Chapter 070. Nutritional Requirements and Dietary Assessment (Part 5)

Physiologic Factors Growth, strenuous physical activity, pregnancy, and lactation increase needs for energy and several essential nutrients, including water. Energy needs rise during pregnancy, due to the demands of fetal growth, and during lactation, because of the increased energy required for milk production. Energy needs decrease with loss of lean body mass, the major determinant of REE. Because both health and physical activity tend to decline with age, energy needs in older persons, especially those over 70, tend to be less than those of younger persons.Dietary CompositionDietary composition affects the biologic availability and utilization of nutrients. ...
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Chapter 070. Nutritional Requirements and Dietary Assessment (Part 5) Chapter 070. Nutritional Requirements and Dietary Assessment (Part 5) Physiologic Factors Growth, strenuous physical activity, pregnancy, and lactation increaseneeds for energy and several essential nutrients, including water. Energy needsrise during pregnancy, due to the demands of fetal growth, and during lactation,because of the increased energy required for milk production. Energy needsdecrease with loss of lean body mass, the major determinant of REE. Because bothhealth and physical activity tend to decline with age, energy needs in olderpersons, especially those over 70, tend to be less than those of younger persons. Dietary Composition Dietary composition affects the biologic availability and utilization ofnutrients. For example, the absorption of iron may be impaired by high amounts ofcalcium or lead; non-heme iron uptake may be impaired by the lack of ascorbicacid and amino acids in the meal. Protein utilization by the body may be decreasedwhen essential amino acids are not present in sufficient amounts. Animal foods,such as milk, eggs, and meat, have high biologic values with most of the neededamino acids present in adequate amounts. Plant proteins in corn (maize), soy, andwheat have lower biologic values and must be combined with other plant oranimal proteins to achieve optimal utilization by the body. Route of Administration The RDAs apply only to oral intakes. When nutrients are administeredparenterally, similar values can sometimes be used for amino acids, carbohydrates,fats, sodium, chloride, potassium, and most of the vitamins, since their intestinalabsorption is nearly 100%. However, the oral bioavailability of most mineralelements may be only half that obtained by parenteral administration. For somenutrients that are not readily stored in the body, or cannot be stored in largeamounts, timing of administration may also be important. For example, aminoacids cannot be used for protein synthesis if they are not supplied together; insteadthey will be used for energy production. Disease Specific dietary deficiency diseases include protein-calorie malnutrition;iron, iodine, and vitamin A deficiency; megaloblastic anemia due to vitamin B 12 orfolic acid deficiency; vitamin D–deficiency rickets; scurvy due to lack of ascorbicacid; beriberi due to lack of thiamine; and pellagra due to lack of niacin andprotein (Chaps. 71 and 72). Each deficiency disease is characterized byimbalances at the cellular level between the supply of nutrients or energy and thebodys nutritional needs for growth, maintenance, and other functions. Imbalancesin nutrient intakes are recognized as risk factors for certain chronic degenerativediseases, such as saturated and trans-fat and cholesterol in coronary artery disease;sodium in hypertension; obesity in hormone-dependent endometrial and breastcancers; and ethanol in alcoholism. However, the etiology and pathogenesis ofthese disorders are multifactorial, and diet is only one of many risk factors.Osteoporosis, for example, is associated with calcium deficiency as well as riskfactors related to environment (e.g., smoking, sedentary lifestyle), physiology(e.g., estrogen deficiency), genetic determinants (e.g., defects in collagenmetabolism), and drug use (chronic steroids) (Chap. 348). Dietary Assessment In clinical situations, nutritional assessment is an iterative process thatinvolves (1) screening for malnutrition; (2) assessing food and dietary supplementintake, and establishing the absence or presence of malnutrition and its possiblecauses; and (3) planning for the most appropriate nutritional therapy. Some diseasestates affect the bioavailability, requirements, utilization, or excretion of specificnutrients. In these circumstances, specific measurements of various nutrients maybe required to ensure adequate replacement (Chap. 72). Most health care facilities have a nutrition screening process in place foridentifying possible malnutrition after hospital admission. Nutritional screening isrequired by the Joint Commission on Accreditation of Healthcare Organizations(JCAHO), but there are no universally recognized or validated standards. Thefactors that are usually assessed include abnormal weight for height or body massindex (e.g., BMI 25); reported weight change (involuntary loss or gainof >5 kg in the past 6 months) (Chap. 41); diagnoses with known nutritionalimplications (metabolic disease, any disease affecting the gastrointestinal tract,alcoholism, and others); present therapeutic dietary prescription; chronic poorappetite; presence of chewing and swallowing problems or major foodintolerances; need for assistance with preparing or shopping for food, eating, orother aspects of self care; and social isolation. Reassessment of nutrition statusshould occur periodically in hospitalized patients—at least once every week. A more complete dietary assessment is indicated for patients who exhibit ahigh risk of malnutrition based on nutrition screening. The type of assessmentvaries with the clinical setting, severity of the patients illness, and stability of hisor her condition.