Low aglycone content in commercial soy drink products.

The effectiveness of soy isoflavones to prevent bone loss in postmenopausal women is controversial. While consumption of soy in Vietnam is very high, we recently reported a prevalence of osteoporosis comparable to that of many Western populations. In the present study, we analyzed the isoflavone content of soy drink products commercially available in Vietnam and Sweden, and we also compared these products to "home-made" soy drink from beans of different origin. The amounts of the bioactive aglycones (daidzein, glycitein and genistein) and their glycoside isomers were quantified by high-pressure liquid chromatography. We found that the total isoflavone content was low in all preparations, around 70-100 mg/L and of this only 10% were bioactive aglycones. Of these, the Vietnamese products contained significantly lower levels of glycitein than the products from Sweden and "home-made" soy drink preparations. The results show that consumption of several liters of soy drink per day would be needed to achieve threshold levels for a protective effect on bone. There was no significant association between total protein and isoflavone content in different products. Accurate labeling of soy drink and other products eg of aglycone and glycoside content would allow health professionals and researchers to better explore the possible benefits of soy in dietary intervention studies.

Ethanol alters the effect of kappa receptor ligands on dopamine release in the nucleus accumbens.

Repeated exposure to ethanol has previously been shown to induce alterations in both midbrain dopamine and dynorphin systems. The aim of this study was to investigate functional changes in the sensitivity of dynorphin/kappa-receptor systems following repeated ethanol administration, using dopamine as an indirect marker. The effects of kappa-opioid receptor ligands on dopamine release in the rat nucleus accumbens were investigated following repeated ethanol administration (2 g/kg body weight, twice daily for 7 days). The selective kappa-receptor agonist U50, 488H reduced dopamine levels in both ethanol- and saline-treated animals, although the decline had a later onset and lasted shorter in the ethanol-treated group. Nor-binaltorphimine, a kappa-antagonist, produced a significant increase of dopamine in ethanol-treated rats, but lacked effect in the saline-treated group. This change in responsiveness of dopamine neurons following repeated ethanol administration could be related to changes in the sensitivity of kappa-receptor systems and/or an increase in dynorphin tone in the nucleus accumbens.