Soy isoflavones increase preprandial peptide YY (PYY), but have no effect on ghrelin and body weight in healthy postmenopausal women.
BACKGROUND
Soy isoflavones show structural and functional similarities to estradiol. Available data indicate that estradiol and estradiol-like components may interact with gut "satiety hormones" such as peptide YY (PYY) and ghrelin, and thus influence body weight. In a randomized, double-blind, placebo-controlled, cross-over trial with 34 healthy postmenopausal women (59 +/- 6 years, BMI: 24.7 +/- 2.8 kg/m2), isoflavone-enriched cereal bars (50 mg isoflavones/day; genistein to daidzein ratio 2:1) or non-isoflavone-enriched control bars were consumed for 8 weeks (wash-out period: 8-weeks). Seventeen of the subjects were classified as equol producers. Plasma concentrations of ghrelin and PYY, as well as energy intake and body weight were measured at baseline and after four and eight weeks of each intervention arm.


RESULTS
Body weight increased in both treatment periods (isoflavone: 0.40 +/- 0.94 kg, P < 0.001; placebo: 0.66 +/- 0.87 kg, P = 0.018), with no significant difference between treatments. No significant differences in energy intake were observed (P = 0.634). PYY significantly increased during isoflavone treatment (51 +/- 2 pmol/L vs. 55 +/- 2 pmol/L), but not during placebo (52 +/- 3 pmol/L vs. 50 +/- 2 pmol/L), (P = 0.010 for treatment differences, independent of equol production). Baseline plasma ghrelin was significantly lower in equol producers (110 +/- 16 pmol/L) than in equol non-producers (162 +/- 17 pmol/L; P = 0.025).


CONCLUSIONS
Soy isoflavone supplementation for eight weeks did not significantly reduce energy intake or body weight, even though plasma PYY increased during isoflavone treatment. Ghrelin remained unaffected by isoflavone treatment. A larger and more rigorous appetite experiment might detect smaller differences in energy intake after isoflavone consumption. However, the results of the present study do not indicate that increased PYY has a major role in the regulation of body weight, at least in healthy postmenopausal women.
Weickert
Martin O
MO
German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany. m.weickert@dife.de
Reimann
Manja
M
Otto
Bärbel
B
Hall
Wendy L
WL
Vafeiadou
Katherina
K
Hallund
Jesper
J
Ferrari
Marika
M
Talbot
Duncan
D
Branca
Francesco
F
Bügel
Susanne
S
Williams
Christine M
CM
Zunft
Hans-Joachim
HJ
Koebnick
Corinna
C
D000368:Aged; D001835:Body Weight / Q000502:physiology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005215:Fasting / Q000502:physiology*; D005260:Female; D054439:Ghrelin; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage*; D008875:Middle Aged; D036361:Peptide Hormones / Q000097:blood*; D019894:Peptide YY / Q000097:blood*; D017698:Postmenopause / Q000097:blood*; D045730:Soy Foods
D054439:Ghrelin; D007529:Isoflavones; D036361:Peptide Hormones; D019894:Peptide YY