By Malathi Mohan

Image: Wikimedia Commons Dietitians are applied nutrition specialists who prescribe suitable diets for health or other special needs that you might have. People have several problems with their digestive systems, which might be as simple as belching, or as complicated as peptic ulcers. Let us consider how the digestive tract deals with food. Digestion starts well before food reaches your mouth. The sight, smell and thought of food excite you and stimulate your salivary glands to produce saliva. Once the food is put into the mouth, the teeth take over. The longer you chew, the better your digestion is -- it also reduces flatulence.

When you start eating, the taste buds recognize the chemicals in the food and send messages to your brain about food tastes - sweet, salty, sour, hot or bitter. The teeth start their work of physically breaking down the food, ably assisted by the tongue, the jaws and the palette. The mucin in moistens food to help it move easily down the oesophagus. Even the fat content in the food helps you to swallow it.

Simple sugars are digested in the mouth. Glucose is directly absorbed into the blood stream. The salivary enzyme works on starches only. The proteins and fats need further treatment. The oesophagus or food pipe is a muscular tube, which expands, and contracts to push food down to the stomach. It takes just six seconds after swallowing for each mouthful to reach the stomach. The food pipe also starts the peristaltic movements in your digestive system. The stomach is a muscular sack with a capacity of 50ml when empty. But it can expand to accommodate 1.5 litres or more, due to its elasticity. The hydrochloric acid in the stomach gets secreted when you are hungry and the stomach starts churning, producing gurgling sounds. One of the reasons for gastric ulcer formation is irregular eating habit. In the absence of food, the acid acts on the stomach linings and causes ulcers. Or in the earlier stages, the acid comes up the food pipe to cause `heart burn`. The stomach churns food, mixing it well with the acid and the protein breaking enzyme, pepsin. Carbohydrates and proteins like, meat, egg and paneer are broken down in the stomach while the stubborn fats are passed in to the intestines as chyme. The time taken by the stomach to digest different foods varies, Sugars and starches need the least time, while proteins and fats require a longer duration.

The intestines first neutralize the acids in the chyme. Digestion is assisted by other departments as well -- the gall bladder provides bile salts for fat digestion, the pancreas provide enzymes and also neutralize the acids, the intestines have fingerlike folds called villi which increase the surface for absorption of the digested food. Actually the surface available here, may equal the surface of a tennis court!

There are other living organisms in your body called probiotics (found in curd) which help in digestion, absorption and in breaking down the waste to leave your body. They are necessary for immunity from harmful bacteria.

Finally, we reach the end of digestion, when the unabsorbed waste matter is transported to the large intestine to form faeces. It is essential to keep the digestive tract clear, healthy and comfortable and to eat a balanced diet at proper intervals.

Ms. Malathi Mohan is Dean, Academy of Fitness Management, FitnessOne, Chennai.