Nutrition

September 19, 2011

Nutrition is the sum of the processes involved in consuming food and assimilating and utilizing it. Nutrition is concerned with all the nutrients that are needed to build sound bodies and promote health such as proteins, fats, carbohydrates, vitamins, minerals, water, and fiber. Good nutrition provides the essential nutrients that the body needs to function normally and to have an optimum nutritional status.

Malnutrition is poor nutritional status resulting from dietary intakes either above or below the required range. Thus a person may be obese, but still be malnourished if he or she has poor stores of protein, iron, or vitamins. Malnutrition can result from poor food choices, fasting, starvation, poor absorption from the gastrointestinal tract, or interference with nutrient utilization by drugs, alcohol, or metabolic diseases.

Protein-energy malnutrition is the result of deficiencies of protein and energy. Fasting and starvation can lead to severe protein-energy malnutrition. This kind of malnutrition causes rapid weight loss and decreased resistance to infection. Anorexia nervosa, a self-induced aversion to food, is a unique type of malnutrition. People with anorexia nervosa take extreme measures to maintain a low body weight, including constant exercise. This disease can be fatal if not treated early.

Marasmus and kwashiorkor are diseases due to protein-energy malnutrition among children. These are widespread nutritional disorders in developing countries especially in children under 5. Marasmus is derived from the Greek word marasmos, meaning wasting or withering. Marasmus is due to the deficiency of protein and calories, while kwashiorkor is due to a deficiency of protein only. When children are weaned from mother’s milk and fed on a starchy low-protein diet, they develop kwashiorkor.

NUTRITIONAL NEEDS THROUGH THE LIFE CYCLE

Nutritional needs vary, depending on the body’s requirements at different stages of life. Growth is most rapid before birth, and therefore maternal nutrition is extremely important. Each stage of life has its own special requirements and meeting these needs is vital for a healthy life.

Nutrition in Infancy

Nutrition during the first year of life lays the foundation for future health, growth, and development. Growth during the first year of life is more rapid than at any other period of life beyond intrauterine life. Without adequate nutrients, signs of nutritional deficiency appear in infants much sooner than in any other age group. The consequences of malnutrition in infancy are more severe, delaying physical and mental development and resulting in learning disabilities.

During infancy, caloric needs per unit body weight exceed those of all other age groups. Infants require more calories because they are very active and have a greater surface area in proportion to their weight, resulting in greater heat loss. By the end of first year of age the birthweight has usually tripled. An intake of about 100 cal/kg is optimal. Intake of less than 80 cal/kg is usually inadequate and intake of more than 120 cal/kg leads to obesity.

Breast-feeding is the optimal way of providing food for infants. Human milk provides important immunologic protection. Breast-fed infants have a slower rate of weight gain than formula-fed infants and lower rates of obesity. Breast-fed infants do not require solid foods during the first 6 months of life. Cow’s milk should not be given until after the first birthday because it can cause intestinal bleeding. For optimal brain development, only whole milk should be used between the ages of 1 and 2.

Nutrition in Childhood and Adolescence

After the first year, the rate of growth slows and changes in body structure begin to occur. Much of the fat present during infancy is lost. Muscles become stronger and bones lengthen and increase in density. Children should participate in vigorous physical activity and establish healthy nutritional habits that will last into adulthood. Children should eat a variety of foods in three meals each day with healthy snacks between meals. Serving milk with all meals increases the protein intake. The nutrients most commonly deficient in childhood are calcium, vitamin C, thiamine, and riboflavin. Instead of soft drinks, candy, and other less nutritional snacks, offer cheese, yogurt, fruits, and raisins, which will supply these essential nutrients.

During adolescence, growth occurs in spurts. Calcium is very important because bone density increases. Adolescents require adequate calories to support their activity level and growth needs. A nutritious breakfast improves mental alertness and provides energy for physical activity until lunchtime.

Nutrition in Pregnancy and Breast-Feeding

A woman’s nutritional status prior to her pregnancy and during pregnancy influences the pregnancy outcome. Adequate weight gain is an important factor in ensuring a healthy pregnancy. Mothers with a weight gain of less than 15 lb are at a greater risk for delivering low-birthweight babies. Babies who weigh less than 5.5 lb have a higher rate of infant mortality and decreased resistance to infection. A normal weight gain for most women is 25-30 lb. Generally a woman should gain 2-4 lb during the first trimester and about 1 lb per week during the second and third trimesters.

The nutritional needs of pregnant women and nursing mothers are greater than in nonpregnant women. During the second and third trimesters, an extra 300 cal/day is required. Women use up an extra 500 cal/day during lactation, which can help breastfeeding mothers return to their prepregnancy weight. The growing baby needs a considerable amount of calcium to develop. If the mother does not take in enough calcium-rich foods, calcium from her bones is used instead. However, the mother’s bones are replenished after breast-feeding stops, and breast-feeding does not seem to increase the risk of osteoporosis. The need for folic acid doubles during pregnancy. Eating adequate amount of folic acid-rich foods during pregnancy and throughout the childbearing years reduces the chance of having a baby with birth defects of the brain and spinal cord known as neural tube defects (anencephaly and spina bifida). Excess vitamin or mineral intake during pregnancy can harm the fetus. Consult a physician before taking any supplements. Alcohol and cigarette smoking are known to cause low birthweight. Excessive caffeine may also impair the growth of the fetus. To maintain fluid balance and increase blood volume, salt intake should not be restricted during pregnancy unless there is a medical reason. Drugs taken by the nursing mother appear in the breast milk. Nursing mothers should exercise caution while nursing and consult with the physician before taking any medication.

Geriatric Nutrition

Physical, mental, and social factors affect the food habits of the elderly. Aging is characterized by a decline in the basal metabolic rate, which decreases by 2% per decade. The elderly are often less active, and as a result have reduced caloric requirements. Older people also need more calcium to prevent bone loss. When planning meals to meet the nutritional needs of elderly people, special attention should be paid to factors that affect their food intake. Since the sense of taste declines with age, plan for colorful and nutritionally dense foods.

SEE ALSO: Diet, Vitamins

Suggested Reading

  • American Council on Science and Health. (1982). Alcohol use during pregnancy: A report. Nutrition Today, 17, 29.
  • Bendich, A., & Deckelbaum, R. J. (Eds.). (2001). Preventive nutrition: The comprehensive guide for health professionals (2nd ed.). Totowa, NJ: Humana Press.
  • Elwood, T. W. (1975). Nutritional concerns of the elderly. Journal of Nutrition Education, 7, 50.
  • McWilliams, M. (1980). Nutrition for the growing years (3rd ed.). New York: Wiley.
  • Mitchell, M. K. (2003). Nutrition across the life span (2nd ed.). Philadelphia: W. B. Saunders.
  • Westcott, P. (2000). Diet and nutrition. Austin, TX: Raintree SteckVaughn.

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