antioxidant (nutritional) — a chemical that slows down a type of chemical reaction called oxidation, which can cause damage inside the body. Examples are vitamins A and C, and the mineral selenium. Antioxidants are essential in the fight against cancer and aging. See free radical.

antioxidant (food additive) — you sometimes see antioxidants listed in the ingredients on food labels of processed food. They are added to help make the food stay fresh longer - they are not necessarily beneficial to your health.

bile — a greenish liquid made by the liver, and stored in the gall bladder between meals. During digestion, bile leaks into the small intestine, where it helps to break up fat globules.

calorie (cal) — a unit of energy, the one most often used when dealing with food. When people say, “calorie,” they normally mean “kilocalorie.” So, if someone tells you a chocolate bar has 200 calories, it actually has 200 kilocalories (200,000 calories).

carbohydrate — any chemical compound made up of the elements carbon, hydrogen and oxygen and no other elements. Sugars, starch and dietary fiber are examples of carbohydrates. Those that can be digested are used by the body to provide energy.

cholesterol — a soft, waxy substance that plays an essential role in many body processes. In the blood, it is carried in globules called lipoproteins. A high level of one form of lipoprotein (called low density lipoprotein, or LDL) is associated with an increased risk of heart disease and stroke. LDL is often called “bad cholesterol,” while the other main lipoprotein, high-density lipoprotein (HDL), is often called “good cholesterol,” because it is not associated with health problems.

DNA — stands for deoxyribonucleic acid; often referred to as the molecule of life. It carries information from generation to generation, and acts as a blueprint and template for building your body.

enzyme — a type of protein that plays a part in important chemical reactions inside living things. There are digestive enzymes, for example, which help to break down large, complex molecules in food into small, simple molecules that can be absorbed into the body.

fat — one of the macronutrients (along with carbohydrates and proteins). It accumulates in fat cells, most of which are just under the skin and around your internal organs. Fat provides insulation and shock absorption. Your body manufactures fat, as an energy store, if you take in more calories than you use up.

fiber — any indeigestable carbohydrate, such as cellulose found in plants. It absorbs water and it passes through your digestive system, preventing your feces from being too dry. Some fiber feeds beneficial bacteria in your large intestine. A high-fiber diet has many health benefits.

free radical — a chemical that easily takes part in chemical reactions. Inside your body, free radicals can damage your cells, contributing to aging. See antioxidant.

glucose — a simple sugar that is the body's main ready supply of energy. When you eat foods with carbohydrates in them, the carbohydrates break down in your digestive system to form glucose, which is absorbed into the blood.

glycogen — a chemical compound similar to glucose, and formed from glucose inside cells in the liver and muscles. When there is more than enough glucose in the blood, the excess is stored away as glycogen; when there is not enough, the glycogen forms glucose again, and is released into the blood.