Chapter 2
DIET AND NUTRITION

“There is only one good, knowledge,” Socrates once said, “and one evil, ignorance.” His observation is certainly true about nutrition because the nutrients we consume–or do not consume–each day help determine our health, our risk of developing chronic diseases, and even our life span.

While these claims may seem extreme, they are, in fact, the conclusions of the largest research effort ever conducted on the ways nutrition directly affects health. For four years, U.S. nutrition experts in the federal government, aided by hundreds of colleagues in universities, professional schools, industries, communities, and state and local government agencies, examined the results of more than 2,500 scientific studies in order to determine the links between diet and disease. Their conclusions were released in 1988 in the first Surgeon General's Report on Nutrition and Health

What we eat may affect our risk for several of the leading causes of death for Americans, notably coronary heart disease, stroke, atherosclerosis, diabetes, and some types of cancer. These disorders together now account for more than two-thirds of all deaths in the United States.

“The Report's main conclusion is that overconsumption of certain dietary components is now a major concern for Americans. While many food factors are involved, chief among them is the disproportionate consumption of foods high in fats, often at the expense of foods high in complex carbohydrates and fiber that may be more conducive to health.”

This chapter details the key recommendations contained in the Surgeon General's Report and summarizes dietary guidelines subsequently issued by four respected U.S. agencies. It also explains how to administer a personal nutritional assessment in order to monitor intelligently a healthy diet as well as daily food and nutrient intake. The central component of this assessment is a food diary that encourages taking an active role in achieving dietary goals.

Everyone knows that the human body is a complex organism that needs certain essential chemical constituents to stay alive. The body cannot produce most of these chemicals itself, however, and must get them from the environment. For example, 60% of the human body is composed of water. Thus it needs a continual supply of fresh water to continue functioning. Otherwise it becomes dehydrated and eventually dies.

Water, however, cannot supply all the chemicals the body needs to grow and rejuvenate itself. The other essential chemicals must be provided by nutrients contained in foods. It is this combination and amounts of foods eaten that constitutes nutrition.

Nutrition is the most important factor in human life and health. In less developed parts of the world too many people do not get enough food or water, and become ill or die as a result. Shortages of water due to droughts cause many deaths annually as do scarcities of food due to famines, poverty, and other adverse circumstances.

The absence of food or water deprives the body of one or several essential nutrients. The absence of a particular essential nutrient in the body is called a nutritional deficiency, while diseases that are caused by a specific nutrient deficiency are called nutritional deficiency diseases. If the body contains too little iron, for example, it is said to have an iron deficiency, and one result is that the body will not produce enough red blood cells. Without adequate red blood cells, a person becomes weak and lacks energy, resulting in an iron deficiency disease called anemia.

Nutritional deficiencies are common in less developed parts of the world, where finding enough essential foods is a daily struggle. In developed countries such as the United States, on the other hand, most people can easily supply themselves with all of the essential foods they need to live long, healthy lives. In the United States, this is accomplished at a grocery or health food store. The challenge lies in deciding which foods to eat and in what amounts.

Because of the complexities of the human body as a biochemical organism, scientists still do not know all of the nutritional chemical factors that contribute to optimal health. For one thing, every person's body is different–it is composed of a chemical structure of atoms and molecules. Even identical twins do not have the same exact proportion of atoms and molecules in their bodies. In addition, every person's body continually changes as chemical constituents are utilized and replaced.

Nevertheless, scientists have learned that although each body does vary to some degree, everyone needs five basic types of chemical substances in addition to water: proteins, carbohydrates, lipids (fats), vitamins, and minerals. How much of these substances people require depends on their age, sex, heredity (their unique genetic structure), amount of exercise, and the amount of toxins (poisons) that exist in the body. Proteins, most carbohydrates, and fats contained in foods are too large to be absorbed directly into the body. They must first be metabolized (broken down) into smaller chemical constituents before they can be utilized. Vitamins and minerals (see Chapters 3 and 4) do not need to be broken down and can be directly absorbed.

When a person eats a piece of meat, for example, it must first be ground down by the teeth and mixed with saliva into smaller particles which can then enter the gastrointestinal tract. These particles eventually reach the stomach and intestines where they are further broken down into proteins and fat and absorbed directly into the blood. The elements of the meat which are not absorbed into the blood are later eliminated through the colon.

Each person's digestive system breaks down proteins, carbohydrates, and fats at slightly different rates. Some people eat faster than others and also eat differing amounts of these substances. Also, everyone's body metabolizes foods at a different rate (their metabolic rate). What people consume and the speed and efficiency by which their bodies convert the food they eat into needed chemicals (proteins, carbohydrates, fats, vitamins, and minerals) largely determines their energy levels and the overall state of their health.