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A critical evaluation of the mineral and nitrogen balance in man
... The balance studies were performed during four-day periods according to Isaksson and Sjogren (1967), using carmine red as markers of faeces. Faeces were homogenized as described by Isaksson (1962). ...
... A theoretical nitrogen balance can be calculated on the assumption that the increase in the body potassium was caused by an increase in the body cell mass and that 1 g of nitrogen corresponds to 3 m-equiv of potassium. The difference between the nitrogen balance actually measured and the Isaksson and Sjogren, 1967), intracellular deficits of potassium, and/or an extracellular deficit of protein. functioning gallbladder. ...
Thirteen patients suffering from Crohn's disease or subjected to small bowel resection were studied under metabolic ward conditions for an average of 32 days. Most of these patients had chronic, severe diarrhoea and varying degrees of steatorrhoea. All were studied at two levels of fat intake, 100 g and 40 g daily.After the introduction of the low-fat diet, there was a marked reduction in the faecal excretion of water and sodium in most patients and 10 of them passed solid faeces. Two other subjects improved only after the addition of cholestyramine. In one patient with an ileostomy, no improvement occurred. On the low-fat diet, there was a positive balance of nitrogen and potassium in many cases. Faecal fat excretion decreased, but there was no change in the fractional absorption of fat.The most gratifying improvement was seen in patients with a functioning gallbladder. Previous resection of the colon seemed to limit the reduction of faecal water and sodium excretion which followed the reduction in fat intake.A fat-reduced diet is recommended in the symptomatic therapy of chronic diarrhoea in patients suffering from diseases of the ileum.
... Nitrogen balance can vary with the method used for collecting and preserving urine and faeces (Isaksson and Sjogren, 1967). Nitrogen retention can differ between slaughter method and feeding. ...
L’objectif général du projet de thèse était de produire des connaissances pour contribuer au développement de bonnes pratiques d’alimentation des caprins, ovins et bovins des régions chaudes. La méthodologie utilisée dans ce projet a croisé des méta-analyses à une approche expérimentale. Les besoins énergétiques d’entretien des caprins,ovins et bovins des régions chaudes seraient plus élevés qu e ceux des ruminants des régions tempérées. Ces différences ont été partiellement attribuées à la capacité des génotypes animaux de ces régions de mobiliser une fraction des nutriments ingérés à des fonctions non productives dont l’adaptation aux stress et le coût énergétique de l’ingestion et la digestion de rations plus fibreuses. Des besoins énergétiques pour la production du même ordre de grandeur que ceux des génotypes des régions tempérées ont été estimés. Nos estimations des besoins protéiques d’entretien et de production indiquent que ceux-ci sont plus élevés avec les génotypes tropicaux comparativement aux génotypes tempérés. La hiérarchie des besoins entre espèces varie avec leurs modalités d’expressions (expression du poids métabolique). Le système d’unité d’alimentation énergétique et protéique de l’INRA, basé sur une approche mécaniste de l’utilisation des aliments, conduit potentiellement à une bonne évaluation des ressources alimentaires. Cependant, certains coefficients doivent être révisés pour tenir compte de la composition spécifique des ressources fourragères disponibles en régions chaudes.
... Nitrogen balance can vary with the method used for collecting and preserving urine and faeces (Isaksson and Sjogren, 1967). Nitrogen retention can differ between slaughter method and feeding. ...
The overall aim of the thesis project was to generate knowledge to contribute to the development of good feeding practices for sheep goats and cattle in warm regions. The methodology used in this project crossed meta-analysis to an experimental approach. The maintenance energy requirements of goats, sheep and cattle in warm regions are higher than those of ruminants in temperate regions. These differences were partly attributed to the capacity of livestock genotypes of these regions to mobilize a fraction of the nutrients ingested for unproductive functions adaptation to stress and the energy cost of ingestion and digestion of more fibrous diets. The estimation for the energy requirements for production was the same order of magnitude as the genotypes of temperate regions. Our estimates of protein requirements for maintenance and production show that they are higher with tropical genotypes compared to temperate genotypes.The hierarchy of needs between species varies with their modes of expression (expression of metabolic weight).The energy and protein supply unit system of INRA, based on a mechanistic approach to the use of feed, potentially leads to a good assessment of food resources. However, some factors must be revised to reflect the specific composition of forage resources in warm regions.
... Nitrogen balance studies tend to give estimates of nitrogen retention which do not always correspond to increases in weight gain in humans or carcass analysis in animals, particularly at high protein intakes. This has been well reviewed (10)(11)(12)(13)(14)(15). Part of the explanation lies in the accumulation of small errors which tend systematically to overestimate nitrogen intake and underestimate nitrogen out put. ...
Sixty-eight primigravidae successfully completed a 12-day nitrogen balance study when they were between 30 and 34 weeks pregnant. Particular attention was paid to ensure that each patient ate a hospital diet quantitatively equal to the home diet; each patient ate the same every day and all food was eaten. There was a significant correlation between nitrogen intake and apparent nitrogen retention but no relationship between apparent nitrogen retention and birth weight or the occurrence of pre-eclampsia. The mean apparent nitrogen retention for the 68 women was 1.2 g/day. Once allowance is made for integumental losses this figure is equal to the estimated daily nitrogen retention for growth of the fetus and reproductive tissues during this time. There was no evidence of maternal storage of surplus protein as has been previously suggested. The previous literature is reviewed and an attempt made to explain the discrepancy between the findings in this study and previous work.
... Comprehensive information on the bioavailability of metal substances should ideally be derived from in vivo toxic kinetic or toxicological tests (Henderson et al. 2012). However, human balance studies are susceptible to considerable error (Isaksson and Sjögren 1967), and in vivo animal studies are problematic with respect to extrapolation to humans (Finch et al. 1978; Hund-Rinke and Kördel 2003). Moreover, in vivo assays of metal absorption are relatively costly and slow, aside from possibly having sample limitations (Drexler and Brattin 2007). ...
To evaluate the potential health hazards caused by extensive vanadium-titanium magnetite mining, the bioavailability and bioaccessibility of metals were assessed in the pluralistic mining-agriculture-residential city of Panzhihua, China. Intensive mining and the related heavy traffic may have contributed to Ni, Cr, and Zn contamination and to Mn and V accumulation in soils and road dusts. The metal bioavailability estimated by water extraction was significantly lower than metal bioaccessibility on the basis of the simple bioaccessibility extraction test (SBET). The bioaccessible metal concentrations were significantly and positively correlated with soil/dust total metal concentrations (P < 0.05). However, bioavailable metal concentrations exhibited no relationship with total metal concentrations except for V. The bioaccessibility of metals significantly varied and exhibited the following order: Pb > Zn > Mn > Ni > V > Cr. Health risk assessment indicated that the carcinogenic and non-carcinogenic risks posed by these metals were at an acceptable level, but Cr in soils of the mining area and V in surface soils along Jinsha River were close to the safe level for children. Therefore, the potential health risk attributed to the exposure of children to metals in surface soils and road dusts in such areas should not be overlooked.
... Nitrogen balance can vary with the method used for collecting and preserving urine and faeces (Isaksson and Sjogren, 1967). Nitrogen retention can differ between slaughter method and feeding. ...
The aim of this work was to establish the response of growing sheep, goats and cattle to different nutritional environments. Data from 590 publications representing 2225 treatments were analysed. The results showed that each 10% increase in NDF was accompanied by 0.11 g/kg live weight (LW) and 0.32 g/kg metabolic live weight (LW0.75) decreases in DMI. Otherwise, the response of DMI to CP (CP%DM) content was curvilinear (P<0.01), without any significant difference in the slope between species. The percentage of concentrate (% CC) affected DMI curvilinearly, without any significant difference between species. This meta-analysis demonstrated the negative linear effect of NDF and the quadratic effect of CP concentration on organic matter digestibility (OMd). For growth performance, the three species responded curvilinearly to variations in metabolisable energy intake (MEI MJ/kg LW0.75) and digestible CP (DCPI g/kg LW0.75) intake (P<0.01). At the same level of MEI, average daily gain (ADG) varied with CP contents of the diet, and only the intercept differences were significant between the three levels (P=0.07). At the same level of DCPI, ADG varied with energy level (below maintenance (LE--), 1 to 1.2×maintenance (LE-), 1.2 to 1.4× maintenance (ME+-), and >1.4, corresponding to maximum growth (HE+)). No significant difference was observed between LE-- and LE-, and no significant difference was observed between ME+- and HE+. For nitrogen balance, no difference was observed between species for a given level of nitrogen intake.
... The patients had been studied under metabolic ward conditions (Isaksson and Sjogren, 1967). This initial study consisted of eight to 16 days with a daily intake of 100 g fat, followed by 12 to 24 days with a daily intake of 40 g fat. ...
Thirteen patients with ileopathy were studied under metabolic ward conditions, first on a 100-g fat diet and later on a 40-g fat diet. Ten of the patients were studied after three to 27 months on a fat-reduced diet. Ten of the patients had a high urinary oxalate excretion on the high-fat diet compared with a control group. The patients with a faecal fat output of more than 15 g a day showed a reduction in oxalate excretion when the fat intake was decreased and in the follow-up study the oxalate excretion was low in all patients except in one with a remaining steatorrhoea. There was a correlation between urinary oxalate excretion and faecal output of fatty acids. It is postulated that a low intraluminal calcium ion concentration, mainly caused by the high fatty acid content, explains the hyperoxaluria. The low fat diet, which also reduced the diarrhoea and increased the urinary output, was acceptable to the patients. The diet is recommended for patients with ileopathy in order to reduce the risk of formation of renal calculi.
... Although subject to much criticism (Isaksson & Sjogren, 1967;Hegsted, 1975), balance studies have been widely used to estimate nutrient requirements. We feel that balance studies can provide useful information, provided results are interpreted with caution. ...
After a 5-week period of low selenium intake, twenty-four Dutch men received 55, 135 or 215 micrograms Se/d as Se-rich meat or bread for a 9-week period. Four unsupplemented subjects served as controls. Plasma Se increased more rapidly than erythrocyte Se levels; the increases were significantly dependent (P less than 0.001) on Se intake level. Glutathione peroxidase (EC 1.11.1.9; GSH-Px) activity in platelets increased rapidly after supplementation and plateaued after 4-9 weeks. At 10 weeks after supplementation ended, plasma Se levels and platelet GSH-Px were still higher than the baseline values whereas erythrocyte Se levels continued to increase. Except for the higher erythrocyte Se levels after supplementation with high-Se meat, there were no differences in bioavailability of Se between meat and wheat products. Daily urinary and faecal Se excretions as well as Se retention increased with an increased Se intake irrespective of the form of the supplement. Regression of Se excretion v. intake indicated that 33 micrograms Se/d is necessary to compensate for urinary and faecal losses.
... The urinary excretion figures were also compared to the measured intakes of nitrogen, sodium and potassium. Two g of nitrogen and 800 mg of potassium were added to the urinary excretion to allow for extrarenal losses (16,30). The measured daily intakes of nitrogen, sodium and potassium were 19.0 ± 7.5 g, 4178 ± 1061 mg and 4167 ± 948 mg, respectively, and the average total excretions for the three collection periods were 17.2 ± 3.6 g, 4257 ± 1451 mg and 4224 ± 786 mg. ...
Average daily intakes of essential and toxic trace elements from self-selected diets consumed by 100 men, selected as a random sample among the population of 30-34 year-old men in one urban and two rural areas of Denmark, were determined by the analysis of 48 h duplicate food portions. Median daily dietary intakes were 11.3 mg for zinc, 1.1 mg for copper, 11.3 mg for iron, 51 micrograms for selenium, 3.9 mg for manganese, 99 micrograms for molybdenum, 7 micrograms for lead and 11 micrograms for cadmium. Median dietary intake of mercury was below the detection limit. The observed nitrogen, sodium and potassium intakes were about 25% lower than the average total daily excretion of these constituents. It is therefore assumed that dietary intakes of nutrients during the duplicate portion sampling period were reduced by about 25% and that the observed intakes of trace elements can be regarded as minimum estimates of habitual intake. Taking this into consideration, it is concluded that the content of essential trace elements in Danish diets seems to be adequate and the amounts of the elements lead, mercury and cadmium are of little concern as regards health aspects.
The dietary fiber hypothesis states: “A diet that is rich in foods that contain plant cell walls is protective against a range of diseases, in particular those prevalent in affluent Western Communities.” Conversely, the hypothesis implies that “in some instances a diet providing a low intake of plant cell walls is a causative factor in the etiology of the disease, and in others it provides the condition under which other etiological factors are more active” (Southgate, 1982).
Solutions containing one of the amino acids 1-alanine, 1-arginine, glycine, 1-histidine, 1-proline or 1-glutamic acid and a basic mixture of the essential 1-amino acids and 1-arginine and 1-histidine were infused intravenously to healthy volunteers on a nitrogen-poor diet. The nitrogen balance and die excretion of urea, ammonia, a-amino nitrogen and creatinine in the urine were determined. Glutamic acid provoked considerable discomfort to the subjects and histidine caused some nausea. In high doses, arginine competed with lysine for renal excretion resulting in a loss of lysine in the urine. Infusion of arginine, proline, alanine and glutamic acid resulted in a nitrogen retention which was higher than that caused by glycine and histidine. It was concluded that the non-essential amino acids best suited for intravenous nitrogen nutrition are arginine, proline and alanine.
Losungen, die eine der nachstehenden Aminosauren: 1-Alanin, 1-Arginin, Glyzin, 1-Histidin, 1-Prolin oder 1-Glutaminsaure bzw. eine Grundmischung der essentiellen 1-Aminosauren mit 1-Histidin und 1-Arginin enthielten, wurden gesunden Freiwilligen, die eine stickstoffarme Diat erhielten, intravenos ver-abfolgt. Dabei wurden die Stickstoffbilanz und die Ausscheidung von Harn-stoff, Ammonium, a-Aminostickstoff und Kreatinin im Harn bestimmt. Glutaminsaure rief ein bedeutendes Gefuhl des Unbehagens hervor imd Histidin verursachte gelegentlich Ubelkeit. In hoheren Dosen war die Nierenausschei-dung von Arginin und Lysin kompetitiv und resultierten in einen Verlust an Lysin im Harn. Infusionen von Arginin, Prolin, Alanin und Glutaminsaure fiihrten zu einer Stickstoffretention, die hoher war als die durch Glyzin und Histidin verursachte. Daraus wird der Schluss gezogen, dass Arginin, Prolin und Alanin die am besten geeigneten nicht-essentiellen Aminosauren fur die intravenose StickstofFzufuhr sind.
Perennial ryegrass (PRG) and white clover (WC) grown during spring and early summer 1967 were harvested and preserved frozen. The frozen herbages were later fed as pure or mixed diets on an or restricted basis to Romney wether hoggets in a 94-day feeding trial from April to July 1968. Nitrogen retention studies were conducted using both comparative slaughter and balance techniques. The balance technique appeared to have a positive bias in estimating N retention.The WC had 20% higher N levels than the PRG feed. N digestibilities, N intakes, total N retention, wool N retention, empty bodyweight gain, and wool growth were all significantly greater for WCfed sheep than for PRG-fed sheep. The results from sheep on mixed diets were not significantly different from the average results of the two pure diets.N retention was highly correlated with N intake, and the N from each diet appeared to be utilised with equal efficiency. The calculated average intakes of feed N and digestible N to support zero N retention were 9.7 and 7.2 g daily respectively for these sheep (average weight 23.1 kg).Partitioning N retention showed that daily retentions in total body, carcass, offal and blood, and wool ranged 0.8-3.5 g, 0.3-1.3 g, 0.1-0.9 g. and 0.4-1.4 g respectively, depending on diet and plane of nutrition.There were significant correlations between total N retention, carcass N retention, and N retention in wool and empty body-weight gain, carcass-weight gain, and wool growth respectively.
Mineralstoffe spielen im Stoffwechsel eine große Rolle. Über den Bedarf des Organismus zur Aufrechterhaltung besteht noch in vielen Fällen Unklarheit. Die Versorgung mit Metallen ist abhängig von deren Bioverfügbarkeit. Methoden der experimentellen Bestimmung der Bioverfügbarkeit werden beschrieben sowie deren Grenzen und Aussagefähigkeit diskutiert.
1. The effect of extrusion cooking, using mild conditions, of a high-fibre cereal product on apparent small bowel absorption of zinc, iron, calcium, magnesium and phosphorus was studied.
2. Seven ileostomy subjects were studied during two periods (each of 4d), on a constant low-fibre diet supplemented with either 54 g/d of a bran-gluten-starch mixture or the corresponding extruded product.
3. The apparent absorption of Zn, Mg and P was significantly decreased (P < 0.05) during the period with extruded product compared with the period with bran-gluten-starch. No difference was found for Fe and Ca.
4. The negative effect of extrusion cooking of a product containing phytic acid on availability of Zn, Mg and P was small but could be of nutritional relevance in foodstuffs that are consumed frequently and in infant formulas.
Thesis--University of Göteborg, 1967.
The stable isotope 26Mg was compared to the radioisotope 28Mg to estimate magnesium absorption in four healthy male subjects confined to a metabolic ward and consuming a constant diet for 146 days. Two isotopes tests were carried out in each subject on days 66 and 109 of the constant-diet period. In test 1, a solution containing 50 mg 26Mg and 30 μC 28Mg were taken orally during breakfast. In test 2, 50 mg 26Mg were administered orally followed three hours later by an i.v. injection of 20 μC 28Mg.True magnesium absorption was estimated by: (1) oral/i.v. ratios of 28Mg in plasma and urine, or oral/i.v. 26Mg/28Mg ratios in urine; (2) the difference between intake and fecal excretion of total dietary magnesium over a period of 10 days, or of a single dose of either isotope, corrected for endogenous fecal magnesium. Estimates made in individual subjects by different procedures based on data derived solely by use of 28Mg varied as much as estimates made by comparable procedures with data derived from either 26Mg or 28Mg. Measurements of 26Mg enrichment in urine and feces were made by neutron activation analysis which loses precision at enrichment levels below 10% above natural abundance. With the doses used in this investigation only fecal samples collected within 3–4 days and urine samples taken wihin 2–24 h contained adequately detectable 26Mg enrichment levels. Despite this limitation, 26Mg significantly expands the scope of investigation of magnesium absorption in man beyond that possible with the short lived 28Mg alone.
After 4 days on a nitrogen-poor diet healthy adult volunteers were nourished only with nitrogen-free carbohydrates given by mouth and amino acid solu tions infused intravenously during 4 consecutive days. In all experiments about 5 g of amino acid nitrogen was administered intravenously on each of these 4 days. The composition of the amino acid solutions was varied so that the mutual ratios between the essentials were constant, as were the mutual ratios between the non-essentials, whereas the ratio essentials/non essentials differed. Five solutions were tested containing 0, 25, 30, 36, and 46 % of their nitrogen as essential amino acids. The nitrogen balance was considerably negative when only non-essential amino acids were administered and significantly less negative when the other solutions were infused. On the other hand, there was no significant difference between the nitrogen balances when the solutions contained 25, 30, 36, or 46 % essential nitrogen.
A method is described for studying the retention of orally administered 47Ca using a whole-body counter. Two μCi 47Ca were given after an overnight fast together with calcium carrier as CaCl2 in water, and the retention was measured after one and two weeks. The error due to geometric and biologic variations was 1.7 per cent of the given dose. In 27 healthy subjects the retention of 47Ca one week after the administration was 35.7 ± 7.6 (S. D.) per cent of the given dose and after two weeks 29.3 ± 7.4 (S. D.) per cent.
Apparent nitrogen balance was studied in 14 patients with advanced renal failure and uremic symptoms during treatment with a 20-g protein diet supplemented with varying amounts of a mixture of the essential amino acids and histidine. Total nitrogen intake and urinary loss of nitrogen were determined by analysis. With an assumed mean loss of 2 g N per 24 hr from feces and skin all patients were in negative nitrogen balance on the 20-g protein diet only. The diet was supplemented with the essential amino acids as proposed by Rose and histidine in amounts corresponding to 1.3 and 2.6 g N per 24 hr iv or 1.3 g N per 24 hr orally. The apparent nitrogen balance was considerably improved with all supplementation schedules. Supplementation with 1.3 g N per 24 hr iv, however, could not bring the patients into nitrogen balance taking fecal and dermal nitrogen losses into account, while about half of the patients were judged to be in nitrogen balance on supplementation with 2.6 g N per 24 hr iv or 1.3 g N per 24 hr orally. Apparent nitrogen balance was better when 1.3 g N was given by mouth than iv and the difference between 1.3 g N by mouth and 2.6 g N iv was less than 1.3 g N. This indicates that the essential amino acids were more efficiently utilized when given by mouth. Supplementation of the 20 g diet with 1.3 g N as essential amino acids and histidine by mouth appears to be sufficient for clinical use. Evaluation of results of long-term treatment necessitates other techniques than short-term nitrogen balance studies.
Optimal nutrition is indispensable for optimal health. This consideration subtends the elaborated studies aimed at defining optimal nutrition in terms of amounts of nutrients to be consumed per unit time. In spite of many approaches, significant uncertainties remain. Historically, the first nutritive norms were yielded by epidemiological studies. The limitations of the epidemiological approach (which has nonetheless produced a wealth of fundamental knowledge) consist of its lack of applicability to the individual and of the uncertainties inherent in determining food consumption in free-living populations. Derivation of nutritional needs from measurement of obligatory losses has been undermined by the many criticisms, both theoretical and practical, leveled at balance techniques, and by our ignorance of the mechanism that regulates the efficient utilization of biological fuel. Recently, combinations of anthropometric criteria and biochemical measurements have been used successfully to gauge the effects of hyperalimentation in malnourished patients. These methods nevertheless do not resolve the theoretical uncertainties. An unresolved philosophical point is the degree of precision required in determining nutritional needs. It appears that adequate criteria exist for the practical purposes of refeeding a depleted patient; but for the more abstract task of understanding the theoretical basis of nutrition, current methods and criteria appear inadequate.
Many official bodies give advice on desirable intakes of calcium but no clear evidence of a calcium deficiency disease in otherwise normal people has ever been given. In Western countries the usual calcium intake is of the order of 800-1000 mg/day; in many developing countries figures of 300-500 mg/day are found. There is no evidence that people with such a low intake have any problems with bones or teeth. It seems likely that normal people can adapt to have a normal calcium balance on calcium intakes as low as 150-200 mg/day and that this adaptation is sufficient even in pregnancy and lactation. Inappropriate concern about calcium intake may divert attention and resources from more important nutritional problems.
Multiple factors, associated with the host and environment, as well as the chemical form of the nutrient, its availability, chemical and metabolic interactions among nutrients, result in a variability in nutrient requirements that is probably well beyond that observed in controlled laboratory studies of small groups of “normal” healthy subjects.
Although many factors are recognized as contributing to the variation in human nutrient requirements, current knowledge is largely of qualitative significance: Garn (40) state that this level of knowledge and investigation “has a long past but no foreseeable future.” It is sad commentary that neither do we know adequately the quantitative extent of biological variation in requirements among individuals for any of the essential nutrients nor the quantitative importance of most of the factors which affect requirements in population groups. We believe that the potential contributions of nutrition toward solving problems of human disease and for maintaining health in populations depend as much on a better definition of the quantitative aspects of human nutrient requirements as on improved understanding of the utilization, function and metabolism of nutrients at the cellular, organ, and whole body level.
Young men consumed a diet that provided 6.0 g of nitrogen, of which rice, wheat, and milk supplied 33, 38, and 29%, respectively, for 28 days following adjustment. This diet contained amounts of essential amino acids that were at least twice the minimal required amounts reported for men. Mean nitrogen balances in four successive 7-day periods were 0.27 +/- 0.13, 0.25 +/- 0.08, 0.10 +/- 0.07 and 0.24 +/- 0.12 g; and the mean for 28 days was 0.22 +/- 0.05 g. Nitrogen retention did not differ significantly between periods. All men who weighed between 65 and 72 kg retained small amounts of nitrogen but one who weighed 78 kg was in slightly negative balance. The mean balances as reported do not provide an allowance for integumental and other losses. The daily protein intake from these sources, equivalent to 0.5 g/kg of body weight, was a critical level slightly lower than the amount appropriate for long-term maintenance of young men weighing 70 kg.
Fecal fat excretion was studied after a mild episode of diarrhea in eight infants for whom adequate control data were available. Mean age of onset of diarrhea was 28 days. Duration of the episode, defined as the number of days until the infant was again feeding and libitum, averaged 5.1 days. Balance studies were carried out 3 to 13 days later. Mean fecal fat excretion rose from a prediarrhea value of 2.9 +/- 1.4 gm/day to 8.7 +/- 3.1 gm/day following diarrhea (P less than 0.001). Restudy of five infants one month later showed persistent steatorrhea in one. Mild transient steatorrhea may follow mild diarrhea in infancy and should be considered in infants who are slow to gain weight subsequent to an episode of diarrhea.
1. The production rates of bacteria in the rumen of buffalo ( Bos bubalis ) calves were estimated using an isotope-dilution technique. A series of fifteen experiments was done with animals given green maize and nine experiments with animals given cowpea ( Vigna unguiculata ).
2. The turnover time ranged from 205 to 567 min in the group given green maize and from 330 to 648 min in animals offered cowpea. The production rates of bacteria were (mean±SE; g/d) 145.77±7.240 and 237.09±11.847 in animals given green maize and cowpea respectively.
3. There was a significant correlation between bacterial production rates and dry matter intake, digestible organic matter and total volatile fatty acids formed in the rumen.
4. Regression equations obtained for the two foodstuffs were different suggesting that the bacterial growth rate may vary depending upon the quantity and quality of foodstuff digested and possibly the ratio nitrogen: energy of the foodstuff.
The absorption of food iron in relation to the diet was studied in 10 phlebotomized normal young male subjects during 3 to 5 months. The iron absorption was calculated from the net increase of the hemoglobin mass. There was pronounced individual variation in the mean dietary absorption ranging between 1.9 and 5.0 mg. There was no correlation between the amount of iron absorbed and the amount of iron ingested. There was no apparent influence of a high or a low intake of animal products, cereals, vegetables, tea, or alcohol on the individual absorption values. A negative correlation between the iron absorption and the total amount of fecal dry substance was observed. This might be ascribed to an influence of dietary fibers on the absorption of food iron.
Six Caucasion male MIT students, age 19 to 23 years, were given a formula diet providing 0.59 g egg protein/kg body weight/day and energy intakes approximately 10% above their usual requirements. Four subjects continued on this diet for 81 to 89 days, but for the two the protein intake was increased after 50 and 59 days because of an excessive rise in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. The elevated serum AST and ALT activities fell to normal rapidly when these subjects received a diet providing 1.5 g protein/kg/day from skim milk powder. Body weight increased in five of the subjects. Four showed cumulative negative N balances, and all showed a net loss of total body 40K, which was significant in three. These findings indicate that the 1973 FAO/WHO "safe level" of egg protein intake of 0.57 g/kg is not sufficient for long-term maintenance of most healthy young men. Moreover, the greater N losses calculated from 40K and creatinine measurements than from the N balance data suggest an integumental N loww approximating 15 mg/kg rather than the 5 mg of the 1973 allowances.
Previously it had been shown that rat pups, malnourished during the 3-week suckling period and the nutritionally rehabilitated for about 30 weeks, showed an increase in the efficiency of dietary protein utilization of the protein was fed at a less than optimal level and if the protein was of poor nutritional quality (J. Nutr. 103, 273, 1973). The present study extends this observation to growing rats malnourished during the first 3 weeks of life and then rehabilitated with a 25% casein diet for 4 weeks. The test proteins were casein, fed at a level of 12%, and wheat gluten, at a level of 25%. Efficiency of nitrogen retention was greater for both proteins in rats previously malnourished than for control, non-malnourished rats. Malnutrition was then imposed on rats malnourished by feeding a low protein diet either during the first 4 weeks postweaning or from the 7th to 11th week of life. After these periods of malnourishment, the rats were rehabilitated for 4 weeks and efficiency of utilization measured for both casein and wheat gluten fed at 10% of the diet. No change in utilization was found for either protein fed to rats rehabilitated from either of these periods of malnutrition.
1. Six Caucasian male Massachusetts Institute of Technology students participated in a 77–87 d metabolic balance study to determine the adequacy of the 1973 FAO/WHO egg protein allowance for men (0.57 g/kg body-weight per d). Each subject was given an initial energy allowance calculated to meet his particular requirements, and these intakes were raised by increments of 10% approximately every 2 weeks until a slightly positive balance was achieved. Each individual's energy intake was maintained at this final level for the remainder of the study.
2. At energy intakes sufficient to meet their estimated requirements, five of six subjects were in negative nitrogen balance. In five subjects, N balance improved with increased energy intake until N balance was achieved. The mean change in N balance was 0.335 mg N/additional kJ consumed. All of the subjects gained weight at the higher energy intakes.
3. Serum aspartate aminotransferase and alanine aminotransferase activities increased with continued intake of the experimental diet and reached abnormal levels in five of the six subjects. In the two subjects showing the earliest increases in serum transferase activity, the levels returned towards normal when protein intake was raised to 0.73–1.0 g/kg body-weight per d. All subjects showed normal serum transferase values on an ad lib. diet 2–3 weeks after termination of the study.
4. The findings indicate that at energy intakes necessary to bring subjects into slightly positive N balance at the level of 0.57 g egg protein/kg per d, a significant proportion of young adults continue to gain weight for as long as 70 d.
5. These findings suggest that the 1973 FAO/WHO safe allowance of 0.57 g egg protein/kg per d is not sufficient for most healthy young men receiving dietary energy intakes appropriate for long-term maintenance of body-weight.
The content of 21 elements (As, Au, Br, Ca, Cd, Co, Cr, Cs, Cu, Fe, Hg, K, La, Mo, P, Rb, Sb, Sc, Se, W and Zn) in normal epidermis has been determined with the aid of neutron activation analysis. The dermal loss of these elements via desquamation has been calculated in view of its possible importance in balance studies. For the bulk elements Ca, K and P, the calculated daily loss is considered to be negligible. For some of the trace elements, however, the loss may be appreciable. The daily loss of Fe by desquamation may be as much as one fourth of the daily urinary iron excretion; the corresponding fraction for Co, Cu, and Zn is one tenth.
To establish conditions for comparisons of mineral bioavailability from plant sources, seven male subjects consumed a constant diet containing bran fiber and phytate. Absorption and retention of Ca, Cu, Mg, Mn, and Zn were measured for 7-day periods through wk 2-7. Intakes of Mg, Mn, and Zn significantly exceeded the RDA; Ca and Cu intakes were only slightly in excess of RDA. All mineral retentions fluctuated from week to week but only Mg and Mn showed a consistent positive trend over time. Phytate excretions showed characteristic individual patterns, but did not appear to change with time. In contrast to previous observations fecal recovery of polyethyleneglycol (PEG) (MW = 4000) was consistently lower than recovery of simultaneously ingested Cr. Only five of the seven subjects returned close to 100% of Cr within 7 days. It was concluded that at least 4 wk were needed for adaptation in investigations involving more than one mineral when the experimental diet is adequate in the nutrients under investigation, that measurements of responses to treatment required 2-3 wk each, and that successive isotopically labeled test meals may overlap if they are spaced at 7-day intervals.
Enteral nutrition was provided by continuous pump-controlled gastrostomy tube feeding for 14 days in 97 guinea pigs bearing a 30% full thickness burn. Seven defined combinations of caloric and protein intake were studied. With a caloric intake of 175 kcal/kg/day, equaling the measured energy expenditure, the animals receiving 10% of calories as protein had a significantly greater postburn weight loss (p less than 0.05) and muscle mass depletion (p less than 0.05), and a significantly lower muscle nitrogen concentration (p less than 0.05), serum albumin level (p less than 0.01) and liver nitrogen content (p less than 0.01). With the same caloric intake but with more than 20% of calories as protein, the weight loss and the muscle wasting were reduced, but not abolished, and the serum albumin level and liver nitrogen content were normalized. Also with the diets containing 200 kcal/kg/day the muscle tissue depletion could not be abolished. However, with this caloric intake, the animals given 20% of calories as protein had a lower weight loss and a higher serum albumin level (p less than 0.01), but also a greater fat infiltration of the liver (p less than 0.01). At both levels of caloric intake, the nitrogen balance correlated significantly with the level of nitrogen intake but did not correlate with the changes of body weight. The incidence of diarrhea was lowest in animals fed 20% protein calories at a caloric intake of 175 kcal/kg/day. All things considered, the best metabolic and nutritional results were obtained with diets containing 20 to 30% of calories as protein and providing a caloric intake that paralleled the measured energy expenditure.
1. A continuous 40 d metabolic nitrogen balance study was conducted on twelve young men aged 25 ( sd 2.6) years to evaluate the adequacy of a previously determined safe level of protein intake.
2. Subjects were fed on diets which they were habitually accustomed to and which provided a protein level of 0.75 g protein (N × 6.25)/kg body-weight per d as the safe level and an energy intake level of 0.2 MJ/kg body-weight per d. N balances, including an estimate for integumental losses as well as certain biochemical variables, were determined for the last 5 d of two consecutive 20 d diet periods.
3. Only two of the twelve subjects were observed to be in negative N balance during the final 5 d of the 40 d period. N balance was generally positive at 8.24 ( sd 8.61) mg N/kg body-weight, thus confirming the adequacy of 0.75 g protein/kg body-weight per d as a safe level of protein intake in the majority of the subjects.
Five healthy men, ages 19-20, were fed a diet for 105 d to measure manganese balance during consumption of conventional foods. The study was divided into five periods of 21, 21, 38, 11 and 14 d, in which the daily dietary intakes of manganese (Mn) were 2.89, 2.06, 1.21, 3.79 and 2.65 mg, respectively. During the last 7 d of each dietary period, subjects resided in a metabolic unit and fasting blood samples were drawn on two mornings. Feces and urine were collected during the last 6 d and integumental losses were collected during the last 60 h of each period. The mean Mn balances for periods 1-5 were -0.083, -0.018, -0.088, +0.657 and +0.136 mg/d, respectively. Corresponding apparent retentions were -2.90, -0.88, -7.40, +17.33 and +5.12%. The mean sum of endogenous and exogenous losses when intake was theoretically zero was calculated to be 392 micrograms/d. When these total losses were combined with the mean positive retention, the theoretical mean dietary level of Mn required for positive balance for these male subjects was 3.5 mg/d or 50 micrograms/kg.
Although nutrient balances are used to determine nutrient assimilation, the balance technique is not well described in the preterm infant. Our purpose is to describe the balance technique; discuss factors that may interfere with complete balance collections; and determine the effects of intake, patient characteristics, and formula fed on nutrient assimilation in the preterm infant. Fifty-four 84-h balances were performed in a group of well premature infants receiving either a casein- (Similac with Iron) or whey-predominant (Similac with Whey plus Iron) infant formula. Mean (+/- SD; range) birth weight, gestation, postnatal age, and balance weight were 1,320 g (+/- 200; 820-1,720), 32.0 weeks (+/- 2.0; 27-34), 36 days (+/- 14.8; 15-87), and 1,729 g (+/- 146; 1,435-2,070), respectively. Although absorption and retention varied, results were comparable with previous studies in the preterm infant. Results of linear regression analysis, using the stepwise regression procedure, indicate that variability in nutrient intake (mg/kg/day) accounted for 97 and 84% of the variability in nitrogen absorption and retention (mg/kg/day). Variability in nutrient intake (mg/kg/day) also accounted for 96 and 57% of the variability in phosphorus absorption and retention (mg/kg/day). Effects due to intake, birth weight, gestation, postnatal age, balance weight, and formula fed also accounted for a substantial part of the variability in calcium, zinc, and copper absorption and retention. The results of this study indicate that factors other than birth weight, gestation, and the type of formula fed have a significant effect on absorption and retention of nutrients and should be considered as confounding variables when interpreting effects due to treatment.
1. Results from two independent metabolic balance studies in patients with ileal resection with or without a remaining colon were examined to assess the precision of the mineral, protein and fat balances obtained.
2. Low day-to-day variation in balances was found in patients with ileostomy/jejunostomy, irrespective of formula diet composition. In contrast, patients with a remaining colon showed considerable variation, with reliable cumulative balances often not reached for many weeks.
3. In conclusion, short-term cumulative balances can be performed with good precision in patients with ileostomy or jejunostomy.
Eight healthy young men participated in a 90-d metabolic balance study designed to assess the adequacy of 1 g of protein (N X 6.25) per kilogram body weight per day provided by a predominantly vegetable diet. The mean gross energy intake of the subjects was 49 kcal/(kg X d). The individuals received the experimental diet for eleven 8-d experimental periods. Three isoenergetic, isonitrogenous meals were served at 0800, 1200 and 1900. Anthropometric measurements and biochemical determinations in blood were made at the beginning of the study and afterwards at regular 15-d intervals. Body weight was measured daily. The mean overall weight change for the group was -0.8 kg. The mean daily urinary nitrogen output decreased from an initial value of 134.6 mg/(kg X d) to a final figure of 115.1 mg/(kg X d) (P less than 0.01), while the daily fecal N decreased from 31.5 to 26.3 mg/(kg X d) (P less than 0.05). Mean cumulative nitrogen balances were slightly positive for seven out of the eight individuals with an overall mean nitrogen balance value of +6.7 mg N/(kg X d). Biochemical and hematological values showed no significant changes throughout the study, except for a decrease in serum cholesterol. It is concluded that the "Chilean" mixed diet fed at the level of 1 g of protein per kilogram body weight per day with sufficient energy meets the long-term protein-energy needs of healthy young men, thus supporting the 1984 FAO/WHO/UNU safe recommended daily protein allowance of 0.75 g of reference protein, with a correction for the lower digestibility of vegetable sources.
Zinc absorption was determined with 67Zn and 70Zn, stable isotopes of zinc, in six young men and six elderly men who were confined to a metabolic unit for 12 wk. Their purified formula diets, supplemented with select food items, contained 15 mg of zinc per day. Zinc absorption was determined twice for each subject by combining zinc enriched with either 70Zn or 67Zn with the formula diet. Serum, urinary, and fecal zinc and zinc balance were determined by atomic absorption spectrometry. Zinc absorption averaged 17% in elderly men, significantly less than average zinc absorption of 31% in young men. Serum zinc was also lower in elderly men and increased in both groups during the course of the study. Zinc balance did not differ between groups, and endogenous zinc losses were less in the elderly than in the young men. The results suggest that while zinc absorption is less in elderly men than in young men, the lower absorption may reflect a lower requirement for absorbed zinc by the elderly. Alternatively, less efficient zinc absorption could result in decreased endogenous losses.
This study was conducted to help decrease the variability of metabolic diets. The effects of production lot and storage time on the trace element content of canned food products were compared. Various production lots of peaches, green beans, and tomatoes, canned in tinplate, were purchased and opened at three different times, spaced at 6-month periods. Storage time contributed more to the variability of tomatoes and green beans than production lot. Production lot was the more important factor in peaches. The following guidelines may be useful for metabolic studies lasting more than a few weeks: Use only frozen foods or foods canned in glass, maintaining constant production lots when possible. If only tin-canned products are available, remove the product from the can and freeze when appropriate. When products are retained in the can, maintain storeroom at a low temperature above freezing. In all cases, purchase specifications should require products to be from the most recent canning season, and kitchen procedures should be constant.
Whole-body nitrogen was measured in man using a new technique of neutron-activation analysis. Patients were irradiated with a small dose of fast neutrons and the capture γ rays arising from neutron interactions with nitrogen nuclei were recorded. Sixty-five patients with various diseases have been studied on 190 occasions. The technique has proved to be highly reproducible and offers a new experimental approach to the study of metabolic disorders in clinical medicine.
The intake of food and water and excretion of urine and nitrogen were measured in 9 patients for 7 days after they had undergone cardiac surgery with the aid of cardiopulmonary bypass. The patients' unrestricted intake amounted to an average of 24.4 ml water/kg/day, 12.1 kcals/kg/day and 72 mg nitrogen/kg/day. The patients on average excreted 25.8 ml urine/kg/day and 165 mg nitrogen/kg/day in the urine. The significance of malnutrition in the postoperative period after cardiac surgery is discussed.
Positive calcium balance of varying degree has been induced by high calcium intake in four patients with frank osteoporosis and in one patient with apparently normal bone. Phosphate retention appeared to be less with calcium gluconate supplementation than with addition of dicalcium phosphate (CaHPO4). There was often modest increase in urinary calcium but not hypercalciuria during high calcium intake, especially during calcium gluconate administration. Slow intravenous administration of calcium gluconate to one patient resulted in marked hypercalciuria. In the normal patient, who showed moderate storage of calcium during dicalcium phosphate supplementation, the laxative effect of the higher dose of calcium gluconate was associated with increased fecal calcium excretion and negative calcium balance. None of the osteoporotic patients showed definite change clinically or on roentgenograms.In view of the evidence available to date, the most likely mechanism for positive calcium balance during high intake is considered to be inhibition of bone resorption. The effect of high calcium intake upon the clinical, structural and chemical course of osteoporosis is as yet unclear. Until this is defined, no statement can be made about the etiologic role of calcium deficiency or the therapeutic usefulness of high calcium intake in osteoporosis.
These data suggest that calcium may be lost during heavy sweating conditions (up to 20 mg calcium/hour) and that this loss should be considered in establishing recommended allowances for calcium.
It was observed that 7 men consuming 441 mg of calcium a day in a study extending for 48 days, excreted 8.1, 11.6 and 20.2 mg/hour of calcium when living at 70, 85 and 100°F. This accounted for 21.8, 25.1 and 33.2% of the total calcium excreted.
These observations are important since they show an additional calcium loss, which has not been reported in previous calcium balance studies in the literature. It is questionable whether an individual, consuming a low calcium diet, ever really attains calcium balance (equilibrium), under heavy sweating conditions.
It was observed that (a) the calcium excreted in sweat, in men working at a moderate rate in extreme heat (100°F), was still fairly high after acclimatization, averaging 17 mg/hour after the first 4 days, and (b) that the daily total calcium in sweat increased as the sweat rate increased. Therefore it appears that the calcium requirements may be increased under these conditions.
It was shown that even after acclimatization the urinary calcium did not decrease in compensation for the losses of calcium in sweat. It is recognized that changes in the urinary excretion of calcium in adjusting to different levels of dietary calcium and the various other metabolic factors, may require months to achieve.
The results of two experiments show that a considerable quantity of nitrogen is lost in sweat, under conditions that produce profuse sweating. These values average 149, 189 and 241 mg/hour during exposures to environmental temperatures of 70, 85 and 100°F, for men performing moderate daily physical activities.
Men performing a daily minimum of physical activity at 100°F showed a decreased excretion of from 300 to approximately 200 mg/hour, after acclimatization. It has been observed that the nitrogen losses in sweat increased with an increase in physical activity and sweat rate.
These observations are important since they show an additional nitrogen loss that has been ignored in many balance studies. Past studies where equilibrium was apparently attained should be reevaluated, with considerations for dermal nitrogen losses.
The increased nitrogen losses in sweat, even after acclimatization, are not compensated by decreased nitrogen losses from the kidneys and alimentary tract. As a result, the protein requirements of 0.35 gm/kg body weight, should be increased by at least 13 to 14% to compensate for the nitrogen losses in sweat.
The free amino acids excreted in sweat averaged more than 1 gm during a 7.5-hour exposure to 100°F temperatures. Data are also presented for other nitrogen compounds in sweat including urea nitrogen, ammonia, creatinine and uric acid.
The results of this study show that a considerable quantity of sodium, potassium, magnesium and iron are lost in sweat of men during 16 consecutive days' exposure to environmental temperatures of 100°F. During a 7.5-hour collection period, the sweat excretions averaged 0.601 gm/hour for sodium, 0.125 gm/hour for potassium, 2.3 mg/hour for magnesium and 0.13 mg/hour for iron. Very small quantities of phosphorus are excreted in sweat, averaging between 0.45 to 0.81 mg/hour.
In the past, with the exception of sodium, very few investigators have recognized the fact that the mineral losses in sweat could be appreciable and as a result these losses have, all too frequently, been neglected in computing mineral balance. This could result in misinterpretation of the data, especially under conditions of profuse sweating. The total mineral loss should include the mineral loss in sweat. This in turn would help in estimating more realistically the minimal daily allowances of minerals.
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Nitrogen balances
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