Nutritional needs for reproduction and growth

Nutritional needs for reproduction and growth – Children’s Nutrition Research Center

The Children’s Nutrition Research Center at Baylor University in Texas is devoted to enhancing our knowledge of the nutritional requirements of infants and children. The highlights of their 1991 annual report include the following.

Protein: Using experimental techniques that involve feeding foods in which various nutrients have been isotopically labeled during growth, CNRC scientists have demonstrated that some amino acids are not synthesized (essential amino acids), are synthesized (non-essential amino acids) or are synthesized only in limited amounts under certain metabolic conditions even although the appropriate metabolic pathways exist (conditionally essential), making it more difficult to develop accurate dietary recommendations. By labeling foods during growth with both carbon and nitrogen, researchers will be able to trace intact food nutrients during absorption and catabolism to understand human nutrient requirements more thoroughly.

Lipids: Endogenous cholesterol synthesis in breast-fed infants who normally consume 120 mg of cholesterol was compared to that of bottle-fed infants who receive no cholesterol using labeled deuterium oxide and labeled water. Although the level of serum cholesterol, triglycerides and apolipoprotein B-100 were greater in breast-fed infants, cholesterol synthesis apparently regulated by a reduction in HMG-CoA reductase was significantly lower. Approximately 3 to 4 mg/kg/d of the 20 mg/kg/d is used for growth and the rest is esterified and stored in the liver, blood and adipose tissue. Once infants are weaned, the high serum cholesterol levels return to normal. By 2 years of age serum cholesterol levels in breast- and formula-fed infants are similar.

Studies on cholesterol metabolism in genetically lean and obese rats showed that cholesterol levels of genetically lean animals that had received 0.5% cholesterol from birth were significantly lower than those of animals receiving no cholesterol from birth. In genetically obese animals those who received cholesterol from birth had higher plasma cholesterol levels. This confirmed the Reiser hypothesis that the consumption of milk cholesterol in infants has a protective effect on plasma cholesterol levels in adulthood in lean but not obese animals.

Energy Expenditure: The energy intake and expenditure of 40 breast- and formula-fed infants were measured at 1 and 4 months of age. Energy intake was measured by 5-day test weighings in combination with bomb calorimeter measurements of the milk. Total daily energy expenditure (TDEE) was determined by using double-labeled water, sleeping metabolic rate (SMR) and minimal observable energy expenditure by indirect calorimetry and activity by the difference between SMR and TDEE. Energy deposition was measured by the difference between energy intake and TDEE. Energy intakes and TDEE were significantly higher among formula-fed infants than among breast-fed infants as were SMR and minimal observable energy expenditure. Rates of weight gain (g/d) and energy deposition (kcal/kg/d) were also greater in formula-fed infants. The response to the varying levels of energy intake in infancy appear to be mediated through growth- and energy-requiring processes but not through physical activity. (Pediatr Res 1992:28:631-41)

Calcium: A 30% increase in the calcium and phosphorus content of parenteral solutions fed for 24 days to low birth weight infants born at 28 weeks gestation resulted in no increase in urinary calcium compared to that of infants receiving the standard parenteral preparation. The net retention of calcium and phosphorus resulted in an enhanced bone mineral content that persisted beyond the period of parenteral nutrition. Other studies of the pattern of accretion of bone mineral in infants confirm older published data that two-thirds of the 30 g of calcium in the skeleton of a full-term infant are deposited in the last 8 weeks of pregnancy.

Effect of Cereal Intake on Cereal Absorption: Eight 1-month-old bottle-fed infants were fed 4 g of [.sup.13C]-labeled rice cereal per 30 ml of formula for 6 days. Cereal absorption was 88%. The significant increase in energy and nitrogen intake was accompanied with a decrease in the coefficient of absorption from 97 to 90% for energy and from 94 to 74% for nitrogen. Fecal weight was increased due to a 7-fold increase in bacterial mass. Fecal nitrogen also increased due to incorporation of nitrogen into bacteria. (J Pediatr 1991;118:39-43).

NEWS FROM THE NATIONAL HEART, LUNG AND BLOOD INSTITUTE

The NHLBI announces the formation of an Obesity Education Initiative (OEI) designed to educate professionals and the public on the relationship of weight and heart disease and weight and lung function. Each involves a two-pronged strategy–one directed to the high-risk population and the other a population-based strategy. The high-risk strategy focuses on the relationship of obesity to high serum triglycerides, increased LDL-cholesterol, and total cholesterol, decreased HDL-cholesterol, high blood pressure and non-insulin-dependent diabetes mellitus, all of which are related to high abdominal fat. It favors sustained negative energy balance, for which habitual activity is key, and stresses the concept that obesity should be treated as a chronic disease for which it is important to develop a consensus on treatment. In the population approach the focus is on preventing obesity on the theory that treatment may be too late in a situation where there is a linear relationship between weight and the relative risk of heart disease. Some risks of heart disease such as high blood pressure and diabetes increase even with moderate degrees of fatness. At the same time it recognizes the threat of potential eating disorders in some groups who tend to emphasize the need to be thin rather than the need to eat right and to exercise. The need to prevent obesity in children by emphasizing sensible eating and physical activity is another key component.

As the lead agency for the Public Health Service in the priority area of heart disease and stroke, the NHLBI reports progress on some of the 17 objectives in the report Healthy People 2000. There is evidence of measurable improvement in the number of people with high blood pressure taking steps to control their condition and people with high blood cholesterol attempting to reduce those levels. Additionally the prevalence of cigarette smoking has declined to 26%. There is concern that the proportion of hypertensive black men who are taking steps to control their condition is decreasing. There has been an increase between 1986 and 1990 from 46% to 65% of the population who have ever had their cholesterol checked and from 74% to 80% in those who had had their blood pressure checked within the last year. In addition to focusing on high blood pressure and blood cholesterol levels, the NHLBI targets smoking, weight control and plans to address physical activity as steps in the primary prevention of heart disease and stroke.

CHANGING ATTITUDES TOWARD NUTRITION NOTED IN MEN

Based on a telephone interview with a random national probability sample of 504 men between 18 years of age and older in March 1992, the American Dietetic Association reports an enhanced concern about nutrition among men 25 to 49 years of age since a similar 1991 survey. Seventy-one percent compared to 59% in 1991 now consider nutrition a “top priority” with 87% compared to 80% expressing at least some concern. However, among older men 50 to 64 years of age there was a drop from 89% to 72% considering nutrition a concern. Although health maintenance and disease prevention were cited as the top reasons for eating right by one-third of the respondents, this was down from 44% who mentioned health-related reasons for eating right in 1992. The respondents made more mentions of physical fitness. One-fourth, almost twice the percentage, reported eating less fat in 1991 than in 1992, 14% were eating less cholesterol and 10% said they were cutting back on sodium. One-fourth also felt that they were “extremely” well informed about healthy eating with the biggest gains from 1991 being noted in the 18 to 24 year olds and in those over 65. One-tenth were eating more vegetables and 5% more fruit. Twenty-five percent of respondents reported doing all the shopping, and 47% said they did at least half. Label reading was common, especially among those over 65. A brochure, “Food Strategies for Men,” and a reading list may be obtained by calling 1-800-366-1655, ADA’s National Center for Nutrition and Dietetics.

COPYRIGHT 1992 Lippincott/Williams & Wilkins

COPYRIGHT 2004 Gale Group