Isoflavone supplements containing predominantly genistein reduce hot flash symptoms: a critical review of published studies.
OBJECTIVE
Several reviews have evaluated the clinical evidence relating isoflavone treatment to the relief of menopausal hot flash symptoms. The majority of these reviews included a variety of isoflavone sources, often without discriminating between the identities of individual isoflavones contained in the study product. An evaluation of published studies using well-characterized isoflavone-containing supplements was conducted to determine whether the observed effects, or lack thereof, were attributable to differences in the composition of isoflavones in study products.


METHODS
Eleven studies that met the inclusion criteria were stratified according to specific isoflavone composition.


RESULTS
All 11 studies contained similar total isoflavone doses. In five studies, involving a total of 177 treated participants, the study product provided more than 15 mg genistein (calculated as aglycone equivalents) per treatment. Each of these five studies consistently reported a statistically significant decrease in hot flash symptoms. In the six studies involving a total of 201 treated participants that provided less than 15 mg genistein per treatment, only one reported a statistically significant decrease in hot flash symptoms. Thus, the reduction in hot flashes was related to genistein dose, not total isoflavone content of the treatments.


CONCLUSIONS
Reports concluding that isoflavone supplements do not significantly reduce hot flash symptoms may be incorrect. The lack of discrimination between individual isoflavones contained in heterogeneous isoflavone mixtures from differing sources can be misleading when designing studies, interpreting results, and conducting reviews. In light of these observations, evaluation of isoflavone effects should focus greater attention to the specific composition within supplements in future studies.
Williamson-Hughes
Patricia S
PS
Archer Daniels Midland Company, Decatur, IL, USA. Patricia_Hughes@admworld.com
Flickinger
Brent D
BD
Messina
Mark J
MJ
Empie
Mark W
MW
D019587:Dietary Supplements; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D005260:Female; D019833:Genistein / Q000008:administration & dosage / Q000627:therapeutic use; D019584:Hot Flashes / Q000188:drug therapy*; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage / Q000627:therapeutic use*; D008593:Menopause / Q000187:drug effects*; D010936:Plant Extracts / Q000627:therapeutic use; D013025:Glycine max
D004791:Enzyme Inhibitors; D007529:Isoflavones; D010936:Plant Extracts; D019833:Genistein