An alphabet soup of lipids
Sunday, October 06, 2013 10:00 PM
This week I want to tackle the alphabet soup of TG, LDL, and HDL. More and more people are attending health fairs and are having their blood fats or "lipids" checked. They get a report from the lab that lists the various types of lipids but they have no idea how to interpret the results.
Dr. John Roberts is a Crawfordsville physician and one of the owners of The Paper. In addition to his weekly column, he writes a daily health tip that can be found on page A1.
What role do lipids play in the body? Besides storing energy, they are critical molecular building blocks for things such as cell membranes. The cell membrane is like a semi-liquid envelope that makes up the outside of each of our trillions of cells. Floating around in the cell membrane are all kinds of other molecular structures that allow things to pass into and out of our cells and also facilitate control of cellular functions. The body also uses lipids to produce various hormones like steroids.
Triglycerides (the TG in the alphabet soup) are the main component of vegetable oils and animal fat. They are one of the major energy-storing molecules in the body and are also responsible for transporting fats that have been absorbed from the diet. Fat and liver cells can also manufacture triglycerides.
They are important in cardiovascular disease. Elevated TGs are a risk factor for the development of atherosclerosis or clogging of arteries by fatty deposits known as plaques. The American Heart Association has developed guidelines for risk based on the levels of TGs: A value less than 150 is considered normal or low risk, 150-199 borderline high, 200-499 high, and over 500 very high risk.
Levels of TGs can be reduced by limiting the intake of fat, carbohydrates and alcohol in the diet. Regular aerobic exercise is also critical to lowering TGs. An intake high in Omega-3 fatty acids (fish & flax oil) as well as niacin can be helpful. Medications like statins can also lower TGs.
There are two lipoprotein particles that are most commonly reported in a screening lipid panel, LDL and HDL. Lipoprotein particles, as their name implies, contain both lipids and proteins. Both LDL and HDL contain cholesterol, but they differ greatly in how they affect the body, especially in regard to the arterial plaques found in atherosclerosis.
Low Density Lipoprotein or LDL is a particle made up of more lipid than protein that transports cholesterol and TGs from the liver to the rest of cells in the body. It also regulates production of cholesterol in the body. LDL is commonly termed "bad cholesterol." An elevated level of LDL, especially one particular subtype of smaller, more dense particles, is a strong risk factor for cardiovascular disease.
LDL levels less than 100 are considered very low risk. Levels of 100-129 are considered good, 139-159 borderline high, 160-189 high and greater than 190 very high risk. Levels less than 70 are recommended for persons with known heart disease and levels less than 80 are recommended for diabetics.
High Density Lipoprotein or HDL is a very small particle manufactured by the liver that has more protein than lipids. These little guys float around in the bloodstream and pick up extra cholesterol from cells and transport it back to the liver for recycling. A high level of HDL in the bloodstream is therefore important in preventing formation of deposits of cholesterol in the walls of arteries.
Desirable levels of HDL are 40 or greater for men and 50 or greater for women. Ways to raise HDL include regular exercise, not smoking, maintaining an ideal weight, limiting saturated fats in the diet and increasing fiber intake. Medications like niacin can also be helpful, though its use has recently come into question.
Lipids are an important lab test to have done starting at age 35 and every five years thereafter. Men who have diabetes, high blood pressure, smoke or have heart disease in their family should be screened earlier.