Function of Nutrients

Food is made up of six classes of nutrients

* Carbohydrates
* Fat
* Protein
* Vitamins
* Minerals
* Water

Some experts list fiber as a seventh nutrient, although technically some fibers are carbohydrates and are usually listed with the carbohydrates. The first three classes are called energy nutrients because they provide energy for the body. Food energy is expressed in the form of kilocalorie. A calorie is the amount of heat required to raise the temperature of a gram of water 1C. A kilocalorie equals 1000 calories of heat energy. Common reference to calories usually excludes the prefix "kilo," mainly for convenience. A gram of carbohydrates provides 4 calories (kilocalorie) of energy, a gram of protein also provides 4 calories, a gram of fat provides 9 calories, and alcohol (which is not a nutrient but is used in beverages) provides 7 calories per gram.

The recommended diet for americans emphasizes complex carbohydrates as the major source of energy. A total of 55% of calories should come from carbohydrates, with at least 45% from complex carbohydrates and no more than 10% from sugar. Data from the national health and nutrition examination survey (NHANES), one of the major national surveys in the national nutrition nonitoring and related research program, reveal that the diet of americans does not conform to recommendations. Presently the typical american diet consists of 34% fat, 16% protein, and 49% carbohydrates . Approximately one half of carbohydrate intake is in the form of sugar, which far exceeds dietary recommendations calling for a maximum of 10% sugar.

The food guide pyramid recommends a minimum of servings from the vegetable, fruit, and grain groups. Although this is more than the average person consumes, many experts believe more servings are necessary. According to a survey of nutrition experts,s the recommended diet should include at least seven servings of fruits and vegetables and six servings of grain products. For a person on a 2000 calorie diet, this meets the goal of 300 grams of carbohydrates recommended in the daily reference values. daily reference values (DRVs), established in 1992 with new food label regulations are guidelines for substances not included in the 1989 RDAs. These substances include carbohydrate, fat, saturated fat, cholesterol, sodium, potassium, and dietary fiber. DRVs can be used to compare levels of these substances in planning diets and purchasing food. They also provide a reference point for substances thought to be highly related to many of the major chronic diseases in the united states.

How are Americans doing with respect to the food guide pyramid? Data reported by the center for science in the public interest are both encouraging and disconcerting. On the encouraging side, americans are consuming more vegetables and fruits, fewer eggs, less beef, more chicken and fish, and less whole milk than their peers of 25 years ago. On average, both men and women meet the 1989 RDA for the majority of nutrients. Men meet the RDA for more nutrients than do women because they tend to eat more than women. Recent surveys reveal that men meet the RDA for 11 of 15 nutrients (protein, vitamin A, vitamin C, thiamin, riboflavin, niacin, folate, vitamin BIZ' calcium, phosphorus, and iron). Women meet the RDA for 9 nutrients (protein, vitamin A, vitamin C, thiamin, riboflavin, niacin, folate, vitamin Bw and phosphorus). On the discouraging side, americans are still far short of dietary recommendations. Average intakes by men of vitamin B 6 , vitamin E, magnesium, and zinc are less than the RDA. Women fall short of the RDA in vitamin B 6 , vitamin E, calcium, iron, magnesium, and zinc.