Heart-Healthy Diet

Description

Alternative Names

Dietary Changes

Heart disease is one of the many complications of America's growing obesity epidemic. In general, experts recommend lower calorie intake when it comes to a heart-healthy diet that address the nation's obesity problem. However, there is much controversy over the best balance of carbohydrates, fats, and protein. A number of dietary approaches for improving the heart are available:

• Therapeutic Lifestyle Changes (TLC) from the National Cholesterol Education Program.
• The Dietary Approaches to Stop Hypertension (DASH) diet. This diet has been designed specifically to help people reduce blood pressure.
• Low-carb diets (e.g., Atkins, South Beach).
• The Mediterranean Diet.
• Very low-fat diets/The Ornish Program.
• Restricted calorie diets.

Although all the major dietary approaches differ in important aspects, they have some recommendations in common:

• Choose fiber-rich food (whole grains, legumes, nuts) and fresh fruits and vegetables.
• Avoid saturated fats and trans fatty acids and choose unsaturated fats.
• In selecting proteins, choose soy, poultry, and fish over meat.
• Weight control and exercise are essential companions of any diet program.

Therapeutic Lifestyle Changes (TLC) from the National Cholesterol Education Program

Guidelines in 2001 from the National Cholesterol Education Program include the following for preventing and managing high cholesterol levels in adults:

• Choose five or more servings of fresh fruits and vegetables and six or more servings of whole grains, legumes. Soluble fiber is preferred (from cereal grains, beans, peas, legumes, and many fruits and vegetables).
• Fats can be up to 35% of daily calories, but no more than 7% should be from saturated fat. (People with high triglycerides or low HDL or both may need a higher fat intake.) Choose fats containing unsaturated fatty acids (from vegetables, fish, legumes, and nuts). Choose margarines containing sterols or stanols (e.g., Benecol, Take Control). Avoid trans fatty acids found in commercial products as much as possible.
• Proteins choices should be limited in general to fat-free and low-fat milk products, fish, legumes, skinless poultry, and lean means.
• Limit cholesterol intake to less than 200 mg per day.
• Maintain healthy body weight and a healthy level of physical fitness.

The DASH Diet and Other Dietary Considerations for Reducing High Blood Pressure

The DASH diet (Dietary Approaches to Stop Hypertension), which emphasizes whole grains, fruits, vegetables, and low-fat dairy products, can reduce blood pressure without the use of medication. A 2003 study found that the DASH diet promoted salt excretion, similar to diuretic drugs widely used to treat high blood pressure. Earlier research demonstrated that the DASH diet significantly lowers blood pressure, but the explanation for the beneficial effects had been unclear.

A diet that is effective in lowering blood pressure is called Dietary Approaches to Stop Hypertension (DASH).

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:

• Avoid saturated fat (although include calcium-rich dairy products that are no- or low-fat).
• When choosing fats, select monounsaturated oils, such as olive or canola oils. (One study reported a reduced need for anti-hypertension medication in people with a high intake of virgin olive oil, but not sunflower oil, a polyunsaturated fat.)
• Choose whole grains over white flour or pasta products.
• Choose fresh fruits and vegetables every day. In one 2002 study people who increased their intake of fruits and vegetables experienced a drop in blood pressure after six 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). Soy in combination with fiber-rich foods or supplements may have specific benefits. Oily fish may also be particularly beneficial. They contain omega-3 fatty acids, which have been associated with heart and nerve protection .

[For more information see Well-Connected Report #14 High Blood Pressure.]

Low-carb Diets

The popularity of low-carb diets has soared recently. But, despite their popularity, professional societies, including the American Heart Association, have cautioned against them. A comprehensive review of the safety and efficacy of low-carb diet studies failed to provide enough scientific evidence to recommend or advise against such diets. Other studies show that low-carb diets have no significant adverse effects on cholesterol levels, blood sugar levels, or blood pressure, at least in the first 6 to 12 months.

Popular low-carb diets include Atkins, South Beach, The Zone, and others. As an example, the Atkins diet has a four-phase program:

• For the first two weeks individuals consume no more than 20 grams of carbohydrates a day (no fruit, bread, grains, starchy vegetables, or dairy products other than cheese, cream or butter.) They eat pure protein and fats. (This phase is not suitable for children, pregnant women, or anyone with kidney disease.)
• After the first phase, individuals continue to lose weight while they increase carbohydrate levels by five grams each week.
• When individuals get close to their weight goal, they add another 10 grams of carbohydrates per week as long as they do not begin to gain weight. Weight loss is very slow at this time, but the individual is now getting used to maintenance.
• Lifetime maintenance is usually between 40 and 100 grams of carbohydrates a week.

Anyone who chooses this diet should prefer fish or soy products to meat as protein sources. Fish, in fact, may reduce leptin, a hormone associated with fat storage and heart diseases, and so be the best protein source. People on this diet should also select monounsaturated fats (as in olive oil) over other fat sources.) Patients often need supplements, at least a multivitamin and possibly calcium, chromium, omega-3 fatty acids (found in fish oil), and other supplements.

Low-carb diets can be very effective in producing short-term weight loss, but their long-term effects on health or on weight maintenance are in question. Centers that promote this approach argue that heart problems from obesity are due to insulin disturbances from sugar imbalances.

In fact, a well publicized 2002 study reported that people on the Atkins diet experienced lower levels of triglycerides (unhealthy fat molecules) and higher HDL (so-called cholesterol), while those on the American Heart Association diet experienced the reverse effects -- which are risk factors for heart disease. It should be noted that in the study, people on the Atkins diet -- and not those on the AHA diet -- were given supplements of omega-3 fatty acids, which are known to be heart-healthy. In assessing the study, some experts suggest that its major contribution to information on diet is the possible limitation of the AHA diet -- not necessarily the healthy implications of the Atkins diet. Long term effects on health are still unknown.

For example, the Atkins diet restricts healthful complex carbohydrates in vegetables and particularly in fruits that are known to protect against serious diseases -- not only heart problems but also cancer. The Atkins diet also causes excessive calcium excretion in urine, which increases the risk for kidney stones and osteoporosis. One byproduct of this diet is the release of substances called ketones, which can cause nausea, lightheadedness, and bad breath. A 2002 study suggested that such diets during pregnancy may increase the risk for high blood pressure in the offspring.

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. On the flip side, experts tend to agree that a high-GI diet can elevate free fatty acids, which can trigger increased insulin responses or even diabetes. It also appears to lower HDL ("good") cholesterol levels. More research is needed.

Mediterranean Diet

The Mediterranean diet is rich in heart-healthy fiber and nutrients, including omega-3 fatty acids and antioxidants. The diet recommends the following:

• A relatively high fat intake (about 35% to 45% of daily calories), but mostly from monounsaturated and polyunsaturated oils. The Mediterranean diet is known specifically for its use of olive oil. Extra virgin olive oil has been associated with lower blood pressure. Other studies have reported an association between olive oil and a lower risk for heart disease as well as possible benefits for people with type 2 diabetes.
• Daily glass or two of wine.
• Protein source is primarily fish. In fact, one 2001 study suggested that fish-consumption was the primary heart-protective ingredient in this diet.
• Carbohydrate choices emphasize fresh fruits and vegetables, nuts, legumes, beans, and whole grains.
• Foods seasoned with garlic, onions, and herbs.

Positive Arguments. Evidence is increasingly strong on the heart-protective properties of the Mediterranean diet. In a 2002 study, it not only enhanced the benefits of a cholesterol-lowering statin drug, it also maintained levels of antioxidant nutrients that are normally decreased with the statin. One study suggested that is significantly lowered the risk for a second heart attack after an average of four years compared to a conservative Western diet. Some studies have reported that it is more beneficial than the previous American Heart Association Step 1 and 2 diets, although there are no comparison studies yet with the more recent AHA approach.

Negative Arguments. Weight gain from the 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 consumption of fewer dairy products. People who use the diet should take the following precautions:

• Cook in iron pans.
• Eat foods that contain iron or are rich in vitamin C, which aids in iron absorption.
• A calcium supplement may also be needed because of 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.

The Ornish Program and Severely Fat-Restricted Diets

The Ornish program limits fats significantly. It aims at reducing saturated fats as much as possible, restricting total fat to 10%, and increasing carbohydrates to 75% of calories. It is a very effective but 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 employed.
• People do not smoke or drink more than two ounces of alcohol per day.

People on low fat diets should consume a wide variety of foods and take a multivitamin if appropriate.

Positive Arguments. A 2001 systematic review of 27 studies reported that reducing dietary fat is associated with a 16% reduction in risk and a 9% decline in mortality rates. 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 one year and a 72% reduction after four 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.
• A major analysis of low-fat diets reported a 9% reduction in mortality rates and 16% reduction in cardiovascular events (such as heart attack and stroke).
• It is effective in keeping weight off.
• It protects against high blood pressure.
• It may possibly protect against certain cancers.

Negative Arguments. The American Heart Association argues that the Ornish program is so difficult to maintain that it will not benefit many people. The comparison study showing the advantage of the Ornish over the Step 2 diet, in fact, was very small because few participants could sustain the efforts needed to fulfill the requirements of the Ornish program for five years.

Some experts argue that it is not clear whether fat-restriction or the other elements in the program, exercise and stress reduction, are mainly responsible for its benefits.

• High-carbohydrate and low-fat diets can reduce HDL levels and increase blood sugar and triglyceride levels. (In such cases, however, people may have chosen their carbohydrates primarily as simple sugars, not the complex carbohydrates found in whole grains and fresh fruits and vegetables.)
• Very low-fat diets may also increase the risk for stroke from hemorrhage in the brain.
• Very low fat diets may reduce calcium absorption, which may be particularly harmful in 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. In fact, in a study of an African community, inhabitants had very-low calorie diets and favorable cholesterol levels in spite of a relatively high intake of saturated fats.

At this point, reducing calories and increasing exercise is still the best method for maintaining weight loss and preventing serious conditions, notably diabetes.

The standard dietary recommendations for losing weight are the following:

• 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) and saturated fats (found in animal products) should be avoided.