title: Influence of soya-based infant formula consumption on isoflavone and gut microflora metabolite concentrations in urine and on faecal microflora composition and metabolic activity in infants and children.
abstract: The urinary excretion of soya isoflavones and gut microflora metabolites was investigated in infants and children who had been fed soya-based infant formulas in early infancy. These infants and children were compared with cows'-milk formula-fed controls, to determine at what age gut microflora metabolism of daidzein to equol and/or O-desmethylangolensin (O-DMA) was established, and whether exposure to isoflavones in early infancy influences their metabolism at a later stage of development. Sixty infants and children (aged 4 months-7 years) participated in the study; thirty in each of the soya and control groups. There were four age groups. These were: 4-6 months (seven in the soya group and seven in the control group); 7-12 months (seven in the soya group and nine in the control group); 1-3 years (six in the soya group and eight in the control group); 3-7 years (ten in the soya group and six in the control group). Urine samples were collected to measure isoflavonoids by MS, and faecal samples were collected to measure gut-health-related bacterial composition, by fluorescent in situ hybridisation with oligonucleotide probes, and metabolic activity. A soya challenge (typically a soya yoghurt alternative product containing 4.8 g soya protein and on average 22 mg total isoflavones) was given to control-group infants (>6 months) and children, and also to soya-group children that were no longer consuming soya, to determine their ability to produce equol and/or O-DMA. Urinary genistein, daidzein and glycitein were detected in all infants (4-6 months) fed soya-based infant formula; O-DMA was detected in 75 % of infants but equol was detected in only 25 %. In the controls (4-6 months), urinary isoflavonoids were very low or not detected. In the older age groups (7 months-7 years), O-DMA was found in the urine samples of 75 % of the soya group and 50 % of the controls, after the soya challenge. Equol excretion was detected in 19 % of the soya-group infants and children, and in only 5 % of the controls. However, in the oldest (3-7 years) children, the proportion excreting O-DMA and equol was similar in both groups. Faecal bacterial numbers for bifidobacteria (P<0.001), bacteroides and clostridia (P<0.05) were significantly lower for the soya group compared with the control group. There appears to be no lasting effect of early-life isoflavone exposure on isoflavone metabolism.
authors.affiliation: Northern Ireland Centre for Food and Health, University of Ulster, Coleraine BT52 1SA, UK.
authors.forename: Leane
authors.initials: L
authors.lastname: Hoey
authors.forename: Ian R
authors.initials: IR
authors.lastname: Rowland
authors.forename: Antony S
authors.initials: AS
authors.lastname: Lloyd
authors.forename: Don B
authors.initials: DB
authors.lastname: Clarke
authors.forename: Helen
authors.initials: H
authors.lastname: Wiseman
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D001419:Bacteria / Q000302:isolation & purification; D002648:Child; D002664:Child Nutritional Physiological Phenomena; D002675:Child, Preschool; D060754:Equol; D005243:Feces / Q000382:microbiology*; D019833:Genistein / Q000652:urine; D006801:Humans; D007223:Infant; D041943:Infant Formula / Q000737:chemistry*; D007227:Infant Nutritional Physiological Phenomena; D007529:Isoflavones / Q000652:urine*; D008892:Milk; D041942:Soy Milk / Q000494:pharmacology*
chemical_list: C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D007529:Isoflavones; D060754:Equol; C004742:daidzein; C086566:glycitein; D019833:Genistein; C050052:O-desmethylangolensin