Changes In Protein Intake Research Articles

Absorption kinetics are a key factor regulating postprandial protein metabolism in response to qualitative and quantitative variations in protein intake

We have previously demonstrated that increasing the habitual protein intake widened the gap in nutritional quality between proteins through mechanisms that are not yet fully understood. We hypothesized that the differences in gastrointestinal kinetics between dietary proteins were an important factor affecting their differential response to an increased protein intake. To test this hypothesis, we built a 13-compartment model providing integrative insight into the sequential dynamics of meal nitrogen (Nm) absorption, splanchnic uptake, and metabolism, and subsequent peripheral transfer and deposition. The model was developed from data on postprandial Nm kinetics in certain accessible pools, obtained from subjects having ingested a (15)N-labeled milk or soy protein meal, after adaptation to normal (NP) or high (HP) protein diets. The faster absorption of Nm after soy vs. milk caused its earlier and stronger splanchnic delivery, which favored its local catabolic utilization (up to +30%) and limited its peripheral accretion (down to -20%). Nm absorption was also accelerated after HP vs. NP adaptation, and this kinetic effect accounted for most of the HP-induced increase (up to +20%) in splanchnic Nm catabolic use, and the decrease (down to -25%) in peripheral Nm anabolic utilization. The HP-induced acceleration in Nm absorption was more pronounced with soy than with milk, as were the HP effects on Nm regional metabolism. Our integrative approach identified Nm absorption kinetics, which exert a direct and lasting impact on Nm splanchnic catabolic use and peripheral delivery, as being critical in adaptation to both qualitative and quantitative changes in protein intake.

Protein supplementation may enhance the spontaneous recovery of neurological alterations in patients with ischaemic stroke

Objective: To determine whether protein supplementation could enhance neurological recovery in subacute patients with ischaemic stroke. Design: Alimentation-independent patients with ischaemic stroke were randomly allocated to either 21 days of protein supplementation (protein-supplemented group; n=20) or to a spontaneous diet only (control group; n=21) in order to investigate the recovery of neurological changes (measured using the National Institute of Health (NIH) Stroke Scale). Setting: Tertiary care rehabilitation in Italy. Participants: Forty-two patients (27 male and 15 female; 66.4 ± 11 years) 16 ±2 days after the acute event. Intervention: Supplementation with a hyperproteic nutritional formula (10% protein). Main outcome measures: NIH Stroke Scale and protein intake. Results: At admission to rehabilitation, both groups of patients were homogeneous for demographic, clinical and functional characteristics. After 21 days from the start of the protocol, the NIH Stroke Scale was found to be enhanced in the group with supplemental proteins (-4.4 ± 1.5 score versus -3 ± 1.4 of control group; P<0.01). When expressed as difference (▵) between baseline and 21 days, the NIH Stroke Scale correlated negatively with change in protein intake (g/day) (r=-0.50, P= 0.001) and positively with change in carbohydrate/protein ratio (r=+0.40, P=0.01) Conclusions: Protein supplementation may enhance neurological recovery in subacute patients with ischaemic stroke.

Change in Protein Intake in Elderly French People Living at Home After a Nutritional Information Program Targeting Protein Consumption

Objective The purpose of the study was to assess the impact of a nutrition information program targeting protein consumption in elderly people. Design and Intervention Participants individually completed a questionnaire on food consumption and answered an attitude questionnaire (first survey period). Half of the participants (message group) participated in an information program targeting protein consumption, whereas the other half (control group) were not given any information. Two weeks after the program, both groups participated in the same surveys again (second survey period). Subjects Eighty-two healthy subjects (65 to 75 years old) living at home participated in this study. Statistical Analyses A two-way multivariate analysis of variance, paired t tests, and χ 2 tests were performed to determine the influence of group (control versus message) and gender on the differences in protein consumption and in attitudes between the first and second survey periods. Results In the second survey period, the control group participants decreased their protein intake by an average of 0.049 g/lb/day, mainly by a reduction in meat product consumption. Conversely, the message group participants increased their protein intake by 0.041 g/lb/day, with a greater increase for the women (0.059) than the men (0.023 g/lb/day). After the nutrition information program, knowledge, perceived control on health, and belief that sensory perception decreased with age were higher among the message group participants. Conclusions Nutrition knowledge and protein intake increased significantly among the message group participants. Thus, it is possible to change dietary practice and knowledge in elderly individuals by information targeting one nutrition message.

Effect of Changes in Protein Intake under Energy Restricted Conditions on Fattening Performance and Various Organ Weights in Lambs

Effect of Changes in Protein Intake under Energy Restricted Conditions on Fattening Performance and Various Organ Weights in Lambs

The IGF-system is not affected by a twofold change in protein intake in patients with type 1 diabetes

Objective In type 1 diabetes the circulating IGF-system is altered with low IGF-I and changes in levels of IGF-binding proteins (IGFBPs) which may be of importance for the development of diabetes complications. Our aim was to study if IGF-I, as supported by experimental data in animals, can be affected by dietary protein intake. Design and methods Twelve patients with type 1 diabetes, age 37.5 ± 10.0 years (mean ± SD), diabetes duration 20.1 ± 9.3 years and HbA1c 6.3 ± 0.6% were allocated to isocaloric diets with either low normal protein content (LNP), (10 E%; 0.9 g protein/kg body weight) or high normal protein content (HNP) (20 E%; 1.8 g protein/kg body weight) in an open randomised cross-over study. Each diet was taken for 10 days with a wash-out period of 11 days in between. Circulating levels of total and free IGF-I and -II, IGFBP-1, -2 and -3 and GH-binding protein (GHBP) as well as ghrelin were measured with validated in-house immunoassays. Results At day 10, urinary urea excretion was 320 ± 75 mmol/24 h during LNP diet compared with 654 ± 159 mmol/24 h during HNP diet ( p < 0.001). There were no changes in body weight or glycaemic control between the diets. Fasting levels of total IGF-I were 121 ± 33 μg/L after LNP and 117 ± 28 μg/L after HNP diet (ns) and the corresponding concentrations of IGFBP-1 were 142(141) and 132(157) μg/L [median (IQR)] (ns). There were no differences in plasma concentrations of total IGF-II, free IGF-I and -II, IGFBP-3, GHBP and ghrelin, whereas a small difference was found for IGFBP-2 (302 ± 97 vs. 263 ± 66 μg/L; LNP vs. HNP; p < 0.04). Conclusions A twofold change of the dietary protein intake does not influence the altered circulating IGF-system in type 1 diabetes. In order to affect the IGF-system other interventions must be used.

The effect of reduced maternal protein intake during pregnancy on placental lipid composition in the rat: effect of glycine supplementation of the low protein diet

The objective of this study was to determine whether consumption of a maternal low-protein (MLP) diet during pregnancy alters placental lipid composition, and whether this was prevented by supplementation of the MLP diet with glycine, that ameliorates some effects of this diet. Rats ( n = 5/group) were fed diets containing 18%(w/w) casein (Control), 9%(w/w) casein (MLP), or MLP plus 3%(w/w) glycine (MLP+G) from conception to 20/21 days gestation. Placental total phosphatidylethanolamine (PE) and triacylglycerol (TAG), but not phosphatidylcholine (PC), concentrations were greater in the MLP group. Docosahexaenoic acid concentration was specifically reduced in placental PC, PE, and TAG in the MLP group, which reflected maternal liver and plasma. These changes were not prevented by the MLP+G diet. These data indicate that placental fatty acid composition is determined by the fatty acid content of maternal liver and plasma, and that reduced maternal protein intake changes placental membrane structure.

Minimum protein intake for the preterm neonate determined by protein and amino acid kinetics.

Lower limits of protein needs in prematurely born neonates have not been adequately studied, yet providing protein in amounts maximizing accretion without excess is a goal in these infants' nutritional care. We hypothesized that with the use of amino acid oxidation methodology, it would be possible to define minimum protein requirement. Our objective was to investigate protein kinetics during short-term changes in protein intake by measurement of nitrogen balance and amino acid flux and oxidation using [(15)N]glycine, [(13)C]phenylalanine, and [(13)C]leucine tracers. Protein kinetics were examined in 21 preterm infants (gestational age: 29 +/- 3 wk; birth weight: 1091 +/- 324 g) at five protein intakes (1.0, 1.5, 2.0, 2.5, and 3.0 g x kg(-1) x d(-1)) with 1 d of adaptation to the test intakes. From nitrogen balance data, a protein need of 0.74 g x kg(-1 x -1) was estimated to achieve zero balance. For all three amino acids, flux and oxidation estimates were not different across protein intakes. Whole-body protein synthesis and breakdown estimates from [(15)N]ammonia data were 14.6 +/- 3.4 and 14.4 +/- 4.1 g x kg(-1) x d(-1), respectively. Glycine flux (680 +/- 168 micromol x kg(-1) x h(-1)) was greater than leucine flux (323 +/- 115 micromol x kg(-1) x h(-1)), which was greater than phenylalanine flux (84.3 +/- 35.2 micromol x kg(-1) x h(-1)). Leucine oxidation (36.7 +/- 15.6 micromol x kg(-1) x h(-1)) was also greater than phenylalanine oxidation (6.64 +/- 4.41 micromol x kg(-1) x h(-1)). Infants in our study were able to adapt to short-term changes in protein intake with little consequence to the overall whole-body protein economy, as measured by the three test amino acids.

Effects of ascites resolution after successful TIPS on nutrition in cirrhotic patients with refractory ascites

OBJECTIVE: Malnutrition is common in patients with decompensated cirrhosis and refractory ascites. The use of transjugular intrahepatic portosystemic stent shunt (TIPS) is effective in eliminating ascites. The purpose of this study was to investigate the effect of TIPS and resolution of refractory ascites on the nutritional status of patients with decompensated cirrhosis. METHODS: Fourteen consecutive patients with refractory ascites and a Pugh score of 9.0 ± 0.5 had a TIPS insertion. Biochemical data, resting energy expenditure (REE), total body nitrogen (TBN), body potassium (TBK), body fat (TBF), muscle force (MF), and food intake were recorded before TIPS, and at 3 and 12 months after the procedure. RESULTS: Ten patients completed the study. Baseline values for REE, TBN, TBF, MF, and energy intake were below normal at baseline. There was a significant increase in dry weight, TBN, and REE at 3 and 12 months compared with baseline. TBF improved significantly at 12 months. There was a trend toward an increase in energy intake ( p = 0.072). There was no change in protein intake, TBK, MF, and Pugh score. CONCLUSION: In cirrhotic patients with refractory ascites, resolution of the ascites after TIPS placement resulted in improvement of several nutritional parameters, especially for body composition.

Effects of ascites resolution after successful TIPS on nutrition in cirrhotic patients with refractory ascites.

Malnutrition is common in patients with decompensated cirrhosis and refractory ascites. The use of transjugular intrahepatic portosystemic stent shunt (TIPS) is effective in eliminating ascites. The purpose of this study was to investigate the effect of TIPS and resolution of refractory ascites on the nutritional status of patients with decompensated cirrhosis. Fourteen consecutive patients with refractory ascites and a Pugh score of 9.0+/-0.5 had a TIPS insertion. Biochemical data, resting energy expenditure (REE), total body nitrogen (TBN), body potassium (TBK), body fat (TBF), muscle force (MF), and food intake were recorded before TIPS, and at 3 and 12 months after the procedure. Ten patients completed the study. Baseline values for REE, TBN, TBF, MF, and energy intake were below normal at baseline. There was a significant increase in dry weight, TBN, and REE at 3 and 12 months compared with baseline. TBF improved significantly at 12 months. There was a trend toward an increase in energy intake (p = 0.072). There was no change in protein intake, TBK, MF, and Pugh score. In cirrhotic patients with refractory ascites, resolution of the ascites after TIPS placement resulted in improvement of several nutritional parameters, especially for body composition.

Effects of an isoflavone-free soy diet on ovarian hormones in premenopausal women.

Soy intakes have been associated with reduced rates of breast cancer in some Asian populations. The isoflavones daidzein and genistein and other components of soybeans may modulate endocrine function and lead to beneficial health effects. This study determined the effects of a soy diet containing minimum amounts of isoflavones on circulating levels of ovarian hormones and gonadotropins. Nine healthy, regularly cycling women consumed a constant soya-containing diet on a metabolic unit starting on day 2 of a menstrual cycle until day 2 of the next cycle. The soy diet was calculated to maintain constant body weight and included a 36-oz portion of soymilk that provided 334 kilocalories and less than 5 mg/day of total isoflavones. The energy distribution of the soy diet was 35.9% fat, 14.0% protein, and 49.8% carbohydrate whereas the home diets averaged 39% fat, 16.6% protein, and 42.5% carbohydrate. For the group, the soya diet provided more carbohydrate (P = 0.002) and less protein (P = 0.005) than the home diets. Daily consumption of the soya diet reduced daily circulating levels of 17beta-estradiol over the entire menstrual cycle by 20% (P < 0.01, paired t test, two-tailed) and progesterone by 33% (P < 0.0001) compared with levels during the home diet period, but had no effect on LH, FSH, or sex hormone-binding globulin. The decreases in follicular phase 17beta-estradiol during the soy diet can be accounted for by changes in energy intakes, nutrient density, and fiber intake, whereas changes in luteal phase 17beta-estradiol were most strongly associated with differences in fiber intake. Changes in progesterone levels were most strongly associated with changes in protein intake and much less with other nutrients. Isoflavones were not detectable in plasma and urine during either the soy or home diet periods. These results suggest that at least under the conditions of this study, a soy diet with low levels of isoflavones and low energy intake from protein can reduce circulating ovarian steroids without altering gonadotropins. Our results are consistent with previous studies showing decreased ovarian hormone levels and decreased risk of breast cancer in populations consuming soya diets and an inverse relationship between animal protein intake and breast cancer risk and, therefore, may have implications for breast cancer prevention.

The mysteries of nitrogen balance

The first part of this review is concerned with the balance between N input and output as urinary urea. I start with some observations on classical biochemical studies of the operation of the urea cycle. According to Krebs, the cycle is instantaneous and automatic, as a result of the irreversibility of the first enzyme, carbamoyl-phosphate synthetase 1 (EC 6.3.5.5; CPS-I), and it should be able to handle many times the normal input to the cycle. It is now generally agreed that acetyl glutamate is a necessary co-factor for CPS-1, but not a regulator. There is abundant evidence that changes in dietary protein supply induce coordinated changes in the amounts of all five urea-cycle enzymes. How this coordination is achieved, and why it should be necessary in view of the properties of the cycle mentioned above, is unknown. At the physiological level it is not clear how a change in protein intake is translated into a change of urea cycle activity. It is very unlikely that the signal is an alteration in the plasma concentration either of total amino-N or of any single amino acid. The immediate substrates of the urea cycle are NH3 and aspartate, but there have been no measurements of their concentration in the liver in relation to urea production. Measurements of urea kinetics have shown that in many cases urea production exceeds N intake, and it is only through transfer of some of the urea produced to the colon, where it is hydrolysed to NH3, that it is possible to achieve N balance. It is beginning to look as if this process is regulated, possibly through the operation of recently discovered urea transporters in the kidney and colon. The second part of the review deals with the synthesis and breakdown of protein. The evidence on whole-body protein turnover under a variety of conditions strongly suggests that the components of turnover, including amino acid oxidation, are influenced and perhaps regulated by amino acid supply or amino acid concentration, with insulin playing an important but secondary role. Molecular biology has provided a great deal of information about the complex processes of protein synthesis and breakdown, but so far has nothing to say about how they are coordinated so that in the steady state they are equal. A simple hypothesis is proposed to fill this gap, based on the self-evident fact that for two processes to be coordinated they must have some factor in common. This common factor is the amino acid pool, which provides the substrates for synthesis and represents the products of breakdown. The review concludes that although the achievement and maintenance of N balance is a fact of life that we tend to take for granted, there are many features of it that are not understood, principally the control of urea production and excretion to match the intake, and the coordination of protein synthesis and breakdown to maintain a relatively constant lean body mass.

Thermal Effects on Net Protein Ratio of Red Kidney Beans (Phaseolusvulgaris L)

Net protein ratio (NPR), predicted-protein efficiency ratio (P-PER), relative NPR (RNPR), and corrected RNPR (CRNPR) of thermally processed red kidney beans were estimated in rats and compared to in vitro protein digestibility-corrected amino acid score (AASIVDP), and computed-protein efficiency ratio (C-PER). Thermal processing had a significant effect on protein intake, NPR, P-PER and CRNPR values of beans. Changes in protein intake suggest that heat processing had an effect on the palatability of the beans. Home-cooked beans and commercially canned beans had higher NPR values than beans autoclaved at 128°C for 20 min, while beans autoclaved at 121°C for 10–90 min had intermediate values. High correlation coefficients between P-PER and C-PER, CRNPR and C-PER, and CRNPR and AASIVDP (r=0·990, 0·992 and 0·960, respectively, P<0·001) were observed.

Nitrogen homoeostasis in man: diurnal changes in nitrogen excretion, leucine oxidation and whole body leucine kinetics during a reduction from a high to a moderate protein intake.

1. The adaptation of the diurnal cycle of nitrogen (N) homeostasis during a change in protein intake was investigated with diurnal measurements of N and leucine balance and turnover during a reduction from a high to a moderate protein intake in normal adults. 2. In experiment 1, during a 9 day period after a reduction from 1.82 to 0.77 g of protein day-1 kg-1, N excretion fell slowly at a similar rate in fed and fasted states so that the lowered intake was unable to replete any of the postabsorptive losses for 3 days. There was a marked negative N balance, which persisted throughout the study, although with a significant reduction in N losses in both fed and fasted states on day 4, balances during days 4-9 (-32.8 +/- 28.3 mg of N day-1 kg-1) were less negative than during days 1-3 (-79.1 +/- 60.4 mg of N day-1 kg-1). 3. In experiment 2, during a 14 day period after a reduction from 1.89 to 0.77 g of protein day-1 kg-1, [1-13C]leucine oxidation and turnover were measured by primed intravenous infusion, during fasting and feeding in subjects before and on days 3, 7 and 14 after the dietary change. Leucine oxidation fell by 32% (P < 0.05) on day 3 in the fed state and by 12% (P < 0.05) during fasting, falling further in each case by day 7 with improved balance.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritional Status and Growth in Children Less than 12 kg Treated with Continuous Ambulatory Peritoneal Dialysis

Various parameters of nutritional status and growth in 13 children with weight less than 12 kg were estimated at the start of continuous ambulatory peritoneal dialysis (CAPD) and 1 year later. A significant improvement in weight, triceps skinfold, and serum albumin was noticed. Height and midarm muscle circumference did not change significantly. However, a significant improvement in height occurred in patients with initial abnormal height (<--2 SDS). There was no significant change in protein intake and urea nitrogen appearance (UNA) during the study period. A significant correlation between protein intake and UNA was noticed. All patients had normal serum insulinlike growth factor. In conclusion, there was no significant change in either height velocity or muscle mass despite the improvement in many nutritional parameters.

Protein intake and blood glucose as modulators of GFR in hyperfiltering diabetic patients

Glomerular hyperfiltration has been claimed to be a risk factor for the development of diabetic nephropathy. Protein intake and hyperglycemia can both increase GFR in diabetic and normal subjects. Our study was designed to explore the relative importance of short-term changes in protein intake and glycemia on the modulation of renal hemodynamics in insulin-dependent diabetic (IDDM) patients with and without glomerular hyperfiltration. The renal hemodynamic response to a protein challenge was studied in eight hyperfiltering (HF) and eight normofiltering (NF) patients after a three week period of low or normal protein diet (LPD, NPD), each study being conducted twice, in random order, under conditions of prevailing hyperglycemia (H) and euglycemia (E). In HF patients GFR failed to increase significantly in response to protein challenge during NPD under conditions of either H or E (Baseline vs. 2 hr H: 151 +/- 4 vs. 155 +/- 6, NS; E 147 +/- 4 vs. 157 +/- 7 ml/min/1.73 m2, NS). A more normal response was restored following LPD with GFR increasing in all but one patient after challenge during H and in all patients during E (Baseline vs. 2 hr H: 130 +/- 7 vs. 145 +/- 8, P less than 0.07; E: 127 +/- 7 vs. 143 +/- 7 ml/min/1.73 m2, P less than 0.01). Changes in RPF paralleled the changes in GFR and filtration fraction remained stable under all study conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Dietary Protein Intake on Whole-Body Protein Turnover in Humans

Methods for measuring rates of protein synthesis and degradation in the whole body of humans with isotopes of carbon and nitrogen are described and attention is drawn to their relative merits and drawbacks for studying the nutritional control of protein metabolism. A review of published work on dietary protein and protein metabolism leads to the conclusion that protein is the major dietary determinant of whole-body protein turnover rates, and that energy intake is comparatively unimportant. Dietary protein affects protein turnover at two levels: an immediate response to the intake of protein in meals and a longer-term adaptation after a change in protein intake. An increase in the level of dietary protein enhances the response to meals, which mainly consists of a decrease in the rate of protein degradation. The adaptation to higher protein intakes involves an increase in the basal (postabsorptive) rates of both synthesis and degradation. Suggestions for future investigation include more detailed studies of the acute and adaptive responses, to facilitate understanding of dietary protein requirements, and the effects of very-high-protein intakes with continued development of techniques for studying protein turnover in individual tissues in humans.

Nitrogen and purine metabolism at varying energy and protein supplies in sheep sustained on intragastric infusion

Wether sheep were fitted with rumen fistulas and polyethylene tubes to the abomasum and were given all nutrients by intragastric infusion. In Expt 1 volatile fatty acids (VFA) were given at 340, 450 and 630 kJ gross energy (GE)/kg metabolic weight (W0-75) and protein at 0, 150, 300, 600, 900 and 1500 mg nitrogen/kg W0-75. In Expt 2 VFA were infused at 450 kJ GE/kg W0-75 and protein at 0 and 300 mg N/kg W0-75. At all levels of energy intake in Expt 1 the N retention was significantly (P less than 0.01) related to N intake. The basal N requirement was estimated to be 281 mg (SE 21.8) N/kg W0-75 at 340 kJ VFA/kg W0-75, 226 (SE 21.8) mg N/kg W0-75 at 450 kJ VFA/kg W0-75 and 207 (SE 19.4) mg N/kg W0-75 at 630 kJ VFA/kg W0-75. Plasma urea concentrations varied markedly in relation to protein intake and to energy supply. On the other hand plasma ammonia, glucose, insulin and creatinine concentrations, and also urinary excretion of purine derivatives and creatinine were not significantly affected by the treatments imposed. It was concluded that the urinary excretion of purine derivatives in ruminants was largely unaffected by moderate changes in energy intake and by large changes in protein intake.

Albumin and labile-protein serum concentrations during very-low-calorie diets with different compositions

Circulating concentrations of albumin and the labile proteins prealbumin (PA) and retinol-binding protein (RBP) were evaluated over 20 d in five groups of obese patients. The patients were given four types of very-low-calorie diets (VLCDs) (less than 500 kcal/d) that provided different amounts of protein or carbohydrate (CHO) plus protein and a conventional 1200-kcal/d hypocaloric diet. Serum albumin concentrations did not vary significantly during any of the diets whereas PA and RBP remained unchanged only during the conventional 1200-kcal/d diet. Similar and significant decreases of serum PA and RBP were observed during the VLCDs studied. The molar ratio of RBP to PA did not vary during dieting. Thus, when less than 500 kcal/d are given, changes of serum short-half-life visceral proteins are not affected by either the addition of CHO to protein or the changes in protein intake. Moreover, serum albumin concentration and RBP/PA do not vary during VLCDs.

Serum transferrin levels in the longitudinal assessment of protein-energy status in preterm infants.

We prospectively measured serum transferrin levels weekly from birth until discharge in 33 preterm newborn infants hospitalized on the newborn intensive care unit (n = 130 weeks) to study whether transferrin levels accurately reflect recent nutritional intakes and predict subsequent changes in anthropometric measurements and serum protein levels. Mean daily protein and caloric intakes were no greater during weeks when transferrin levels increased than when levels decreased. There were weak but statistically significant linear relationships between protein intake and transferrin levels (r = 0.24, p less than 0.01), caloric intake and transferrin levels (r = 0.27, p less than 0.01), and magnitudes of weekly changes in protein intake and transferrin levels (r = 0.31, p less than 0.001), and magnitudes of weekly changes in caloric intake and transferrin levels (r = 0.27, p less than 0.01). Transferrin levels did not reflect same-week weight or midarm circumference (MAC) gains, nor did they predict the following week's gains. Mean anthropometric measurement gains were similar following weeks when transferrin levels increased or decreased. There were no positive linear relationships between the magnitudes of changes in transferrin levels and same-week weight gain (r = -0.35), same-week MAC gain (r = -0.27), or following-week MAC gain (r = 0.01). Weak correlations were found with following-week albumin levels (r = 0.32, p less than 0.001) and with same-week transthyretin levels (r = 0.44, p less than 0.001). Weekly serum transferrin levels are not useful for longitudinal surveillance of protein-energy status in preterm infants.

Serum Transferrin Levels in the Longitudinal Assessment of Protein‐Energy Status in Preterm Infants

We prospectively measured serum transferrin levels weekly from birth until discharge in 33 preterm newborn infants hospitalized on the newborn intensive care unit (n = 130 weeks) to study whether transferrin levels accurately reflect recent nutritional intakes and predict subsequent changes in anthropometric measurements and serum protein levels. Mean daily protein and caloric intakes were no greater during weeks when transferrin levels increased than when levels decreased. There were weak but statistically significant linear relationships between protein intake and transferrin levels (r = 0.24, p &lt; 0.01), caloric intake and transferrin levels (r = 0.27, p &lt; 0.01), and magnitudes of weekly changes in protein intake and transferrin levels (r = 0.31, p &lt; 0.001), and magnitudes of weekly changes in caloric intake and transferrin levels (r = 0.27, p &lt; 0.01). Transferrin levels did not reflect same‐week weight or midarm circumference (MAC) gains, nor did they predict the following week's gains. Mean anthropometric measurement gains were similar following weeks when transferrin levels increased or decreased. There were no positive linear relationships between the magnitudes of changes in transferrin levels and same‐week weight gain (r = −0.35), same‐week MAC gain (r = −0.27), or following‐week MAC gain (r = 0.01). Weak correlations were found with following‐week albumin levels (r = 0.32, p &lt; 0.001) and with same‐week transthyretin levels (r = 0.44, p &lt; 0.001). Weekly serum transferrin levels are not useful for longitudinal surveillance of protein‐energy status in preterm infants.