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 soyabased 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. Soya isoflavone metabolism: Equol: Soya-based infant formula: Gut bacterial microflora

Effect of temperature and water availability during late maturation of the soybean seed on germ and cotyledon isoflavone content and composition

“…Owing to reports of their possible hormonal effects, the safety of isoflavones in infant formulas has been questioned 13 and is still being debated. 14,15 As a result many national health authorities have recommended safe upper limits in daily isoflavone intake. 16,17 Thus, in the soyfood industry there is a growing demand for soybeans with low isoflavone content.…”

Influence of dietary components on development of the microbiota in single-stomached species

“…Hoey et al (2004) used fluorescent in situ hybridisation with rRNA-targeted oligonucleotide probes to investigate the influence of a soya-based infant formula on faecal microbial composition in infants compared with cows' milk-fed controls, between 4 and 12 months of age. It was found that faecal bacterial numbers for bifidobacteria, bacteroides and clostridia (and total bacteria counts) were significantly lower for the soya group compared with the cows' milk group.…”

Developmental Status of 1-Year-Old Infants Fed Breast Milk, Cow’s Milk Formula, or Soy Formula

“…4 Infants fed soy protein-based formula consume significant levels of isoflavones (6-11 mg kg 21 body weight per day) compared with negligible levels in breastfed (BF) infants (,0.01 mg kg 21 body weight per day), resulting in serum and urinary isoflavone levels in the range of 0.4-1.5 mM. [5][6][7][8] These isoflavones can bind and activate estrogen receptors a and b, raising the possibility of potential estrogenic effects. 9 Numerous studies have evaluated the effects of soy protein-based formula feeding on growth (weight, length, and head circumference) compared with MF or BF infants, 10 -16 but behavioral (mental, psychomotor, and language) development in SF infants compared with MF or BF infants has not yet been characterized.…”