Definition

Origins

Description

Function

Benefits

Precautions

Risks

Research and general acceptance

Resources

Definition

Hypertriglyceridemia is an elevation of triglyceride levels in the bloodstream.

Origins

Hypertriglyceridemia is a condition characterized by elevated triglyceride levels. Triglycerides are the chemical form in which more than 90% of dietary fat and body fat exist. There are two sources of triglycerides: they are either obtained from the diet (dietary triglycerides) or manufactured by the body itself in the liver. They circulate constantly with all the lipoprotein carriers of the blood. The most important lipoproteins are:

• Very high-density lipoprotein (VHDL). VHDL consists of proteins and a high concentration of free fatty acids.
• High-density lipoprotein (HDL). HDL helps remove fat from the body by binding with it in the bloodstream and carrying it back to the liver for excretion in the bile and disposal. A high level of HDL may lower chances of developing heart disease or stroke, this is why it is called the “good cholesterol”.
• Intermediate-density lipoprotein (IDL). IDLs are formed during the degradation of very-low-density lipoproteins; some are cleared rapidly into the liver and some are broken down to low-density lipoproteins.
• Low-density lipoproteins (LDL). LDL transports cholesterol to extrahepatic tissues (outside the liver) to other parts of the body. A high LDL level may increase chances of developing heart disease, this is why it is referred to as the “bad cholesterol”.
• Very low-density lipoprotein (VLDL). VLDLs carry triglycerides from the intestine and liver to fatty (adipose) and muscle tissues; they contain primarily triglycerides. A high VLDL level can cause the buildup of cholesterol in arteries and increase the risk of heart disease and stroke.
• Chylomicrons. Proteins that transport cholesterol and triglycerides from the small intestine to tissues after meals.

A blood cholesterol test usually reports on both cholesterol and triglyceride levels. The American Heart Association endorses the National Cholesterol Education Program (NCEP), a division of the National Institutes of Health (NIH), and its guidelines

(Illustration by GGS Information Services/Thomson Gale.).

for the detection of high cholesterol. The following are considered normal results:

• Total cholesterol (100-199 mg/dL)
• LDL (less than 100 mg/dL)
• HDL (40-59 mg/dL)
• Triglycerides (less than 150 mg/dL)

Hypertriglyceridemia is a common disorder in the United States. It is made worse by uncontrolled diabetes mellitus, obesity, cirrhosis of the liver and sedentary habits, all of which are more common in industrialized countries than in developing nations. The condition generally occurs in people who have low protein and high carbohydrate diets, but also has genetic causes, not very well-defined. One inherited form is “familial hypertriglyceridemia”, affecting about 1 out of 300 individuals in the United States. Hypertriglyceridemia can also result from a disorder of lipoprotein metabolism (dyslipidemia). Triglyceride levels increase gradually in men until about age 50 years and then decline slightly. In women they continue to increase with age.

In 2001, the National Cholesterol Education Program (NCEP) released recommendations on triglyceride levels that should determine whether hypertriglyceridemia treatment is required or not:

• Normal: less than 150 mg/dL
• Borderline: 150-199 mg/dL
• High: 200–499 mg/dL
• Very high: higher than 500 mg/dL

In the Fredrickson classification of hyperlipide-mias, the general term for elevated lipids in the blood, hypertriglyceridemia is classified as four different types:

• Type I: This is a rare disorder characterized by severe elevations in chylomicrons and extremely elevated triglyceride levels, always well above 1000 mg/dL and reaching as high as 10,000 mg/dL or higher. Because chylomicrons also contain cholesterol, blood cholesterol levels are also quite high.
• Type IIb: This is a mixed hyperlipidemia (high cholesterol and triglycerides) caused by elevations in both LDL and VLDL.
• Type III: This form is characterized by elevated total cholesterol and triglyceride levels. This type is easily confused with type IIb, but type III also features elevations in IDL.
• Type IV: This type is characterized by abnormal elevations of VLDL, with triglyceride levels almost always lower than 1000 mg/dL. Blood cholesterol levels are normal.

When levels exceed 150 mg>dL, health care practitioners will recommend a diet aimed at lowering levels.

Description

• Total fat intake should be restricted if weight loss is also required. If triglyceride levels are greater than 1000 mg/dL, allowing no more than 10% of total calories from fat usually lowers levels quickly and significantly.
• If dietary intake of white flour products is significant, restricting simple carbohydrates and increasing dietary fiber can lower triglyceride levels substantially.
• Alcohol should be avoided or limited to no more than 1 standard alcoholic beverage per day.
• Omega-3 fatty acids, found mainly in fatty fish and some plant products such as flax seed have a significant effect on triglyceride levels. In large amounts (10g daily or more), they lower triglycerides by 40% or more. To achieve this dose however, requires supplements or eating very large amounts of fatty fish, such as sardines, herring, and mackerel.
• Refined sugars increases triglyceride levels, and people with elevated levels should accordingly lower their intake of sugar, sweets, and other sugar-containing foods.
• Individuals who consume a lot of tea and coffee should change to decaffeinated products, as eliminating caffeine has been shown to reduce triglyceride levels.
• Water-soluble fibers, such as pectin found in fruit, guar gum and other gums found in beans, and beta-glucan found in oats, may be particularly beneficial in lowering triglycerides.

Most foods contain several different types of fats and some kinds are better, not only to reduce fat during a hypertriglyceridemia diet, but for improving overall health. The four main types of fats are:

• Saturated fats: These fats consist of fatty acid chains that have no double bonds between the carbon atoms of the chain. They are called saturated because they are fully saturated with hydrogen atoms and cannot incorporate more. They are solid at room temperature and are most often of animal origin. Examples are butter, cheese, and lard.
• Monounsaturated fats: These are composed mostly of monounsaturated fatty acids, meaning molecules with one double-bonded carbon, with all the others carbons being single-bonded. They are liquid at room temperature. Examples are olive, peanut and canola oil.
• Polyunsaturated fats: These fats are composed mostly of fatty acids such as linoleic or linolenic acids which have two or more double bonds in each molecule, as for example corn oil and safflower oil. They are also liquid at room temperature and can be further divided into the omega-6 and the omega-3 families. Fatty fish contain omega-3s, and they are also found in walnuts and some oils like soybean and rapeseed.
• Trans fatty acids. Unsaturated fats come in different chemical structures: a bent cis form or a straight trans form. When they adopt the trans form, they are called trans fatty acids. They are produced by the partial hydrogenation of vegetable oils and present in hardened vegetable oils, most margarines, commercial baked foods, and many fried foods.

Unsaturated, monounsaturated and polyunsaturated fats are considered better than others to lower your risk of heart disease since they lower the total and LDL cholesterol levels. Omega-3 fatty acids may be especially beneficial to the heart. They appear to decrease the risk of coronary artery disease and may also protect against irregular heartbeats and help lower blood pressure levels. Saturated and trans fats are considered less healthy because they can increase the risk of heart disease by increasing total and LDL cholesterol levels. Tips to limit fat in the diet are accordingly focused on reducing foods high in saturated and trans fats. For example, the Mayo Clinic offers the following:

• Cook with olive oil instead of butter.
• Use olive oil instead of vegetable oil in salad dressings and marinades. Use canola oil when baking.
• Sprinkle chopped nuts or sunflower seeds on salads instead of bacon bits.
• Snack on a small handful of nuts rather than potato chips or processed crackers.
• Add slices of avocado, rather than cheese, to sandwiches.
• Prepare fish such as salmon and mackerel, which contain monounsaturated and omega-3 fats, instead of meat one or two times a week.

Function

The function of a hypertriglyceridemia diet is to bring triglyceride levels back to normal recommended levels (less than 150 mg/dL).

Benefits

The benefits of normal triglyceride levels are numerous. Triglycerides carry fat-soluble vitamins A, D, E and K to where they are required, they help the synthesis of some hormones and protect cell membranes. The fat tissues in which they are stored also cushion and protect organs such as the kidneys and provide thermal insulation.

Precautions

The National Heart, Lung and Blood Institute (NHLBI), through its National Cholesterol Education Program (NCEP), recommends that the triglycerides of diabetic individuals should be checked regularly. Diabetes can increase triglycerides significantly, especially when blood sugar is out of control. Healthy adults over 40 should get their triglycerides tested at least once a year, and more often if levels are high until they reach the desirable level.

Fat restriction should be carefully evaluated. When reducing fat intake results in a required weight loss, triglyceride levels usually improve. When they are severely elevated (>1000 mg/dL), a low-fat diet will decrease chylomicron and VLDL. However, when triglycerides are only moderately elevated, a low-fat diet will increase them and may also decrease HDL levels.

Risks

Triglycerides do not cause complications until elevations of 1000 mg/dL or more are reached. There is a risk of chylomicronemia syndrome when levels are 800 mg/dL or higher. The syndrome causes recurrent episodes of abdominal pain that may be accompanied by nausea and vomiting. Extreme elevations of triglycerides, usually greater than 1000 mg/dL, may cause an inflammation of the pancreas (pancreatitis). The pancreas is the organ that makes insulin and substances to help digest food and pancreatitis is accordingly a serious disorder. People with hypertriglyceridemia are also at risk for fatty liver, the accumulation of fat in liver cells. Triglyceride levels of 4000 mg/dL or higher, may cause a condition known as lipemia retinalis, in which eye examination reveals retinal blood vessels that have a pale pink, milky appearance.

Women with elevated triglycerides before conception may develop severe hypertriglyceridemia with levels well above 1000 mg/dL, and the associated risk of pancreatitis. These women require counseling for diet, exercise, and weight management before becoming pregnant and should be monitored closely during their pregnancies.

Research and general acceptance

The NCEP triglyceride recommendation of less than 150 mg/dL per day has recently been challenged. Cardiologists at the University of Maryland Medical Center have presented evidence that the recommended level may still represent a significant risk for heart disease. Their study suggests that less than 100 mg/ dL would be more appropriate.

Resources

BOOKS

American Heart Association. American Heart Association Low-Fat, Low-Cholesterol Cookbook, 3rd Edition: Delicious Recipes to Help Lower Your Cholesterol. New York, NY: Clarkson Potter, 2005.

Freeman, M. W., Junge, C. E. Harvard Medical School Guide to Lowering Your Cholesterol. New York, NY: McGraw-Hill, 2005.

Kowalski, R. E. The New 8-Week Cholesterol Cure: The Ultimate Program for Preventing Heart Disease. New York, NY: Collins, 2002.

Larson Duyff, R. ADA Complete Food and Nutrition Guide, 3rded. Chicago, IL: American Dietetic Association, 2006.

McGowan, M. P. 50 Ways to Lower Cholesterol. New York, NY: McGraw-Hill, 2002.

Mierzejewski, A. Bring Your Triglycerides Down Naturally: A Drug-Free Solution to High Blood Lipids. Peterborough, ON: Full of Health Inc., 2006.

ORGANIZATIONS

American Heart Association (AHA). 7272 Greenville Avenue, Dallas, TX 75231. 1-800-242-8721. <www.americanheart.org>.

Center for Disease Control (CDC). Division for Heart Disease and Stroke Prevention, 4770 Buford Hwy NE, Atlanta, GA 30341-3717. 770-488-2424. <www.cdc.gov/cholesterol/faqs.htm>.

National Heart Lung and Blood Institute (NHLBI). P.O. Box 30105, Bethesda, MD 20824-0105. 301-592-8573. <www.nhlbi.nih.gov>.

Nutrition.gov. USDA National Agricultural Library, Food and Nutrition Information Center, Nutrition.gov Staff, 10301 Baltimore Avenue, Beltsville, MD 20705-2351. <www.nutrition.gov>.

Monique Laberge, Ph.D.