Harvard Heart Letter

In with the good, out with the bad

Fat, carbohydrate, and protein are all good for you — as long as you make smart choices.

The rule for healthy eating used to be so simple: If you ate, you were healthy; if you didn't, you weren't. Of course, that rule applied at a time when the average adult didn't make it much beyond his or her 40s. Now that we are living to 80 or beyond, healthy eating isn't quite so straightforward. There's more to it than just getting the calories you need. Why? The foods that supply these calories govern the health of your heart and influence whether or not you will develop cancer, osteoporosis, age-related vision or memory loss, or a host of other chronic conditions.

So which foods, or nutrients, are best? You know part of the answer: fruits and vegetables. But when it comes to fats, carbohydrates, and protein, many people are in the dark, confused by widely promoted diet claims and flip-flops from research.

Rethinking meals

Two meals that deliver approximately equal amounts of protein, carbohydrates, fat, and calories — how different can they be? Pretty darned different. The salmon meal below has less than half the saturated fat and cholesterol, more than twice the fiber and unsaturated fats, and more slowly digested carbohydrates than the meatloaf meal.

Not-so-great meal

Excellent meal

Meatloaf (3 ounces)

Mashed potatoes (1 cup)

Corn (½ cup)

Iceberg lettuce (1 cup)

Ranch dressing (2 tablespoons)

Chocolate ice cream (½ cup)

Salmon (3 ounces)

Bulgur (1 cup)

Almonds (½ ounce)

Carrots (½ cup)

Green beans (½ cup)

Spinach salad (1 cup)

Olive oil and vinegar (2 ounces)

Orange sherbet (½ cup)

742

Calories

745

31.3

Protein

30.3

7.1

Fiber

17.3

72.3

Carbohydrates

72.2

11.9

Saturated fat

5.8

18.7

Unsaturated fat

28.2

113

Cholesterol

54

Fat isn't a four-letter word

For nearly 50 years, one misguided message has trumped all others: "Fat is bad." That just isn't true. In fact, some fats — the unsaturated fats found in olive oil, canola and some other vegetable oils, nuts, and oily fish like salmon and sardines — are utterly good for you. Others, of course, aren't. Artificial trans fat is a disaster for your arteries and general good health. It is found in fried fast foods, stick margarines, many commercially prepared baked goods, and any food made with partially hydrogenated vegetable oil or vegetable shortening. Saturated fat, found mainly in red meat and animal fat, vegetable oils like palm and coconut oil, and full-fat dairy products, is somewhere in between — okay if eaten in moderation, but trouble if you overdo it.

When it comes to fats, don't be afraid to embrace the positive. Your choices are varied and tasty, from pungent olive oil to creamy avocados and crunchy walnuts. Olive oil is an excellent source of monounsaturated fat. Use it to sauté vegetables, chicken, or fish; drizzle it over steamed vegetables; choose it for making your own mayonnaise, sauces, or salad dressings; even dip bread in it at the table. Canola oil, peanut oil, avocados, walnuts, and most other nuts are other good sources of monounsaturated fat. To get more polyunsaturated fats in your diet, use vegetable oils such as corn and soybean oil for cooking and in salad dressings. Soybeans and soy products are other good sources, as are sunflower, sesame, and flax seeds.

At the same time, cut back on saturated fat. Swapping meat for fish or beans is one good way to do this. Switching to skim- or low-fat milk is another. Finally, avoid trans fats whenever you can. Check food labels for trans fat content. If the ingredient list includes "partially hydrogenated vegetable oil" or "vegetable shortening," there's some trans fat in the product.

Degassing beans

No matter how tasty and healthful beans may be, they're often shunned because of their gaseous aftereffects. The culprits are fiber and short chains of sugar molecules known as oligosaccharides. Here are some tips to help you turn off the gas:

Soak your beans. The California Dry Bean Board advises cooks to boil dry beans in a quart or two of water for two to three minutes, then turn off the heat and let them soak for several hours or even overnight. Pour off the soaking water, rinse, add clean water, and cook (www.calbeans.com/beanbasics.html).

Choose wisely. Some beans seem to create less gas than others. These include adzuki and mung beans, lentils, and black-eyed, pigeon, and split peas. Heavy-duty gas formers include lima, pinto, navy, and whole soy beans.

Start slow. Let your body get used to fiber and oligosaccharides by having a small serving once or twice a week. Then gradually increase your intake, either by taking larger servings or eating beans more frequently.

Put your teeth to work. The more thoroughly you chew beans, the more you expose them to natural oligosaccharide-digesting enzymes in your saliva.

Bring on the Beano. A tablet or a few drops of this safe, natural enzyme product helps sensitive guts digest oligosaccharides. Sprinkle it on a bean dish or right on the tongue before your first bite of beans. You can find Beano in most grocery stores or pharmacies.

Slow carbs, not low carbs

Carbohydrates, the essence of wheat, rice, potatoes, and other starchy foods, were once the go-to gang for healthy eating. When the Atkins diet blasted carbohydrates as the villain responsible for weight gain and poor health, millions of Americans turned their backs on bread, pasta, and even fruits and vegetables. The truth about carbs is somewhere in between.

As with fats, carbohydrate-rich foods come in different shades of good and bad. What makes one a better source of carbohydrate than another? Two things: its effect on blood sugar, and the other nutrients that come with the carbs.

Your body turns foods made of highly processed carbohydrates, like white bread and cornflakes, into blood sugar in a flash. Eat these at every meal and for snacks in between, and the resulting roller coaster of blood sugar and insulin can lead to weight gain and type 2 diabetes. Highly processed carbohydrates have also been stripped of important nutrients.

By contrast, whole grains and other slowly digested carbohydrates smooth out the peaks and troughs of blood sugar and insulin. They also deliver much-needed fiber, unsaturated fats, vitamins, minerals, and other phytonutrients. International studies show that people who eat whole grains are less likely to develop heart disease or diabetes, or have heart attacks or strokes.

Comparing carbohydrates

Some carbohydrate-rich foods boost blood sugar and insulin levels higher and faster than pure glucose. A scale called the glycemic index ranks the impact of various foods on blood sugar. Those with a low glycemic index (under 55) have a slow, steady effect on blood sugar and insulin. Medium glycemic index foods have scores between 56 and 69, while high glycemic foods weigh in at 70 or above. Foods with low values — fruits, vegetables, beans, nuts, and whole grains — can help keep your blood sugar, along with your hunger and maybe your waistline, in check.

A searchable database listing the glycemic index of nearly 1,600 foods is available at www.glycemicindex.com.

More power to protein

The low-carb craze turned much-needed attention to what protein can do for health besides behind-the-scenes tasks such as building muscle and maintaining the immune system. It turns out that eating protein instead of refined starches can make you feel full longer, and that the body spends more energy digesting protein than it does digesting carbohydrates. Some head-to-head trials suggest that a high-protein diet helps some people lose weight faster and keep it off longer than a low-fat diet. Eating protein in place of easily digested starch also improves blood levels of cholesterol, triglycerides, and other risk factors for heart disease. A few long-term studies have shown that higher-protein diets, especially those with more protein from plants, offer some protection against heart disease.

To your body's protein-making machinery, it doesn't much matter where you get your protein. In terms of long-term health, though, it does. The protein package — the fats and other nutrients that come with it — can affect your health for better or worse. Your heart doesn't benefit from the wallop of saturated fat that comes with a steak or dish of ice cream, but it responds beautifully to the healthful oils in salmon and nuts or the fiber in beans.

Putting it together

How do you put this information into practice? You can build your own diet, of course. Or you can follow one of the four proven strategies we outline in "Translating good food into better diets."