Introduction
University of Hawai‘i at Mānoa Food Science and Human Nutrition Program and Human Nutrition Program
ʻO ke kahua ma mua, ma hope ke kūkulu
The foundation comes first, then the building
Learning Objectives
By the end of this chapter, you will be able to:
- Describe basic concepts in nutrition
- Describe factors that affect your nutritional needs
- Describe the importance of research and scientific methods to understanding nutrition
What are Nutrients?
The foods we eat contain nutrients. Nutrients are substances required by the body to perform its basic functions. Nutrients must be obtained from our diet, since the human body does not synthesize or produce them. Nutrients have one or more of three basic functions: they provide , contribute to body structure, and/or regulate chemical processes in the body. These basic functions allow us to detect and respond to environmental surroundings, move, excrete wastes, respire (breathe), grow, and reproduce. There are six classes of nutrients required for the body to function and maintain overall health. These are , , proteins, , vitamins, and . Foods also contain non-nutrients that may be harmful (such as natural toxins common in plant foods and additives like some dyes and preservatives) or beneficial (such as antioxidants).
Macronutrients
Nutrients that are needed in large amounts are called macronutrients. There are three classes of macronutrients: carbohydrates, lipids, and proteins. These can be metabolically processed into cellular energy. The energy from macronutrients comes from their chemical bonds. This chemical energy is converted into cellular energy that is then utilized to perform work, allowing our bodies to conduct their basic functions. A unit of measurement of food energy is the . On food labels the amount given for “calories” is actually equivalent to each calorie multiplied by one thousand. A (one thousand calories, denoted with a small “c”) is synonymous with the “Calorie” (with a capital “C”) on nutrition food labels. Water is also a in the sense that you require a large amount of it, but unlike the other macronutrients, it does not yield calories.
Carbohydrates
Carbohydrates are molecules composed of carbon, hydrogen, and oxygen. The major food sources of carbohydrates are grains, milk, fruits, and starchy vegetables, like potatoes. Non-starchy vegetables also contain carbohydrates, but in lesser quantities. Carbohydrates are broadly classified into two forms based on their chemical structure: , often called simple sugars; and .
Simple carbohydrates consist of one or two basic units. Examples of simple sugars include , the type of sugar you would have in a bowl on the breakfast table, and glucose, the type of sugar that circulates in your blood.
Complex carbohydrates are long chains of simple sugars that can be unbranched or branched. During digestion, the body breaks down digestible complex carbohydrates to simple sugars, mostly glucose. Glucose is then transported to all