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Isoflavone bioavailability after soy intake during childhood and effects by oral antibiotic treatment
Author(s) -
Franke Adrian A.,
Halm Brunhild M.,
Hebshi Sandra,
Ashburn Leslie,
Custer Laurie
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a11-b
Subject(s) - bioavailability , urine , genistein , daidzein , antibiotics , isoflavones , urinary system , physiology , excretion , medicine , zoology , chemistry , endocrinology , food science , pharmacology , biology , biochemistry
Soy intake is increasingly suggested to protect against breast cancer when exposure happens at early ages, and soy isoflavones (IFL) may play an important role in this respect. IFL levels after soy intake have been studied extensively in adults but not in children nor after oral antibiotic treatment. Applying usual dietary doses of soy (0.22 g roasted nuts per kg body weight (BW)) we repeatedly measured IFL by LC/MS in plasma and/or urine from children ages 5–17 and their parents, and from infants breastfed by soy‐consuming mothers or fed tofu shortly after weaning. In all cases, urinary IFL excretion rates were highly correlated with plasma IFL levels when area under curves for corresponding time intervals were used. The plasma‐to‐urine ratio of daidzein relative to genistein was 3–4 times smaller, indicating a higher bioavailability of genistein. Compared to their mothers, breastfed babies had less IFL in plasma and urine after adjustment for dose and BW. Tofu‐fed infants aged 0.8 to 2 years showed much higher IFL values in plasma (up to 1.8 μM) and urine than adults after adjustment for dose and BW approaching values seen in soy formula‐fed babies. Oral antibiotics surprisingly increased bioavailability possibly be decreasing IFL degrading gut bacteria. We conclude that IFL values from urine reflect those in the circulation, that children appear to take up IFL from soy foods more efficiently than adults, and that the gut flora influences IFL bioavailability.