Probiotics Do Not Increase Phytoestrogen Bioavailability 28676

Probiotics Do Not Increase Phytoestrogen Bioavailability

MINNEAPOLIS--Probiotics do not protect soy phytoestrogens frommetabolization by intestinal bacteria or increase plasma levels of isoflavonesin postmenopausal women with or without a history of breast cancer, according toa study published in the August issue of The Journal of Nutrition (134,8:1998-2003, 2004) (www.nutrition.org).

Twenty breast cancer survivors and 20 controls completed four six-weektreatments of supplementation with soy protein (S), soy protein and probiotics(S+P), milk protein (M) and milk protein and probiotics (M+P). The probioticsupplement used in the study consisted of Lactobacillus acidophilusDDS+1, Bifidobacterium longum and 15 to 30 mg fructooligosaccharide/d.

Plasma phytoestrogen levels did not differ between controls and survivors orbetween the S and S+P diets. In addition, plasma concentrations and urinaryexcretion of equol (a substance produced in the intestine as a metabolite ofsoybeans and soy foods) in two subjects differed by more than seven-fold betweenthe two diets.

The researchers concluded the probiotic supplement used in the study does notgenerally affect plasma isoflavone levels, although the significant differencesbetween plasma and urinary equol in some subjects suggests equol producer statusmay be modifiable in some individuals.