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Cardiologists at the University of Maryland Medical Center have developed more evidence that the “normal” or “desirable” levels of triglyceride, a type of blood fat, may still pose a significant risk of heart disease. This new research data, which tracks the breakdown of fat from a milkshake, will be presented at the American Heart Association’s Scientific Sessions in Anaheim, California, November 13. The study provides a potential rationale for advocating much lower fasting triglyceride levels than those currently considered “desirable.”
“The results give us more reason to believe that lower triglyceride levels are better for you,” says Michael Miller, M.D., director of preventive cardiology at the University of Maryland Medical Center and an associate professor of medicine at the University of Maryland School of Medicine.
Current recommendations are based on what is called “fasting triglyceride,” the level of triglyceride circulating in the blood after fasting overnight. It is one of several indicators, including cholesterol and blood pressure, used to gauge a person’s risk of coronary disease. The higher the number, the higher the risk.
The National Cholesterol Education Program has recently revised the “desirable” fasting triglyceride cutoff point downward to less than 150 milligrams per deciliter (mg/dL). Earlier, “desirable” was defined as less than 200 mg/dL. But Dr. Miller says his study suggests less than 100 mg/dL is more appropriate, because once a meal is consumed, triglyceride levels rise.
“Our study shows that even when people have acceptable fasting levels, after a high fat meal their triglyceride shoots up into levels that could put them at higher risk of heart disease. If we can help them lower their baseline triglyceride levels with diet changes and exercise, their heart disease risk may drop throughout the day, even after high fat meals,” says Dr. Miller.
The new study evaluated the implications of “desirable” fasting triglyceride in 50 healthy, non-obese men and women with normal cholesterol levels, whose average age was 35. After their fasting triglyceride was measured, each volunteer was given a milkshake, standardized at 70 grams of fat per square meter of body surface. Their triglycerides after the shake were measured at intervals of two, four, six, eight and ten hours.
For volunteers with a fasting triglyceride between 101 and 149, the triglyceride level at the peak, four hours after consuming the shake, averaged 200 mg/dL, putting them at dangerously high levels, despite the acceptable fasting levels. However, in volunteers with a fasting triglyceride of less than 100, the four-hour peak triglyceride after the milkshake was only 124 mg/dL on average.
Dr. Miller headed a 1998 study that found people with triglyceride levels at or above 100 were 50 percent more likely than those with lower levels to suffer from future heart attacks, need bypass surgery or angioplasty, or die from heart disease.
“The average triglyceride level in the United States is 134 mg/dL and is considerably higher than triglyceride levels below 100 mg/dL commonly observed in countries where heart disease rates are low," says Dr. Miller. "The higher triglyceride levels are associated with both increases in body weight and the disturbing increase in diabetes. It’s a two-sided problem, because people with high triglycerides often develop insulin resistance, a major factor in the most common type of diabetes. In some cases, high triglycerides are identified years before the onset of diabetes."
Triglyceride is a fat that always circulates in the blood, especially after a meal high in saturated fat. Enzymes normally break down these fat particles, but when the process is not working efficiently, triglycerides that are only partially broken down can cause fatty deposits in blood vessels, leading to atherosclerosis, also known as hardening of the arteries. Triglycerides can increase the risk of blood clots, which combine with fatty deposits in the coronary vessels to cause heart attacks.
Dr. Miller says a combination of diet changes and exercise can reduce triglyceride levels by as much as 30 percent. These fats respond to regular exercise, weight loss, and a diet low in saturated fat and high in omega 3 fatty acids. Sources include such fresh fish as salmon, herring, mackerel, and sardines and tuna that is either fresh or packed in its own oil. Certain medications, including niacin (Niaspan, Slo-Niacin, Niacor), gemfibrozil (Lopid) and fenofibrate (Tricor) can lower triglyceride levels significantly.
Angeliki Georgopoulos, M.D., of the Veterans Affairs Medical Center at the University of Minnesota co-authored the study with Dr. Miller. The research was supported by funding from the American Heart Association, the Veterans Affairs Medical Center and the National Institutes of Health.
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