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Application of gel permeation chromatography and nonaqueous reverse phase chromatography to high performance liquid chromatographic determination of retinyl palmitate and alpha-tocopheryl acetate in infant formulas.

A high performance liquid chromatographic (HPLC) method was developed for determining retinyl palmitate and alpha-tocopheryl acetate in infant formulas. The lipid-soluble components were extracted from the aqueous phase by homogenizing in a solvent mixture of isopropanol and methylene chloride with magnesium sulfate added to remove water. The vitamins were fractionated from the lipid material by using high pressure gel permeation chromatography (HP-GPC) followed by quantitation using non-aqueous reverse phase (RP)-HPLC. Three muStyragel (100A) columns connected in series were used for HP-GPC fractionation of sample extracts in methylene chloride. A Zorbax ODS (6 micron) column and methylene chloride-acetonitrile-methanol (30 + 70 + 0.2) were used for RP-HPLC quantitation. The 32 commercial infant formulas that were analyzed represent a wide variety of formulations manufactured at various fortification levels. Vitamin A results ranged from 89 to 242% of the declared levels. Vitamin E values, determined as the supplemental form alpha-tocopheryl acetate, ranged from 83 to 272% of the declared levels. Determination of vitamin A in 6 samples and vitamin E in one sample by this method and the official AOAC method gave comparable results. This method, which requires no saponification, was successfully used to determine vitamins A and E in ready-to-use, liquid concentrated, and powdered infant formulas.

Chromatography, Gel↗

Immunoreactive substance P and calcitonin-gene-related peptide (CGRP) in rat milk and in human milk and infant formulas.

This study examined the presence of substance P and calcitonin-gene-related peptide (CGRP) immunoreactivities in various milks and infant formulas. Rat milk was obtained from lactating dams between parturition and weaning (0, 2, 5, 10, 15, and 20 d postpartum). Samples of human milk were obtained from seven multiparous, nonsmoking white women, and newborn infant formulas were purchased from local stores. Substance P and CGRP were measured by competitive enzyme immunoassay using acetylcholinesterase-peptide conjugates as tracers. In rats, substance P and CGRP were below detectable concentrations in amniotic fluid from the last day of gestation. In contrast, in milk the concentrations of substance P and CGRP-like immunoreactivities were high on the first day of lactation (3.1 +/- 0.2 and 23.1 +/- 1.5 micrograms/L, respectively), then dropped after day 2 (1.6 +/- 0.7 and 7.5 +/- 0.4 microgram/L, respectively) and remained fairly constant until weaning. Significant concentrations of substance P and CGRP were found in human milk (129.2 +/- 27 ng/L and 4.5 +/- 0.7 microgram/L, respectively, at 15 wk), but substance P or CGRP could not be detected in any of the formulas tested. These data show that milk contains high concentrations of immunoreactive substance P and CGRP. In rats the absence of peptides in amniotic fluid suggests that there is a flood of peptides into the gastrointestinal tract of neonates when suckling is initiated. Significant concentrations of substance P and CGRP in human milk but not in infant formulas may therefore have physiologic implications for neonatal nutrition.

Amniotic Fluid↗

Background levels of carbon-13 reduced in breath and stool by new infant formula.

Studies of the absorption and bioavailability of nutrients naturally enriched with 13C require accurate measurements of small increases of 13C in respiratory CO2 and stool carbon. The sensitivity of these measurements would be increased if the natural background of 13C in these excreta were reduced. We have developed a 13C-depleted infant formula based on lactose, whey, and casein from New Zealand cows that consume only C3 vegetation naturally low in 13C. This formula, designated CNRC3, was produced by a commercial infant formula manufacturer and was comparable with a 60:40 whey/casein product. To test the ability of the formula to reduce baseline levels of 13C in infant excreta, 10 formula-fed infants 28-60 days old and free of metabolic disorders were enrolled in the 9-day study. Two stool samples were collected daily. Infants received their usual formula on days 1 and 2 and were switched to CNRC3 formula for days 3-9. On days 2 and 9, seven breath samples were collected at 30-min intervals with a face mask. Breath and stool samples were analyzed for 13C content by gas isotope ratio mass spectrometry. Infants consuming their commercial formula had breath delta 13C values of -21.1 +/- 0.6% over the 3-h collection period; stool values were -22.9 +/- 0.4%. After 7 days on the CNRC3 formula, delta 13C values of breath declined by 5.6% to -26.7 +/- 0.7%; stool values declined by 3.0% to -25.6 +/- 0.5%. The reduced background of 13C achieved by the CNRC3 formula can improve resolution of excess 13C from naturally enriched substrates in infant breath by approximately 50% and in stool by approximately 30%.

Breath Tests↗

Safety evaluation of sources of docosahexaenoic acid and arachidonic acid for use in infant formulas in newborn piglets.

Human milk provides small quantities of preformed docosahexaenoic acid (DHA) and arachidonic acid (ARA), usually less than 1% of total fatty acids. Vegetable oil blends commonly used in infant formulas have, until recently, provided the essential fatty acid precursors for these long-chain polyunsaturated fatty acids (LCPUFA), but no preformed DHA and ARA. This study evaluated the safety of ingredient sources of DHA and ARA for use in infant formulas in a neonatal piglet model. Newborn piglets were allowed to suckle for 3 days and then divided into 4 feeding groups of 6 males and 6 females. Piglets were bottle-fed at frequent feeding intervals until 19 days of age. The composition of the piglet formulas was modeled after standard milk-based formulas for human infants while meeting nutritional requirements for piglets. Formulas were a control formula (no added DHA or ARA), a DHA formula providing 55 mg DHA/100 Cal, an ARA formula providing 96 mg/100 Cal ARA, and a DHA+ARA formula providing 34 mg DHA and 62 mg ARA/100 Cal. All formulas were equal in fat content and provided approximately 1000 Cal/l. The ARA-rich oil was from a fermentation product of Mortierella alpina (40 wt.% fatty acids as ARA) and DHA was from high DHA tuna oil (25 wt.% fatty acids as DHA). There were no test article related effects of DHA and/or ARA indicative of an adverse health consequence to the animals seen in the clinical signs, body weights, food consumption, clinical chemistry, hematology, organ weights or gross or histopathology. The findings in this neonatal animal study support the safety of these ingredient oil sources of DHA and ARA for use in infant formulas.

Animals↗

Effect of protein source and iron content of infant formula on stool characteristics.

Formula-fed, term infants were evaluated in two studies that assessed the influence on stool characteristics of protein source and iron content of the formula. Parental observations of infants' stool characteristics were recorded on standard forms. Green was the primary stool color for infants receiving whey-predominant formula containing iron at 12 mg/L. A low-iron (1.5 mg/L), whey-predominant formula produced yellow stools. A casein-predominant, iron-fortified (12 mg/L) formula produced primarily yellow or brown stools, although many of the infants fed this formula also had green stools. Soft stools were common in infants fed either whey- or casein-predominant formulas. However, more infants receiving whey-predominant formulas passed watery or slimy stools than did infants receiving casein-predominant formulas. We conclude that green stools in the absence of signs of disease should be considered a normal variation of stool color.

Caseins↗

Heat processing in infant formulas induces changes in copper tissue levels in suckling and weanling rats.

AIM: To assess the effects of dehydration, conventional in-bottle sterilization, and ultrahigh-temperature (UHT) sterilization, involved in the production of infant formulas, on the copper bioavailability in rats at two stages. METHODS: Two-week-old suckling rats were fed a reconstituted powder (P1) and an in-bottle-sterilized liquid infant formula (SC1) in a drinking bottle for 7 days. Weanling rats were fed P1, SC1, another powder (P2), and a liquid UHT formula (UHT2) complemented with a standard rat diet. Intake, body weight, and percentage copper absorption were calculated, and whole-body, serum, liver, skin, and erythrocyte copper concentrations were determined. RESULTS: Food intake, body weight, and copper intake were reduced in suckling rats consuming SC1, but the percentage copper absorption increased, and whole-body and tissue copper concentrations were unaffected, except for the erythrocyte copper concentration which was significantly higher as compared with pups fed P1. In weanling rats, the only difference observed was the significantly higher liver copper concentration in animals fed the diet containing P1 as compared with the diets containing SC1 and UHT2. CONCLUSIONS: Consuming the SC1 formula induced high erythrocyte copper levels in suckling rats, whereas the equivalent dehydrated formula (P1) induced elevated liver copper concentrations in weanling rats. This is associated with the different Maillard reaction products resulting from the processing of each infant formula and with the developmental stage of the animals.

Analysis of Variance↗

Influence of purine intake on uric acid excretion in infants fed soy infant formulas.

OBJECTIVE: These studies tested the hypothesis that increasing intake of purines, delivered as RNA from soy protein-based infant formula, would increase urinary uric acid excretion in infants. METHODS: Study One examined the influence of feeding on serum uric acid in a total of 178 infants from four separate trials with infants fed commercial and experimental soy-based and milk-based infant formulas or human milk. Studies Two and Three compared the effect of a standard purine soy formula (STD Purine; 180 mg purines/L from RNA) and a reduced purine soy formula (Reduced Purine; 65 mg purines/L; 26 mg/L from RNA and 39 mg/L from ribonucleotides) on urinary uric acid excretion in infants. In Study Two, 11 infants ranging in age from 16 to 128 days of age were fed both formulas in a random crossover design. Complete 72-hour urine collections were done at the end of each 11-day feeding period. Urinary uric acid excretion was expressed as mmol/day. In Study Three, 33 infants were enrolled before eight days of age and randomized to one of the formulas one week later. Spot urine samples were collected at 28 and/or 56 days of age and urinary uric acid concentration was expressed as mmol/mmol creatinine. RESULTS: In Study One, each of the feedings resulted in mean serum uric acid levels within normal reference ranges. Soy formula led to higher serum uric acid levels than human milk, and human milk to levels indistinguishable from cow milk-based formulas. In Study Two, infants excreted significantly more uric acid in the urine when fed the STD Purine formula compared to the Reduced Purine formula (0.86+/-.04 vs. 0.57+/-.04 mmol/d) (p = 0.006). In Study Three, infants fed the STD Purine formula had a significantly higher concentration of uric acid in their urine compared to those fed the Reduced Purine formula (2.1+/-0.2 vs. 1.4+/-0.1 mmol uric acid/mmol creatinine) (p = 0.0001). CONCLUSION: These data indicate that healthy infants can digest RNA and subsequently absorb the liberated purine ribonucleotides as determined by urinary uric acid concentration.

Cross-Over Studies↗

DDT residues in butter and infant formula in India, 1977.

Samples of commercial brands of butter and infant formula from different parts of India were examined for DDT residues. All 18 samples of butter representing nine brands were contaminated. Levels of DDT residues ranged from 0.42 to 11.36 ppm and exceeded the Food and Agriculture Organization/World Health Organization practical residue limit of 1.25 ppm in 90 percent of the samples. All four brands of infant formula contained DDT residues above the practical residue limit. Most DDT residues were in the form of p,p-TDE in both commodities. This contamination of milk with excessive amounts of DDT residues seems to be widespread in India.

Animals↗

Improved storage stability of model infant formula by whey peptides fractions.

The purpose of this study was to evaluate the shelf-life stability (6 months) of model infant formula with whey protein hydrolysates or peptidic fractions as carrageenan replacers. Whey protein hydrolysates were prepared with trypsin and followed by ultrafiltration of the hydrolyzed mixture, and peptidic fractions were isolated from the ultrafiltered tryptic hydrolysate by anion- or cation-exchange chromatography. The stability of the model infant formula was evaluated using a stratification method based on fat content differences between the top and bottom strata of the samples. With protein hydrolysate-based formulations, the creaming rate of the fat in the product was slightly higher than in the standard formulation (with carrageenan), which is indicative of lower storage stability. The addition of cationic fractions to model infant formula also resulted in lower product stability, whereas the fat creaming rate was retarded in anionic fraction based formulations. The physicochemical characteristics of certain peptides combined with the reported high emulsifying properties of peptidic sequences found within these fractions may account for their ability to act as carrageenan replacers.

Animals↗

Red blood cell and tissue phospholipid fatty acid profiles of weanling rats fed infant formula fat blends containing soy and/or corn oil.

Soy oil or corn oil may be employed to provide essential fatty acids in infant formulas. Both of these sources are high in linoleic acid; soy oil contains modest levels of alpha-linolenic acid, while corn oil contains very low levels of this essential omega 3 fatty acid. We examined the omega 3 long-chain polyunsaturated fatty acid (LCP) accretion in red blood cells, liver, and brain phospholipids of rats on diets containing infant formula fat blends with essential fatty acids provided from soy and/or corn oil. Although modest alterations occurred in the red blood cell omega 3 LCP fatty acid status, substantially larger changes were noted in liver LCP profiles. Due to the relatively mature nature of the rats employed in this experiment, no alterations were noted in brain fatty acid profiles. In conclusion, we have observed substantial tissue differences in animals fed soy or corn oil containing diets. It appears that corn oil is inappropriate for use in infant formulas.

Animals↗

Liquid concentrates are lower in bioavailable tryptophan than powdered infant formulas, and tryptophan supplementation of formulas increases brain tryptophan and serotonin in rats.

The bioavailability of tryptophan in powdered and/or liquid concentrate forms of milk-based infant formulas was determined by studying rat growth response by using a slope ratio method (food conversion efficiency: weight gain/food consumed vs. tryptophan consumed). A gelatin basal diet formulated to be adequate in all nutrients, except tryptophan (0.03%), for rat growth was supplemented with graded levels of crystalline L-tryptophan (0.02, 0. 04, 0.06, 0.08, 0.10, 0.12 and 0.14%, standard diets) or infant formulas providing 0.04 and 0.08% supplemental tryptophan (test diets). These diets were fed to weanling rats for 2 wk. Tryptophan bioavailabilities of various formulas varied from 83 to 95%, with some of the liquid concentrates having the lowest values. The levels of bioavailable tryptophan in the liquid concentrate forms (9.7-12.6 mg/g protein) and the powdered forms (11.1-13.1 mg/g protein) were considerably lower than those of human milk (17-19 mg/g protein). Supplementation of the liquid concentrates with graded levels of L-tryptophan (0.1, 0.5 and 1.0%) had no effect on protein quality indices, based on rat growth, but resulted in a dose-related increase in the concentrations of tryptophan in the plasma and brain and of serotonin and 5-hydroxyindole-3-acetic acid in the brains of rats. This study supports further research to investigate the influence of tryptophan supplementation of infant formulas, to more closely simulate tryptophan composition of human milk, on tryptophan metabolites and their potential related effects on sleep latency and neurobehavioral developments in infants.

Animals↗

Concentrations of iron, copper and zinc in human milk and powdered infant formula.

Concentrations of iron, copper and zinc were determined in 56 samples of mature human milk from Canarian women and 5 samples of powdered infant formula. According to the literature our data fall within the normal limits in each kind of milk. The mean concentration of Fe, Cu and Zn of powdered infant formula was significantly higher than those concentrations found in the human milks. Significant differences among the concentrations of the studied metals for the milks of considered mothers were observed. The Fe, Cu and Zn intakes of infants fed with human milk are lower than the requirements recommended by the Food and Nutrition Board (1989). However, the infants fed with powdered infant formula had consumed an adequate intake of Fe and Cu. A progressive decrease of the metal concentrations with the lactation stage was observed. The human milk obtained in spring presented Fe and Zn concentrations lower than in autumn, which could be due to changes in nutritional habits of the mothers. Age of mother and number of previous children seem to influence the Zn and Cu concentrations of human milk.

Adult↗

Acute lung injury after instillation of human breast milk or infant formula into rabbits' lungs.

BACKGROUND: Recent interest in shortening the fasting interval after ingestion of milk products demonstrated large volumes of breast milk in the stomach 2 h after breastfeeding. Although aspiration is a rare event, if it were to occur with human breast milk, it is important to understand the extent of the lung injury that might occur. Therefore, the response to instillation of acidified breast milk and infant formula in the lungs of adult rabbits was studied. METHODS: In 18 anesthetized adult rabbits, 1 of 3 fluids (in a volume of 0.8 ml.kg-1 and pH level of 1.8, acidified with hydrochloric acid); saline, breast milk, or infant formula (SMA, Wyeth, Windsor, Ontario), was instilled into the lungs via a tracheotomy. The lungs were ventilated for 4 h after instillation. Alveolar-to-arterial oxygen gradient and dynamic compliance were measured before and at hourly intervals after instillation. After 4 h, the rabbits were killed and the lungs were excised. Neutrophil infiltration was quantitated by a pathologist blinded to the instilled fluid. A histologic control group of four rabbits was ventilated under study conditions without any intratracheal fluid instillation. RESULTS: Alveolar-to-arterial oxygen gradient increased and dynamic compliance decreased significantly during the 4 h after instillation of both breast milk and infant formula compared with baseline measurements and with saline controls (P < 0.05). The neutrophil counts in the lungs from the saline, breast milk, and formula rabbits were significantly greater than those in the control group. CONCLUSIONS: Instillation of acidified breast milk or infant formula (in a volume of 0.8 ml.kg-1 and pH level of 1.8) into rabbits' lungs induces acute lung injury of similar intensity that lasts at least 4 h.

Acute Disease↗

Uptake and retention in suckling rats of 51chromium fed with human milk or infant formulas.

Optimum concentration of Cr for infant formulas has not been established. Such components as soy protein or supplemental Fe could influence absorption and retention. Suckling rat pups were used to evaluate the influence of three commercial formulas and human milk, all of which had been incubated with 51CrCl3 for 1 h, on the uptake and retention of the added 51Cr. After fasting 3 h, the pups were intubated with a single dose of 25 microCi 51CrCl3 in either a cow's milk-based formula, an Fe-supplemented cow's milk-based formula, a soy-based formula, or human milk. Six hours later, 51Cr was counted in five organs, thymus, blood, and total urine. Absorption of 51Cr was low. At 6 h, percent 51Cr in blood was < 0.2% of the dose, and total 51Cr excretion in urine was < 1.8%. The uptake and retention of 51Cr and its concentration in any of the organs, thymus, blood, and urine were not influenced by different types of formula or by human milk.

Animals↗

Fatty acid content and composition of infant formulas and cereals.

The lipid content and fatty acid composition of commercial infant formulas and cereals were determined. The lipid content of formulas ranged from 3 to 7 percent by weight and provided from 30 to 47 percent of the total calories supplied by the formula. The fatty acd distribution in several formulas was similar to that of fat in human milk. Linoleic acid, ranging from 13 to 53 percent, supplied from 5.7 to 24 percent of total calories. The infants' requirements for linoleic acid (2.7 percent of total calories) would be adequately satisfied by any of the commercial formulas. No significant level of trans fatty acid isomers was found in any commercial formula. Infant cereals had low levels of fat, with 21 to 49 percent of the fatty acids being linoleic acid.

Edible Grain↗

Proximate and elemental analysis of infant formula.

The Nutrient Surveillance Branch has been conducting a survey of infant formula products for Fiscal Year 1981. Each product has been carefully analyzed and the results compared to the label declaration and the minimum-maximum limits specified by the American Academy of Pediatrics' Committee on Nutrition (CON/AAP). Proximate and elemental analyses were made. Protein, fat, ash, and total solids (moisture) were determined by AOAC methods. Osmolality, density, and fatty acids (linoleic) were also determined. Carbohydrates were calculated by difference and caloric content was calculated by using the general Atwater factors. Elemental analysis for Ca, P, Mg, Fe, Zn, Cu, Mn, Na, and K were performed by induction coupled plasma absorption spectroscopy. Chloride was assayed by potentiometric titration with AgNO3. A summary of the findings from the infant formula survey have been compared with CON/AAP recommendations. In general, there were only a few exceptions where the label claims and the CON/AAP requirements were not met. However, in none of these cases was the difference considered to be of public health significance.

Dietary Carbohydrates↗

Epidermal growth factor concentrations in human milk, cow's milk and cow's milk-based infant formulas.

OBJECTIVE: Because maternal epidermal growth factor (EGF) may be an adaptive response to accelerate growth and maturation in premature infants, we compared the EGF content in fresh cow's milk and cow's milk-based infant formulas with full and preterm mother's milk. METHODS: EGF content of 57 human colostrum from mothers delivering prematurely and at term, 4 different fresh cow's milk and 8 different cow's milk-based infant formulas was determined by radioimmunoassay (RIA). RESULTS: Human milk from mothers of premature infants had a higher EGF content compared to that from mothers of term infants (28.2 +/- 10.3 nmol/L vs. 17.3 +/- 9.6 nmol/L). EGF content in human milk negatively correlated with gestational age and birth weight of neonates. EGF content in fresh cow's milk (13.8 - 18.2 nmol/L) was similar to that in human term milk. EGF levels in non-hydrolyzed protein formulas were much lower (5.6 - 8.6 nmol/L), and were undetectable in hydrolyzed protein formulas. CONCLUSION: The high EGF content in premature milk may represent a maternal compensatory mechanism to accelerate the growth and development of immature infants. Feeding infants with breast milk from their own mother should be advocated since there is lack of EGF in cow's milk-based infant formulas.

Animals↗