Nutrition in Human beings
Human beings require food to grow, reproduce, and maintain good health. Without food, our bodies cannot stay warm, build or repair tissue, or maintain a heartbeat. Eating the right foods can help us avoid certain diseases or recover faster when illness occurs. Chemical substances in our food called nutrients fuel the other important functions.
When we eat a meal, nutrients are released from food through digestion. Digestion begins in the mouth by the action of chewing and the chemical activity of saliva, a watery fluid that contain an enzyme called salivary amylase/ptyalin which helps in breaking down the starch present in food. Further digestion occurs as food travels through the stomach and the small intestine, where digestive enzymes from the liver, pancreas and stomach liquefy food and thereby muscle contractions push it along the digestive tube. Nutrients are absorbed from the small intestine into the bloodstream and carried to the sites in the body where they are needed. At these sites, several chemical reactions occur that ensure the growth and function of body tissues. Certain foods that are not absorbed continue to move down the intestines and are eliminated from the body as faeces.
Once digested, carbohydrates, proteins and fats provide the body with the energy it needs to maintain its many functions. Scientists measure this energy in kilocalories, the amount of energy needed to raise 1 kilogram of water through 1 degree Celsius. In nutrition discussions, scientists use the term calorie instead of kilocalorie as the standard unit of measure in nutrition. The food is broken down by O2 to release energy and this whole process of metabolism involves two processes catabolism which is a destructive processes and anabolism which is a constructive processess.