Looking for a heart-healthy diet? Confused about all of the fads and hype? Antoinette Sulpizi, MD, Paoli Hospital cardiologist, helps you digest all of the confusing nutritional information out there and help you determine which diets are best for your heart.
Is there a simple way to evaluate which diet may be best for my heart?
Years of research into diets and cardiovascular disease have produced the complex picture of dietary advice the public gets today. Low fat, low carb, names like DASH and South Beach -- wherever you turn, you can read or hear something about diet and heart health. There's really no simple answer to the diet question.
You also have to understand that diet alone will not combat heart disease. Do you smoke? Are you sedentary? Most researchers recommend that keeping your heart healthy means eating well, controlling your weight, and getting regular exercise.
What are the current recommendations regarding fat intake?
The American Heart Association recommends a low-fat diet of 55 percent of total calories from carbohydrates derived primarily from foods rich in complex carbohydrates such as whole grains, fruits and vegetables, 30 percent from fat, of which less than 5% should be saturated fat, and 15 percent from protein, with cholesterol restricted to less than 300 milligrams per day. The diet should contain 20 to 30 grams of fiber per day and trans fatty acids should be kept at a minimum.
What are the advantages of a low-carbohydrate diet?
Dr. Atkins' New Diet Revolution put the focus on low-carbohydrate diets in the 1990s. It recommended two weeks of extreme carbohydrate restriction, following a diet composed of 68 percent of total calories from fat, 27 percent from protein, and 5 percent from carbohydrates. Other popular low-carb diets soon followed -- Protein Power, The Zone Diet, the South Beach Diet.
Low-carb diets lead to a drastic reduction in carbohydrates and therefore an overall decrease in caloric intake, which, in turn results in weight loss. Five clinical trials found that restricting carbohydrates improved levels of HDL (good) cholesterol and decreased harmful triglycerides, but they also increased total cholesterol and LDL (bad cholesterol) levels after six and 12 months. For now, the American Medical Association says there's not enough evidence to recommend low-carb diets for the prevention of cardiovascular disease and that more research is needed.
What are glycemic index diets?
The South Beach Diet, Zone Diet, and Sugar Busters are some of the popular diets that allow carbohydrate consumption as long as the foods have a low glycemic index-a measure of the blood glucose response to a carbohydrate. In the South Beach Diet, for example, carbohydrates are severely restricted for the first two weeks, followed by a gradual reintroduction of low-GI carbohydrates, such as whole grains.
A high GI diet is believed to increase the risk of diabetes, obesity, and coronary artery disease. Several well-known, long-term studies -- the Nurses' Health Study, the Health Professionals' Survey, and the Iowa Women's Health Study -- all showed an association between diabetes and high GI diets. No randomized, controlled trials have looked at the effects of low-glycemic diets on cardiovascular disease. But the diets do encourage consumption of "good" carbs and mono- and polyunsaturated fats instead of simple, refined carbs.
I've heard that heart disease is not as big a health problem in other areas of the world. Could the difference be due to diet?
You must be thinking of the Mediterranean Diet, which originates from the Greek island of Crete. Cretans and other Greeks are 20 percent less likely to die of coronary artery disease than Americans and have one-third less cancer.
So, what is this diet? It's higher in fat (40 percent) than the American Heart Association's recommendations. But it has an abundance of plant foods, nuts, cold-water fish, which contain omega-e oils, olive oil as the principal source of fat, moderate amounts of dairy products, fish, and poultry, and moderate consumption of wine with meals.
This diet contains little of the two kinds of fats known to raise cholesterol levels-saturated and trans fat-and it rarely includes read meat. The diet also contains minimally processed, fresh and seasonally available foods such as those locally grown. Desserts are typically comprised of fresh fruits.
Multiple randomized, controlled trials of the Mediterranean Diet summarized in the Journal of American Cardiology point to reductions in fatal heart attacks, unstable angina, heart failure, and stroke. As a whole, followers of the Mediterranean Diet:
- Lose more weight.
- Have less insulin resistance.
- Have lower total cholesterol and triglyceride levels and higher HDL levels.
- Have lower levels of C-reactive protein, a marker of inflammation that has been tied to the risk of heart disease, heart attack, and stroke.
- Are less likely to have metabolic syndrome, a significant risk factor for heart disease.
There are three keys to the diet:
- Substitute non-hydrogenated unsaturated fats for saturated and trans fats.
- Increase consumption of omega-3 fatty acids.
- Consume more fruits, vegetables, nuts, and whole grains and avoid refined grain products.
What is the DASH Diet?
DASH stands for Dietary Approaches to Stop Hypertension. It is similar to the Mediterranean diet in that it emphasizes fruits, vegetables, low-fat dairy products, whole grains, nuts, fish, and poultry. By also reducing total and saturated fats, sweets, and sugar-containing beverages, the result is a diet high in potassium, calcium, magnesium, and fiber, which lowers the cardiovascular risk of high blood pressure.
If you had to pick one of these diets for weight loss and cardiovascular health, which would it be?
None of the diets in and of themselves are perfect for weight loss and cardiovascular health. But the take-home message is that you can extract something beneficial from each of them.
- Decrease your carbohydrate intake, especially of refined and high-glycemic carbs.
- Eat more fruits, vegetables, and whole grains.
- Increase your consumption of plant oils and fish.
- Eat moderate amounts of low-fat dairy products and nuts.
In fact, a study by the Harvard School of Public Health advocated combining the good features of low-fat and low-carb diets. Analyzing data from the long-running Nurses' Health Study, the researchers found the percentage breakdown of calories from fats, carbohydrates, or proteins had no influence on a woman's heart disease risk. But women who got more of their calories from healthier sources of protein and fat were 30 percent less likely to develop heart disease. The American Heart Association's revised diet and lifestyle recommendations also emphasize the whole diet-not a focus on individual nutrients and foods.
For more information on heart health, visit the Main Line Health Heart Center.