Recommended daily allowances for specific nutrients are calculated based on epidemiological studies, meaning that many people are studied across a large population and their diets, vitamin levels, and rates of disease are calculated. Based on this information the government developed a set of Recommended Dietary Allowances, or RDAs, for Americans, by age group. These have since been replaced by an updated set of recommendations called the Dietary Reference Intakes, or DRIs, although it is not uncommon to hear people refer to the RDAs. Certain individuals will need more or less of a given nutrient based on their specific health concerns, so it is best to consult with a dietitian, physician or other health care professional to determine an individual's best nutrition plan.
Calories are a measure of the energy found in foods. Fats contain 9 calories per gram, alcohol contains 7 calories per gram, protein and carbohydrates contain 4 calories per gram. According to the U.S. Department of Agriculture, standards used for DRIs are based on a 2000-calorie diet. Some people need more and others less depending on their age, size, metabolic rate and other considerations. Very active people and pregnant women, for example, will need more calories. Sedentary individuals need fewer calories. Persons trying to gain weight, such as bodybuilders, need to consume more calories than they burn. Persons trying to lose weight need to consume fewer calories than they burn. Those who are maintaining their present weight should ingest as many calories as they burn.
Carbohydrates are categorized as simple or complex sugars. The carbohydrate known as glucose is the primary source of fuel for the cells in the body. Different forms of these nutrients are found in such foods as corn, pasta, rice, potatoes and candy. Based on a 2000-calorie diet, the recommended intake of carbohydrates is 130 grams for most people, though this differs somewhat by age and circumstances. For example infants from birth to age 6 months of age and 7 to 12 months of age are recommended to have 60 and 95 grams of carbohydrate, respectively. Pregnant and lactating women are recommended to have 175 and 210 grams, respectively.
Sodium is a mineral responsible for normal cell functioning and regulating the fluid volume of the body. Many processed foods have had sodium added. These include such foods as cottage cheese, salted meats and nuts. Salt is 40 percent sodium by weight. Most average healthy people are recommended to have about 1.5 grams of sodium per day. Excessive use of sodium can lead to heart and blood vessels disease, strokes and high blood pressure, and certain people should maintain a lower sodium diet.