Inulin Effects on Bioavailability of Soy Isoflavones and Their Calcium Absorption Enhancing Ability

Abstract

The effect of inulin on isoflavone absorption and the effect of isoflavones and synergy with inulin on calcium absorption in rats was investigated. Rats (n = 48) were divided into three groups and fed inulin (50 mg/g), isoflavone (8 mg/g) or inulin + isoflavone (50 mg/g + 8 mg/g) diets for 21 days. After a 2-h fast, rats were given (45)Ca orally or intraperitoneally, together with 25 mg of calcium as calcium acetate. Blood and femurs were collected 4 days later. Sera were analyzed for isoflavones using HPLC-MS, femurs for (45)Ca by beta-scintillation counting, and total femoral calcium by atomic absorption spectroscopy. Both groups fed isoflavones had similar and significantly higher weight-adjusted total femoral calcium content compared to the inulin-fed group (p < 0.0001). (45)Ca absorption was significantly higher (p < 0.01) when isoflavones were added to the diet, and serum equol was significantly lower (p < 0.01) when inulin was added to the diet containing isoflavones. We conclude that isoflavones enhance calcium absorption, without synergy from inulin, and that inulin decreases equol production.

Supplemental Dietary Racemic Equol Has Modest Benefits to Bone but Has Mild Uterotropic Activity in Ovariectomized Rats , ,

“…Serum concentrations corresponded to (28)(29)(30). Serum concentrations are also similar to levels in clinical participants (postmenopausal women) from our laboratory, classified as equol producers, who consumed between 120-150 mg isoflavones/d (20).…”

The Effect of Soy Food Intake on Mineral Status in Premenopausal Women

“…We examined the effect of soy foods on biochemical markers of bone turnover because of speculation that soy isoflavones, similar to estrogen, might inhibit bone resorption 30,31 and enhance calcium absorption 58 and, hence, might maintain BMD. 4,5 Moreover, calcium intake is less in young adults compared to adolescents because of their lower milk consumption.…”

Fermentation of Calcium‐Fortified Soymilk with Lactobacillus: Effects on Calcium Solubility, Isoflavone Conversion, and Production of Organic Acids

“…These are an isomeric class of flavanoids with aglycone structures similar in form to estrogen, that may mimic the functions of estradiol in the human body (Setchell and Cassidy 1999). Studies indicate that consumption of isoflavones can have bone‐sparing effects over the long term (Setchell and Lydeking‐Olsen 2003) not only by attenuating bone loss (Chen and others 2003; Atkinson and others 2004) but also by enhancing calcium absorption (Zafar and others 2004). …”