Human Nutrition

Carbohydrates are the key source of energy of the human body, which uses them to produce sugar glucose to help maintain tissue protein, metabolize fat and fuel the nervous system (MSN Encarta 2006). The major carbohydrates are starches and sugars. Examples of common starches are whole-grain breads and cereals, pasta, corn, beans, peas and potatoes. Natural sources of sugar include fruits and many vegetables, milk products, honey, maple sugar and sugar cane (MSN Encarta).

Dietary proteins are compounds, which build and repair body tissues, speed up chemical reactions in the body, serve as chemical messengers, fight infection and bring oxygen from the lungs to the body tissues (MSN Encarta 2006). Excellent sources of animal proteins include eggs, milk, meat, fish and poultry. Examples of plant sources are vegetables, grains and beans (MSN Encarta).

Fats are the most concentrated energy-producing nutrients, which play a significant role in building the membranes surrounding body cells and in forming blood clots (MSN Encarta 2006). Fats also help the body absorb certain vitamins, cushion vital organs and protect the body from extreme cold and heat. Examples of sources of animal fats are eggs, dairy products and meats. Examples of vegetable fats include avocados, olives, some nuts and vegetable oils (MSN Encarta).

Vitamins enhance the body's use of carbohydrates, proteins and fats; help in forming blood cells, hormones, neurotransmitters and the genetic material called DNA; and prevent many health disorders (MSN Encarta 2006). Minerals are metallic elements required for the healthy growth of teeth and bones and in other cellular functions. Excellent food sources of vitamins and minerals include oranges, milk, and sweet potatoes (MSN Encarta).

Dietary fiber is either soluble or insoluble (MSN Encarta 2006, Feinberg 2005). Soluble fiber is found only in plants, such as oats, barley, beans, peas, apples, strawberries and citrus fruits. Insoluble fiber is found in vegetables, whole-grain products and bran. Soluble fiber prevents or reduces the absorption of potentially dangerous substances from food in the small intestines, binds dietary cholesterol and carries it out of the body to prevent high blood pressure, heart disease and strokes. Insoluble fiber provides roughage, which hastens elimination of feces and reduces the risk of colon cancer (MSN Encarta, Feinberg).

Bibliography

1. Feinberg School. (2005). Dietary Fiber. Northwestern University. http://www.feinberg.northwestern.edu/nutrition/factsheets/fiber.html

2. MSN Encarta. (2006). Human Nutrition. Microsoft Corporation. http://encarta.msn.com/encyclopedia_761556865/Human_Nutrition.html