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.

Kinds of vitamins

The 13 vitamins are vitamins A; B complex, which is actually a group of 8 vitamins; and C, D, E, and K. Scientists divide vitamins into two general groups, fat-soluble vitamins and water-soluble vitamins. The fat-soluble vitamins--vitamins A, D, E, and K--dissolve in fats. The water-soluble vitamins--the B-complex vitamins and vitamin C--dissolve in water.

Vitamin A

Vitamin A, also known as retinol, occurs naturally only in animals. Eggs, liver, and milk provide much vitamin A. Some plants contain substances called carotenes, or provitamins A, which the body converts into vitamin A. These plants include cantaloupes, carrots, sweet potatoes, dark green leafy vegetables, and deep yellow vegetables.

Vitamin A is essential for the development of babies before birth and the growth of children. It is especially needed for the growth of bones and teeth. Vitamin A keeps the skin healthy and helps produce mucous secretions that build resistance to infection. People who do not get enough vitamin A may develop xerophthalmia, in which the surface of the eye becomes dry and likely to develop infection. Vitamin A also forms part of the two pigments that help the eyes to function normally in light that varies in intensity. Night blindness is an early symptom of a deficiency of vitamin A.

Geriatrics

The branch of medicine dealing with the study of aging, old age, and its diseases. Ex. In contrast to pediatrics which is concerned with the very young, geriatrics is the clinical application of knowledge to aging men and women toward maintaining their health and in treating their peculiar illnesses

Casein

Casein is the chief protein in milk. It is also the main ingredient in cheese. Casein separates as curd when milk sours, or when acid is added. It also separates from sweet milk when the enzyme rennin is added. Casein contains carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Pure casein is a tasteless, odorless, white solid. Cow milk contains about 3 per cent casein.

Casein is produced commercially from skim milk. The curd is washed, dried, and ground. Commercially prepared casein is pale yellow and has a pleasant odor. It is widely used in medicines, cosmetics, and as a sizing (coating) for paper. Casein is also used in waterproof glues, casein paints, and certain plastic articles such as buttons.

Lactose

Lactose, also called milk sugar, makes up about 5 per cent of cow's milk. A molecule of lactose consists of a molecule of glucose and a molecule of galactose. Maltose, or malt sugar, remains after the brewing process. It is used to flavor some candy. A molecule of maltose consists of two molecules of glucose.

Triglyceride

Triglyceride is one of the major fatty substances in the blood. Another is cholesterol. High blood levels of triglycerides are often associated with high cholesterol levels, which are a primary cause of heart disease. An extremely high level of triglycerides in the blood also increases the risk of pancreatitis (inflammation of the pancreas).

Each triglyceride molecule consists of one molecule of glycerol combined with three molecules of fatty acids. Triglycerides are consumed in food. During digestion, they break down into separate molecules of fatty acids and glycerol. These molecules may be used by cells for energy, or they may be recombined into triglycerides and stored as fat for later use.

In adults, a triglyceride level of less than 200 milligrams per deciliter of blood is considered desirable. Higher triglyceride levels are often associated with an increased risk of heart disease. People who have triglyceride levels of more than 1,000 milligrams per deciliter are at high risk of pancreatitis.

Several factors lead to elevated triglyceride levels. They include alcohol, stress, weight gain, certain medications, and a diet high in carbohydrates. People can lower their triglyceride levels by reducing the amount of calories and fat in their diet and by exercising regularly.

Cholesterol

It is a fatty substance found in animal tissues. The human body produces cholesterol, but this substance also enters the body in food. Meats, egg yolks, and milk products, such as butter and cheese, contain cholesterol. Such organs as the brain and liver contain much cholesterol.

Cholesterol is a type of lipid, one of the classes of chemical compounds essential to human health (see LIPID). Cholesterol makes up an important part of the membranes of each cell in the body. In addition, the liver uses cholesterol to make bile acids, which aid digestion. The body also uses cholesterol to produce vitamin D and certain hormones, including sex hormones.

Cholesterol and triglycerides, another lipid, are two of the major fatty substances in the blood. Triglycerides may be used by cells for energy, or they may be stored for later use. Doctors often measure the amount of cholesterol and triglycerides in blood to help determine a patient's overall health. High levels of cholesterol, particularly if accompanied by high levels of triglycerides, increase the risk of heart disease.

Both cholesterol and triglycerides are carried through the bloodstream in large molecules called lipoproteins. There are two chief types of cholesterol-carrying lipoproteins, low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Cholesterol in blood can thus be identified as either LDL-cholesterol or HDL-cholesterol, depending on which lipoprotein carries it. High levels of LDL-cholesterol in blood are a primary cause of heart attacks. LDL can be found in the wall of heart arteries. Low levels of HDL-cholesterol also increase the risk of heart attack. Some scientists believe that HDLs help remove cholesterol from tissues.

Factors that cause high cholesterol levels.
The amount of cholesterol in the human body is controlled by cellular molecules that are called LDL-receptors. These molecules allow LDL-cholesterol to attach to and be used by the cell. LDL-cholesterol accumulates in blood in large amounts when the LDL-cholesterol in the body far exceeds the number of available LDL-receptors. This condition most commonly occurs in people whose diets are high in cholesterol or in saturated fats. Saturated fats are found primarily in animal fats and in certain vegetable fats, such as coconut oil and palm oil.

People also may have high cholesterol levels if they have an abnormal gene that prevents a full number of LDL-receptors from forming. This inherited disorder is called familial hypercholesterolemia. Other factors that can cause high blood cholesterol include a malfunctioning thyroid gland, kidney disease, diabetes, and the use of various medicines, including certain diuretics.

Cholesterol and heart disease.
In adults, a cholesterol level of less than 200 milligrams per 1 deciliter (3 ounces) of blood is considered desirable. Above that level, the risk of heart disease increases dramatically. Adults also are at an above-average risk of heart disease if they have an LDL-cholesterol level of more than 160 milligrams per deciliter of blood or an HDL-cholesterol level of less than 35 milligrams per deciliter.

Besides cholesterol levels, other factors increase the risk of heart disease. These factors include cigarette smoking, high blood pressure, diabetes, a family history of premature heart disease, and being a male over 44 years of age or a female over 54. Individuals with two or more of these factors have high risk of heart attack, particularly if they also have atherosclerosis (narrowing of the arteries because of fatty deposits).

Treatment of high blood cholesterol consists of first reducing the amount of saturated fat and cholesterol in the diet. Poultry and fish are low in cholesterol. Cereals, fresh fruit, and vegetables contain no cholesterol. Regular aerobic exercise--such as bicycling, running, and swimming--can further lower the cholesterol level. Medication should be considered only for people who are at high risk of heart disease and who have been unable to control their cholesterol with diet. Medications shown to reduce cholesterol levels and the risk of heart disease include cholestyramine, colestipol, gemfibrozil, lovastatin, and niacin.

Clinical research trials have indicated that lowering the amount of cholesterol in the blood can reduce the risk of heart attack in middle-aged men who had no history of heart disease. In men and women with atherosclerosis, reducing cholesterol in blood prevents further narrowing of the heart arteries.

lipid

Lipid is one of a large group of oily or fatty substances essential for good health. Lipids, carbohydrates, and proteins are the classes of compounds in all living things. Animal fats and plant oils are lipids. So are animal sex hormones and vitamins A, D, E, and K. Egg yolks, liver, and embryos of grains are rich in lipids.

Importance of lipids.
Lipids are vital to animals and plants in many ways. They are a concentrated source of food energy and yield about twice as many calories as an equal weight of protein or carbohydrate. Many kinds of organisms store food in lipid form. For example, the seeds of many plants contain lipids as food reserves for their embryos. The bone marrow, tissues beneath the skin and in the intestines, and tissue surrounding body organs in animals consist mostly of stored lipids.

Certain lipids form an essential part of the membranes that enclose and protect every living cell. Similar membranes surround all bodies within the cell, so that each cell body can do its job without unwanted interference from other cell bodies. Lipids repel water, but they are valuable solvents (dissolving substances) for vitamins A, D, E, and K, which do not dissolve in water.

Kinds of lipids.
Lipids are classified as simple lipids or complex lipids, according to their structure.

Simple lipids contain only carbon, hydrogen, and oxygen. They consist of an alcohol in combination with certain organic acids containing a variable number of carbon atoms. A molecule of triglyceride (fat), the most common type of simple lipid, contains one molecule of an alcohol called glycerol and three molecules of fatty acid (a kind of organic acid). Fats include butter, lard (pig fat), tallow (beef or mutton fat), blubber (whale fat), castor oil, coconut oil, and olive oil. Waxes, another common group of simple lipids, contain an alcohol molecule that is larger than the glycerol molecule.

Complex lipids have a more complicated structure than simple lipids. They include phospholipids (lipids that contain phosphorus), steroids (lipids made up of four rings of carbon atoms joined together), and other compounds such as glycolipids (lipids with one or more sugar molecules), fat-soluble vitamins (vitamins A, D, E, and K), and terpenes (yellow pigments like carotene).

Phospholipids are found in all bacteria, and in the cells of all plants and animals. They are most plentiful in sperm, eggs, embryos, and brain cells. A molecule of phospholipid contains a molecule of glycerol, a phosphate ion, and two molecules of fatty acid. Most phospholipids also have a nitrogen compound. Some contain inositol, a substance found in vitamin B complex.

Steroids make up an important part of living things. Many animal hormones, including the sex hormones and those produced by the cortex (outer part) of the adrenal glands, are steroids. Cholesterol, a substance found in the membranes of animal cells, is a steroid. Yeasts and other fungi and the seeds of higher plants also contain steroids.