A healthy diet consists of carbohydrates, proteins and fats. But what's the right combination? Which carbohydrates do you need? How much protein? What kind of fat?
Here are some answers from nutrition experts.
Protein is an essential component of bone, muscle, skin, hair, and other parts of your body. The body makes protein from amino acids found in protein-rich foods, but it can't store amino acids, so you have to eat protein every day.
Sources: The amino acids that make up proteins are often called essential and nonessential amino acids. Essential amino acids are those the body can't make so they must be in a daily diet; nonessential amino acids are those the body is able to make. "Complete proteins" are proteins that contain all the essential amino acids. Complete proteins are found in red meat, fish, poultry, milk, and eggs. An egg white is an excellent source of complete protein, with milk a close runner-up. Meat is also a good source of complete protein; different types of meat may vary in fat content, but all meat contains the same amount of protein. "Incomplete proteins" are those that do not contain all the essential amino acids. These are found in plants. Some plants contain more protein than others, but no plant contains all the essential amino acids. By eating a variety of plant foods, your diet can include all the essential amino acids. Vegetarians can easily obtain adequate amounts of essential amino acids from plant proteins as long as they consume adequate calories and a variety of foods.
For good health: Eat a variety of proteins from different food groups.
Carbohydrates include sugars, starches, and fiber. Sugars and starches are important to a balanced diet because they provide energy for the body. During digestion, sugars and starches break down into the simple sugar glucose and enter the bloodstream. Although fiber is a carbohydrate, the body uses it for other purposes than as a source of energy.
Sources: Simple carbohydrates, which are naturally occurring sugars, are found in milk, honey, fruits, and, to a lesser extent, vegetables. Complex carbohydrates, the starches, are found in vegetables, grains, and beans. Fiber, another complex carbohydrate, is found in both fruits and vegetables. Fiber is either soluble (dissolves in water) or non-soluble (doesn't dissolve in water). The skin of an apple, for instance, contains nonsoluble fiber; the pulp of the apple contains a soluble fiber called pectin.
For good health: Get most of your carbohydrates from less-processed whole foods, such as fresh fruits, vegetables, and whole grains. Eat 2 cups of fruit, 2-1/2 cups of vegetables, and three to eight servings, in 1-ounce equivalents, of grains daily. At least half of your servings should be whole grains. One slice of bread, 1 cup of ready-to-eat cereal, or a half cup of cooked rice, cooked pasta, or cooked cereal count as one serving of grains.
The body needs fat for energy, to pad organs and to transport vitamins. Too much fat can fuel obesity, high cholesterol, and heart disease. But not all fats harm you if eaten in moderation. Monounsaturated and polyunsaturated fats may actually help lower cholesterol. Saturated fats and trans fats may increase cholesterol and are associated with an increased risk for heart disease. All fats have 9 calories per gram; this is more calories than protein or carbohydrates.
Sources: Monounsaturated fats are found mainly in olive oil, canola oil, and nuts. Polyunsaturated fats are found mainly in vegetable oils, such as soybean, corn, and canola oils. Saturated fats are found mainly in red meat, but butter, cheese, poultry, palm oil, lard, solid shortenings, and whole or reduced-fat milk also contain saturated fat. Trans fats, although found in small amounts naturally in some foods, are mostly created by the process of hydrogenating vegetable oils. Like saturated fats, trans fats can increase a person's cholesterol levels.
For good health: Limit fast food and processed foods, use low-fat dairy products, and replace saturated fats, such as butter with monounsaturated fats like olive oil.
The Food and Nutrition Board of the Institute of Medicine suggests these guidelines for a healthy diet:
Carbohydrates: 45 to 65 percent of total daily calories
Fat: 20 to 35 percent of total daily calories
Protein: 10 to 35 percent of total daily calories