A preliminary study of the safety, feasibility and cognitive efficacy of soy isoflavone supplements in older men and women.
BACKGROUND
a small number of reports exist on the cognitive effects of soy isoflavones, the findings from which are mixed. Isoflavone efficacy is dependent upon conversion of glycosides contained in soy foods and supplements to the biologically active aglycons. Of particular interest is the production of the metabolite, equol, which is dependent upon intestinal microflora and an integrous digestive system, both being altered by age and age-associated conditions. Unfortunately, few studies enrolled adults over the age of 70, and none included older men.


OBJECTIVE
we examined safety, feasibility and cognitive efficacy of soy isoflavone administration in older nondemented men and women (age 62-89 years).


METHODS
in this randomised, placebo-controlled, double-blind pilot study, subjects ingested either 100 mg/day soy isoflavones (glycoside weight) or matching placebo tablets for 6 months.


RESULTS
active and placebo-treated subjects exhibited a comparable side-effect profile. Plasma levels of genistein and daidzein (P < 0.001), but not equol, increased with isoflavone administration. While similar at baseline, the two groups differed across 6 months of treatment on 8 of 11 cognitive tests administered. Isoflavone-treated subjects improved on tests of visual-spatial memory (P < 0.01) and construction (P = 0.01), verbal fluency (P < 0.01) and speeded dexterity (P = 0.04). Placebo-treated participants were faster than isoflavone-treated subjects on two tests of executive function (P < 0.05).


CONCLUSIONS
these data suggest that administration of 100 mg/day of isoflavones was well tolerated. Plasma genistein and daidzein levels, but not equol, increased with isoflavone administration. Finally, data support the potential cognitive effects of soy isoflavones in older adults.
Gleason
Carey E
CE
Section of Geriatrics and Gerontology, Department of Medicine, University of Wisconsin, Madison, WI 53705, USA. ceg@medicine.wisc.edu
Carlsson
Cynthia M
CM
Barnet
Jodi H
JH
Meade
Sarah A
SA
Setchell
Kenneth D R
KD
Atwood
Craig S
CS
Johnson
Sterling C
SC
Ries
Michele L
ML
Asthana
Sanjay
S
D000368:Aged; D000369:Aged, 80 and over; D003071:Cognition / Q000187:drug effects*; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D060754:Equol; D005260:Female; D019833:Genistein / Q000009:adverse effects* / Q000097:blood / Q000494:pharmacology*; D015577:Geriatric Assessment; D006801:Humans; D007529:Isoflavones / Q000009:adverse effects* / Q000097:blood / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D017063:Outcome Assessment, Health Care; D010865:Pilot Projects
C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D007529:Isoflavones; D060754:Equol; C004742:daidzein; D019833:Genistein