Context Postmenopausal estrogen therapy has been posited to have some beneficial
effects on aging processes, but its use has risks. Isoflavones, estrogenlike
compounds naturally occurring in plant foods, might confer positive effects
with fewer adverse effects.
Objective To investigate whether soy protein with isoflavones improves cognitive
function, bone mineral density, and plasma lipids in postmenopausal women.
Design, Setting, and Participants Double-blind, randomized, placebo-controlled trial of 202 healthy postmenopausal
women aged 60 to 75 years, recruited from a population-based sample in the
Netherlands, conducted between April 2000 and September 2001.
Intervention Participants were randomly assigned to receive 25.6 g of soy protein
containing 99 mg of isoflavones (52 mg genistein, 41 mg daidzein, and 6 mg
glycetein or total milk protein as a powder on a daily basis for 12 months.
Main Outcome Measures Cognitive function was assessed using the following instruments: dementia,
Mini-Mental State Examination; memory, Rey Auditory Verbal Learning Test,
immediate recall, delayed recall, and recognition, the Digit Span forward
and reversed, and the Doors test; complex attention tasks, Digit Symbol Substitution
and Trailmaking, A1, A2, and B; and verbal skills, Verbal Fluency A and N,
animals and occupations, and the Boston Naming Task. Bone mineral density
of the hip and lumbar spine was assessed using dual-energy x-ray absorptiometry
scanning. Lipid assessment included lipoprotein(a), total cholesterol, low-density
lipoprotein, high-density lipoprotein, and triglycerides.
Results A total of 175 women completed the baseline and at least 1 postintervention
analysis and were included in the modified intent-to-treat analysis. Adherence
was good (median plasma genistein levels, 17.2 and 615.1 nmol/L for placebo
and soy group, respectively). Cognitive function, bone mineral density, or
plasma lipids did not differ significantly between the groups after a year.
Conclusion This double-blind randomized trial does not support the hypothesis that
the use of soy protein supplement containing isoflavones improves cognitive
function, bone mineral density, or plasma lipids in healthy postmenopausal
women when started at the age of 60 years or later.