Human Nutrition
The
Community and Nutrition Programs
Connections between nutrition and health have probably been understood, at least to some degree, among all people of all places and times. For example, around 400 BC Hippocrates said, "Let food be your medicine and medicine be your food." Understanding the physiological needs of our cells helps us understand why food has such an impact on overall health. In this chapter we introduce nutrition by examining how cells use different nutrients and then discuss disease conditions that are tied to nutritional problems.
Nutrition and Health in the Community
The nutritional status of people in our communities is a concern not only for quality of life, but also for economics (treating illness costs far more than preventing it). Various public health agencies are striving to prevent nutritional deficiencies and improve overall health. In the U.S., the government supplies a variety of resources such as state assistance, WIC (Women Infant and Child), and so forth. In addition, there have been many government agencies and voluntary health and scientific associations, such as the American Heart Association, that focus on life style and dietary factors that prevent chronic and life-threatening diseases. The U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (USDHHS) developed dietary guidelines in 1977 that were compiled and displayed as the food guide pyramid. The food guide pyramid was revised as "My Pyramid," but this new chart is confusing to most people. Harvard School of Public Health developed an alternative healthy eating pyramid (shown at left) based on long-term nutritional studies. This pyramid differs from the old USDA pyramid in several key aspects: for example, exercise is at the bottom to remind us of its important role in our health. Also, not all carbohydrates are at the bottom (white bread, white rice, and potatoes are now at the top with sugars), and not all oils are at the top (plant oils are at the bottom). Other resource, such as the Recommended Daily Allowance (RDA) have helped people become more aware of nutritional needs, yet obesity and chronic health problems continue to rise.Nutritional Requirements
Our bodies have both caloric and nutritional needs. Living tissue is kept alive by the expenditure of energy in ATP molecules, which energy came from the break down of food molecules. Caloric need refers to the energy needed each day to carry out the varied chemical reactions in each cell. When looking at a nutritional label, we can easily see how many Calories are in a serving. These Calories (big "C") are actually kilocalories (1000 calories). Technically, a calorie (little "c") is the amount of energy needed to raise the temperature of 1 mL of water by 1 °C. How many Calories a person needs daily varies greatly by age, sex, height, and physical activity levels. If the amount of energy taken in exceeds the amount of energy used, then the excess energy is stored as adipose tissue (fat), regardless of the source of the energy.In addition to daily energy needs, there are nutritional needs to prevent the body from losing its own fats, carbohydrates, and proteins. Such molecules are continuously broken down, and must be replaced regularly. Essential amino acids and essential fatty acids are particularly important building blocks in replacing these molecules. Vitamins and minerals are not used as energy, but are essential in tissue and enzyme structure or reactions.
