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Heart-healthy diet

Description

An in-depth report on how to build the best diet for your heart's health.

Alternative Names

Diet - heart health

Dietary Changes

Low Carbohydrate Diets

The Atkins diet restricts healthful complex carbohydrates in vegetables and particularly in fruits that are known to protect against heart disease. The Atkins diet also causes excessive calcium excretion in urine, which increases the risk for kidney stones and osteoporosis, and the release of ketones. An overload of ketones leads to ketosis, which can cause nausea, lightheadedness, and bad breath. A 2002 study suggested that such diets during pregnancy may increase the baby's risk for high blood pressure.

Low-carb diets such as South Beach, The Zone, and Sugar Busters rely on a concept called the "glycemic index," or GI, which ranks foods by how fast and how high they cause blood sugar levels to rise. Foods on the lowest end of the index take longer to digest. Slow digestion wards off hunger pains. It also helps stabilize insulin levels. But some doctors are having a tough time buying into this idea, which suggests that fruit or fruit products like orange juice and bananas, both high on the glycemic index, are bad for you.

A 2006 review of low-carbohydrate diets found that they did help weight loss in the short term. However, while these diets appeared to lower triglyceride and raise HDL (“good”) cholesterol levels, they also raised overall and LDL (“bad”) cholesterol levels. There is not yet enough evidence to indicate whether the good heart effects of these diets outweigh the bad effects. At this time, experts do not recommend low-carbohydrate diets for heart disease prevention.

Mediterranean Diet

The Mediterranean diet is rich in heart-healthy fiber and nutrients, including omega-3 fatty acids and antioxidants. The diet consists of fruits, vegetables, and unsaturated “good” fats, particularly olive oil. Olive oil has been associated with lower blood pressure, a lower risk for heart disease, and possible benefits for people with type 2 diabetes.

There are several variations to the Mediterranean diet but general recommendations include:

• Limit red meats.
• Drink one or two glasses of wine each day if alcohol is enjoyable and there are no reasons to restrict its use.
• Limit dairy products.
• Eat moderate amounts of fish and poultry. Fish is the diet’s main protein source. One study suggests that fish is the primary heart-protective ingredient in this diet.
• Eat plenty of fresh fruits and vegetables, nuts, legumes, beans, and whole grains.
• Season foods with garlic, onions, and herbs.

Positive Arguments. Even though fats make up about 40% of the calories found in the traditional Mediterranean diet, they are largely unsaturated. Growing evidence continues to support the heart-protective properties of the Mediterranean diet. Research has shown that such a diet reduces the risk for a second heart attack and helps cholesterol-lowering statin drugs work better.

Seniors who combine a Mediterranean diet with healthy lifestyle habits live longer lives, according to a 2004 study in The Journal of the American Medical Association . Researchers observed the effect of a Mediterranean diet on more than 2,000 elderly people for a period of 10 years, and measured the diet's effects on death rates alone and in combination with three risk factors: smoking, physical activity, and alcohol use. Overall, seniors who followed the Mediterranean diet decreased their risk of death from all causes by 23%. The elimination of each additional risk factor boosted their life expectancy rate even more. For example, non-smoking seniors on the diet who exercised regularly and drank only a moderate amount of alcohol reduced their death rates by 65%.

Negative Arguments. Weight gain due to a high intake of fats and risk for alcohol abuse can be problems with the Mediterranean diet. Other concerns include reduced iron levels and possible calcium loss resulting from a reduced consumption of dairy products. People on the diet should eat foods rich in iron or vitamin C, which aids in iron absorption. They should also ask their doctor if a calcium supplement may be needed because of a lack of dairy products. People should avoid wine if they have risk factors for complications from alcohol. Such people include women who are pregnant or at risk for breast cancer and anyone prone to alcohol abuse.

DASH Diet

The DASH diet (Dietary Approaches to Stop Hypertension) is proven to help lower blood pressure. Results are sometimes seen within a few weeks. Restricting sodium improves results. The diet appears to have antioxidant effects and may help lower LDL cholesterol levels, although beneficial HDL levels also decline. This diet is not only rich in important nutrients and fiber but also includes foods that contain far more electrolytes, potassium, calcium, and magnesium than are found in the average American diet.

The dietary recommendations are as follows:

• Reduce saturated fat (although include calcium-rich dairy products that are non- or low-fat.)
• When choosing fats, select monounsaturated oils, such as olive or canola oils.
• Choose whole grains over white flour or pasta products.
• Choose fresh fruits and vegetables every day. In one study people who increased their intake of fruits and vegetables experienced a drop in blood pressure after 6 months. Many of these foods are rich in potassium, fiber, or both which may help lower blood pressure.
• Include nuts, seeds, or legumes (dried beans or peas) daily.
• Choose modest amounts of protein (preferably fish, poultry, or soy products.)

Slight changes to the DASH diet might help lower blood pressure even more, as well as improve cholesterol and lipid levels. Researchers reporting in the Journal of the American Medical Association and at the 2005 American Heart Association meeting said that replacing some carbohydrates in the DASH diet with protein-rich foods from plant sources (nuts, seeds, soy) or monounsaturated fats (canola or olive oil) may help reduce heart disease risk factors.

Low-Fat Diets

Dietary guidelines recommend keeping total fat intake to 20 - 30% of total daily calories, with saturated fat less than 10% of calories. Low-fat diets generally restrict fat intake to 20% or less of total daily calories. The Ornish program, which is recommended for some heart disease patients, limits fats even more drastically. It aims at reducing saturated fats as much as possible, restricting total fat to 10%, and increasing carbohydrates to 75% of calories.

The Ornish program is a very demanding regimen:

• It excludes all oils and animal products except nonfat yogurt, nonfat milk, and egg whites.
• Foods stressed are whole grains, legumes, and fresh fruits and vegetables.
• People in the program exercise for 90 minutes at least three times a week.
• Stress reduction techniques are used.
• People do not smoke or drink more than two ounces of alcohol per day.

Positive Arguments.

• Low-fat programs may help keep weight off.
• Low-fat diets that are high in fiber, whole grains, legumes, and fresh produce offer health advantages in addition to their effects on cholesterol.
• The Ornish program directors have reported a 91% reduction in angina after 1 year and a 72% reduction after 4 years in spite of significant HDL cholesterol reduction. One study reported that the diet reduced LDL levels to recommended levels without the addition of a cholesterol-lowering drug.

Negative Arguments.

• In 2006, the largest study-to-date on low-fat diets found that they did not help prevent heart disease or cancer. Women in the study reduced their fat consumption to 24 – 29% of total daily calories. Some critics say that the study did not do enough to distinguish between good types of fats (monounsaturated omega-3 polyunsaturated) and bad fats (saturated and trans fats).
• The American Heart Association notes that the Ornish program is so difficult to maintain that it will not benefit many people.
• Very low-fat diets may reduce calcium absorption, which may be particularly harmful for women at risk for osteoporosis.
• Many people who reduce their fat intake do not consume enough of the basic nutrients, including vitamins A and E, folic acid, calcium, iron, and zinc. People on low fat diets should consume a wide variety of foods and take a multivitamin if appropriate.

Calorie Restriction

Calorie restriction has been the cornerstone of weight-loss programs. Restricting calories in such cases also appears to have beneficial effects on cholesterol levels, including reducing LDL and triglycerides and increasing HDL levels. At this point, reducing calories and increasing exercise is still the best method for maintaining weight loss and preventing serious conditions, notably diabetes. A 2006 study reported that a low-calorie, but nutritionally balanced, diet can help prevent an aging-associated change in heart function. Patients in the small study took in 1,400 - 2,000 calories a day for an average of 6 years.

The standard dietary recommendations for losing weight are:

• As a rough rule of thumb, one pound of fat equals about 3,500 calories, so one could lose a pound a week by reducing daily caloric intake by about 500 calories a day. Naturally, the more severe the daily calorie restriction, the faster the weight loss.
• To determine the daily calories requirements for specific individuals, multiply the number of pounds of ideal weight by 12 to 15 calories. The number of calories per pound depends on gender, age, and activity levels. For instance a 50-year old woman who wants to maintain a weight of 135 pounds and is mildly active might require only 12 calories per pound (1,620 calories a day). A 25-year-old female athlete who wants to maintain the same weight might require 25 calories per pound 2,025 (calories a day).
• Fat intake should be no more than 30% of total calories. Most fats should be in the form of monounsaturated fats (such as olive oil). Saturated fats (found in animal products) should be avoided.

Guidelines for Weight Loss Lifelong changes in eating habits, physical activity, and attitudes about food and weight are essential to weight management. Unfortunately, although many people can lose weight initially, it is very difficult to maintain weight loss. People with type 2 diabetes may have a particularly difficult time. Here are some general suggestions that may be helpful: Start with realistic goals. When overweight people achieve even modest weight loss they reduce risk factors in the heart. Ideally, overweight patients should strive for 15% weight loss or better, particularly people with type 2 diabetes. A regular exercise program is essential for maintaining weight loss. If there are no health prohibitions, choose one that is enjoyable. Check with a doctor about any health consideration. [For more information, see In-Depth Report #29: Exercise.] Hunger pangs should not be taken as cues to eat. A stomach that has been stretched by large meals will continue to signal hunger for large amounts of food until its size reduces over time with smaller meals. Be honest about how much you eat, and track calories carefully. Studies on weight control that depend on self-reporting of food intake frequently reveal that subjects badly misjudge how much they eat (typically underestimating high-calorie foods and overestimating low-calorie foods). In one study, even dietitians underreported their calorie intake by 10%. People who do not carefully note everything they eat tend to take in excessive calories when they believe they are dieting. For patients who cannot lose weight with diet alone, effect weight-loss medications are now available, including sibutramine (Meridia) and orlistat (Xenical). Orlistat may have particular benefits for patients with type 2 diabetes. This drug may delay or even prevent the onset or progression of diabetes. It may also improve cholesterol levels, regardless of weight loss. Sibutramine is also helpful in weight loss but should not be used by patients with high blood pressure or kidney or liver problems. Once a person has lost weight, maintenance is required. To maintain a healthy weight, make careful decisions about how many calories you consume in food and how many calories you expend through physical activity. Such thinking will eventually become automatic. A procedure known as bariatric surgery has been very helpful in producing rapid weight loss and improving insulin and glucose levels in people with diabetes. Even repeated weight loss failure is no reason to give up. [For more information, see In-Depth Report #53 : Weight control and diet.]

• Review Date: 4/11/2006
• Reviewed By: Harvey Simon, M.D., Editor-in-Chief; Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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