Antioxidant

Antioxidant, is any of a group of chemical compounds that may prevent certain types of cell damage. Antioxidants block the effects of oxidation, a chemical reaction in which a substance loses electrons, often while combining with oxygen. Antioxidants are important because they protect cells from the effects of free radicals, unstable molecules produced by oxidation. Scientists believe free radicals may be involved in the aging process as well as in a number of diseases.

In the human body, cells create free radicals when oxygen combines with food molecules to produce energy. Radiation, cigarette smoke, and air pollution also trigger the production of free radicals. Free radicals can attract and "steal" electrons from almost any nearby molecule to replace the electrons they lost during oxidation. Such attacks can damage the cell and can cause changes in genes. Antioxidants are the body's defense against free radicals. An antioxidant can provide an electron to a free radical before the free radical attacks important cell structures.

The body naturally produces certain enzymes that are antioxidants. In addition, vitamins C and E and certain plant chemicals, such as carotenoids and flavonoids (often called bioflavonoids), are antioxidants.

Fruits and vegetables are rich sources of dietary antioxidants. Citrus fruits are a rich source of vitamin C. Vitamin E is found in vegetable oils and nuts. Foods plentiful in beta-carotene or other carotenoids tend to be deep yellow or green, such as carrots and spinach. Flavonoids occur in many fruits and vegetables. Some studies have connected a diet rich in antioxidants with a reduced risk of cancer, heart disease, cataracts, and other diseases common among older people. Scientists are trying to determine if these reduced risks are due to the antioxidants or to some other factor.

Insulin

Insulin is a hormone that regulates the body's use of sugar and other food. It is produced in specialized cells in the islets of Langerhans, a part of the pancreas. Certain insulin-related abnormalities cause the disease diabetes mellitus, often simply called diabetes. In this disease, the body cannot use sugars properly and glucose (a form of sugar) builds up in the blood. Insulin also affects the body's use of protein, fat, and mineral products, such as potassium and phosphate.

How insulin acts in the body
When food is absorbed into the bloodstream, the pancreas increases the secretion of insulin into the blood. Insulin speeds the movement of nutrients from the bloodstream into target cells located mainly in liver, muscle, and fat tissues. Specialized protein molecules called insulin receptors lie on the surface of the target cells. The insulin receptors bind to insulin, which activates the receptors. The activated receptors on cells hasten the entry and utilization of the nutrients. Glucose and other simple sugars, produced by the digestion of more complex carbohydrates, are used for immediate energy or converted to glycogen for storage. Amino acids, produced by the digestion of proteins, move into cells and there form the building blocks for proteins. Fatty acids, produced by the digestion of fats, are converted to tryglycerides for storage and later used for energy.

Vitamin

Vitamin is a chemical compound that the human body needs in small amounts. Vitamins make up one of the major groups of nutrients (food substances necessary for growth and health). Vitamins regulate chemical reactions by which the body converts food into energy and living tissues. There are 13 vitamins. Five of them are produced in the body itself. These vitamins are biotin, niacin, pantothenic acid, vitamin D, and vitamin K. Biotin, pantothenic acid, and vitamin K, which are made by bacteria in the human intestine, are usually produced in sufficient quantities to meet the body's needs. In addition, sunlight on the skin can produce an adequate amount of vitamin D. But the other nine vitamins must be supplied in a person's daily diet.