Effects of dietary fibre and tea catechin, ingredients of the Japanese diet, on equol production and bone mineral density in isoflavone-treated ovariectomised mice

Abstract

Equol is a metabolite of the isoflavone daidzein (Dz) and is produced by the bacterial microflora in the distal intestine and colon. Some epidemiological studies have reported an association between increased equol production and intakes of green tea or dietary fibre, which are ingredients of the standard Japanese diet. We examined the effects of a diet supplemented with Dz and tea catechin or dietary fibre on equol production and bone mineral density in ovariectomised (OVX) mice. Female mice of the ddY strain were either sham operated or OVX. OVX mice were fed a control diet, a 0·1 % Dz-supplemented diet or a 0·1 % Dz diet supplemented with one of the food components commonly consumed in the Japanese diet. The mice were given 1 % tea catechin (w/w) as part of the diet in Expt 1 or 5 % polydextrose (PD) and 5 % raffinose (Raf) (w/w) as part of the diet in Expt 2. Catechin reduced serum equol levels and attenuated the beneficial effect of Dz on femoral bone loss. The soluble dietary fibres PD and Raf stimulated equol production, and enhanced the bone-protective effects of Dz on femoral bone. These results suggest that dietary fibre, in particular, PD, may alter the bioavailability of isoflavones and prevent osteopenia in OVX mice.

Effects of daidzein and kiwifruit on bone mineral density and equol production in ovariectomised rats

“…Caecal content was increased in weight with Dz and the combination of Dz and both kiwifruitcontaining diets compared to the normal diet groups. The data were consistent with a previous report that flavonoids and fibre added to the diet of rats or mice induced significant enlargement of the caecum compared to rats fed a control diet (Aprikian et al, 2003;Tousen et al, 2012). Kiwifruit contain nonstarch polysaccharides that make up the fruit cell walls and are considered a good source of both soluble and insoluble dietary fibre (Henare & Rutherfurd, 2013), and the polysaccharides from kiwifruit have water-holding and faecal-bulking capacities (Mishra & Monro, 2012).…”

“…In addition, higher intake of dietary fibre has been associated more strongly with equol producers than equol nonproducers among female subjects (Lampe et al, 1998). Therefore, several studies have examined the effect of dietary fibre on equol production in an attempt to establish the beneficial effects of isoflavones (Larkin et al, 2007;Ohta et al, 2002;Tousen et al, 2011aTousen et al, , 2012. For example, fructooligosaccharides or resistant starch, a component of starch, has been reported to promote equol production and prevent bone loss in OVX animals (Ohta et al, 2002;Tousen et al, 2011a).…”

Flavonoid metabolism: the interaction of metabolites and gut microbiota

“…In OVX mice, we reported that post-OVX bone loss can be most effectively prevented with a diet containing both FOS and isoflavone glycoside conjugates, thus correlating with increased equol production [88]. Non-digestible sugars such as FOS, cello-oligosaccharides, polydextrose, and raffinose [121,122] as well as resistant starch (non-digestible starch) enhance equol production and inhibit bone loss in OVX mice [121,123]. In an in vitro study, however, FOS inhibited equol production [98].…”

Isoflavone metabolism and bone-sparing effects of daidzein-metabolites

“…(57) Non-digestible sugars such as FOS, polydextrose, and raffinose as well as resistant starch (non-digestible starch) could enhance equol production and inhibit femoral or tibial bone loss in OVX mice. (58,59) In an in vitro study, however, FOS inhibited equol production. (49) There is a discrepancy between results from the in vivo and in vitro studies.…”