Saturday, June 9, 2012

FUNCTIONS AND FOOD SOURCES OF CARBOHYDRATES


FUNCTIONS AND FOOD SOURCES OF CARBOHYDRATES
FUNCTIONS OF CARBOHYDRATES: Carbohydrates have many important functions in the body:
  1. The primary function of carbohydrates in the body is to supply energy. Each gram of carbohydrate, as starch and sugar, provides 4 kcal/g. Carbohydrates are a source of readily available energy, which is needed for physical activities as also the work of the body cells. The brain and the central nervous system are dependent on the constant supply of glucose from the blood to meet their energy needs.
  2. Carbohydrates act also as reserve fuel supply in the form of glycogen, stored in muscles and liver. Then total amount of glycogen in the body is over 300 g. But it must be maintained by regular intake of carbohydrates at frequent intervals, so that the breakdown of fat and protein tissue is prevented.  
  3. Carbohydrates serve other special functions in the body. Carbohydrates provide chemical framework, which combine with the nitrogen to synthesize non-essential amino acids in the body.
  4. Carbohydrates and their derivatives work as precursors of important metabolic compounds. These include nucleic acids, the matrix of connective tissue and galactosides of nerve tissue.
  5. Lactose, the milk sugar, provides galactose needed for brain development. It aids absorption of calcium and phosphorous, thus helping bone growth and maintenance.
  6. Lactose forms lactic acid in the intestinal track due to the action of the bacteria (lactobacilli) present there. These lactobacilli synthesize some of the B-complex vitamins. It aids, bacteria (lactobacilli) present to suppress the activities of putrefactive bacteria and protects us from their undesirable effects.
  7. Carbohydrates are an important part of some compounds, which increase our resistance to infection (immunopolysaccharides). Ribose, a five carbon sugar, is an essential part of DNA and RNA. Carbohydrates are a part of important compounds, which are components of nervous tissue (galactolipid), heart value, cartilage, bone and skin (chondroitin sulfate).
  8. Carbohydrates are needed for ensuring complete normal metabolism of fats, thus preventing acidosis.
  9. Carbohydrates are needed to prevent dehydration. A low carbohydrate diet causes loss of water from tissues as also electrolytes ( especially sodium and potassium) in the urine and can lead to involuntary dehydration.
  10. Dietary fiber acts like a sponge and absorbs water. It helps smooth movement of food waste through the digestive tract and the soft, bulky stools are comfortably eliminated.

FOOD SOURCES OF CARBOHYDRATES: Carbohydrates are synthesized by plants and occur in several forms. Starch is found in plant seeds (cereals and legumes) and roots and tubers. These foods are the primary energy sources in the human dietary.
The intake of complex carbohydrate in the form of cereals, dals and legumes, in normal Indian dietary is sufficient. Cereals, which are the staple food in the Indian dietary, contribute major part of the energy  and proteins and some minerals and vitamins. Dals and legumes provide significant amounts of proteins, iron and B-vitamins, in addition to energy. Potatoes, yams, jack fruit are good source of starch in the diet. Vegetables and fruits provide dietary fiber, minerals and vitamins. Milk is the only animal food, which is the source of a very important sugar—lactose--- in the diet.
Table: Carbohydrate Content of Foods
Food
Carbohydrate
Calories/ unit
g / 100g
g / unit
Rice, rice flakes, rawa, vermicelli, etc.
75-78
19
86-88
Wheat flour (atta), jowar
69-72
17-18
82-87
Dals
58-60
15
84-87
Tapoica or cassava
18
19
80
Banana
27
22
95
Potato, colocasia, ehiku, peas, yam, jackfruit
16-22
8-11
40-49
Mango
17
9
37
Orange, guava, pear,apple, carrot, onion, cluterbeans
7-13
3-6
24-30
Leafy and other vegetables
1-4
1-2
6-17
Milk
5
7
100
Sugar
100
5
20

Sugars are found in fruits, the percentage is about three in melons, ten in citus fruit and guava and seventeen in mango. Thus fruits are an excellent snack food as they are a dilute source of quick energy and other nutrients.
Sugars found in plant sap or juice (sugar-cane and beetroot) is extracted to give pure 100 per cent sugar. It must be used judiciously, as it provides only energy. The intake of foods high in added sugars, such as soft drinks, syrups and sweets needs to be controlled to avoid obesity.

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