There are six classes of nutrients:
Carbohydrates
Fats
Proteins
Vitamins
Minerals
Water
Carbohydrates
These are the chief source of energy for body functioning and muscle activity. Carbohydrates are necessary for the regulation of protein and fat metabolism. The main carbohydrates found in foods are sugars, starches and fiber. Simple sugars are found in fruits, honey and refined sugar and are easily digested. Starches are more complex
and are found in plants, vegetables and grains. These more complex carbohydrates require greater digestive action to be broken down into simple sugars. Fiber, although contributes little to energy needs, is helpful in regulating sugars in the body and aid in intestinal elimination.
All sugars and starches are converted, by the process of digestion, into glucose which is a simple sugar. This simple sugar is used as fuel for the body or is stored in the muscle and liver as glycogen. Once the glycogen storage capacity is filled up, the excess glucose is converted to fat to be used as a reserve source of fuel. Carbohydrates are the primary source of energy and are the most efficient at producing energy.
Fats
Fats are lipids and are the most concentrated form of energy from the foods we eat. We also can manufacture fats from the overabundance of carbohydrates. Fats are a secondary source of energy when carbohydrate sources can not meet the demand and also act as carriers for some of the vitamins. There are essential fatty acids that we
must ingest because the body can't produce them and are necessary for good health. Fats are composed of saturated, monounsaturated and polyunsaturated fatty acids. Excess saturated fat has been associated with high cholesterol levels. Cholesterol is a fat
related substance and is necessary for good health. It is also manufactured by the body. An over abundance of cholesterol however has been linked to cardiovascular problems. Fats should not provide more than 30% of your daily caloric intake.
Proteins
Protein is considered the primary building material for blood, skin, hair, nails, organs and muscles. Protein is used as a fuel source only when carbohydrate and fat supplies are inadequate. Protein is composed of twenty two amino acids, eight of which the body can not produce and must be ingested. These are called essential amino acids.
All amino acids must be present for the body to synthesize protein and develop various protein based tissues of the human body. Protein is also necessary for the formation of hormones, the regulation of various body functions and the manufacture of enzymes. Excessive protein will be converted by the liver and stored as fat.
Vitamins
In general ,the body can not manufacture vitamins and therefore they must be supplied by the diet. They have no energy value but are important as a component to almost all metabolic reactions. Vitamins aid in the development of body structures and help convert fat and carbohydrates into energy. There are two classes of vitamins, fat soluble and water soluble. Fat soluble vitamins include A, D, E, and K. These can be stored in the body and an overabundance can lead to toxic levels. Water soluble vitamins include C, B complex and bioflavanoids.
Minerals
Minerals occur in the environment and are absorbed up the food chain into plants and animals. All minerals known to be important to human functioning can not be produced by the body and have to be supplied by the human diet. They assist with metabolism, biological reactions, water balance, hormone production, and bone development. Minerals that have high concentrations in the body are called macro-minerals. Those minerals found in minute amounts in the body are called trace-minerals.
Water
Water constitutes of 70% to 80% of the human body. Water helps gives structure and form to the body, it allows an environment necessary for cell metabolism, and provides a way for the body to maintain a stable temperature. All the water outside the body cells is called extracellular fluid. The majority of extracellular fluid is contained in the blood plasma. Water inside the cells is called intracellular fluid and composes the majority of the body's total water weight.
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