Uncovering a Hidden Source of Cardiovascular Disease RiskMarch 2007
Strategies for Reducing Postprandial Lipoproteins
Saturated fats, like those found in butter, shortening, and fried foods, are especially potent inducers of excess postprandial lipoproteins. Because postprandial disorders cause fats to linger longer, avoiding unhealthy fats is doubly important. Minimizing these fats is advisable for other reasons, such as reducing LDL, blood pressure, inflammation, and cancer risk. While avoiding saturated fats will not eliminate postprandial lipoproteins, it will help reduce them.29 A polyunsaturated omega-6 fatty acid—linoleic acid derived from safflower oil—also raises postprandial lipoprotein levels, just as saturated fats do.3
Although the immediate cause of persistent and increased postprandial lipoproteins is an unhealthy fat-containing meal, two varieties of fat reduce postprandial lipoproteins:
• Monounsaturated oils, like olive oil, modestly reduce postprandial lipoproteins. Monounsaturated oils may thus be a preferable form of oil for cooking and everyday use.3,30
• Polyunsaturated omega-3 fatty acids reduce postprandial lipoproteins dramatically. It is not uncommon to see omega-3 supplementation eliminate abnormal postprandial patterns entirely. Sources of omega-3 fatty acids include fish oil, flaxseed oil, and walnuts.
If undesirable saturated fats lead to increased postprandial lipoprotein particles, does a low-fat diet reduce postprandial lipoproteins? Paradoxically, it does not. All too often, low-fat diets can evolve into diets rich in processed carbohydrates, which cause postprandial lipoprotein particles to multiply out of control.31 Diets that are rich in monounsaturated fats, omega-3 fats, fiber, and lean proteins, and low in saturated fats and processed carbohydrates, are effective tools in reducing postprandial lipoproteins.32
The following strategies can reduce triglycerides dramatically, and help reduce or eliminate IDL and postprandial lipoproteins:
• Weight loss can greatly reduce triglycerides and postprandial lipoproteins, particularly with a diet that is low in carbohydrates and high in protein and monounsaturated fats. Cutting out processed carbohydrates (such as breads, crackers, breakfast cereals, bagels, and pretzels) alone can yield a 30% reduction in postprandial lipoproteins.33,34 Increasing your intake of yogurt, cottage cheese, and other low-fat dairy products, raw almonds and walnuts, and fish, chicken, turkey, and other sources of lean protein will also yield substantial reductions in postprandial lipoprotein particles. Weight loss restores the insulin responsiveness lost in metabolic syndrome, which also reduces postprandial lipoproteins.31
• Omega-3 fatty acids in fish oil exert powerful effects in reducing postprandial lipoproteins. Ingesting just 1200 mg of EPA/ DHA from fish oil can easily lower IDL by 50%, and higher doses can produce even greater reductions. When fasting triglycerides are higher than 200 mg/dL, or when IDL is increased, higher doses of fish oil may be indicated to fight excess postprandial lipoproteins. Omega-3 fatty acids decrease liver production of VLDL by 30% or more, and lower IDL by 70% or more.35,36 Omega-3s also activate the enzyme known as lipoprotein lipase, which accelerates clearance of postprandial lipoproteins from the blood.37 Fish oil can safely augment the cholesterol-lowering effects of statin drugs such as Lipitor®, yielding dramatic improvement in triglycerides, VLDL, and postprandial lipoproteins.38
• Soy protein (20 grams per day) from tofu, soy milk, soy protein powder, and other sources can lower LDL by 10-20 mg/dL and reduce postprandial lipoproteins by 10%.39
• Green tea contains catechins (flavonoids) that can decrease postprandial lipoproteins by up to 30%. Approximately 600-700 mg of green tea catechins are required to achieve this effect, the equivalent of 6-12 servings of brewed tea. Nutritional supplements also provide green tea catechins at this dose.40 Green tea’s effectiveness in accelerating weight loss may augment its ability to reduce postprandial lipoproteins.
• White bean extract blocks the sugar-digesting enzyme known as alpha-amylase, thereby reducing the absorption of sugars. A recent study showed that participants who took 1500 mg of white bean extract twice a day for eight weeks lost an average of four pounds and lowered their triglycerides by an average of 26 mg/dL.41
• Vigorous exercise can reduce postprandial lipoproteins by 30%.42
• Diabetes treatment (with insulin or oral hypoglycemic drugs, for example) significantly reduces postprandial lipoprotein levels.43,44 The thiazolidinedione drug Actos® may be especially effective for its postprandial lipid-suppressing effects; a similar agent, Avandia®, may be modestly effective.45,46 The agent metformin also reduces fasting and postprandial triglycerides by 25%.47 (Caution: Like other thiazolidinediones, Actos® and Avandia® can cause fluid retention, which may lead to or exacerbate heart failure. Actos® and Avandia® should be discontinued if any deterioration in cardiac status occurs.)
• Statin drugs such as Zocor®, Crestor®, and Lipitor® not only lower cholesterol, but can reduce postprandial lipoproteins by 30-80%.48
• Fibrates (cholesterol-lowering drugs such as Lopid® and Lofibra®) can reduce postprandial lipoproteins by 70%. They can be a useful second-line strategy if fish oil, weight loss, and nutritional efforts fail to do the job.49
Clearly, choosing the right foods and fish oil supplements should be your first choice in controlling a postprandial disorder. Fish oil is safe, inexpensive, and easy to take, yet it provides an extraordinary array of benefits, including reduced risk of sudden cardiac death, stroke, and depression.50 Weight loss, exercise, soy protein, and green tea can all increase your likelihood of success. Because of their possible side effects, prescription drugs should always be your last choice for correcting postprandial patterns and other disorders.
Why Fasting Is Necessary for Blood Work
When you have blood drawn to measure cholesterol and other markers, you are instructed to fast for 8-12 hours beforehand. If postprandial disorders (such as IDL or an exaggerated increase in triglycerides) become apparent only after eating, why not have blood drawn after a meal?
Doctors instruct their patients to fast for cholesterol tests because triglycerides rise after a meal, and triglycerides are used to calculate LDL. Because LDL is usually the sole focus of the conventional approach to heart disease prevention, the fact that triglycerides are elevated, postprandial or fasting, is simply ignored. Thus, over the years, doctors have failed to recognize elevated triglycerides in the after-meal period as a powerful, independent indicator of risk.
In the future, there will be growing recognition of our over-reliance on LDL as the only important value for gauging the risk of atherosclerotic disease, and measures of postprandial triglycerides and other postprandial lipoproteins will gain increased recognition. Rather than fasting for your blood work, it may be obtained in the first few hours after a meal. Right now, however, there are insufficient data to justify this practice on a broad scale, though we occasionally do such testing on certain patients in our clinical practice.
Improvements over conventionally calculated LDL that requires fasting will also allow blood to be drawn in a non-fasting state. Measures that are superior to calculated LDL—such as directly measured LDL, VLDL, and LDL particle number and size (all available through VAP™ lipoprotein testing)—can eliminate the need for fasting while providing more clinically useful information.
As experience grows, standard meals (that is, specific preparations of known fat, protein, carbohydrate, nutrient, and fiber composition) will be used to develop standards to better diagnose postprandial disorders. This way, people and populations can be compared based on their response to a standardized meal. Because the meals you choose yourself can vary tremendously in composition, postprandial blood obtained for analysis can likewise vary, whether or not you have a postprandial disorder.
Until then, we are left with reasonably good insight into postprandial patterns provided by fasting triglycerides, VLDL, and IDL levels. Mindful attention to these critical blood markers can greatly enhance and preserve your vascular health.
Dr. William Davis is an author and cardiologist practicing in Milwaukee, Wisconsin. He is author of the book, Track Your Plaque: The only heart disease prevention program that shows you how to use the new heart scans to detect, track, and control coronary plaque. He can be contacted through www.trackyourplaque.com.
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