholesterol, which for decades has been wrongfully blamed for causing heart disease.

The latest guidelines accurately state that there is no such link. According to the report, “cholesterol is not a nutrient of concern for overconsumption.”

Until now, the guidelines have recommended limiting dietary cholesterol to 300 milligrams (mg) per day, which amounts to about two eggs. As noted by Steven Nissen, chairman of the department of cardiovascular medicine at the Cleveland Clinic:

“Many of us for a long time have believed the dietary guidelines were pointing in the wrong direction. It is long overdue.