Urinary isoflavones and their metabolites validate the dietary isoflavone intakes in US adults.
BACKGROUND
Isoflavones are derived from dietary sources and considered to promote health by preventing the onset of such chronic diseases as cardiovascular disease, cancer, and osteoporosis. Valid and reliable estimation of isoflavone intake is a prerequisite to establishing biological functions of isoflavones on health risks.


OBJECTIVE
This study aimed to validate the approach of estimating dietary isoflavone intake with respective urinary isoflavone concentrations in US adults.


METHODS
Data from the US Department of Agriculture isoflavone database and dietary recalls of 2,908 US adults with urinary isoflavone data in the 1999-2002 National Health and Nutrition Examination Survey were used.


RESULTS
Dietary isoflavone was consumed by only 35% of adults in a day with an average intake of 3.1 mg/day, which resulted in a mean intake of 1.0 mg/day for all US adults. The isoflavone intakes were from genistein (55%), diadzein (35%), glycitein (7%), biochanin A (2%), and formononetin (2%). Both daily total and energy adjusted isoflavone intake differed by race/ethnicity subgroups (P<0.05) and was associated positively with income (P<0.01) and inversely with body mass index (P<0.05). Geometric mean urinary isoflavone concentration was 5.0 ng/mL among isoflavone consumers and the urinary genistein and daidzein excretion correlated with their isoflavone intake levels (P<0.01).


CONCLUSIONS
In large population-based studies, estimated dietary isoflavone intake can be validated by urinary isoflavones. Further studies are needed at an individual level to validate dietary isoflavone intake by urinary isoflavone concentration.
Chun
Ock Kyoung
OK
Department of Nutritional Sciences, University of Connecticut, Storrs, CT 06269-4017, USA. ock.chun@uconn.edu
Chung
Sang Jin
SJ
Song
Won O
WO
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D000368:Aged; D000428:Alcohol Drinking; D015415:Biomarkers / Q000652:urine; D003430:Cross-Sectional Studies; D004032:Diet / Q000208:ethnology; D015444:Exercise / Q000502:physiology; D005260:Female; D019833:Genistein / Q000008:administration & dosage / Q000652:urine; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage* / Q000378:metabolism / Q000652:urine*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D011203:Poverty; D012907:Smoking; D045730:Soy Foods; D014481:United States; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
D015415:Biomarkers; D007529:Isoflavones; C004742:daidzein; C086566:glycitein; D019833:Genistein