Association Between Soy Based Formula in Infancy and Puberty
Condition: Puberty and Body Composition
Study type: Observational

Summary: 
      Background: Children in industrialized and developing countries have a higher tendency to
      present earlier signs of puberty. One hypothesis includes the hormonal effects of
      phytoestrogens found in soy products.

      Objective: to examine the association between consumption of soy-based food in early infancy
      and childhood and the incidence of early or precocious puberty and overweight in school-aged
      children.

      Methods: the study population for this case control study is randomized from a prospectively
      followed cohort of all babies born at Assaf Haroffeh medical center and followed for milk
      allergy signs and food intake until the age of 3 years (A nested cohort). It is divided to
      those who were allergic to milk, and thus consumed only soy based formula and food during
      infancy and childhood (soy group) and a randomized control group who consumed non-soy based
      intake. For both groups data are available of food habits during infancy and collected from 3
      days food diaries during the current study. Physical examination, including weight , height,
      blood pressure and Tanner Pubertal Staging will performed annually.
    

Detailed description: 
      Soy and soy-based products are widely used in modern day nutrition. It is widely consumed
      among all populations, especially among vegetarians, vegans, those with milk allergy, and in
      the general population who consume processed foods .Soy-based infant formula is commonly
      used, and may account for nearly 25 % of the infant formula sold . Soy products contain
      phytoestrogens (isoflavones) that were suggested to function as weak hormonal disruptors due
      to their functional similarity to mammalian estrogens and their active metabolites. Studies
      regarding the effects of soy consumption on pediatric growth and body mass have been
      inconclusive. Infants who are fed soy-based formulas have higher isoflavones blood
      concentration compared to breast-fed and milk-based formulas fed babies . Several studies
      discuss its effect on infantile physiologic telarche . Several retrospective, case-control
      and case studies were reported trying to elucidate the possible clinical association between
      consumption of soy products during infancy and childhood and pubertal and menarchal timing.
      However, there results are contradictory and inconclusive .Furthermore, in some of the
      studies there is no discussion of the association or confounding effect of overweight which
      is also associated with pubertal timing. Despite the importance of the topic, there is
      paucity of prospective data regarding the impact of soy based products consumption on puberty
      and body mass index (BMI).

      Thus, this prospective study will examine the relationship between the consumption of soy-
      based formulas in early infancy with the development of early puberty and changes in
      anthropometric measures in school-aged children. The goal of this study is to test the
      association between early consumption of soy based formula and the timing of onset of
      secondary sexual characteristics in a prospective mannor and with consideration of current
      dietary intake and confounding factors as BMI and familial trends.

      MATERIALS AND METHODS Study Population The study population is based on a large cohort study
      initiated and performed during 2004-2006 by Katz Y et al ,which followed prospectively all
      newborns born during this time period at Assaf Haroffeh Medical Center, Zerifin, Israel.The
      study looked into their nutritional intake, development of sensitivity to milk and milk
      allergies. The population included a total of 13019 children, out of which 66 developed an
      IgE-mediated Cow Milk Allergy (CMA), 71 developed milk-sensitivity, and 12638 were healthy.
      Our study population includes all CMA group and a randomized group from the healthy
      population (nested cohort).

      Inclusion criteria : all participants from initial study . Exclusion criteria:lack of data
      regarding food intake during infancy in both groups. In the non-allergic children, from the
      non soy based group those who consumed soy - based formula for religious or ideological
      reasons will be excluded.

      Study design This is a case-control study, including a specific sub-population from a large
      cohort population including prospectively collected data on infantile food consumption. All
      original cohort participants, who fulfill the inclusion criteria will be approached for
      participation in the current study. The current study will include demographic and clinical
      data collection, an interview and 3 days of food diary preparation and dietician analysis and
      a physical examination by a pediatric Endocrinologist.

      Demographic and clinical data Collection Data will include the information from the initial
      prospective follow up at infancy including birth weight, birth week, parental origin,
      infantile food habits, maternal age and allergy classification. Data collected at the current
      session: family health history including obesity, early or delayed puberty, ,age of maternal
      menarche and age of paternal shaving, parental height. The child physical activity levels and
      nutritional habits, illnesses, medications . Height and weight were measured and body mass
      index [BMI] will calculated and reported as BMI-SDS . Tanner score was used to characterize
      sexual maturation. The pre-pubertal state was defined as Tanner stage 1 genitalia and
      testicular volume ≤3 ml in boys and absence of breast development in girls. A specific
      description of axillary odor and axillary hair and pubertal hair will be performed for
      adrenarche signs.

      Dietary intake analysis All participants will fill a detailed 3 days food diary (two weekdays
      and one weekend day) according to guidance by the study dietician. The nutritional data from
      the food records will be analyzed using the Tzameret Program (or A computer program, based on
      local food tables, developed by Israeli ministry of Health) ).Results of the analysis will be
      reported as percent-Dietary Reference Intakes (DRI).
    

Intervention name(s): soy based formula at infancy
Intervention type(s): Behavioral
Intervention description(s): The intervention is only past history of soy consumption
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        The study population is based on a large cohort study initiated and performed during
        2004-2006 by Katz Y et al , which followed prospectively all newborns born during this time
        period at Assaf Haroffeh Medical Center, Zerifin, Israel . The study looked into their
        nutritional intake, development of sensitivity to milk and milk allergies. The population
        included a total of 13019 children, out of which 66 developed an IgE-mediated Cow Milk
        Allergy (CMA), 71 developed milk-sensitivity, and 12638 were healthy. Our study population
        included all CMA group and a randomized group from the healthy population (nested cohort).
      
Keywords: soy based formula; overweight; adrenarche,; gonadarache