When you're trying to eat healthier, it's good to know a little about what the different types of food do for your body. This can help you make better food decisions based upon your lifestyle, and can also provide insight into the link between what you eat, your energy levels and your weight. Carbohydrates, sugars and starches form the majority of your diet and are vital to the proper operation of your body.
At their most basic level, sugars are made of carbon and water. On a more complex level, they are your body's primary energy source. The simplest sugars are monosaccharides -- fructose is found in fruit, galactose is found in dairy foods, and glucose is your body's primary fuel source. When these simple sugars link together, they form disaccharides -- glucose and fructose link to form sucrose, or common table sugar, while glucose and galactose link to form lactose, the sugar in milk. Glucose is the most important sugar nutritionally because not only does it fuel your body, but it is also the major building block for many of the foods you eat.
When hundreds of glucose molecules link together, they form polysaccharides, or starches. Starch serves as an energy storage unit for plants, which explains why you get starch from plant-based foods. When you eat starchy foods like rice, grains and corn, digestive enzymes break the starch molecules back down into glucose so your body can use it. In people, glucose links together to form glycogen, which is how your body stores energy. The glycogen is stored in your muscles and liver until you need it, then it is broken back down into glucose that can be used for fuel.
When about 1,500 glucose molecules link together they form cellulose, which is the major structural component of plants. You eat cellulose when you eat whole grains, fruits and vegetables, but your digestive system can't break it down because it is such a strong molecule -- cellulose is the main component of wood, so that gives you an idea of its strength. It's important in your diet though, because it adds bulk to your stool and promotes regularity. When referred to as a nutritional component, cellulose is called fiber.
Sugars form starches, glycogen and cellulose, and all of these things are carbohydrates. The word "carbohydrate" refers to the structure of these molecules as having a carbon molecule attached to water molecules -- essentially, all carbohydrates have the same chemical makeup of simple sugars, but the difference is in how the sugars are linked and how many there are. Carbohydrates are a vital part of your diet and should make up between 40 and 60 percent of your food intake. Too few carbs, and you'll feel sluggish because your body won't have the fuel it needs to make energy. Too many carbs, and your body will store all the excess, and you'll end up fatter. Your intake depends upon the demands you place on your body -- sedentary people need very few carbs, while athletes need very high amounts.