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Infant Soy Formulas

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  • 1. Infant Soy Formulas NATALIE MESTEL NSD648 DIETETICS IN THE LIFESPAN
  • 2. Background: Safety Concerns  Soy formula contains phytoestrogens, including isoflavones. Potential negative effects:        Sexual development and reproduction Neurobehavioral development Immune function Thyroid function Conversely, epidemiologic studies have suggested protective effect of isoflavones against adult chronic diseases, including CHD, breast, endometrial, and prostate cancers [2] Infants go through developmental stages sensitive to estrogens. Infants more likely to be vulnerable to effects of phytoestrogens in soy [1] AAP committed to use of human milk as ideal source of nutrition for infants [2]
  • 3. NIH Addresses Soy Formula 2010 NTP (National Toxicology Program) and expert panel used fivelevel scale to express conclusions: likelihood of adverse human health effect resulting from exposure soy infant formula [2] o o o o o Serious Concern Concern Some Concern Minimal Concern Negligible Concern
  • 4. Use of Soy Protein-Based Formulas in Infant Feeding (2008) [2]   Updates 1998 AAP review of SF and addresses ongoing concern of phytoestrogens With term infants, although SF may provide nutrition for normal growth and development, few indications for use in place of CMF. Indications include:     (a) infants with galactosemia and hereditary lactase deficiency  For infants with documented cow milk protein allergy, extensively hydrolyzed protein formula should be considered, because 10% to 14% of these infants will also have soy protein allergy o Allergy is reported more often CMF (1.8% - 3.4% vs 0.5% - 1.1%) o Hydrolyzed formula: protein has been broken down so immune system less likely to recognize it as allergen  SF may be indicated when secondary lactose intolerance occurs (b) in situations in which a vegetarian diet is preferred SF has no advantage over CMF, unless infant has 1 of indications noted previously Despite limited indications, SF accounts for about 20% of formula market in U.S [2]
  • 5. Use of Soy Protein-Based Formulas in Infant Feeding (2008) [2]  SF composition meets FDA and AAP guidelines for vitamin, mineral, and electrolyte content and provides 67 kcal/dL:      Protein: Soy isolate protein, L-methionine, L-carnitine, and taurine, 2.45-2.8 g/100 kcals Fat: mostly vegetable oils, 5.02-5.46 g/100 kcals Carbohydrate: corn maltodextrin, corn syrup solids, and sucrose, 10.26-10.95 g/100 kcals SF contain 20% more calcium and phosphorus than CMF and are fortified with iron and zinc No clear evidence that soy isoflavones have adverse effects on human development, reproduction, or endocrine function:    Soy isoflavones have different absorption, distribution, metabolism, and excretion according to age, sex, and cultural group Male infants: no increased feminization Infants with hypothyroidism fed with soy formula have prolonged elevation of thyroid-stimulating hormone What does primary literature say???
  • 6. Body Fat and Bone Mineral Content of Infants Fed Breast Milk, Cow's Milk Formula, or Soy Formula During the First Year of Life (2013) [3]    Study Design: Prospective Cohort Study Setting & Sample o Infants assessed at age 3, 6, 9, and 12 months o N=207, 84.5% Caucasian, 62% boys, 100% appropriate for gestational age at birth o No significant differences among 3 feeding groups in terms of race, sex, gestational age, birth weight, birth length, or SES (Table II) Measures/Variables o To characterize growth, fat mass (FM), fat-free mass (FFM), and bone mineral content (BMC) in healthy infants fed breast milk (BM), cow's milk formula (CMF), or soy formula (SF) during 1st year of life o Standard anthropometric techniques for growth, dualenergy X-rays for body comp. o Mixed-effects models with repeated measures adjusted for race, SES, gestational age, birth weight, birth length, sex, age, and diet history
  • 7.  Results ① Infants fed BM had higher FM at age 3 months, and lower FFM at age 6-12 months (P < .001) ① Infants fed SF had greater FFM at age 6 months and 9 months compared with infants fed CMF (P < .001) ① ① BMC was higher in infants fed BM and lower in infants fed SF at age 3 months (P < .001), but by age 12 months, BMC was significantly higher in infants fed SF ② ① ③ ③
  • 8.  Results ① Infants fed BM had higher FM at age 3 months, and lower FFM at age 6-12 months (P < .001) ① Infants fed SF had greater FFM at age 6 months and 9 months compared with infants fed CMF (P < .001) ① BMC was higher in infants fed BM and lower in infants fed SF at age 3 months (P < .001), but by age 12 months, BMC was significantly higher in infants fed SF
  • 9. Body Fat and Bone Mineral Content of Infants Fed Breast Milk, Cow's Milk Formula, or Soy Formula During the First Year of Life (2013) [3]    Implications o CMF and SF infants significantly different fat and bone growth trajectories, all formula fed infants significantly different BM infants o SF infants: leaner body phenotype during 1st year, lower bone mineralization at 3 months, greater bone mineral growth during 1st year compared with infants fed BM or CMF o Implications for long-term health outcomes and bone health remain unclear Strengths o Use of precise and accurate technology to measure body comp. and BMC o Future findings may offer insight into long-term consequences of early effects b/c will be followed up to age 6 years Weaknesses     Unclear how 3 body comp. phenotypes predict later body comp. outcomes in later life Inconsistent results in other studies due to technological differences 84.5% Caucasian, 62% male Observational cohort, not a randomized control trial  Parents chose which diet to feed infants before study  Study could have benefited from having 3 diet groups start respective diets at birth
  • 10. Developmental Status of 1-Year-Old Infants Fed Breast Milk, Cow’s Milk Formula, or Soy Formula (2012) [4]    Study Design: Prospective Cohort Study Setting & Sample o N = 391, age 1-2 months, assessed at 3, 6, 9, and 12 months o Mothers: No diagnoses or meds known to affect fetal/infant development during pregnancies, nonsmokers, no alcohol and no use of soy products during pregnancy or lactation o Infants all term (≥37 weeks), avg. 6-9 lbs at birth, no medical diagnoses, no meds o Other exclusion criteria: change of formula after age 2 months and before age 12 months, complementary foods before 4 months, body weight at 3 months <5 kg (11lbs) Measures/Variables o To characterize mental, motor, and language developmental status of BF, CMF, or SF infants during 1st year of life o Development evaluated using Bayley Scales of Infant Development and Preschool Language Scale-3 o Mixed effects models used while adjusting for SES, mother's age and IQ, gestational age, gender, birth weight, head circumference, race, age, and diet history
  • 11. Bayley Scales of Infant Development and Preschool Language Scale-3 Bayley Scales:  MDI (Mental Development Index) and PDI (Psychomotor Development Index) assess motor skills, language, and cognitive development at 0-3 years [5]   Children presented with tasks designed to produce observable set of behavioral responses assessed on scales:  Cognitive Scale (91 items)  Language Composite Scale (97 items) with Receptive and Expressive Language subscales  Motor Composite Scale (138 items) with Fine and Gross Motor subscales Parent questionnaire with two scales: Social-Emotional and Adaptive Behavior Preschool Language Scale-3:  Assesses receptive and expressive language skills in infants and young children considered to be language precursors using scales [6]:       Attention Semantics Structure Integrative Thinking Vocal Development Social Communication
  • 12.  Results ① MDI (Mental Developmental Index) scores: BF infants slightly higher than SF and CMF at 6-12 months (P < .05) ① ② PDI (Psychomotor Development Index scores): BF infants higher than SF infants at age 6 months and higher ② ② ③ PLS-3 (Preschool Language Scale-3) SF scores higher than CMF infants at 3 and 6 months (P < .05) ③
  • 13.  Results o Generally, no differences found between CMF versus SF. o BF consistently scores better for MDI and PDI compared with SF and CMF infants. Behavioral standardized scores for BF (solid circles), MF (open circles), and SF (inverted triangles) infants during the first year of life.
  • 14. Developmental Status of 1-Year-Old Infants Fed Breast Milk, Cow’s Milk Formula, or Soy Formula (2012) [4]   Implications o All scores on developmental testing were within established normal ranges o SF scored within normal limits on standardized testing and did not differ from CMF o Breastfed infants have a slight advantage on cognitive development compared with CMF and SF Strengths o Findings similar to other studies: comparable cognitive development between CMF and SF Results similar after adjusting for confounding factors Large sample size of carefully characterized infants at 4 time points during 1st year of life   o Weaknesses o Differences between BF, CMF, and SF were small in magnitude and difficult to interpret in terms o o of potential clinical relevance Results are limited by observational characteristics of study Validity of Bayley Scales of Infant Development assessment needs follow-up of study group at school age
  • 15. Early Life Soy Exposure and Age at Menarche (2012) [7]    Study Design: Prospective Cohort Study Setting & Sample: o N=2920 girls o Subjects participants in Avon Longitudinal Study of Parents and Children (ALSPAC) in United Kingdom o Mothers enrolled during pregnancy o Eligible subjects limited to term, white females Measures/Variables: o To examine timing of menarche in relation to effects o o o o of soy isoflavone exposure in SF Infant feeding questionnaires administered during infancy Grouped into BM, ECMF, ESF, and LSF Age at menarche assessed through questionnaires administered annually between ages 8-14.5 Kaplan-Meier survival curves and Cox hazards models used to assess age and risk of menarche
  • 16. Kaplan-Meier Survival Curves and Cox Proportional Hazards Models Kaplan-Meier Curves    Performs survival analysis Used in study interested in time until participants present specific event or endpoint  Cox Hazard Models   In this study: point of menarche Usually, end of study reached before all participants presented event, and outcome of remaining patients is unknown. Outcome unknown of LTF participants (censored data) [8]  Hazard is a measure of how rapidly event of interest occurs Can be interpreted as chance of event occurring in treatment arm divided by chance of event occurring in control arm Endpoints depicted using KaplanMeier survival curves   S= Number of subjects living at start – Number of subjects died Number of subjects living at start Curve represents odds of endpoint having occurred at each point in time (hazard) Hazard ratio is relationship between hazards in two groups and represents distance between Kaplan-Meier plots [8]
  • 17.  Results o 2% mothers reported soy products introduced to at or before 4 months (Early Soy, ESF) o Median age at menarche: 153 months, 12.8 years o Median age at menarche for ES girls: 149 months, 12.4 years o Compared to ECMF, ESF girls at 25% higher risk of menarche throughout follow up (Hazard Ratio 1.25 [95% CI, 0.92, 1.71])
  • 18. Early Life Soy Exposure and Age at Menarche (2012) [7]    Implications o Girls fed ESF may have increased risk of early menarche o Association needs more in-depth evaluation for future study o Replication of findings is imperative before meaningful conclusions can be drawn Strengths o Analysis used large, longitudinal cohort study that is generalizable to U.K. o Maternal age, education, breastfeeding duration, and child health not associated with age at menarche, so should not bias o Maternal age at menarche and prenatal smoking adjusted to control for bias related to LTF o Survival analysis showed subtle link between SF and menarche not found in previous studies Weaknesses o Few subjects (54 girls) in ESF, only Caucasian o Unclear if formula products in U.K. differed from in U.S.: results can not be generalized o Exact soy intake in sample unknown, so true dose relationship could not be assessed o ECMF and LSF differed demographics: potential for confounding in these groups relative to ECMF and ESF o Selection bias in final study sample: excluded girls had lower birth weight, shorter breast feeding duration, more likely to be ill as infants, exposed to prenatal tobacco smoke, and born to younger, heavier mothers.
  • 19. References         [1] http://www.niehs.nih.gov/health/topics/agents/sya-soy-formula/ [2] Bhatia MD, Jatinder, Greer MD, Frank, Committee on Nutrition. (2008). Use of Soy ProteinBased Formulas in Infant Feeding. Pediatrics. 121:5, 1062 -1068 [3] Andres, Aline PhD., Casey, Patrick H. MD., Cleves, Mario A. PhD., Bader, Thomas M. PhD., (2013). Body Fat and Bone Mineral Content of Infants Fed Breast Milk, Cow's Milk Formula, or Soy Formula during the First Year of Life. The Journal of Pediatrics, 163,1: 49-54 [4] Andres, Aline PhD., Cleves, Mario A. PhD., Bellando, Jayne B. PhD., Pivik, R.T. PhD., Casey, Patrick H. MD., Bader, Thomas M. PhD., (2012). Developmental Status of 1-Year-Old Infants Fed Breast Milk, Cow’s Milk Formula, or Soy Formula. Pediatrics: Official Journal of the American Academy of Pediatrics, 129,6: 1134-1140. [5] http://archive.acf.hhs.gov/programs/opre/ehs/perf_measures/reports/resources_measuring/res_me as_cdif.html [6] http://clas.uiuc.edu/special/evaltools/cl02539.html [7] Adgent, Margaret., Daniels, Julie., Rogan, Walter., Adair, Linda., Edwards, Lloyd., Westreich, Daniel., Maisonet, Mildred., Marcus, Michele. (2012) Early Life Soy Exposure and Age at Menarche. National Institutes of Health. 26,2: 163-175 [8] http://en.wikipedia.org/wiki/Kaplan%E2%80%93Meier_estimator
  • 20. Conclusions and Questions to Consider  AAP states term infants fed with soy formula have normal growth and development, energy intake, serum albumin, and bone mineralization; there are no clinical problems with nutrition, sexual development, thyroid disease, or immune function [2]  Even with no stated advantage over CMF, if primary articles, NIH, and AAP generally express safety of soy formulas…  Why does AAP state there are few indications for SF use in place of CMF?  Why is SF only recommended for allergy to CMF and dietary preference and not for everyday use along with CMF? Is there discrepancy between the primary literature and public recommendations?