Water
The human body is two-thirds water. Water is an essential nutrient that is involved in every function of the body.

Water helps transport nutrients and waste products in and out of cells.
Water is necessary for all digestive, absorption, circulatory, and excretory functions
Water is needed for the utilization of the water-soluble vitamins.
It is needed for the maintenance of proper body temperature.
It is recommended that you drink at least eight 8-ounce glasses of water each day.

Carbohydrates are divided into two groups-simple carbohydrates and complex carbohydrates. Simple carbohydrates, sometimes called simple sugars, include fructose (fruit sugar), sucrose (table sugar), and lactose (milk sugar), as well as several other sugars. Fruits are one of the richest natural sources of simple carbohydrates. Complex carbohydrates are also made up of sugars, but the sugar molecules are strung together to form longer, more complex chains. Complex carbohydrates include fiber and starches. Foods rich in complex carbohydrates include vegetables, whole grains, peas, and beans.

Carbohydrates are the main source of blood glucose, which is a major fuel for all of the body's cells and the only source of energy for the brain and red blood cells. Except for fiber, which cannot be digested, both simple and complex carbohydrates are converted into glucose. The glucose is then either used directly to provide energy for the body, or stored in the liver for future use. When a person consumes more calories than the body is using, a portion of the carbohydrates consumed may also be stored in the body as fat.

When choosing carbohydrate-rich foods for your diet, always select unrefined foods such as fruits, vegetables, peas, beans, and whole-grain products, as opposed to refined, processed foods such as soft drinks, desserts, candy, and sugar. Refined foods offer few, if any, of the vitamins and minerals that are important to your health. In addition, if eaten in excess, especially over a period of many years, the large amounts of simple carbohydrates found in refined foods can lead to a number of disorders, including diabetes and hypoglycemia (low blood sugar). Yet another problem is that foods high in refined simple sugars often are also high in fats, which should be limited in a healthy diet. This is why such foods-which include most cookies and cakes, as well as many snack foods-are usually loaded with calories.

Dietary fiber is the part of a plant that is resistant to the body's digestive enzymes. Only a relatively small amount of fiber is digested or metabolized in the stomach or intestines. Most of it moves through the gastrointestinal tract and ends up in the stool.

Although most fiber is not digested, it delivers several important health benefits. First, fiber retains water, resulting in softer and bulkier stools that prevent constipation and hemorrhoids. A high-fiber diet also reduces the risk of colon cancer, perhaps by speeding the rate at which stool passes through the intestine and by keeping the digestive tract clean. In addition, fiber binds with certain substances that would normally result in the production of cholesterol, and eliminates these substances from the body. In this way, a high-fiber diet helps lower blood cholesterol levels, reducing the risk of heart disease.

It is recommended that about 60 percent of your total daily calories come from carbohydrates. If much of your diet consists of healthy complex carbohydrates, you should easily fulfill the recommended daily minimum of 25 grams of fiber.

When protein is consumed, the body breaks it down into amino acids, the building blocks of all proteins. Some of the amino acids are designated nonessential. This does not mean that they are unnecessary, but rather that they do not have to come from the diet because they can be synthesized by the body from other amino acids. Other amino acids are considered essential, meaning that the body cannot synthesize them, and therefore must obtain them from the diet.

Whenever the body makes a protein-when it builds muscle, for instance-it needs a variety of amino acids for the protein-making process. These amino acids may come from dietary protein or from the body's own pool of amino acids. If a shortage of amino acids becomes chronic, which can occur if the diet is deficient in essential amino acids, the building of protein in the body stops, and the body suffers.

Because of the importance of consuming proteins that provide all of the necessary amino acids, dietary proteins are considered to belong to two different groups, depending on the amino acids they provide. Complete proteins, which constitute the first group, contain ample amounts of all of the essential amino acids. These proteins are found in meat, fish, poultry, cheese, eggs, and milk. Incomplete proteins, which constitute the second group, contain only some of the essential amino acids. These proteins are found in a variety of foods, including grains, legumes, and leafy green vegetables.

Although it is important to consume the full range of amino acids, both essential and nonessential, it is not necessary to get them from meat, fish, poultry, and other complete-protein foods. In fact, because of their high fat content-as well as the use of antibiotics and other chemicals in the raising of poultry and cattle-most of those foods should be eaten in moderation. Fortunately, the dietary strategy called mutual supplementation enables you to combine partial-protein foods to make complementary protein-proteins that supply adequate amounts of all the essential amino acids. For instance, although beans and brown rice are both quite rich in protein, each lacks one or more of the necessary amino acids. However, when you combine beans and brown rice with each other, or when you combine either one with any of a number of protein-rich foods, you form a complete protein that is a high-quality substitute for meat. To make a complete protein, combine beans with any one of the following:

Yogurt is the only animal-derived complete-protein source recommended for frequent use in the diet. Made from milk that is curdled by bacteria, yogurt contains Lactobacillus acidophilus and other "friendly" bacteria needed for the digestion of foods and the prevention of many disorders, including candidiasis. Yogurt also contains vitamins A and D, and many of the B-complex vitamins.

Do not buy the sweetened, flavored yogurts that are sold in supermarkets. These products contain added sugar and, often, preservatives. Instead, either purchase fresh unsweetened yogurt from a health food store or make the yogurt yourself, and sweeten it with fruit juices and other wholesome ingredients.

Fats are composed of building blocks called fatty acids. There are three major categories of fatty acids-saturated, polyunsaturated, and monounsaturated. These classifications are based on the number of hydrogen atoms in the chemical structure of a given molecule of fatty acid.

Saturated fatty acids are found primarily in animal products, including dairy items, such as whole milk, cream, and cheese, and fatty meats like beef, veal, lamb, pork, and ham. The fat marbling you can see in beef and pork is composed of saturated fat. Some vegetable products including coconut oil, palm kernel oil, and vegetable shortening-are also high in saturates.

The liver uses saturated fats to manufacture cholesterol. Therefore, excessive dietary intake of saturated fats can significantly raise the blood cholesterol level, especially the level of low-density lipoproteins (LDLs), or "bad cholesterol. " Guidelines issued by the National Cholesterol Education Program (NCEP), and widely supported by most experts, recommend that the daily intake of saturated fats be kept below 10 percent of total caloric intake. However, for people who have severe problems with high blood cholesterol, even that level may be too high.

Polyunsaturated fatty acids are found in greatest abundance in corn, soybean, safflower, and sunflower oils. Certain fish oils are also high in polyunsaturated fats. Unlike the saturated fats, polyunsaturated fats may actually lower your total blood cholesterol level. In doing so, however, large amounts of polyunsaturated fats also have a tendency to reduce your high-density lipoproteins (HDLs)-your .good cholesterol." For this reason-and because, like all fats, polyunsaturated fats are high in calories for their weight and volume-the NCEP guidelines state that an individual's intake of polyunsaturated fats should not exceed 10 percent of total caloric intake.

Monounsaturated fatty acids are found mostly in vegetable and nut oils such as olive, peanut, and canola. These fats appear to reduce blood levels of LDLs without affecting HDLs in any way. However, this positive impact upon LDL cholesterol is relatively modest. The NCEP guidelines recommend that intake of monounsaturated fats be kept between 10 and 15 percent of total caloric intake.

Although most foods-including some plant-derived foods contain a combination of all three types of fatty acids, one of the types usually predominates. Thus, a fat or oil is considered 'saturated" or "high in saturates' when it is composed primarily of saturated fatty acids. Such saturated fats are usually solid at room temperature. Similarly, a fat or oil composed mostly of polyunsaturated fatty acids is called "polyunsaturated," while a fat or oil composed mostly of monounsaturated fatty acids is called "monounsaturated."

One other element, trans-fatty acids, may also play a role in blood cholesterol levels. Also called trans fats, these substances occur when polyunsaturated oils are altered through hydrogenation, a process used to harden liquid vegetable oils into solid foods like margarine and shortening. One recent study found that trans-monounsaturated fatty acids raise LDL cholesterol levels, behaving much like saturated fats. Simultaneously, the trans-fatty acids reduced HDL cholesterol readings. Much more research on this subject is necessary, as studies have not reached consistent and conclusive findings. For now, however, it is clear that if your goal is to lower cholesterol, polyunsaturated and mono-unsaturated fats are more desirable than saturated fats or products with trans-fatty acids. just as important, your total calories from fat should not constitute more than 20 to 25 percent of daily calories.