Canadian recommendations underestimate energy needs of women over fifty years as determined by doubly-labelled water.

Accurate estimations of energy requirements at the population level are crucial because of disease processes associated with energy imbalance. The present objective was to compare energy expenditure with existing Recommended Nutrient Intakes for Canadians (RNIC) and determine whether the RNIC provides a true index of energy requirement in middle-aged and elderly Canadian women. A second objective was to compare energy expenditure and the RNIC to Food and Agriculture Organization, World Health Organization, United Nations University (FAO/WHO/UNU) predictions. Seventy-six women were recruited for the study (67.3 +/- 11.5 y, 63 +/- 11.7 kg, BMI 24.8 +/- 4.4 kg x m(-2)). The two-point doubly-labelled water (DLW) method was used over 13 days to assess energy expenditure while subjects carried out their routine activities. Subjects were stratified to enable age specific requirements for middle-aged and elderly women. At weight maintenance, energy needs were underestimated using the RNIC (7.1 +/- 1.6 MJ x d(-1), 1698 +/- 391 kcal x d(-1)) compared to total energy expenditure (10.0 +/- 3.2 MJ x d(-1), 2395 +/- 746 kcal x d(-1)) as determined by DLW as a whole and for each age group. The RNIC recommendations were lower than the FAO/WHO/UNU estimations even for light activity. Results indicate that mean energy expenditure was 29% greater than the RNIC recommendations created using formulas based on age and weight, whereas the FAO/WHO/ UNU estimations closely approximated energy expenditure based on heavy activity in women 49-79 y and light activity in women over 80 y old. These data suggest a systematic underestimation of Canadian energy recommendations for women.

Four-day multimedia diet records underestimate energy needs in middle-aged and elderly women as determined by doubly-labeled water.

Systematic problems exist in the quantification of food intake in populations using traditional self-reported measures. The objective of this study was to determine the effectiveness of an innovative multimedia diet record (MMDR) for dietary energy intake assessment. Dietary intake was estimated by combining the use of a microcassette tape recorder and 35-mm camera in 53 women whose ages ranged from 50 to 93 y (64.9 +/- 11.3 y), with body weights of 62.4 +/- 12.2 kg and body mass indexes (BMI) of 24.4 +/- 4.0 kg/m(2). Using household measures, subjects voice-recorded and photographed all food and beverages consumed for four consecutive days. A two-point doubly-labeled water (DLW) method was used over 13 d to calculate carbon dioxide production, total body water, and subsequently, total energy expenditure (TEE) through the use of a food quotient. Mean body weight did not change between d 1 and 14. TEE and reported energy intake were compared using MMDR. Mean reported energy intakes 7.5 +/- 1.9 MJ/d (1774 +/- 476 kcal/d) were lower (P < 0.01) than TEE by 10.4 +/- 3.1 MJ/d (2477 +/- 736 kcal/d), indicating underreporting of food intake. Reporting accuracy (reported energy intake/TEE' 100%) was 76.0 +/- 22.9%. Mean energy expenditure (MJ/d), as determined by doubly-labeled water, was higher (P < 0.01) in each stratified age range when compared to reported energy intake by MMDR. There were no significant differences in reporting accuracy among the stratified age groups. Using the MMDR method, this population of weight-stable women underreported their food intakes compared to their determined energy expenditure estimated by DLW.

Precision and accuracy of total body bone mass and body composition measurements in the rat using x-ray-based dual photon absorptiometry.

Lean body mass (LBM), total body bone mineral mass (BMC), total body bone areal density (BMD), and body fat mass (FM) were measured in rats by dual photon absorptiometry (DXA), using two different instruments. The coefficients of variation for repeated measurements of LBM and FM were about 0.4 and 2.5%, respectively, over an animal body weight range of 150 to 600 g. For BMC and BMD, the coefficients of variation were less than 2%. The correlation coefficients for LBM, FM, BMC, and BMD measured on the two densitometers were all greater than 0.94. The slope of the regression line relating LBM measured by DXA and LBM measured by carcass analysis was 0.999, and the correlation coefficient was 0.99. For FM the slope was 1.05, and the correlation coefficient was 0.98. BMC measures by DXA were falsely low in small animals. For larger animals, the correlation between BMC and ash weight was 0.93, but the slope of the regression line was 0.78. DXA measures of LBM and FM were accurate and reproducible for rats weighing between 150 and 600 g. There was a size-dependent error in BMC, which will be significant in longitudinal measurements of bone mass.

Validation and application of dual-energy x-ray absorptiometry to measure bone mass and body composition in small infants.

Precision and validity of dual-energy x-ray absorptiometry (DXA) for analysis of whole-body composition in infants were assessed by 1) scanning piglets in triplicate to calculate CVs, and 2) comparing DXA estimates with chemical analysis of whole carcass. The mean CVs for all DXA measures in small piglets and large piglets were < 2.5%, except for fat mass, which were 6.3% and 3.5%, respectively. In large piglets DXA provided reasonable estimates of chemical analysis for bone mineral content (BMC), lean body mass, and fat mass, but only for lean body mass in small piglets. DXA overestimated fat by twofold and underestimated BMC by a third in small piglets. Scans of prematurely born infants (n = 17) at term and at 3, 6, and 12 mo corrected age demonstrated that changes in BMC, lean body mass, and fat mass can be quantitated by DXA. However, further refinement of DXA technology is necessary before reliable measures of BMC and fat mass in small infants are attainable.

Energy metabolism of broiler breeder hens. 1. The partition of dietary energy intake.

The partitioning of AME intake (MEI) and recovered energy (RE; defined as MEI minus heat production) was investigated on Hubbard broiler-breeder hens (BB) by using indirect calorimetry and energy balance. The regression of RE on MEI was linear (R2 = .96; P less than .01) with a slope of .817 +/- .024 (SE) and a y-intercept of -238.3 +/- 10.7 (SE). The maintenance energy requirement was 292 kilojoule (kJ) per kg per day (367 kJ per kg.75 per day). The regression of body RE, defined as RE minus egg energy, on MEI was linear (R2 = .96; P less than .01) with a slope of .799 +/- .045 (SE) and a y-intercept of -344.9 +/- 19.7 (SE). Therefore, an MEI of 432 kJ per kg per day was required by BB hens to maintain body energy equilibrium when they were laying at approximately 85% production. At an MEI of less than 432 kJ per kg per day, body energy was used for egg production. The AME cost of depositing 1 kJ of body, egg, protein, or fat energy was (mean +/- SE) 1.21 +/- .06, 91 +/- .32, 1.96 +/- .71, and 1.05 +/- .15 kJ, respectively. The results indicate that individually caged BB hens between 28 and 36 wk of age in a thermal-neutral environment (21 C) require approximately 1.6 megajoule (MJ) of AME per bird per day for normal growth (3 g/per day) and egg production (85%).

Energy metabolism of broiler breeder hens. 2. Contribution of tissues to total heat production in fed and fasted hens.

In vitro rates of O2 consumption were investigated using excised biopsies from the liver, ileum, magnum, and latissimus dorsi muscle of Hubbard (H) broiler-breeder hens fed four levels of ME intake. Diet had no effect on O2 consumption of any tissue. The overall mean initial O2 consumption (microL of O2 per mg of dry weight per h) for latissimus dorsi, liver, ileum, and magnum tissues were 4.38, 13.33, 10.54, and 8.01, respectively. The Na+ and K(+)-adenosine triphosphatase-dependent respiration (ouabain-sensitive respiration) was 16% of the initial rate for latissimus dorsi, liver, and magnum tissues and 22% for ileum tissues. Fasting heat production of H and Arbor Acre (AA) meat-type hens measured over 3 days following an initial 24-h fast was 219 and 216 kilojoules (kJ) per kg per day (1 kJ = .239 kcal). There were no strain differences in the partitioning of O2 consumption into tissue components of fasted H and AA hens. Fasting metabolism accounted for 75% of the maintenance energy requirement in the hens. The liver, gut, and reproductive tract, which together make up 5 to 6% of BW, account for 26 and 30% of the total energy expenditure in fed and fasted hens, respectively.

Effect of frequency of feeding of diets containing free or protein-bound lysine on the oxidation of [14C]lysine or [14C]phenylalanine by growing pigs.

The effect of frequency of feeding (once daily or six equal portions at intervals of 3 h) of diets containing lysine (6.4 g/kg) supplied as either protein-bound or free lysine on the metabolism of essential amino acids was investigated in pigs over the 23-34 kg weight range. The amounts of radioactivity from 14CO2 produced by the pigs given oral doses of [14C]lysine or [14C]phenylalanine were determined. [14C]Lysine was confirmed to be unsuitable presumably because the oral dose was diluted by the dietary free lysine or was absorbed ahead of the protein-bound lysine, or both. With [14C]phenylalanine addition, there was a significantly (P less than 0.01) greater production of 14CO2 by pigs fed once daily on the diet containing free lysine. However, with frequent feeding, there was no significant difference (P less than 0.05) in the amount of 14CO2 produced by pigs from [14C]phenylalanine for either diet. Growth responses of the pigs were lower when the diet containing free lysine was given once daily (P less than 0.01) but were similar when the diets were given frequently. It is concluded that the more rapid absorption of free lysine by growing pigs fed once daily results in an imbalance of amino acids at the sites of metabolism. This leads to greater oxidation of essential amino acids than occurs when all the amino acids are supplied in the protein-bound form. With frequent feeding, a better balanced supply of amino acids is absorbed, leading to similar rates of oxidation of excess essential amino acids from diets containing either free or protein-bound lysine.

Exercise and postexercise energy expenditure in growing pigs.

Young pigs (ca. 10 kg) were trained to run on a motor-driven treadmill for 1 h each day. After a 2-week training period the gas exchange of exercised and control animals was measured using an open circuit, indirect calorimeter. The exercised pigs ran for 2 h in the calorimeter, and then rested for 2 h. They received a day's allocation of feed and remained in the calorimeter for a total of 23 h. The total heat production of the exercised pigs was 523 kJ/kg, compared with 433 kJ/kg of the controls. Monitoring the heat production throughout the 23-h period showed that only 43% of the extra heat dissipated by the exercised pigs was lost during the 2 h of exercise, with a higher rate of heat production for the remaining 21 h accounting for the 57% of the extra energy dissipated as heat. The results suggest that exercise increases energy expenditure well beyond the time devoted to the activity itself.

A role for tryptophan in regulation of protein synthesis in porcine muscle.

Experiments were conducted to determine the effect of varying concentrations of dietary tryptophan on growth rate and protein synthesis in edible muscle tissues of growing swine. A total of 45 immature swine (initial weight approximately 24 kg) were fed corn-gelatin diets containing 0.5 (n = 8), 0.8 (n = 10), 1.3 (n = 10), 1.5 (n = 7) or 2.0 (n = 10) g tryptophan/kg diet for 35 d. Animals fed 0.5 and 0.8 g tryptophan/kg grew more slowly, consumed less feed and had a lower efficiency of feed utilization than animals fed higher concentrations of tryptophan. Thirty similar animals were used in a second experiment. Diets containing 0.5, 0.8, 1.0, 1.5 or 2.0 g tryptophan/kg diet (n = 6) were fed for 14 d, after which all animals were killed and samples were taken of longissimus dorsi, triceps brachii and biceps femoris. Protein synthetic activity was determined by monitoring the incorporation of [14C]phenylalanine into protein in vitro. There was no significant difference in synthetic activity between different muscle types. There was no effect of diet on the activity of the muscle soluble protein fraction. The activity of the muscle ribosomal fraction, however, was positively correlated with increasing concentrations of dietary tryptophan. It was concluded that tryptophan has the potential to regulate muscle protein synthesis in a manner beyond serving simply as a component of protein.

Effect of cold exposure on energy metabolism in the young pig.

Twenty-four piglets were weaned at 3 weeks of age and received 615 kJ metabolizable energy/(kg body weight X day). The temperature was reduced from 29 to 25 degrees C by 4 weeks of age. Six pigs were exposed to cold by reducing the temperature to 10 degrees C by 5 weeks of age while the other six were exposed to 23 degrees C. These two temperatures were maintained for 3 weeks. Each week the three pigs closest to the mean weight of each group were used for measurements of heat production for 23 h by open-circuit calorimetry and glucose turnover by continuous infusion of [6-3H]- and [U-14C]-glucose. The animals were sacrificed at 8 weeks of age, a sample of their intercostal muscle was used for in vitro measurement of muscle respiration, and the carcass was analyzed. There was no change in heat production, glucose turnover, and rectal temperature during the 3 weeks of cold exposure, so the data were pooled. Cold exposure increased heat production by 50%, forced mobilization of fat reserves (1000 g over the 3 weeks), and increased glucose replacement rate by 20%. The decline in rectal temperature to 37.6 from 38.8 degrees C could be regarded as a strategy to reduce energy needed to regulate body temperature. In the cold, heat production equalled metabolizable energy intake, but protein deposition was maintained at the same level as that in the pigs at the thermoneutral temperature, using the energy derived from the mobilization of body fat. The increase in Na+-K+ ATPase dependent respiration accounted for 70% of the increase in O2 consumption of muscle from cold-exposed pigs and thus is potentially an important component of cold-induced thermogenesis in the pig.

Influence of dietary lysine concentration on the oxidation of an indicator amino acid by growing boars.

The influence of dietary lysine concentration on the oxidation of 14C-phenylalanine by growing boars was determined. Forty-five crossbred boars (30 to 40 kg) were fed a ground corn diet fortified with crystalline L-lysine to provide .28, .50, .85, 1.00, 1.25 and 1.54% total lysine. All other essential amino acids were supplemented to provide 135% of NRC (1979) recommendations. Release of 14CO2 from L-[1-14C]-phenylalanine was measured for 1 h following a meal of the experimental diet, which contained 20 mu Ci 14C-phenylalanine. Increasing dietary lysine concentration from .28 to .85% decreased 14CO2 production. Regression analysis of the data using a two-phase linear regression crossover model indicated that phenylalanine oxidation was minimized at a dietary lysine concentration of .65%. It was concluded that a concentration of .65% lysine minimized the oxidation of amino acids and provided them as possible substrates for protein deposition. The oxidation of an indicator amino acid can, therefore, be used to determine the effect of dietary lysine concentration on the partition of amino acids between metabolic fuels and body protein.

The effect of diarrhea on the oxidation of 14C-phenylalanine in piglets receiving diets varying in protein and proline concentration.

The oxidation rate of L-[1-14C]phenylalanine in piglets suffering from diarrhea and receiving diets varying in concentration of protein or proline was compared to the oxidation rates in healthy animals. Phenylalanine oxidation was used to indicate the partition of absorbed amino acids between protein synthesis and oxidation. Piglets receiving adequate protein diets and suffering from diarrhea oxidized significantly more phenylalanine (P less than 0.001) than healthy piglets. Piglets receiving additional proline and with symptoms of diarrhea oxidized phenylalanine at rates 50 to 70% higher than healthy piglets. The results show that piglets with diarrhea are less able to retain absorbed amino acids for protein synthesis than healthy pigs. The reduced nitrogen retention commonly observed in animals with diarrhea may be partly explained by the increased catabolism of absorbed amino acids.

Energy balance in low birth weight infants fed formula of high or low medium-chain triglyceride content.

We tested the effect on energy balance of the partial substitution of medium-chain for long-chain triglycerides in the diet of growing low birth weight infants. Fifteen infants were studied in a randomized double-blind crossover clinical trial in which each infant was fed each of two formulas, which were of equal gross energy and protein content but differed in fat composition. The high medium-chain triglyceride (MCT) formula contained medium- and long-chain triglycerides in a weight/weight ratio of 46:54; in the low MCT formula the ratio was 4:96. The hypothesis tested was that under conditions of equal gross energy intake the two diets would differ in their digestible and metabolizable energy contents and would produce differences in the infants' rates of energy expenditure and energy storage. Gross energy intakes averaged 562 and 555 kJ/kg/day (134 and 133 kcal/kg/day) with the high and low MCT formulas, respectively. With each diet, coefficients of energy digestibility (0.93) and metabolizability (0.91) were identical; the rates of energy expenditure were 262 (high MCT) and 265 (low MCT) kJ/kg/day (63 kcal/kg/day for both diets), and of energy storage were 246 (high MCT) and 239 (low MCT) kJ/kg/day (59 and 57 kcal/day). These differences were not significant. There were also no significant differences between the two diets in coefficients of nitrogen retention (mean 0.70) or in rate of weight gain (mean 21.5 gm/kg/day). The use of high MCT content in infant formula neither provided a nutritional advantage in energy digestibility or metabolizability nor resulted in an increased rate of energy expenditure or of energy storage.

Influence of dietary protein concentration on the oxidation of phenylalanine by the young pig.

1. Piglets were weaned at 3 d of age and reared to 2.5 kg on a liquid diet in which the protein was supplied by dried skim milk and a mixture of free amino acids. The oxidation of L-[1-14C]phenylalanine was measured as an indication of the partition of amino acids between retention and catabolism in pigs (2.5 kg) offered meals containing varied concentrations of crude protein (nitrogen x 6.25). 2. The dietary protein concentration was varied either by increasing the inclusion of a mixture of free amino acids in a series of diets containing 100 g protein/kg from skim milk, or by increasing the level of inclusion of the skim milk in a series of diets containing the equivalent of 100 g protein/kg from the free amino acid mixture. 3. The oxidation of phenylalanine was minimized by dietary protein concentrations of 240 and 258 g/kg for the diets containing increasing concentrations of free amino acids or skim milk respectively. 4. These results show that a mixture of free amino acids is used more effectively than intact protein for promoting retention of essential amino acids. 5. The recovery of radioactivity in expired carbon dioxide was inversely related to the recovery of radioactivity in liver tissue when the concentration of dietary crude protein was increased from deficient to adequate, demonstrating that the fractional oxidation of the indicator amino acid was inversely related to protein synthesis.

Proline as an essential amino acid for the young pig.

1. The catabolism of L-[1-14C]phenylalanine was used to indicate the effects of single amino acid supplementation of an inadequate protein diet (200 g crude protein (nitrogen x 6.25)/kg) on the utilization of dietary amino acids in pigs of 2.5 kg body-weight reared on an adequate protein diet (240 g crude protein/kg) containing skim milk and a mixture of free amino acids. 2. The oxidation of phenylalanine was decreased by the addition of proline or arginine to the inadequate protein diet but not by the addition of threonine, methionine, lysine or a mixture of essential amino acids, indicating that proline and arginine were limiting the utilization of dietary amino acids in the inadequate protein diet. 3. Dietary proline concentrations of 13.9 and 14.2 g/kg minimized phenylalanine oxidation in diets containing 200 or 260 g protein/kg. This indicates a dietary proline requirement of 14 g/kg. 4. Increasing the dietary arginine concentration in a diet containing 240 g protein/kg showed that an arginine concentration of 5.1 g/kg minimized phenylalanine oxidation. However, increasing the arginine concentration in a diet containing 200 g protein/kg increased phenylalanine oxidation, suggesting an amino acid imbalance involving arginine at this lower level of protein.

Tryptophan requirement of growing swine as determined by the oxidation of an indicator amino acid.

The tryptophan requirement of growing swine was determined using the oxidation of L-[1-14C]-phenylalanine as an indicator of the adequacy of the dietary tryptophan level. Forty crossbred boars (30 to 45 kg) were fed a basal diet containing 16% protein supplied by corn and gelatin. A series of experimental diets containing .05, .08, .10, .15, .20 and .25% L-tryptophan were prepared. The diets were supplemented with crystalline amino acids to provide 135% of the recommended levels. Release of 14CO2 was measured for 1 h following a meal of the experimental diet containing 20 microCi 14C phenylalanine. Increasing dietary tryptophan from .05 to .13% decreased release of 14CO2. Further increases in dietary tryptophan concentration did not significantly influence 14CO2 production. Regression analysis using a two-phase linear regression crossover model indicated that phenylalanine oxidation was minimized by a dietary tryptophan concentration of .13%. It was concluded that at a concentration of .13%, tryptophan was no longer limiting the retention of the other amino acids, thus this is the requirement for maximum protein retention by the young, growing boar.

Time course of the total and radioactive carbon dioxide production by piglets receiving dietary [14C]phenylalanine.

The influence of experimental protocol (i.e., timing of feeding and of the collection of expired carbon dioxide) upon the sensitivity of using the oxidation of a labelled amino acid as an indicator of the adequacy of the dietary amino acid balance was investigated using 2.5-kg piglets confined in ventilated chambers. In the first experiment it was shown that consumption of two meals, each of 20 g and separated by 2 h, after an overnight fast resulted in a rapid rise in carbon dioxide concentration in the air withdrawn from the chamber. The concentration peaked 12 min after the second meal and remained elevated for 50 min. In the second experiment the piglets received two meals containing three levels of either lysine (8, 10, and 12 g/kg) or tryptophan (1.3, 1.8, and 2.0 g/kg) plus 10 microCi L-[alanine-1-14C]phenylalanine (1 Ci = 37 GBq) in each meal. Radioactivity released as 14CO2 peaked in the second hour following the last meal, but there was such great variation in the mean for the three diets that they were not statistically different. However, in the third hour following the second meal both the means and their variances had decreased with the differences between the diets being statistically significant for this time period. An experiment with varying levels of tryptophan showed a similar effect of meal consumption on 14CO2 release. The third experiment confirmed the effect of time of collection upon the statistical significance of the dietary amino acid balance measured by the release of radioactivity from [14C]phenylalanine.

Energy intake and the nature of growth in low birth weight infants.

Growth is accompanied by and depends on energy storage in growing tissue. The rate of energy storage in growing low birth weight infants depends on the rate of energy intake and on the rates of energy excretion and expenditure, both of which (on a body weight basis) are much higher than in adults, and both of which increase with increments of gross energy intake. Energy-balance studies of growing low birth weight infants on gross energy intakes approximating 500 kJ X kg-1 X d-1 of mothers' milk or of infant formula indicate that the composition of extrauterine weight gain of the low birth weight infant differs from that of the fetus of similar gestation, in that the energy storage cost of growth is much higher. Attempts to increase metabolizable energy intake beyond 500 kJ X kg-1 X d-1 by energy supplementation alone do not result in proportionately increased rates of weight gain; low birth weight formulae, in which energy, protein, and mineral contents are all increased can result in large weight gains with proportionate increases in rates of protein and fat accretion.