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Author: Extension Food and Nutrition Specialist, Department of Extension Home Economics, New Mexico State University. (Print Friendly PDF)
You make choices every day about the foods you eat. Some of these choices may seem trivial, others important. But as insignificant as a single choice may seem, made over and over, it can have a major impact on your health and your life.
Nutrition is the science of how the body uses food to nourish itself. Nutrients are chemical substances the body needs for building, maintaining, and repairing body tissues and for efficient body functioning. Specifically, nutrients provide:
- Materials necessary for growth, maintenance, and repair of body tissues. Protein, minerals, vitamins, and water are necessary for the body to build and repair bones and tissues throughout life.
- Regulators for all body processes. Vitamins, minerals, water, and proteins do this job.
- Fuel for energy for work and play. Carbohydrates, fats, and proteins are fuel nutrients.
Nutrients fall into six general classes: carbohydrates, proteins, fats, vitamins, minerals, and water. Carbohydrates, fats, and proteins furnish fuel to provide energy for the body. Both carbohydrates and proteins provide 4 calories per gram, while fat provides 9 calories per gram. Vitamins and minerals are necessary for regulating body processes. Water accounts for about 50% of a woman's body weight and about 60% of a man's body weight. Water is part of all body fluids and is necessary for regulating temperature, digesting food, transporting nutrients to the cells, and eliminating body wastes.
Although everyone needs the same nutrients, they need different amounts. For example, children need more protein per unit of body weight to build tissues as they grow. Men and women also have varying requirements for different nutrients. For example, women need more iron than men. Active people require more nutrients than inactive people. People recovering from an accident or illness need more of certain nutrients than healthy people. Also, people who have an immune deficiency from disease, such as cancer or AIDS, require more nutrients.
The body needs more than 40 different nutrients. Although nutrients are found in all foods, some foods are better sources of nutrients than others. The body needs the following key nutrients in proper amounts.
Protein is critical for building and repairing body tissue. Protein breaks down into simpler compounds called amino acids. The body needs 22 amino acids, and all but eight can be manufactured by an adult body, while a child's body can manufacture all but nine. These amino acids that cannot be manufactured by the body are called essential amino acids and must be obtained from food. Foods containing all eight (or nine) essential amino acids in adequate amounts include meat, fish, poultry, eggs, milk, cheese, and soybeans. Dried beans and peas, nuts, peanuts, and peanut butter also contain large amounts of essential amino acids. An adult can get adequate amounts of all essential amino acids by consuming animal products or a variety of plant products. Because children have higher protein needs, a person should consult with a dietitian before eliminating all animal protein sources from a child's diet.
Carbohydrates are used by the body as a source of readily available energy, to help the body use fat efficiently, and to spare protein from use as an energy source. They can be classified as simple carbohydrates, complex carbohydrates, and fiber. Fiber does not count as a source of energy because it cannot be broken down by human digestive enzymes. Carbohydrates are widely distributed in plant foods, while milk is the primary animal source. Sugars, including honey, molasses, and other sweets, also provide carbohydrates.
Fats and oils are a concentrated source of energy. They are a precursor for cholesterol and sex hormone synthesis, components of cell membranes, and carry fat-soluble vitamins. The fat content of many foods, including the amount of total fat, saturated fat, trans fat, and cholesterol in a serving, can be found on the Nutrition Facts panel on food packages. Fats are found in most foods but are found in higher amounts in oils, butter, margarine, and salad dressing.
Calcium plays major structural and functional roles in the body, including building the structure of bones and teeth, aiding in muscle and nerve activity and blood clotting. Most calcium in the body is stored in the bones and is made available to the fluids and soft tissues that regulate vital body processes. The best sources of calcium are milk and milk products. Other good sources are dark green leafy vegetables, canned fish with bones, dry beans, and corn tortillas. The body needs phosphorus and vitamin D for calcium to be used properly; phosphorus is found in foods that contain protein and calcium. A good supply of these foods will ensure enough phosphorus.
Iron is essential for the formation of red blood cells and for helping red blood cells carry oxygen to the cells of the body. Good sources of iron are red meat, poultry, fish, dark green vegetables, peas and beans, dried fruits, dark molasses, and whole grains or enriched breads and cereals.
Magnesium plays a regulatory role in the body. It is required for energy metabolism, is a cofactor of enzymes, and is needed for nerve and muscle function. Magnesium is found in seafood, legumes, nuts, chocolate, and unprocessed grains.
Zinc is important for cell maturation and immune function, and is a vital component of proteins. Zinc is found in shellfish, fortified cereals, meat, legumes, and chocolate, and its absorption is influenced by many factors.
Vitamin A is important for growth, normal vision, and keeping the skin, eyes, and linings of the body healthy. Although vitamin A is found only in meat and other animal foods, a precursor or provitamin called beta-carotene is converted by the body into vitamin A and is found in deep yellow and dark green leafy vegetables. Vitamin A and beta-carotene are found in liver, butter, margarine, egg yolks, fortified milk, and cheese. Broccoli, carrots, spinach, pumpkin, sweet potatoes, cantaloupe, and red chile contain only beta-carotene.
Vitamin D, in combination with calcium and phosphorus, is necessary for forming strong bones and teeth. In recent years, scientists have discovered many new roles for vitamin D. Vitamin D comes from egg yolks, butter, liver, sardines, salmon, shrimp, and vitamin D-fortified milk. It can also be produced by the body when the skin is exposed to sunlight.
Vitamin C, also called ascorbic acid, acts as an antioxidant and helps keep blood vessels and connective tissue strong. It is also necessary for forming teeth and bones and healing wounds. The best sources of vitamin C are citrus fruits, green peppers, green chile, and strawberries. Other good sources are tomatoes, cabbage, melons, broccoli, and potatoes.
Of all the B vitamins, thiamin, riboflavin, and niacin are the best known. The B vitamins are important for a good appetite and healthy digestion, healthy skin, and proper nerve functioning. Meats, whole grains, and enriched breads and cereals are good sources. Milk is an excellent source of riboflavin and pork is a good source of niacin.
Folate, a B vitamin, is also called folic acid or folacin. Folate is necessary for proper red blood cell formation and cell growth. It is also important prior to becoming pregnant to ensure prevention of spina bifida. Some health care professionals recommend that all women of child-bearing age consume 600 micrograms (mcg or µg) of folate per day because adequate folate is most critical in the very beginning of pregnancy, before most women realize they are pregnant. Good sources of folate include dried beans and peas, green leafy vegetables, liver, oranges and orange juice, peanuts, and sunflower seeds. Fortified breakfast cereals, pasta, and breads are also good sources.
It isn't necessary to shop with a nutrient guide to select healthy foods. Follow the guidelines in Table 1 to ensure you get plenty of all 40 nutrients. In general, vegetables and fruits with darker color have a higher amount of beta-carotene and folate. Choose dark green vegetables and deep yellow or orange vegetables and fruits often. Consume a variety of nutrient-dense foods and beverages within the groups listed below. Choose foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol.
Variety is the key to getting the array of nutrients offered by each food group. Variety starts with including foods from every food group and continues with consuming a variety of different foods from within each group. The nutritional adequacy of diets planned using MyPyramid depends greatly on the selection of a variety of foods.
Table 1. Guidelines for Nutrient Consumption in Food
|Food Group||Serving Size||Nutrient Contribution|
1 ounce equivalent =
1 slice of bread
1 cup of ready-to-eat cereal
1/2 cup of cooked cereal, rice, or pasta
|carbohydrate, thiamin, riboflavin, niacin, folate, magnesium, iron, zinc, fiber|
1 cup =
1 cup of raw or cooked vegetables
1 cup of vegtable juice
2 cups of raw leafy greens
|carbohydrates, beta-carotene, Vitamin C, folate, magnesium, potassium, fiber|
1 cup =
1 cup of fruit
1 cup of 100% fruit juice
1/2 cup of dried fruit
|carbohydrate, beta-carotene, vitamin C, folate, magnesium, potassium, fiber|
1 cup =
1 cup of milk or yogurt
1 1/2 ounces of natural cheese
2 ounces of processed cheese
|calcium, phosphorus, carbohydrate, protein, riboflavin, Vitamin D, magnesium, zinc|
Meat & beans group
1 ounce equivalent =
1 ounce of meat, poultry, or fish
1 tablespoon of peanut butter
1/4 cup of cooked dry beans
1/2 ounce of nuts or seeds
|protein, thiamin, riboflavin, niacin, vitamin B-6, folate, vitamin B-12, phosphorus, magnesium, iron, zinc|
1 teaspoon of vegetable or fish oil
1 teaspoon of oil-rich foods (e.g., mayonnaise, soft margerine)
|fat, essential fatty acids, vitamin E|
Source: USDA's MyPyramid
MyPyramid provides a more individualized approach to improving diet and lifestyle than previous food guides. An innovative aspect of MyPyramid is the interactive technology found at the www.mypyramid.gov Web site. The program allows the user to create an individualized plan based on age, gender, and activity level.
Original Author: Mae Martha Johnson, food and nutrition specialist. Previous revisions by Alice Jane Hendley, Extension specialist emerita, and Martha Archuleta, former Extension food and nutrition specialist.
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Revised and electronically distributed October 2009, Las Cruces, NM