The trouble with high triglycerides

Triglyceride levels are one of the things that a doctor checks when she orders the cholesterol blood test. 

Diabetes can boost your triglyceride levels. And even though triglycerides don't get the same amount of attention as some other kinds of fats that float in your bloodstream—namely low-density lipoproteins (LDL) and high-density lipoproteins (HDL)—elevated triglycerides can add to atherosclerosis, the artery-clogging process at the root of most heart disease. Here's an article from the Harvard Heart Letter that explains what triglycerides are and what you can do to lower your levels:

All fats have one thing in common: they all contain triglycerides. These particles consist of three fatty acid chains linked by an alcohol called glycerol. When you eat a cheeseburger, your digestive system rips apart the triglycerides in the meat and cheese into their individual fatty acids. These are small enough to enter intestinal cells called enterocytes. Enterocytes stitch together fatty acids into new triglycerides, pack them with protein and cholesterol into huge particles called chylomicrons, and release them into the bloodstream. Chylomicrons ferry triglycerides to tissues, where they are burned for energy or stored. The liver also packages triglycerides into large particles called very-low-density lipoproteins (VLDLs).

As chylomicrons and VLDLs give up their fats to the body's cells, they shrink, becoming dense, cholesterol-rich particles. One of these is LDL, which readily burrows into artery walls. This is a key early step in the process that ends with cholesterol buildup in arteries.

Transformation into LDL isn't the only issue with high blood levels of triglycerides. The more abundant they are, the less HDL the body makes. That's a problem, because HDL scavenges LDL from the blood and from artery walls.

The amount of triglycerides in the bloodstream rises and falls throughout the day. After a fatty meal, triglycerides can be so abundant they give blood a milky tint. Within a few hours, they're mostly cleared out. Doctors traditionally test for triglycerides after an overnight fast so the results aren't thrown off by what you've just eaten. Categories are based on these fasting levels.

Fatty foods aren't the only cause of high blood levels of triglycerides. Other contributors include

• eating a lot of rapidly digested carbohydrates
• an underactive thyroid gland
• kidney disease
• diabetes
• overproduction of the hormones aldosterone or cortisol
• excess weight, especially extra pounds around the waist
• inactivity
• smoking
• medications such as high-dose thiazide diuretics or beta blockers, estrogen, tamoxifen, steroids, isotretinoin, and some anti-HIV drugs.

Inheritance also plays a role. Some people have high triglycerides due to genetic disorders, such as familial combined hyperlipidemia and familial hypertriglyceridemia.

One reason triglycerides have long been shunted into the background is that their precise connection with heart disease has been iffy — some studies have shown a connection, others haven't. The latest meta-analysis, published in 2007 in Circulation, combined the results of 29 studies with more than 260,000 participants. In this report, people with high triglyceride levels were 70% more likely to have developed heart disease over an average of 10 years than those with normal levels. Some of this increase disappeared, though, when high LDL, low HDL, and other cardiac risk factors were taken into account.

That disappearance captures the big controversy over triglycerides: Are they harmful on their own, or are they stand-ins for other problems? It's a difficult question to answer, since high triglycerides are usually part of a pack of problems that also includes low HDL, high blood pressure, high blood sugar, and a large waist. These run together so often that, as a group, they are called the metabolic syndrome.

In other people, high triglycerides are a lone wolf. Even when they stand alone, however, they predispose individuals to heart disease.

Here's some good news about triglyceride levels and how you can change them.  When high triglycerides are accompanied by high LDL and low HDL — the usual scenario — they aren't the main focus of therapy. Guidelines recommend going after high LDL first, usually with a statin drug. Then it's time to work on triglycerides and HDL. Unless your triglycerides are extremely high, lifestyle changes are the best place to start. These can lead to impressive reductions in triglycerides.

Beware of bad fats. Cutting back on saturated fat (in red meat and full-fat dairy foods) and trans fat (in restaurant fried food and commercially prepared baked goods) can lower triglycerides.

Go for good carbs. Easily digested carbohydrates (white bread, white rice, cornflakes, and sugared soda) give triglycerides a definite boost. Eating whole grains and cutting back on sugared soda can help control triglycerides.

Check your alcohol. Moderate drinking is good for the heart. But in some people, alcohol dramatically boosts triglycerides. The only way to know if you are one of these "responders" is to avoid alcohol for a few weeks and have your triglycerides tested again.

Go fish. Omega-3 fats in salmon, tuna, sardines, and other fatty fish can lower triglycerides. Having fish twice a week is fine.

Aim for a healthy weight. If you are overweight, losing 5% to 10% of your weight can help drive down triglycerides. Losing more is even better.

Get moving. Exercise lowers triglycerides and boosts HDL.

Stop smoking. It isn't good for triglyceride levels or anything else.

Although lifestyle changes are the first line of defense against high triglycerides, some people need more help. The four main medicines are statins, niacin, fibrates, and fish oil.

If you're diabetic, it's very important that you keep an eye on your cholesterol levels (among other things) to make sure you're doing all you can to prevent heart disease, a common complication of diabetes. Do you know your cholesterol level? What about your triglyceride level?

Julie K. Silver, M.D., is an assistant professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School. She is also the Chief Editor of Books for Harvard Health Publications.

Heart Letter
The Harvard Heart Letter provides eight pages of monthly heart news, directly from the more than 8,000 doctors and researchers at Harvard Medical School. It's a source of expert advice for people who may already suffer from heart disease (or their family members) and for people concerned about their risk who wish to take steps towards positive change.

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