Download Chapter 1 Summary

Chapter 1 Summary
The study of nutrition represents a wide spectrum of scientific disciplines. This is because what we eat
influences every physiological system in the body. The term nutrition refers to how the body uses
substances in food to promote and sustain life. Some nutrients must come from our foods; these are called
essential nutrients. Other nutrients—the non-essential nutrients—can be used by the body, but we can
make them when needed. When the body cannot make a typically nonessential nutrient in adequate
amounts, the nutrient is considered conditionally essential. Nutrients can also be classified as
macronutrients or micronutrients depending on the amount the body needs. Water, carbohydrates,
proteins, and lipids are macronutrients; vitamins and minerals are micronutrients. The term organic is
used by chemists to describe most substances that contain carbon, whereas “organic foods” are those that
are produced without using synthetic fertilizers, hormones, or other drugs. Phytochemicals and
zoonutrients are compounds found in plant and animal foods, respectively, that are not essential
nutrients but may improve health. Foods that contain phytochemicals essential nutrients, or zoonutrients
are called functional foods.
Carbohydrates, proteins, and lipids all provide energy and are referred to as energy-yielding nutrients.
Energy is defined as the capacity to perform work, and the energy found in foods is transformed to
usable energy (ATP) within the body. Carbohydrates, proteins, and lipids provide 4, 4, and 9 kcal per
gram, respectively. Macronutrients perform a variety of other functions in the body, including those
related to structure, movement, growth, and development. Water makes up about 60% of total body
weight and serves as the medium in which all chemical reactions occur, helps eliminate waste products,
regulates body temperature, and provides insulation and protection. Vitamins are classified as being
either water or lipid soluble and serve many purposes. Similarly, many essential minerals have specific
functions regarding structure, regulation, and energy use.
Most research is conducted using a three-step process called the scientific method. Scientific method
involves making an observation, generating an explanation (or hypothesis), and testing the explanation
by conducting a study. With each of these steps, several considerations must be made. For example, one
must be careful that the observation is valid, the hypothesis should be well grounded in scientific
evidence or theory, and the study should be appropriate for the hypothesis. Epidemiologic studies are
conducted to investigate associations or correlations, whereas intervention studies can test causal
relationships. Scientists use many techniques to decrease bias in studies. These include randomization,
control groups, placebos, and blinding. Sometimes it is not possible or practical to test a hypothesis using
humans as participants. In these cases, researchers turn to animal models or cell cultures.
When it comes to nutrition claims, separating fact from fiction can be difficult. However, by doing some
investigative work, it is possible to largely determine the validity of any nutrition claim. Publication in a
peer-reviewed journal indicates the information is probably reliable, and most reputable research is
conducted by people affiliated with a research university or health-related agency. Although most
research is not influenced by the source of funding, consider whether the funding agency might have
biased the conclusions made by the investigators. Also, it is important to consider whether the design of
the study was appropriate and whether major public health groups support the study conclusions.
Nutrition is an important factor in assuring optimal health. Over the past century, the primary public
health concerns have shifted from infectious disease and nutritional deficiencies to chronic disease and
overnutrition. These shifts are reflected in morbidity and mortality rates of various diseases as well as life
expectancy. Whereas infant mortality rates and mortality from infectious disease have decreased, life
expectancy has increased. This “graying of America” has been accompanied by a phenomenon called the
nutrition transition, which is the shift from undernutrition to overnutrition or unbalanced nutrition as a
society becomes more industrialized. The National Health and Nutrition Examination Surveys
(NHANES) are a series of federally funded, epidemiologic studies begun in the 1970s and designed to
collect information related to nutrition and health in the United States. Many studies suggest that poor
dietary practices are associated with a growing prevalence of chronic disease. Thus understanding the
relationship between diet and health has never been more important.