There’s the old saying “You are what you eat,” and it’s especially true in heart disease. It’s not just a matter of Americans having “supersized” themselves into an obesity epidemic, although that is certainly the case. Indeed, researchers have proven that the main reason so many Americans are struggling with their weight is simply because we are eating more and exercising less.

One recent study shows that average food portions in the United States have significantly increased in size over the last few decades. Researchers looked carefully at the average portion sizes from 1977 to 1996 and found a remarkable trend. The average portion size for salty snacks increased by 93 calories. Hamburgers increased by about 100 calories. Soft drinks increased by about 50 calories.

These changes may seem modest for any given portion but over the course of a year they add up. Quantity isn’t the only issue. It’s increasingly clear that what you eat is as important as how much you eat and has a direct effect on both your propensity for heart disease and your ability to recover from it.

Most of the studies that demonstrate the heart benefits of certain approaches to diet are what scientists call “observational studies.” They are called “observational” because they involve observing people over time. In many cases researchers work backward to figure out what factors might have made a difference in whether someone did or did not develop the disease in question.

In this case, the studies have tracked the diet-related experiences of large groups of people over time. But in observational studies it is often difficult to disentangle the effects of diet from other factors, many of which may not even be measured.

For example, people with healthy diet habits may also exercise more, deal more effectively with stress, and have other health habits that affect their long-term well-being as significantly as their diet. We know with certainty that diet is a crucial factor in managing blood pressure, blood sugar, cholesterol, and obesity, but research on the direct effect of dietary choices on heart disease is still emerging.

Much of what we do know about diet and heart disease comes from three long-term observational studies: the Nurses’ Health Study (involving more than 86,000 female nurses); the Physicians’ Health Study (involving 22,000 male physicians); and the Health Professionals’ Follow-Up Study (involving 50,000 male dentists, veterinarians, pharmacists, optometrists, osteopathic physicians, and podiatrists).

In each study, participants completed detailed questionnaires about their dietary and lifestyle habits and then had their health tracked for more than a decade.

Since none of the participants had heart disease at the outset of these studies, researchers have been able to examine the role of diet in those who subsequently developed heart disease as well as those who did not. As a result of these and other studies, doctors and nutritionists are revising the definition of a healthy diet.

Rebuilding the Pyramid

Remember the “food pyramid” you learned about in school? It was an attempt by nutritionists at the U.S. Department of Agriculture (USDA) to give people a sense of the proper proportions of types of food they should be eating every day. At the base of the pyramid, representing the largest proportion of food that should be in your diet, were the starches bread, cereal, rice, and pasta, for example.

At the peak of the pyramid, representing the smallest quantity recommended, were fats butter, oils, margarine. In between were all the other food groups fruits and vegetables, dairy, and proteins. But if you never learned about the food pyramid in school, you needn’t worry: it’s changed.

Research conducted over the past three or four decades has made it clear that some of the blocks in the pyramid were in the wrong place and that some of the items in each block were, in some cases, more complicated than they’d first seemed. A diet high in starches, for example, can lead to obesity and other health problems in a sedentary population.

There seems to be a difference in the health effects of whole grains compared with refined grains. Fruits and vegetables have been found to have a variety of disease-preventing properties. And while some fats are clearly bad for you, others are actually beneficial.

As a result of these discoveries, the USDA is working on a revision of the food pyramid. Meanwhile, some experts have proposed that whole-grain foods and plant oils (e.g., olive, canola, soy, corn, sunflower, and peanut) form the foundation of the new pyramid. The next level up would be vegetables and fruit, followed by nuts and legumes.

Fish, poultry, and eggs would be next. At the top, representing the smallest quantity of the diet, would be red meat, butter, and refined carbohydrates. Alcohol, is also recommended in moderation. Although this new pyramid has not yet been widely accepted, it is based upon stronger evidence than the old pyramid.

The American Heart Association has modified its dietary guidelines as well. We’ll look at the research on several of the major food groups in a moment, but here’s a summary of what the AHA recommends to keep your heart healthy:

• Eat a variety of fruits and vegetables and choose at least 5 servings per day.
• Eat a variety of grain products, including whole grains, and choose at least 6 servings per day.
• Include fat-free and low-fat milk products, fish, legumes (beans), skinless poultry, and lean meats.
• Choose fats and oils with 2 grams or less of saturated fat per tablespoon, such as liquid and tub margarines, canola oil, and olive oil.
• Choose foods that are low in saturated fat, trans fat, and cholesterol.
• Limit your intake of foods that are high in calories and low in nutrition, such as sugary soft drinks and candy.
• Eat less than 6 grams of salt (sodium chloride) per day (2.4 grams of sodium).

Most packaged foods now carry nutrition labels that let you know how much of certain items calories, various fats, carbohydrates, proteins, vitamins, and minerals, for example is contained in a standardized serving. But other aspects of food labeling, like sodium content, can be confusing.

Here’s a key to what the advertising really means in the case of salt (by way of reference, there are 2.6 grams ofsodium in a single teaspoon of table salt, and there are 1,000 milligrams in a gram):

• “Sodium-free” - less than 5 mg of sodium per serving.
• “Very low-sodium” - 35 mg or less per serving.
• “Low-sodium” - 140 mg or less per serving.
• “Unsalted” - no salt added, but it still contains the sodium that is a natural part of the food itself.

Good and Bad Fats

As researchers have begun to understand the effects of different kinds of fats on both “good” and “bad” cholesterol in your bloodstream, they’ve established new guidelines for “good” and “bad” fats in your diet. Bad fats include saturated fats, trans fatty acids (trans fats), and cholesterol. Saturated fats are found in whole milk, cream, ice cream, whole-milk cheeses, butter, lard, and meats.

They’re also found in palm, palm kernal, and coconut oils and in coconut butter. Trans fats are made when food manufacturers add hydrogen to vegetable oil. They are found in the partially hydrogenated vegetable oils used to make hard “stick” margarine (but not soft “tub” margarine) and are also typically used in commercially manufactured cookies, cakes, crackers, french fries, fried onions, and doughnuts, among other snack foods.

In the past, scientists have focused on the dangers of saturated fats, but new research by the Institute of Medicine suggests that trans fats increase bad (LDL) cholesterol and also decrease good (HDL) cholesterol. No other dietary factor has both of these bad effects, and trans fats can damage arteries as much as or more than saturated fats.

Cholesterol exists on its own, of course, in varying concentrations in most animal products meats (and especially organ meats, like liver or heart), egg yolks, dairy products, and, to a much lesser extent, fish and poultry.

On the other hand, it is increasingly clear that some fats actually help lower your bad cholesterol levels and increase good cholesterol. These good fats include polyunsaturated fats such as safflower, sesame, soy, corn, and sunflower oils, seeds and nuts, and monounsaturated fats such as olive, canola and peanut oils, and avocados.

On the basis of these new findings, researchers and physicians encourage you to use polyunsaturated and monounsaturated fats wherever possible. It’s worth noting, however, that even these “good” fats are high in calories and therefore should be consumed in moderation.

The Importance of Fruits and Vegetables

It’s long been known that fruits and vegetables contain substances that help protect against a number of medical conditions, including cancers of the lung, mouth, esophagus, and colon. They may also help prevent breast and prostate cancers. New research suggests that the fiber, minerals, and antioxidants in fruits and vegetables also protect your heart.

A large study that included participants from both the Nurses’ Health Study and the Health Professionals’ Follow-Up Study found that each extra serving of fruits and vegetables consumed per day was related to a 4 percent lower risk of heart attack and a 6 percent lower risk of stroke.

These findings have not been confirmed in a formal clinical trial, and it is possible that the people in this and similar studies who ate more fruits and vegetables were healthier at the outset. But the researchers involved in this study have concluded that increasing your intake of fruits and vegetables could lower your risk of heart problems by 5 to 20 percent over the long term.

Fiber and Your Heart

Dietary fiber provides many benefits. Certainly it is beneficial for digestive diseases, as studies show it prevents constipation, hemorrhoids, and diverticulosis. Others studies have even suggested that fiber can reduce the risk of certain types of cancer. There is also evidence that fiber is useful as a strategy to reduce the risk of heart disease.

A recent study evaluated ten well-conducted studies, including more than 300,000 people. The study showed that fiber from cereals and fruit is associated with a 10 to 30 percent lower risk of heart disease for each 10-grams-per-day increase of total fiber from these sources.

Interestingly, vegetable fiber did not have a strong effect, leading some people to speculate that any beneficial effect of vegetable fiber could be offset by adverse effects of common starchy and highly processed vegetables. Unfortunately the studies often lacked the details needed to understand whether there are differences among the types of vegetables.

Another issue concerns soluble versus insoluble fiber. Both soluble and insoluble fiber pass through our bodies without being digested. Neither of these food components is absorbed into the bloodstream or used as an energy source. Soluble fiber becomes a gel or liquid as it mixes with fluid, and insoluble fiber does not.

Many foods contain both soluble and insoluble fiber. The study mentioned above found benefits associated with both types of fiber, though the benefits from soluble fiber were a bit stronger. Nevertheless, the authors stated that their results supported recommendations to increase consumption of all types of fiber-rich foods.

The Benefits of Whole Grains

The grain that’s used for most of the starchy foods we eat white bread, pastries, cakes, cookies, pasta, and white rice, for example has been “refined.” By “refined” we mean that the outer layer of bran and the inner germ of the grain have been removed to make the product whiter.

Whole grains, on the other hand, retain those components of the natural grain. That’s important, because the bran and germ of grains include fiber, essential fatty acids, and substances called phytochemicals, which have been proven to be good for your health.

The manufacturers of refined grains and flours often add vitamins and minerals to try to make up for what has been removed, but the resulting products still don’t match the health benefits of whole grains. Grain fiber is especially good at reducing cholesterol, and while fiber also exists in some fruits and vegetables, research suggests that grain fiber may be more effective at protecting your heart.

How effective? In the Nurses’ Health Study we mentioned earlier, researchers found that women who ate an average of at least three servings of whole grains per day had a 20 percent lower risk of getting heart disease than women who ate little or no whole grains. But we need to be somewhat cautious about these results.

In the absence of additional research, it is hard to determine whether these benefits are due to the nutrients and fiber found in whole grains, or to the fact that people who eat whole-grain foods tend to eat and live healthier than other people to begin with.

This reservation aside, however, the additional health benefits of eating whole grains (such as improved digestion) suggest that it is a good idea to increase the role of whole grains in your diet.

The Protective Value of Nuts

As with whole grains, eating nuts seems to have the effect of protecting the heart. The Nurses’ Health Study found that women who ate at least five servings of nuts or peanut butter per week had a 20 percent lower rate of developing diabetes.

In an earlier study of the same population, researchers also found that women who ate at least five ounces of nuts per week had a 30 percent lower risk of having a heart attack than women who did not eat as many nuts or who ate none at all. In addition, the Physicians’ Health Study found that men who ate nuts at least twice a week had a 30 percent lower risk of dying from heart disease than those who never or rarely ate nuts.

A few other studies have yielded similar findings, suggesting that nuts contain substances that protect the heart and blood vessels. Still (as with whole grains), more research is needed to determine whether these health effects can be attributed to eating nuts or to the generally healthier diet and lifestyle of those who eat nuts regularly.

One promising small study recently showed that when people with high cholesterol snacked on almonds, their LDL cholesterol was lowered by almost 10 percent. The FDA is actually allowing product labels for walnuts to claim that they lower the risk of heart disease.

The label states specifically that “Supportive but not conclusive research shows that eating 1.5 ounces of walnuts per day, as part of a low saturated fat and low cholesterol diet, and not resulting in increased caloric intake, may reduce the risk of coronary heart disease.” Other nut producers are petitioning for similar claims.

But there is yet another issue to consider: most nuts are very high in calories a potential problem for people who are trying to lose weight. Therefore, researchers suggest that if you want to increase your consumption of nuts, you must decrease your consumption of refined-grain products or meats, so as to maintain a healthy intake of calories.