A Guide to Fats
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Cholesterol is sort of a “cousin” of fat. Both fat and cholesterol belong to a larger family of chemical compounds called lipids. All the cholesterol the body needs is made by the liver. It is used to build cell membranes and brain and nerve tissues. Cholesterol also helps the body produce steroid hormones needed for body regulation, including processing food, and bile acids needed for digestion.
People don't need to consume dietary cholesterol because the body can make enough cholesterol for its needs. Only foods of animal origin contain cholesterol.
Cholesterol is transported in the bloodstream in large molecules of fat and protein called lipoproteins. Cholesterol carried in low-density lipoproteins is called LDL-cholesterol; most cholesterol is of this type. Cholesterol carried in high-density lipoproteins is called HDL-cholesterol.
LDL-cholesterol and HDL-cholesterol act differently in the body. A high level of LDL-cholesterol in the blood increases the risk of fatty deposits forming in the arteries, which in turn increases the risk of a heart attack. Thus, LDL-cholesterol has been dubbed “bad” cholesterol.
On the other hand, an elevated level of HDL-cholesterol seems to have a protective effect against heart disease. For this reason, HDL-cholesterol is often called “good” cholesterol.
Triglycerides and VLDL
Triglyceride is another form in which fat is transported through the blood to the body tissues. Most of the body's stored fat is in the form of triglycerides. Another lipoprotein—very low-density lipoprotein, or VLDL—has the job of carrying triglycerides in the blood.
It is not clear whether high levels of triglycerides alone increase an individual's risk of heart disease. However, they may be an important clue that someone is at risk of heart disease for other reasons.
Source: The U.S. Food and Drug Administration