Triglycerides belong to a group of fat-related substances called lipids. An increase in levels of certain lipids—a condition called “hyperlipidemia”—contributes to heart disease.

To test for hyperlipidemia, physicians rely on blood tests called lipid profiles that measure triglycerides as well as two types of the lipid cholesterol: low-density lipoprotein (LDL) or “bad” cholesterol, and high-density lipoprotein (HDL) or good cholesterol.

In many people with hyperlipidemia, elevation of LDL predominates. Drugs in the statin family work particularly well at treating this form of hyperlipidemia. (For information on natural treatments for this condition, see the High Cholesterol article.)

In some people with hyperlipidemia, however, high triglyceride levels are the primary problem. These people are just as much at risk for heart disease as people with elevated LDL cholesterol. Furthermore, if triglyceride levels get high enough, the pancreas may become inflamed, causing a dangerous condition called pancreatitis. Skin lesions called xanthomas may occur as well.

Common causes of elevated triglyceride levels include genetic predisposition, diabetes, excessive alcohol intake, and various medications (including estrogen, tamoxifen, glucocorticoids, thiazide diuretics, and some beta-blockers).

People with high triglycerides may not respond well to statin drugs. Instead, they may need to use high-dose niacin or drugs in the fibrate family. Exercise (with or without weight loss) may also lower triglycerides. Diet, except when weight loss occurs, may not help, as a low-fat, high-carbohydrate diet can actually raise triglyceride levels.

Fish oil has shown distinct promise for treating hypertriglyceridemia. More than 2,000 people have participated in well-designed studies of fish oil for reducing triglyceride levels.1 Most studies ran from about 7 to 10 weeks.

It appears that fish oil supplements can reduce triglycerides by about 25% to 30%. Although not all studies have been positive, in a detailed review of 47 randomized trials, researchers concluded that fish oil is capable of significantly reducing triglyceride levels with no change in total cholesterol levels and only slight increases in HDL (“good”) cholesterol and LDL (“bad”) cholesterol.35 However, it should be noted that in some studies, use of fish oil has markedly raised LDL cholesterol, which might offset some of the benefit.

For more information, see the full High Cholesterol article.

Fish oil has been studied for reducing triglyceride levels specifically in people with diabetes, and it appears to do so safely and effectively.3Furthermore, in people using statin drugs to control lipid levels, the addition of fish oil or its isolated component DHA appears to improve results.4, 34

Fish oil is a source of omega-3 fatty acids, healthy fats that the body needs as much as it needs vitamins. The most important omega-3 fatty acids found in fish oil are named EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). According to some, but not all, studies, EPA may be more important than DHA for reducing triglyceride levels.5-10, 32

In addition, a slightly modified form of fish oil (ethyl-omega-3 fatty acids) has been approved by the FDA as a treatment for hypertriglyceridemia (high triglycerides).33 This specially processed product, sold under the trade name Omacor, is widely advertised as more effective than ordinary fish oil. However, it should be noted that Omacor has undergone relatively little study itself; the physician prescribing information notes only two small trials to support its effectiveness for this use. This is far less evidence than usually required for drug approval, and also substantially less than the body of evidence supporting standard fish oil as a treatment for high triglycerides.

For more information, including dosage and safety issues, see the full Fish Oil article.