Japanese citrus fruit (sudachi) juice is associated with increased bioavailability of calcium from whole small fish and suppressed bone resorption in rats

Shirasuboshi (boiled and semi-dried whitebait) is a processed fish food that contains abundant calcium. It is eaten whole and commonly consumed in Japan. In this study, the effect of sudachi (Citrus sudachi) juice on calcium, magnesium and phosphorus bioavailability, and bone metabolism in rats was examined. After 14 d of diets low in calcium and phosphorus, male Sprague-Dawley rats were fed shirasuboshi diets containing dried shirasuboshi powder treated with 20% (S20) or 40% (S40) sudachi juice, or distilled water (C) (0.5% Ca; 0.3% P) for 14 d. The apparent absorptions and retentions of calcium, magnesium and phosphorus from shirasuboshi were determined. Bone formation was calculated by measuring serum osteocalcin, and bone resorption by measuring urinary pyridinoline and deoxypyridinoline. The apparent absorption and retention of calcium and magnesium in the S20 group were significantly higher than in the C and S40 groups. Although serum osteocalcin was not affected by the addition of sudachi juice, the urinary pyridinoline and deoxypyridinoline concentrations in the S40 group were significantly lower than in the C and S20 groups. Our results indicate that sudachi juice added to shirasuboshi was associated with increased calcium bioavailability and suppressed bone resorption in rats.     

Nondigestible oligosaccharides increase calcium absorption and suppress bone resorption in ovariectomized rats

Nondigestible oligosaccharides (NDO) including inulin and fructooligosaccharides (FOS) have been reported to stimulate calcium absorption. Here we report the effect of a mixture of inulin and FOS (Raftilose Synergy 1, Orafti) on calcium and bone metabolism in ovariectomized (OVX) rats. OVX rats (6 mo old) were fed a semipurified diet for 3 mo in our animal care laboratory for stabilization after ovariectomy. They were then divided into two groups (n = 13/group) and fed either a control or a NDO-supplemented diet (55 g/kg) for 21 d. Catheters were placed in their jugular veins. After 2 d, a tracer ((45)Ca) was administered by gavage or i.v. and blood was sampled for up to 300 min. Urine and fecal samples were collected for 4 d after (45)Ca administration. Femurs were measured for bone mineral density (BMD), breaking strength, and total calcium. Calcium absorption, femoral calcium content, BMD, and bone balance (V(bal)) were significantly increased (P < 0.05) by NDO, whereas the bone resorption rate relative to the bone formation rate was significantly depressed by NDO. We conclude that feeding NDO at 5.5 g/100 g for 21 d has a positive effect on calcium absorption and retention in ovariectomized rats.     

Effects of taurine supplementation on bone mineral density in ovariectomized rats fed calcium deficient diet

Taurine supplementation has been shown to have a beneficial effect on femur bone mineral content in ovariectomized rats. It therefore seemed desirable to find out whether the beneficial effect of taurine on ovariectomized rats fed calcium deficient diet could also be reproduced. Forty female Sprague-Dawley rats were divided into two groups. One group was OVX and the other group received sham operation (SHAM), and received either control diet or a taurine supplemented diet for 6 weeks. All rats were fed on calcium deficient diet (AIN-93: 50% level of calcium) and deionized water. Bone mineral density (BMD) and bone mineral content (BMC) were measured in spine and femur. The serum and urine concentrations of calcium and phosphorus were determined. Bone formation was measured by serum osteocalcin and alkaline phosphatase (ALP) concentrations. Bone resorption rate was measured by deoxypyridinoline (DPD) crosslinks immunoassay and corrected for creatinine. Urinary calcium and phosphorus excretion, osteocalcin in blood and cross link value were not significantly different among the groups. Within the OVX group, the taurine supplemented group had not higher femur bone mineral content than the control group. This study established the need for a study on the taurine effect on bone with different calcium levels.     

Consumption of legumes improves certain bone markers in ovariectomized rats

Soybeans are known to protect against osteoporosis, but other legumes frequently consumed in Asia have not been studied to learn if they have a similar protective effect. This study investigated the hypothesis that consumption of soybean, mung bean, cowpea, and adzuki bean has beneficial effects on bone biomarkers in ovariectomized rats. Female Sprague-Dawley rats were either sham operated (sham; n = 7) or surgically ovariectomized and then fed a regular AIN-93M diet (OVX; n = 7) or AIN-93M containing soybean (n = 7), mung bean (n = 7), cowpea (n = 7), or adzuki beans (n = 7) for 10 weeks. No bean consumption significantly altered the body, subcutaneous fat, or uterus weight; however, consumption significantly increased the serum calcium/phosphorous ratio and decreased urinary calcium excretion compared with those of the OVX group. Serum concentration of 17β-estradiol was significantly lower in the OVX group compared with that of the sham group and was lowest in the group fed OVX diet containing soybean. Serum osteocalcin concentration was significantly higher in all OVX rats given a diet with beans compared with the same diet without, but urinary deoxypyridinoline excretion was lowest in the group fed OVX diet containing cowpea. There were no significant differences in bone mineral density or bone mineral content of the right femur, tibia, or lumbar spine or in the trabecular bone volume of the tibia among the diet groups. In conclusion, the consumption of soybean, mung bean, cowpea, and adzuki bean in OVX rats improved osteocalcin, but only those fed cowpea showed decreased bone resorption biomarker, suggesting that cowpea may have the most protective effect on bone in OVX rats.     

Soybean isoflavones dose-dependently reduce bone turnover but do not reverse established osteopenia in adult ovariectomized rats

We assessed the dose-dependent effects of daily soybean isoflavone (IF) consumption in reversing bone loss in adult ovariectomized rats. On d 0, female Wistar rats (7 mo old; n = 55) were either sham-operated (SH; n = 14) or ovariectomized (n = 41). On d 80, intermediate rats (SH: n = 5; ovariectomized: n = 5) were killed to confirm the ovariectomy-induced bone loss. The remaining ovariectomized rats were randomly assigned to one of four groups of nine rats each and fed soybean IF (mixed with a soy protein-free semipurified diet) at 0 (OVX), 20 (IF20), 40 (IF40) or 80 (IF80) mg/(kg body. d) for 84 d. Simultaneously, SH rats were fed the semipurified diet without any additional compound and killed on d 164, as were the other rats. As expected, both bone mineral density in the total femur and in its diaphyseal and metaphyseal subregions and cancellous bone area/measured surface in the distal femur metaphysis were lower in OVX than in SH rats (P: < 0.05). OVX rats had higher plasma osteocalcin concentration and urinary deoxypyridinoline excretion than SH rats (P: < 0.05). On d 164, osteocalcin and deoxypyridinoline concentrations were lower in IF40 or IF80 rats than in OVX rats (P: < 0.05). Nevertheless, neither bone mineral density nor cancellous bone area was greater in IF-fed rats than in OVX rats. Therefore, in adult ovariectomized rats, daily soybean IF consumption decreased bone turnover but did not reverse established osteopenia.     

Resveratrol attenuates ovariectomy-induced hypertension and bone loss in stroke-prone spontaneously hypertensive rats

We examined the effect of resveratrol (3,4',5-trihydroxy stilbene), a phenolic compound found in the skins of most grapes, on blood pressure and bone loss in ovariectomized (OVX), stroke-prone spontaneously hypertensive rats (SHRSP). Nineteen-week-old female SHRSP were divided into a sham-ovariectomized (sham) group fed a control diet and two OVX groups fed either a control diet (OVX-Cont) or a diet supplemented with resveratrol (5 mg/kg per d; OVX-Resv). Ovariectomy induced significant increases in systolic blood pressure (SBP). Resveratrol lowered the SBP by 15%) by the third week of administration, and this effect was maintained throughout the study. Resveratrol treatment also significantly enhanced endothelium-dependent vascular relaxation in response to acetylcholine (ACh) in OVX rats. Finally, femur breaking energies measured for the resveratrol-treated (OVX-Resv) group were significantly higher than those of the resveratrol-untreated (OVX-Cont) group. While no significant differences in calcium, magnesium and phosphorus content were found between the femurs of OVX-Cont and OVX-Resv rats, the femur hydroxyproline content in the OVX-Resv group was significantly higher than of the OVX-Cont group. We conclude that, in OVX-SHRSP, resveratrol acts by a similar mechanism to mammalian estrogens, lowering blood pressure by increasing dilatory responses to ACh. The present study also demonstrated that resveratrol was able to prevent ovariectomy-induced decreases in femoral bone strength.     

Massive large bowel resection decreases bone strength and magnesium content but not calcium content of the femur in rats

We examined the effects of massive large bowel resection (cecocolonectomy) on calcium and magnesium absorption and bone characteristics in rats. Male Sprague-Dawley rats were divided into two groups: sham-operated and cecocolonectomized rats. The rats were fed a sucrose-based diet containing casein at 250 g/kg diet for 10 d after a 9- to 10-d postoperative recovery period. Apparent magnesium absorption but not calcium absorption was lower in the resection group than in the sham group. There was a tendency of lower serum magnesium concentration (P = 0.070) but not calcium concentration (P = 0.418) in the resection group compared with the sham group. The maximum breaking force and magnesium content but not the calcium content of the femur were lower in the resection group than in the sham group. These results suggest that massive large bowel resection influences magnesium kinetics and decreases bone strength through reduction of the magnesium content of the femur in rats. Femoral breaking force was positively correlated (r = 0.617, P = 0.011) with only the magnesium content. We conclude that the changes in magnesium kinetics caused by cecocolonectomy could contribute to the fragility of bone.     

Effects of tuna bone and herbal extract on bone metabolism in ovariectomized rats

This study was conducted to examine the effects of herb extract addition on bone metabolism of ovariectomized (OVX) rats fed a diet with tuna bone as a source of calcium. The experimental groups were sham–control (CaCO₃ [CC]), OVX-CC (OVX-control), OVX–CC + herb extract, OVX–tuna bone powder (TB), OVX–tuna bone powder + herb extract, OVX–citrated tuna bone powder (CTB), and OVX–citrated tuna bone powder + herb extract (CTBH). The herb extract included Rehmanniae radix and Angelicae gigantis radix, following the prescribed theories of Oriental herb medicine. In the OVX-CTBH group, the level of fecal (33.6%) and urinary calcium excretion (45.8%) greatly decreased compared with the TB groups. Osteocalcin concentrations were significantly lower in the OVX-CC group and higher in the OVX-CTB group. The deoxypyridinoline value was significantly influenced by ovariectomy. It was elevated in all OVX groups compared with the sham group, and it was reduced by 12.8% in rats supplemented with the herb extract. The bone density value per 100-g body weight was lowest in the TB group, and it was higher in the tuna bone powder + herb extract, CTB, and CTBH groups. We concluded that TB can be a good calcium source, and it was effective in maintaining skeletal metabolism of OVX rats when it was fed in the form of citrated or herb extract–supplemented diets.     

The effect of calcium intake on bone composition and bone resorption in the young growing rat

A low Ca intake by both rats and man increases bone resorption, decreases bone mass and increases the risk of osteoporosis. The skeletal effect of high Ca intakes is less clear, particularly during periods of bone mineral accrual. Twenty-four female 5-week-old rats, Wistar strain, were randomized by weight into three groups of eight rats each and fed ad libitum a semi-purified diet containing 2 (Ca-restricted), 5 (normal) or 20 (Ca-supplemented) g Ca/kg for 3 weeks. When compared with the normal Ca diet, urinary Ca excretion was unaffected by the dietary restriction of Ca for 3 weeks, but was greater (P<0.001) in Ca-supplemented rats. Urinary pyridinoline (Pyr) and deoxypyridinoline (Dpyr) levels were significantly greater during weeks 2 (Pyr P<0.05, Dpyr P<0.001) and 3 (Pyr P<0.01, Dpyr, P<0.001) of dietary Ca restriction, but were unaffected by Ca supplementation. Femoral dry weight and the concentration of Mg and P in femora were unaffected by dietary Ca concentration. Femoral Ca concentration was reduced (P<0.05) in the Ca-restricted group compared with the other two groups. In conclusion, these results suggest that increasing dietary Ca intake, well above the recommended level, had no effect on bone mineral composition or bone resorption (as assessed with urinary pyridinium crosslinks) in young growing female rats. In addition, these results confirm the findings of previous studies which have shown that bone Ca content in young growing rats was reduced by dietary Ca restriction and that this reduction results, at least in part, from an increased rate of bone resorption.     

Fructooligosaccharide consumption enhances femoral bone volume and mineral concentrations in rats

We examined whether the enhanced mineral absorption resulting from fructooligosaccharide (FOS) consumption affects femoral bone structure and mineral concentrations, using histomorphometrical and X-ray microanalysis. Male Wistar rats (n = 16; 42 d old) were divided into two groups, a control group (n = 8) and a FOS group (5 g/100 g FOS in the diet, n = 8). After a 3-d adaptation period, constant amounts of calcium (95 mg/d) and magnesium (8 mg/d) were fed to the rats in each group, using a pair-feeding protocol. At age 60 d, a 3-d metabolic study was initiated. Calcium and magnesium absorptions were calculated. The rats were then killed, and the right femur was embedded in polyester resin. The distal metaphysis was sagittal-sectioned, and the middle of the diaphysis and neck were cross-sectioned. Calcium, magnesium and phosphorus concentrations in the three samples were then measured. Calcium and magnesium absorptions were significantly greater in FOS-fed rats. Trabecular bone volume at the metaphysis and bone volume at the neck of the femur in FOS-fed rats were also significantly greater than those in control rats. The mineral concentration (Ca, Mg and P) in each region of the bone surface was greater in FOS-fed rats. There was a significant relationship between absorbed calcium and calcium concentrations in bone (r = 0.722, P < 0.001), and a similar relationship was found for magnesium (r = 0.720, P < 0.001). These results suggest that the enhanced calcium and magnesium absorption due to FOS consumption might enhance femoral bone volume and mineral concentrations.     

Olive oil and its main phenolic micronutrient (oleuropein) prevent inflammation-induced bone loss in the ovariectomised rat

The present study was designed to evaluate the effect of olive oil and its main polyphenol (oleuropein) in ovariectomised rats with or without inflammation. Rats (6 months old) were ovariectomised or sham-operated as control. Ovariectomised rats were separated into three groups receiving different diets for 3 months: a control diet with 25 g peanut oil and 25 g rapeseed oil/kg (OVX), the control diet with 50 g olive oil/kg or the control diet with 0.15 g oleuropein/kg. The sham-operated group was given the same control diet as OVX. Inflammation was induced 3 weeks before the end of the experiment by subcutaneous injections of talc (magnesium silicate) in one-half of each group. The success of ovariectomy was verified at necropsy by the atrophy of uterine horns. Inflammation, oleuropein or olive oil intakes did not have any uterotrophic activity, as they had had no effect on uterus weight. The plasma concentration of alpha-1-acid glycoprotein (an indicator of inflammation) was increased in OVX rats with inflammation. With regard to bone variables, osteopenia in OVX was exacerbated by inflammation, as shown by a decrease in metaphyseal and total femoral mineral density. Both oleuropein and olive oil prevented this bone loss in OVX rats with inflammation. At necropsy, oleuropein and olive oil consumption had had no effect on plasma osteocalcin concentrations (marker of bone formation) or on urinary deoxypyridinoline excretion (marker of bone resorption). In conclusion, oleuropein and olive-oil feeding can prevent inflammation-induced osteopenia in OVX rats.     

Bioavailability of milk micellar calcium phosphate-phosphopeptide complex in rats.

We evaluated the bioavailability of two types of calcium from milk in two experiments. One was a micellar calcium phosphate-phosphopeptide (MCP-PP) complex in which the chemical form was similar to the original form of milk, and the other was a commercial whey calcium in which the chemical form was different from that of milk. In experiment 1, the calcium absorption, bone mineral density, and bone strength were examined when growing female rats were fed either MCP-PP complex or whey calcium as the sole source of calcium for 46 d. In experiment 2, the calcium solubility in the small intestine was measured when female rats were meal-fed either MCP-PP complex or whey calcium. The apparent calcium absorption rate in both groups decreased time-dependently during the experimental period, but the time-dependent change in the apparent calcium absorption rate was statistically different. It decreased more slowly in rats fed the MCP-PP diet than in rats fed the whey calcium diet. The bone mineral density of the femur in rats fed the MCP-PP diet was significantly higher than that of the rats fed the whey calcium diet. The bone strength (breaking force and energy) of the femur in rats fed the MCP-PP diet was higher than in the rats fed the whey calcium diet. The amount of soluble calcium in the small intestinal contents in rats at 2.5 h after ingestion of the MCP-PP diet was approximately three times higher than that found in rats fed the whey calcium diet. These results indicate that the calcium bioavailability of MCP-PP complex is higher than that of whey calcium, and this difference is due in part to the solubility in the intestine.     

Effect of dietary legumes on bone-specific gene expression in ovariectomized rats

In previous studies, we found that the consumption of legumes decreased bone turnover in ovariectomized rats. The purpose of the present study is to determine whether the protective effects on bone mineral density (BMD) and the microarchitecture of a diet containing legumes are comparable. In addition, we aim to determine their protective actions in bones by studying bone specific gene expression. Forty-two Sprague-Dawley rats are being divided into six groups during the 12 week study: 1) rats that underwent sham operations (Sham), 2) ovariectomized rats fed an AIN-93M diet (OVX), 3) ovariectomized rats fed an AIN-93M diet with soybeans (OVX-S), 4) ovariectomized rats fed an AIN-93M diet with mung beans (OVX-M), 5) ovariectomized rats fed an AIN-93M diet with cowpeas (OVX-C), and 6) ovariectomized rats fed an AIN-93M diet with azuki beans (OVX-A). Consumption of legumes significantly increased BMD of the spine and femur and bone volume of the femur compared to the OVX. Serum calcium and phosphate ratio, osteocalcin, expression of osteoprotegerin (OPG), and the receptor activator of nuclear factor κB ligand (RANKL) ratio increased significantly, while urinary excretion of calcium and deoxypyridinoline and expression of TNF-α and IL-6 were significantly reduced in OVX rats fed legumes, compared to OVX rats that were not fed legumes. This study demonstrates that consumption of legumes has a beneficial effect on bone through modulation of OPG and RANKL expression in ovariectomized rats and that legume consumption can help compensate for an estrogen-deficiency by preventing bone loss induced by ovarian hormone deficiency.     

The effect of high salt and high protein intake on calcium metabolism, bone composition and bone resorption in the rat

The effects of salt (NaCl) supplementation of rat diets (50 g/kg diet), with normal (200 g/kg) or high (500 g/kg) dietary casein content, were studied in 3-week-old male rats over a 3-week period. Weight gain was reduced by dietary salt but was unaffected by dietary casein. Salt-supplemented rats exhibited a two- and three-fold increase in urinary Mg and Ca excretion respectively, irrespective of dietary casein content. Dietary casein had no effect on urinary Ca or Mg. Salt reduced femoral mass but not femoral mass expressed relative to body weight, but neither variable was affected by dietary casein. Femoral Mg and P contents and concentrations were unaffected by dietary salt or casein. While femoral Ca concentration was unaffected by dietary salt, the Ca content was reduced by salt supplementation, irrespective of dietary casein content. Neither the content nor concentration of Ca in femora was affected by dietary casein. Urinary pyridinoline and deoxypyridinoline levels were increased by salt supplementation, irrespective of dietary casein content, but were unaffected by casein. Net Ca absorption was unaffected by dietary salt or casein. In conclusion, these results show that salt supplementation over the short-term increased the rate of bone resorption in rats. This was as a consequence of Na-induced calciuria. On the other hand, a high dietary protein intake had no effect on Ca metabolism, bone composition or bone resorption, nor did it augment the Na-induced calciuria or increased rate of bone resorption.     

Milk whey protein enhances the bone breaking force in ovariectomized rats

We studied the effects of whey protein (WP) and fractionated WP (HWP; heat-stable WP, LWP; low M.W. WP, EWP; ethanol-precipitated WP) on calcium and bone metabolism in ovariectomized (OVX) rats. Six-week-old female Sprague-Dawley rats were ovariectomized and fed a low-calcium diet (0.03% Ca, 0.3% P) for 4 weeks. The rats were divided into five groups, Cont, WP, HWP, LWP and EWP group, and were fed a Cont diet (20% casein, 0.3% Ca) or a diet (19% casein, 0.3% Ca) containing 1% WP, HWP, LWP or EWP for 4 weeks. There were no significant differences in the calcium balance, serum calcium and calcitonin levels among the experimental groups. However, serum ALP activity of the HWP and EWP groups at 14 wks. were lower than that of the Cont group. The bone breaking strength and energy of femur of the HWP, LWP and EWP groups were higher than those of the Cont group. As for the amount of calcium, phosphorus, and magnesium in the femur, there were no significant differences among the experimental groups; however, the amounts of total amino acids in the femur of the HWP, LWP and EWP groups were higher than that of the Cont group. The amounts of proline and hydroxyproline (typical amino acids of collagen) in the femur of the HWP, LWP and EWP groups were also higher than those of the Cont group. These data indicate that milk WP contains active components that influence bone metabolism in OVX rats by increasing in bone protein such as collagen and enhance the bone breaking force (strength and energy). These results suggest that the active components are existed in heatstable, low M.W. and 30–70% ethanol-precipitated fraction, respectively.     

Absorption of calcium, magnesium, phosphorus, iron and zinc in growing male rats fed diets containing either phytate-free soybean protein or soybean protein isolate or casein

The effect of dietary phytate-free soybean protein (PFS) on intestinal mineral absorption and retention was examined in growing male rats using a three-day mineral balance technique. The rats were fed diets containing PFS, soybean protein isolate (SPI) or casein at a 20% level for 5 wk. Total calcium (Ca), magnesium (Mg), phosphorus (P), iron (Fe) and zinc (Zn) contents in diets were adjusted to 0.35, 0.05, 0.7, 0.0035 and 0.003%, respectively, by supplementation of the diet with their salts. Mineral absorption and retention ratios in rats fed the PFS diet were significantly higher than those in rats fed either the SPI or casein diet. These results suggest that PFS may be a promising dietary protein source for improving the mineral bioavailability in humans.     

Dietary calcium supplementation suppresses bone formation in magnesium-deficient rats

The purpose of this study was to clarify the effects of dietary calcium (Ca) supplementation on bone metabolism of magnesium (Mg)-deficient rats. Male Wistar rats were randomized by weight into three groups, and fed a control diet (control group), a Mg-deficient diet (Mg- group) or a Mg-deficient diet having twice the control Ca concentrations (Mg-2Ca group) for 14 days. Trabecular bone volume was significantly lower in the Mg- and Mg-2Ca groups than in the control group. Trabecular number was also significantly lower in the Mg- and Mg-2Ca groups than in the control group. Mineralizing bone surface, mineral apposition rate (MAR), and surface referent bone formation rate (BFR/BS) were significantly lower in the Mg- and Mg-2Ca groups than in the control group. Furthermore, MAR and BFR/BS were significantly lower in the Mg-2Ca group than in the Mg- group. These results suggest that dietary Ca supplementation suppresses bone formation in Mg-deficient rats.     

Dietary lactose improves endochondral growth and bone development and mineralization in rats fed a vitamin D-deficient diet

Lactose promotes the intestinal absorption of calcium independent of the vitamin D endocrine system. The purpose of this study was to determine the effect of lactose supplementation on endochondral bone growth, bone development and mineralization in weanling rats fed a vitamin D-deficient diet. Rat pups were weaned from vitamin D-deficient dams and fed a vitamin D-deficient diet containing sucrose as the primary carbohydrate source or a similar diet but containing 20% lactose. After 4 wk, body weights, serum calcium levels and endochondral bone elongation rates in the lactose-fed animals were higher than in rats fed the sucrose diet. In addition, bone weights, bone calcium content, percent bone ash of bone dry weight, percent metaphyseal osseous tissues and bone osteoid content in the lactose-fed rats were different from those in the rats fed the sucrose diet. In all cases the changes in osseous tissues that were observed in the animals fed the lactose-supplemented diet were toward normal values as observed in age-matched animals fed a vitamin D-replete diet. The improvements in bone growth and development due to lactose supplementation occurred independent of the vitamin D endocrine system and are likely the result of improved calcium absorption in the intestine.     

Prolonged feeding of difructose anhydride III increases strength and mineral concentrations of the femur in ovariectomized rats

This study demonstrates that feeding difructose anhydride III (DFAIII) improves bone strength and femoral mineral concentrations in a rat model of oestrogen deficiency. We showed the relationship between Ca, Mg and P absorption and bone characteristics in rats. Two groups of female Sprague-Dawley rats (6 weeks old) underwent bilateral ovariectomy (ovariectomized rats, OVX rats) or bilateral laparotomy (sham rats). At 10 weeks old, OVX and sham rats were divided into three subgroups and fed a control, 1.5 % DFAIII or 3 % DFAIII diet for 8 weeks, respectively. Ca but not Mg absorption rates were lowered by ovariectomy; however, ingestion of the 1.5 % and 3 % DFAIII diets similarly restored the reduced Ca absorption in OVX rats at 4 and 8 weeks after feeding of the test diets. DFAIII increased Mg absorption dose-dependently in sham and OVX rats. The bone strength, femoral Ca and Mg concentrations, and distal bone mineral density in the 3 % DFAIII group were higher than those in the control group in OVX rats. The absorption rates of Ca and Mg were significantly correlated with femoral Ca and Mg concentrations and strength, which suggests that increasing both Ca and Mg absorption improves bone characteristics in OVX rats. There were no differences in any of the variables in the femur between the 1.5 % and 3 % DFAIII groups in OVX rats. In conclusion, feeding of a low dose of DFAIII increased intestinal Ca and Mg absorption, and the promotive effect of DFAIII persisted for over 8 weeks. This effect was associated with prevention of ovariectomy-induced osteopenia.     

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

In this study, we investigated the synergistic effects of daidzein (Dz) and kiwifruit on bone and equol production in ovariectomised (OVX) rats. Female Sprague-Dawley rats were randomly assigned to one of five groups: sham operated, OVX control, OVX fed 0.1% Dz-supplemented diet (OVX?+?Dz), OVX fed 0.1% Dz and green kiwifruit (GRK)-supplemented diet (OVX?+?Dz?+?GRK) and OVX fed 0.1% Dz and gold kiwifruit (GOK)-supplemented diet (OVX?+?Dz?+?GOK). There were no significant differences in whole body and femur bone mineral density (BMD) among groups at week 8. BMD in the OVX group significantly decreased at week 8; however, BMD in the OVX?+?Dz?+?GRK was not significantly different from baseline in the end of the study. However, supplementation with kiwifruit did not affect urinary equol concentrations, urinary ratios of equol to Dz and the composition of caecal microbiota. These results suggest that the combination of Dz and GRK may slightly reduce bone loss caused by oestrogen deficiency but does not affect equol production.