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S J Fomon

Publications and source records attributed to S J Fomon.

At least 37 records · Page 2Linked to original sources
PubMed1991

Reference data on gains in weight and length during the first two years of life.

Serial data from studies of infants at the University of Iowa and from the Fels Longitudinal Study were used to develop sex-specific percentiles for increments in weight and recumbent length for selected intervals during the first 24 months of life. Weight increments are presented for 1-month intervals from birth to 6 months, 2-month intervals from birth to 12 months, and 3-month intervals from birth to 24 months. Length increments are presented for 2-month intervals from birth to 6 months, and for 3-month intervals from birth to 24 months of age. Weights and lengths at the target ages were obtained for the Iowa data by simple interpolation, and for the Fels data by fitting families of three-parameter mathematical functions to the serial data from ages 1 to 24 months. The tabular presentations are based on the Iowa data from birth to 3 months of age, on the combined Iowa and Fels data from 3 to 6 months of age, and on the Fels data from 6 to 24 months of age. We believe that these reference data will be useful in screening for deviations from normal growth and may aid in early detection of failure to thrive or excessive weight gain during early life.

Age Factors↗
PubMed1991

Gender-related differences in iron absorption by preadolescent children.

In a study of absorption of iron from meals by preadolescent children (Tanner stage 1), we had noted that erythrocyte incorporation of the extrinsic iron label was somewhat greater by girls than by boys. Although the difference was not significant, the observation seemed to warrant further study. Study A: A precisely determined quantity of ferrous sulfate enriched with the stable isotope 58Fe was given without food to 15 boys and 15 girls (Tanner stage 1) after an overnight fast and was immediately followed by a dose of 70 mg of ascorbic acid. 58Fe enrichment of the erythrocytes was determined by inductively coupled plasma mass spectrometry at baseline and 14 and 42 d after administration of the 58Fe dose. Geometric mean erythrocyte incorporation of the 58Fe label was 35.2% of intake by boys and 45.0% of intake by girls. The difference was significant (analysis of covariance with serum ferritin as covariate, p = 0.035). Study B: Fifteen boys and 15 girls (Tanner stage 1) were fed a breakfast labeled with 58Fe. Geometric mean erythrocyte incorporation of the 58Fe label was 14.8% of intake by boys and 24.7% of intake by girls. The difference was significant (analysis of covariance with serum ferritin as covariate, p = 0.004). Because serum ferritin concentrations were similar in boys and girls, the gender-related difference in iron absorption (as reflected by erythrocyte incorporation of the label) does not appear to be explained by a difference in body stores of iron. We hypothesize that hormonal differences between boys and girls in Tanner stage 1 favor iron absorption by girls.

Ascorbic Acid↗
PubMed1991

Requirements and recommended dietary intakes of protein during infancy.

Two approaches have been used to arrive at estimates of the requirement for protein by infants. The factorial approach consists of adding the requirement for growth to the requirement for replacement of inevitable losses in urine and feces and from the skin. Protein requirement estimated in this way was 1.98 g.kg-1.d-1 during the 1st mo of life and decreased rapidly to 1.18 g.kg-1.d-1 by 4 to 5 mo of age, then remained at about that level to age 1 y. Believing that protein intakes of the breast-fed infant are near the level of the requirement, researchers used the intakes of breast-fed infants as a second estimate of requirement. Although intakes of protein by breast-fed infants during the first 2 mo of life are generally similar to the requirement values estimated by the factorial approach, intakes from 2 to 6 mo of age are less than the requirement values estimated by the factorial approach. Possible explanations for the discrepancy are presented. Recommended dietary intakes of protein somewhat greater than the requirements estimated by the factorial approach are proposed. These recommended intakes are less than those proposed by the FAO/WHO/UNU "safe levels of protein intake" and are less than the Recommended Dietary Allowances of the Food and Nutrition Board.

Breast Feeding↗
PubMed1990

Formulas for older infants.

We explored the possibility that standard infant formulas designed as the sole source of nutrients for small, rapidly growing infants may not be equally suitable for older, larger, and less rapidly growing infants who obtain a portion of energy intake from beikost. Our approach was to consider the probable nutrient intakes of a 6-month-old hypothetic infant receiving 80% of energy intake from a standard formula and 20% from beikost, and nutrient intakes of a 10-month-old hypothetic infant receiving 50% of energy intake from a standard formula and 50% from beikost. The assortment of beikost items consumed by infants is moderately high in protein and low in fat. Calculated nutrient intakes of the 10-month-old hypothetic infant were compared with intakes of infants of similar age in two national surveys. We conclude that standard infant formulas designed for young infants are reasonably well suited to meeting the nutrient needs of infants during the latter half of the first year of life.

Aging↗
PubMed1990

Cow milk feeding in infancy: further observations on blood loss from the gastrointestinal tract.

Because feeding of cow milk causes normal infants to lose increased amounts of occult blood from the gastrointestinal tract, we conducted a prospective trial to measure intestinal blood loss quantitatively and to monitor iron nutritional status. Fifty-two infants entered the trial at 168 days of age and were assigned at random to receive either cow milk or a milk-based formula. Initially, 31 infants had been breast-fed and 21 had been fed formulas. With the feeding of cow milk, the proportion of guaiac-positive stools increased from 3.0% at baseline to 30.3% during the first 28 days of the trial (p less than 0.01), whereas the proportion of positive stools remained low (5.0%) with the feeding of formula. The proportion of guaiac-positive stools among cow milk-fed infants declined later, but for the entire trial it remained significantly (p less than 0.01) elevated. Stool hemoglobin concentration increased markedly with the introduction of cow milk, rising from a mean (+/- SD) of 622 +/- 527 micrograms/gm dry stool at baseline to 3598 +/- 10,479 micrograms/gm dry stool during the first 28 days of ingestion of cow milk. Among infants fed formula, stool hemoglobin did not increase and was significantly (p less than 0.01) less than in the cow milk group. Among infants fed cow milk, the increase in hemoglobin concentration tended to be greater for those who had initially been fed human milk than for those who had initially been fed formulas. Iron nutritional status was not significantly different between the two feeding groups. However, one infant became iron deficient after 4 weeks of ingesting cow milk. We conclude that cow milk feeding leads to increased intestinal tract blood loss in a large proportion of normal infants and that the amount of iron lost is nutritionally important.

Animals↗
PubMed1989

Gain in weight and length during early infancy.

Although rate of growth is generally recognized as a valuable indicator of health status, few reference data are available for gain in weight or length during the period of most growth in infancy. We have therefore summarized our data concerning gains in length and weight of 203 breast-fed males, 216 breast-fed females, 380 formula-fed males, and 340 formula-fed females. Seven sets of measurements (at ages 8, 14, 28, 42, 56, 84 and 112 days) were made with each infant. The 5th, 10th, 25th, 50th, 75th, 90th and 95th centile values together with the means and standard deviations are presented for selected age intervals on a feeding-specific (i.e. breast-fed or formula-fed) and sex-specific basis. We believe that these data will be useful as a reference for interpreting results of infant studies.

Aging↗
PubMed1989

Potential renal solute load of infant formulas.

The potential renal solute load (PRSL) of infant feedings is the sum of dietary nitrogen (expressed as mmol of urea, i.e., mg nitrogen divided by 28), sodium, potassium, chloride and phosphorus. The PRSL determines the renal solute load, and, therefore, the osmolar concentration of the urine. When water intake is reduced and/or water losses are increased, the renal concentrating ability may be exceeded, and negative water balance (dehydration) may ensue. Under these circumstances, feedings providing high PRSL lead more rapidly to dehydration than do feedings providing lower PRSL. On the basis of simulated clinical situations and epidemiologic data, it is concluded that conventional infant formulas (PRSL 135-177 mosmol/l, or 20-26 mosmol/100 kcal) provide a satisfactory margin of safety. A feeding providing the upper limits for concentrations of protein and electrolytes specified by the Food and Drug Administration rule does not afford a satisfactory margin of safety. It is recommended that the upper limit for protein content of infant formulas be decreased from 4.5 g/100 kcal to 3.2 g/100 kcal and that an upper limit for phosphorus concentration of infant formulas be set at 93 mg/100 kcal. Maximum PRSL will then be 221 mosmol/l (33 mosmol/100 kcal).

Electrolytes↗
PubMed1989

Failure to label baboon milk intrinsically with iron.

The widely held belief that 50% of the iron in human milk is absorbed is based on studies that have used an extrinsic radioactive iron tag. To determine the validity of an extrinsic tag, it is necessary to label the milk intrinsically with one isotope and to compare absorption of this isotope with absorption of another isotope added as the extrinsic tag. We chose the baboon as a model and infused 59Fe intravenously. In each of three attempts we failed to label the milk intrinsically.

Absorption↗
PubMed1989

Iron absorption from infant foods.

To determine the bioavailability of iron from iron-fortified infant foods, we have determined erythrocyte incorporation of the stable isotope, 58Fe, after feeding the following foods extrinsically labeled with 58Fe: 1) rice cereal with apples and bananas ("cereal-fruit product"), 2) Mead Johnson Enriched Baby Food (MJEBF), a vitamin, mineral, and protein-enriched rice cereal, 3) vegetables and beef ("vegetable-beef product"), 4) grape-juice, and 5) MJEBF. Foods 1-4 were fortified with ferrous sulfate, and food 5 was fortified with ferrous fumarate. Blood was obtained at ages 140, 168, and 196 d of age, and the test meal was fed under standardized conditions at 154 d of age. Erythrocyte incorporation of the 58Fe label was determined from the increase in the mass isotope ratio, 58Fe/57Fe, from the baseline value (at 140 d of age) to the follow-up values. The mass isotope ratio was determined by inductively coupled mass spectrometry. Geometric mean total iron incorporation into erythrocytes from the test meal of MJEBF fortified with ferrous sulfate (food 2) was 0.05 mg, and from the vegetable-beef product test meal (food 3) was 0.08 mg. The low value for MJEBF is presumably explained by the low level of iron fortification. The low value for the vegetable-beef product may reflect the presence of inhibitors of iron absorption. Geometric mean erythrocyte incorporations of iron from the test meals with foods 1, 4 and 5 were 0.15, 0.14, and 0.18 mg, respectively. These erythrocyte incorporation values are 20 to 26% of the estimated 0.7 mg requirement for absorbed iron, and therefore seem nutritionally important.

Biological Availability↗
PubMed1988

Use of the stable isotope, 58Fe, for determining availability of nonheme iron in meals.

Because of reluctance to use radioisotopes for studies of iron absorption in children, we have explored the feasibility of using the least abundant stable isotope of iron, 58Fe (natural abundance, 0.322 weight %) in a study of nonheme iron absorption. With a balanced cross-over design, each of 16 school-age children was fed a standardized lunch on 3 consecutive days and, 28 days later, an alternate standardized lunch on 3 consecutive days. The lunch included either a beef patty or a beef-soy patty. The mass isotope ratio, 58Fe/57Fe (MIR58/57), was measured in blood by inductively coupled plasma mass spectroscopy before and 14 days after (i.e. study day 15) consuming the three lunches. The MIR58/57 on study day 15 was used as a baseline value for lunches fed on study days 29, 30, and 31. Incorporation of 58Fe into erythrocytes was greater from the lunch with beef patty than from the lunch with beef-soy patty (geometric mean values 2.02 and 1.05% of the dose, p less than 0.03). Based on the similarity of our results with those obtained in adults with radioisotopes, we conclude that 58Fe is a satisfactory tag for studies of nonheme iron absorption from meals.

Child↗
PubMed1988

Erythrocyte incorporation of ingested 58-iron by infants.

The least abundant stable isotope of iron, 58Fe (natural abundance 0.322 weight %), was administered orally to infants to explore the feasibility of using a stable rather than a radioisotope in studies of iron absorption. The dose of 58Fe was given between feedings at age 126 days. The mass isotope ratio, 58Fe/57Fe, was determined in blood by inductively coupled plasma mass spectroscopy and at ages 140, 168, and 196 days. The percentage of the 58Fe dose entering the circulation (3.2 to 16.0%) was inversely correlated with serum ferritin concentration (r = -0.867, p less than 0.01). For individual infants the SD of the percentage of administered dose of iron appearing in the circulation ranged from 0.22 to 1.28. We conclude that the method is likely to be suitable for within-subject comparisons of iron availability from foods. Because of the large between-subject variation, we are pessimistic for this age group about the usefulness of study designs based on group comparisons.

Absorption↗
PubMed1988

Lack of adverse reactions to iron-fortified formula.

Some physicians are reluctant to recommend feeding of iron-fortified formulas to infants because of a fear of adverse reactions. In crossover studies, parents' records were compared with regard to their infant's behavior (fussiness, cramps, regurgitation, flatus, colic) and stool characteristics during periods when iron-fortified formulas were fed and periods when non-iron-fortified formulas were fed. No statistically significant feeding-related difference was noted except for stool color.

Double-Blind Method↗
PubMed1987

Bioavailability of dietary urea nitrogen in the infant.

Because the human body has no enzymes capable of hydrolyzing urea, nitrogen from this source becomes bioavailable only by release of ammonia from urea by bacterial hydrolysis in the intestines, with subsequent absorption and utilization of ammonia. To explore extent to which urea ingested in milk becomes bioavailable, we fed di-15N-urea (both nitrogen atoms in the form of the stable isotope 15N) and determined urinary excretion of di-15N-urea (excreted without having become bioavailable) and mono-15N-urea (urea containing only one atom of 15N and therefore reflecting excretion of absorbed ammonia). The largest percentage of the ingested di-15N-urea was excreted promptly in the urine still in the form of di-15N-urea. We conclude that most of the urea ingested by a normal infant is not bioavailable.

Animals↗
PubMed1987

Reflections on infant feeding in the 1970s and 1980s.

In 1985 35% of US infants were breast-fed until at least age 4 mo whereas in 1971 the corresponding figure was only 10%. Breast-feeding is less common among lower income than among higher income groups. In 1985 10% of infants aged 6 mo were fed fresh fluid cow milk--down from 70% in 1971. Most formula-fed infants receive iron-fortified formulas (12 mg Fe/L). Beikost is now commonly fed to infants less than age 2 mo. The Infant Formula Act of 1980 resulted in promulgation of new quality control and labelling requirements for infant formulas. Over the past 15 y, salt and sugar concentrations of commercially prepared beikost items have been decreased, and certain modified food starches are no longer used. There is considerable doubt about the bioavailability of the electrolytic iron powder used to fortify most of the dry infant cereals.

Breast Feeding↗
PubMed1986

Erythrocyte incorporation of ingested stable isotope of iron (58Fe).

Because of a possible hazard from the use of radioisotopes to determine iron absorption by infants, the use of stable isotopes for this purpose has much appeal. We have applied the method of inductively coupled plasma mass spectrometry (ICP/MS) to determine the mass ratio, 58Fe/57Fe, in blood before and after oral administration of 58Fe. From the increase in erythrocyte enrichment with 58Fe, we have calculated percentage absorption of iron. We have shown that the coefficient of variation of measured mass isotope ratio is 0.1-1.0%, depending on the conditions of the measurement. The method has been applied to a feasibility study involving four infants. Each infant was given 58Fe either as a single dose or as one dose on each of two consecutive days. Each dose provided 1.945 mg iron and 1.440 mg 58Fe. Samples of blood were obtained before isotope administration and at 14, 42, and 60 days thereafter. Isotopic analysis of the samples demonstrates that this approach results in a sufficiently large isotope enrichment to permit satisfactory measurement of iron availability. It is concluded that this new method is highly promising for studies of iron availability in infants and children.

Absorption↗