Too much fat and salt
What happens to fatty food when you eat it? First it is swallowed. Then it is churned up in the stomach. Finally it is squirted out of the stomach into a short tube called the duodenum. This is the place where the digestion of fat begins.

There are two other tubes which open into the duodenum. One is called the bile duct and comes from a small bag called the gall bladder. The other tube is from an organ called the pancreas. It is called the pancreatic duct.

The gall bladder is close to the liver and collects a range of substances from it. The liver is a very busy organ. It performs many tasks to keep the body alive. While performing some of these tasks, the liver makes wastes that it does not need. For example, the liver destroys old red blood cells and some of their parts find their way into the gall bladder. The juice that the liver makes is called bile. The gall bladder collects and stores the bile then lets it flow down the bile duct when a meal is being eaten.

The fat in a meal forms lumps in the liquid that is squirted into the duodenum. The lumps are difficult for the body to digest so bile makes digestion easier. The bile mixes with the fat and breaks it down into small droplets. You can see a similar thing happening when you wash up a dirty frying pan. The washing-up liquid attacks the lumps of fat in the pan and turns them into tiny droplets so that they can be washed away more easily.

After the fat in the duodenum has been broken into droplets, it is attacked by a chemical from the pancreas. This chemical passes down the pancreatic duct in a juice called pancreatic juice. The chemical is called an enzyme. It mixes with the droplets and breaks down the fat into even smaller particles. These tiny particles dissolve in the water around them. When the food leaves the duodenum it enters the small intestine. Here the dissolved fat particles pass through the intestine wall and eventually reach the blood.

Cholesterol is a fatty substance. If it is present in large amounts in the blood, some of it sticks to the walls of the arteries. An artery is a tube, which carries blood away from the heart. The blood is moved by the pumping action of the heart and needs clear tubes if it is to flow along efficiently. When the cholesterol sticks to the walls of an artery it can build up a thick layer which partly blocks the path of the blood. This makes it more difficult for the blood to pass so the heart has to pump harder. In time this extra work can strain the heart and produce heart disease.

When cholesterol forms in the wall of an artery it rarely goes away again and can stick there for life. The way to prevent cholesterol building up is to eat only small amounts of fatty food. By doing this the walls of the arteries will stay clear, the blood will flow freely and the heart will beat healthily.

Are different food groups digested in different places?
Yes, they are. The digestion of carbohydrates begins in the mouth where some of the starch in food is broken down into sugar. Protein digestion begins in the stomach. Fat digestion begins in the duodenum, then the digestion of all food groups is completed in the small intestine. The digested food is absorbed by the wall of the small intestine and passes into the blood.

How does the food travel in the blood?
Blood is a watery liquid and all the food travels as dissolved particles in the blood. There are red and white cells in the blood but they are not involved with the transport of food. The red cells carry oxygen and the white cells attack any bacteria which invade the body.

Does the body have a use for fat?
Yes. Fat is used to make cells and as a store of energy. The body draws on this store of energy when the diet does not provide enough. Fat also forms an insulating layer under the skin, which helps to keep you warm.

Does the body have a use for cholesterol?
Yes, it does. Cholesterol is used to make the walls of cells and so is needed for the growth and repair of the body. The body also makes chemicals called hormones. They flow around in the blood and control how the body behaves. You can feel the effect of one hormone when you are frightened. This hormone is called adrenaline. It stops blood flowing to your stomach and gives you the feeling sometimes described as 'butterflies in the stomach'. Adrenaline also widens the blood vessels in your muscles and makes your heart pump faster. All these actions prepare you for extra power so you can run away from danger. Cholesterol is used to make some of the hormones in the body. Only small amounts of cholesterol are needed. If there is more cholesterol in the blood than the body needs, it sticks to artery walls.

Why do people put salt on their food?
The salt can improve the taste of food. Some people even like the salty taste and shake a lot of salt onto their food.

Why do some foods contain a large amount of salt?
Salt is a preservative. This means that it can keep food edible. The salt prevents bacteria feeding and breeding on the food. When they do, they make the food inedible. We say the inedible food has 'gone bad' or 'gone off'. Bacteria need water in order to feed and breed. They travel in the air in spores. If they land on salted food and break out of the spores, the salt draws water out of their bodies and kills them.

Why do we need salt?
We need salt to control the amount of water in our body. Salt is made from two chemicals called sodium and chlorine. They are joined together in salt to make a substance called sodium chloride. The body uses sodium from salt to help make the nerves work.

How can too much salt damage the heart?
If the body contains too much salt it holds on to too much water and this enters the blood. The extra water increases the volume of the blood. This means that the heart has more blood to pump and in time this can cause heart disease to develop.