What are triglycerides?

Triglycerides are common types of fats (lipids) essential for good health when present in normal amounts. Like cholesterol, triglycerides are consumed through food and are also manufactured in the liver. They are transported through the bloodstream by the proteins present in various types of lipoproteins.

Cholesterol is mostly transported through the bloodstream by high-density lipoproteins (HDLs, or “good” cholesterol) and low-density lipoproteins (LDLs, or “bad” cholesterol). In contrast, triglycerides are a main component of – and transported by – lipoproteins known as chylomicrons, as well as very low-density lipoproteins (VLDLs, or “very bad” cholesterol). Chylomicrons are only a temporary storage unit for triglycerides. They disappear shortly after appearing in the bloodstream.

Triglycerides are the body’s major form of energy storage. Their presence in the blood is closely related to eating. Triglyceride levels rise dramatically after eating, especially after consuming simple carbohydrates, such as sugar or alcohol. This is because any sugars that are not used immediately as energy are converted to triglycerides and are stored as body fat. The release of stored triglycerides is regulated by hormones, depending on the body’s energy needs. Fasting will stimulate the release of stored triglycerides.

Together with cholesterol, triglycerides form the blood lipids, or blood fat. By measuring the level of fasting triglycerides, physicians can evaluate how much fat is circulating in a patient’s blood. This measure has proven valuable when it comes to diagnosing and predicting cardiovascular disease. High triglyceride levels may contribute to cardiovascular disease by increasing the blood’s stickiness” (viscosity). High triglycerides are considered to be a risk factor for heart disease. They are associated with low HDL levels, high LDL levels and obesity. Because of this association, physicians will often try to lower triglyceride levels in their patients.

Very low triglyceride levels may also be cause for concern. Although low levels are not associated with an increased risk of heart disease, they may be an indication of malnutrition, an overactive thyroid gland (hyperthyroidism) or malabsorption syndrome.

According to the U.S. National Heart, Lung and Blood Institute, the most current classifications for triglyceride levels are as follows in milligrams per deciliter (mg/dL):