Frequently Asked Questions
Chapter 35: Nutrition

What is the difference between fat-soluble and water-soluble vitamins?

Fat-soluble vitamins (vitamins A, D, E, and K) are stored in the body in fat cells. They can accumulate and become toxic. Water-soluble vitamins (vitamin C and the B-complex vitamins) are not stored at all. If not used, they are excreted through the urine.

What are the purposes of vitamins A, D, E, and K, and how is the body affected when they are deficient?

Vitamin A is an antioxidant that is also involved in the formation of epithelial tissue, retinal pigmentation, and the immune system. Vitamin A deficiencies can cause skin problems, night blindness, and increased risk for infections and cancer. Vitamin D is responsible for bone and tooth development and may enhance immune function in the elderly. Vitamin D deficiencies can cause rickets and delayed dentition in children and osteomalacia in adults. Vitamin E is an antioxidant that is necessary for the formation of red blood cells and the utilization of vitamin K. Vitamin E deficiencies can cause anemias or destruction to nerves. Vitamin K is responsible for the formation of prothrombin and blood clotting, bone formation and repair, and the synthesis of osteocalcin. Vitamin K deficiencies include hemorrhage and osteoporosis.

What are the purposes of vitamin C and the B-complex vitamins, and how is the body affected when they are deficient?

Vitamin C is responsible for capillary wall integrity, the metabolism of amino acids, and the prevention of oxidation of other vitamins. Vitamin C deficiencies result in bleeding gums, bruising, poor healing, retardation of bone growth, fragile blood vessel walls, and gum lesions. “Scurvy” is the vitamin C deficiency characterized by poor wound healing, retardation of bone growth, fragile blood vessel walls, and gum lesions. B-complex vitamins are generally involved in metabolism and energy metabolism. B-complex vitamin deficiencies result in neurological problems (deficiencies of thiamine, niacin, riboflavin, vitamin B12, vitamin B6), gastrointestinal disturbances (deficiencies of thiamine, niacin, riboflavin, vitamin B6), or skin disorders (deficiencies of niacin, vitamin B6). The GI disturbance known as “beriberi” is caused by a deficiency of thiamin. The irritation of the GI tract known as “pellagra” is caused by a deficiency of niacin.

What are the functions of minerals in the diet?

Several minerals are crucial for metabolism. For example, copper and iron are needed for hemoglobin formation. Copper is also involved in the synthesis of certain fats and enzymes. Iron is also needed for the synthesis of vitamins, purines, and antibodies. Fluoride is needed for teeth formation and the prevention of dental caries. Iodine is the primary component of the thyroid hormones. Selenium is necessary for vitamin E formation and the immune system. Zinc is important for wound healing, connective tissue integrity, the formation of enzymes and insulin.

How are the purposes of carbohydrates, fats, and proteins similar, and how are they different?

Carbohydrates are the body’s major source of energy. They are also “protein-sparing,” meaning that, when adequate amounts are available, protein does not need to be metabolized. Proteins are responsible for growth and replacement; immunity; and fluid, electrolyte, and acid-base balance. They are also a source of energy. Fats are likewise a source of energy. They also are responsible for cell membrane integrity; the absorption of fat-soluble vitamins; the maintenance of body temperature; and the synthesis of bile salts, steroid hormones, and vitamin D.

What is the process of protein metabolism?

Proteins are made up of amino acids, which are used for anabolism (building up) and repair. Surplus amino acids are processed in the liver, where they are degraded into nitrogen and other particles and used for energy or converted to glycogen (a carbohydrate) or adipose tissue.

What are obesity and overweight, and why are they becoming a public health problem in the United States?

Obesity is defined as a Body Mass Index (BMI, a predictor of chronic disease based on the relationship of weight to height) of >30; overweight is defined as a BMI of 25 to 30. Obesity is becoming a problem in the United States due to the abundance of food; the easy of availability of food in convenience stores, fast-food restaurants, and vending machines; larger portion size; emotional stress; and technological advances that limit calories expended.

How do the purposes of various diet therapies differ?

The Nothing by Mouth (NPO) status is used to rest the GI track, particularly prior to surgery or diagnostic tests or after surgery to prevent diarrhea and vomiting. The clear-liquid diet is used post-operatively to prevent residue in the GI tract. A liquid or full-liquid diet is used to provide more nutrients and calories as a person on a clear-liquid diet progresses to solid fluid. A soft diet is used when a client has difficulty chewing and swallowing or has a condition that results in impaired digestion or absorption. A variation of this diet, the mechanical soft diet, is used for people who cannot chew thoroughly. A pureed diet is prescribed for clients who have difficulty swallowing. A low-residue diet has reduced fiber and cellulose to prevent GI irritation for clients who have such conditions as diverticulitis, ulcerative colitis, and Crohn’s disease. A high-fiber diet is used for diverticulosis because the bulk in the diet pushes wastes forward more efficiently. A liberal bland diet eliminates irritants, such as fried foods, alcohol, and caffeine, to reduce GI irritation in clients with gastritis and ulcers. A fat-controlled diet eliminates fats or controls the type of fat a client takes in, to reduce atherosclerosis and heart disease and to control obesity. The sodium-restricted diet is used to treat clients with excess fluid volume, heart problems, hypertension, and kidney problems. The lactose intolerance diet controls the amount of lactose (the sugar found in milk) for those who are allergic to it. A lactose intolerance diet eliminates milk products, with the exception of yogurt.