Janet M. Gilchrist

The health implications of soy infant formula

Soy formula (SF) has been fed to millions of infants worldwide. It has been shown to promote growth and development as well as milk-based formula (MF). Controversy has developed over the adequacy and safety of SF. Most concerns are based on in vivo and in vitro data that raise the possibility of estrogenic effects of isoflavones contained in SF. There are few studies of children who were fed SF, and thus insufficient data are available to judge if SF feeding results in clinically significant developmental effects and if there are any long-term health consequences (adverse or beneficial). However, the Arkansas Childrens Nutrition Center is conducting a prospective longitudinal study comparing growth, development, and health of breastfed children with formula-fed (SF and MF) children from birth through age 6 y. After 5 y of study, children in all 3 groups (n > 300) are growing and developing within normal limits, and there are no indications of adverse effects in the soy-fed children. Neonatal pig studies comparing SF, MF, and breast milk (BM) have shown diet-specific gene expression profiles in various target tissues. Therefore, although SF differed significantly from BM, MF also differed from BM, and SF differed from MF. Nonetheless, these animals grew and developed normally, and SF piglets had several health benefits (eg, increased bone quality) and no observable adverse effects. Thus, to date, our results suggest that SF supports normal growth and may have advantages in promoting bone development.

Longitudinal body composition data in exclusively breast-fed infants: a multicenter study.

Reference %fat and total fat‐free mass data is necessary for evaluating growth in infants. We aimed to develop longitudinal %fat and total fat‐free mass data in infants from birth to 6 months of age. An observational, multicenter, prospective cohort study was conducted with assessments at birth, 1 week, 2 weeks, 1, 2, 3, 4, 5, and 6 months of age. Subjects were exclusively breast‐fed and were enrolled at three centers. Whole‐body composition (i.e., %fat and total fat‐free mass) were assessed using air‐displacement plethysmography (ADP) (PEA POD; Life Measurement, Concord, CA). Maternal prepregnancy BMI, gestational weight gain, and infant anthropometric data were collected. A total of 160 infants (boys = 84) were assessed from birth to 4 months of age. Mean birth weight was 3.46 ± 0.39 kg %fat and fat‐free mass significantly increased from birth to 4 months of age (P < 0.0001). Gender‐specific %fat and total fat‐free mass curves for infants from birth to 4 months of age were created. This study will be beneficial to health‐care professionals in evaluating normal growth and nutritional patterns in the first months of life.

Ultrasonographic Patterns of Reproductive Organs in Infants Fed Soy Formula: Comparisons to Infants Fed Breast Milk and Milk Formula

OBJECTIVE To determine if differences exist in hormone-sensitive organ size between infants who were fed soy formula (SF), milk formula (MF), or breast milk (BF). STUDY DESIGN Breast buds, uterus, ovaries, prostate, and testicular volumes were assessed by ultrasonography in 40 BF, 41 MF, and 39 SF infants at age 4 months. RESULTS There were no significant feeding group effects in anthropometric or body composition. Among girls, there were no feeding group differences in breast bud or uterine volume. MF infants had greater (P < .05) mean ovarian volume and greater (P < .01) numbers of ovarian cysts per ovary than did BF infants. Among boys, there were no feeding group differences in prostate or breast bud volumes. Mean testicular volume did not differ between SF and MF boys, but both formula-fed groups had lower volumes than BF infants. CONCLUSIONS Our data do not support major diet-related differences in reproductive organ size as measured by ultrasound in infants at age 4 months, although there is some evidence that ovarian development may be advanced in MF-fed infants and that testicular development may be slower in both MF and SF infants as compared with BF. There was no evidence that feeding SF exerts any estrogenic effects on reproductive organs studied.

Early Infant Diet and the Omega 3 Fatty Acid DHA: Effects on Resting Cardiovascular Activity and Behavioral Development During the First Half-Year of Life

This investigation evaluated variations in resting heart rate (HR) measures during the first half year of life in healthy, full-term infants who were either breast-fed (BF), or fed formula with (milk-based: MF; soy-based: SF) or without (soy-based: SF−) commercially supplemented DHA (decosahexaenoic acid). In infants fed the DHA-deficient diet, higher HR and lower values for heart rate variability measures were observed, indicating decreased parasympathetic tone in this group. These effects, appearing at 4 months and continuing for the remainder of the study period, are consistent with suggestions that the 3–5-month postnatal interval may be an important period in the development of cardiovascular regulation. The absence of these effects in SF infants receiving the DHA-supplemented formula suggests that neither soy protein nor the associated phytochemicals in soy formula contribute to these effects to any appreciable extent. In general, the results do not indicate differences in any of the study variables attributable to soy formula per se.

A longitudinal study of differences in electroencephalographic activity among breastfed, milk formula-fed, and soy formula-fed infants during the first year of life.

BACKGROUND The extent to which adequate nutrition from infant diets differentially influence developmental outcomes in healthy infants has not been determined. AIM To compare the effects of the major infant diets on the development of brain electrical activity during infancy. STUDY DESIGN Scalp EEG signals (124 sites) recorded from the same infants during quiet wakefulness at 3, 6, 9, and 12months. SUBJECTS Healthy, full-term infants (40/group; gender matched) either breastfed (BF) or fed milk formula (MF) or soy formula (SF) through the first 6months. OUTCOME MEASURES Power spectral values for frequencies in the 0.1-30Hz range. RESULTS Significant diet-related differences were present across frequency bands and included effects that were time- [peaks in 0.1-3Hz at 6 (MF,SF) and 9months (BF); 3-6Hz at 6months (MF, SF>BF); increases in 6-9Hz from 3 to 6months (MF>BF) and from 6 to 9months (MF>SF)] and gender-related (9-12Hz and 12-30Hz: at 9months BF>MF, SF boys, and MF>SF girls). CONCLUSIONS The development of brain electrical activity during infancy differs between those who are breastfed compared with those fed either milk or soy formula, but is generally similar for formula-fed groups. These variations in EEG activity reflect diet-related influences on the development of brain structure and function that could put infants on different neurodevelopmental trajectories along which cognitive and brain function development will proceed.

Cortical responses to speech sounds in 3- and 6-month-old infants fed breast milk, milk formula, or soy formula.

Controversy exists about the safety of soy formula, with the main concern relating to potential estrogenic effects of soy protein. Since estrogens influence early brain development, we compared behavioral development and cortical responses (event-related potentials; ERPs) to speech sounds in infants fed either breast milk or formula (milk- or soy-based). Across-groups ERP measures were generally similar and behavioral measures were within normal ranges, suggesting no important influences of soy formula on behavioral development and brain function during the study period. Analyses relating ERP and behavioral measures revealed diet- and gender-specific emphases that may reflect differences in developmental trajectories of brain–behavior relationships.

No difference indicated in electroencephalographic power spectral analysis in 3‐ and 6‐month‐old infants fed soy‐ or milk‐based formula

Increasing concern has been recently raised on the possible effects of soy-derived phyto-oestrogens on the development of cognitive functions in infants. However, limited studies have been conducted to date, and no data have been made available for determining whether infant soy formula can affect normal development of the human brain. We compared electroencephalographic (EEG) spectral power derived from high-density recordings of infants fed milk-based or soy formula (46 fed milk-based formula and 39 fed soy formula) at 3 and 6 months of age. The spectral parameters included absolute power, relative power and spectral edge frequency (SEF) at 85%, 90% and 95% levels. The frequency domain contained four bands (0.1-3, 3-6, 6-9 and 9-12 Hz). EEG signals were collected from eight brain areas in each hemisphere. The results showed that the highest spectral power was mainly distributed in the low-frequency bands and was predominant in the frontal and anterior temporal areas. None of the spectral variables significantly differed between the soy- and milk-fed infants (anova, all P > 0.2). However, significant effects were indicated on the SEFs for factors of sex, age and brain area (all P < 0.01). Hemispheric differences in the absolute and relative power were also indicated. Our results suggest that the EEG power spectral development of soy-fed infants does not differ from that of infants fed milk-based formula. In addition, EEG spectral development appears more advanced in female than in male infants at 6 months.

The influence of infant diet on early developmental changes in processing human voice speech stimuli: ERP variations in breast and milk formula-fed infants at 3 and 6 months after birth.

The purpose of this investigation was to determine if processing of language stimuli during the first half year of life in breast-fed infants differs from that of formula-fed infants. This question was addressed by examining the brain event-related potentials of healthy infants receiving breast milk (n = 15) or milk-based formula (n = 18) recorded in response to consonant vowel syllables presented in an oddball paradigm. The same infants were studied when they were 3-months and 6-months-old. The two groups were comparable on several measures relating to biological and home environment variables previously reported to influence development, including gestation period, birth weight, mothers IQ, and family socioeconomic status, and did not differ in weight or mental or motor development at the times of the visits. In general, ERP response features previously documented in studies of syllable processing in 3–6-month-old infants were observed in this study, including positive components at ∼ 190 msec (P1), ∼ 370 msec (P2), and ∼ 600 msec (P600), and negative components at ∼ 250 msec (N250), ∼ 450 msec (N450), and a late, negative going slow wave between 655 and 995 msec (LSW). For both groups there were instances where specific components were either poorly defined, e.g., P1 and N250 to the infrequent syllable at 3 months, N450 and P600 to this syllable at both ages, or not present in many infants, e.g., the P600 to the frequent syllable at 6 months. These variations appeared to be related to individual differences in development or paradigm-related features, i.e., ISI and frequency of syllable occurrence. Developmental variations (changes from 3 to 6 months) common to both feeding groups included latency decreases for P1, decreased P2 amplitude, and increased amplitudes for N250 and LSW components. Within this framework, group differences were detected in areas involving the development of response components, the development of processing capabilities, and syllable discrimination. In all cases, these effects related to components following initial stimulus registration, i.e., to the processing of sound content rather than sound acoustic features. The pattern of these differences suggests advantages for BF infants in the development and processing of language stimuli during the first 6 months of life.

Effects of Breast Milk and Milk Formula Diets on Synthesized Speech Sound-Induced Event-Related Potentials in 3- and 6-Month-Old Infants

Effects of breast milk and milk formula supplemented with docosahexaenoic acid and arachidonic acid on speech processing were investigated by recording event-related potentials (ERPs) to synthesized /pa/ and /ba/ (oddball paradigm, 80%:20%) at 3 and 6 months of age. Behavioral assessment was also obtained. A major positive component (P200) was elicited by both types of sounds. It had a maximal scalp distribution in the fronto-central areas in both groups of infants. The mean latencies did not differ between the groups or between the stimulus types. However, the latencies decreased across age in both groups. The mean P200 amplitude in the formula-fed infants was lower than that in the breast-fed infants, but the difference was not significant. The between-stimulus differences in frontal P200 amplitudes were positively correlated with the behavioral scores of Bayley Index of Infant Development. These data suggest that the processing of the present speech stimuli is not affected by the investigated diets in the early infancy.

P2-123 Maternal obesity at conception programs obesity in the offspring

Risk of obesity in adult life is subject to programming during gestation. To examine whether in utero exposure to maternal obesity increases the risk of obesity in offspring, we developed an overfeeding-based model of maternal obesity in rats utilizing intragastric feeding of diets via total enteral nutrition. Feeding liquid diets to adult female rats at 220 kcal/kg(3/4) per day (15% excess calories/day) compared with 187 kcal/kg(3/4) per day for 3 wk caused substantial increase in body weight gain, adiposity, serum insulin, leptin, and insulin resistance. Lean or obese female rats were mated with ad libitum AIN-93G-fed male rats. Exposure to obesity was ensured to be limited only to the maternal in utero environment by cross-fostering pups to lean dams having ad libitum access to AIN-93G diets throughout lactation. Numbers of pups, birth weight, and size were not affected by maternal obesity. Male offspring from each group were weaned at postnatal day (PND)21 to either AIN-93G diets or high-fat diets (45% fat calories). Body weights of offspring from obese dams did not differ from offspring of lean dams when fed AIN-93G diets through PND130. However, offspring from obese dams gained remarkably greater (P < 0.005) body weight and higher % body fat when fed a high-fat diet. Body composition was assessed by NMR, X-ray computerized tomography, and weights of adipose tissues. Adipose histomorphometry, insulin sensitivity, and food intake were also assessed in the offspring. Our data suggest that maternal obesity at conception leads to fetal programming of offspring, which could result in obesity in later life.