Prebiotics and Iron Bioavailability—Is There a Connection?

ABSTRACT: Poor bioavailability of dietary iron, especially from diets rich in cereals and legumes, is a major factor contributing to the high prevalence of nutritional iron deficiency in developing countries. Dietary modification to increase intake of components that promote iron absorption from low-bioavailability meals is an effective strategy for combating nutritional iron deficiency. Prebiotics are nondigestible oligosaccharides that selectively stimulate the growth and activity of specific species of bacteria in the colon with benefits to human health. Common prebiotics such as inulin and fructooligosaccharides occur naturally in a wide variety of plant-based foods and have recently been suggested to have an enhancing effect on iron absorption. The hypothesis that prebiotics enhance iron absorption is biologically plausible because fermentation of prebiotics by natural microflora present in the colon may decrease the pH of the luminal content, promote reduction of Fe(III) to Fe(II), stimulate proliferation of epithelial cells to expand the absorptive surface area, and potentially stimulate expression of mineral-transport proteins in epithelial cells. However, data available in the literature characterizing the enhancing properties of prebiotics on iron absorption are inconsistent, and mechanisms of actions involved are poorly understood. The notion that the colon can function as a significant site of iron absorption in response to stimulation by prebiotics, and the effect of long-term exposure to prebiotics on the iron status of iron-deficient subjects remain to be clarified. This review discusses the functional properties of prebiotics as a promising dietary factor that enhances iron absorption. Keywords: prebiotics, iron, colon, oligosaccharides, inulin     

Bioavailability of calcium,magnesium and phosphorus in rats fed probiotic,prebiotic and synbiotic powder follow‐up infant formulas and their effect on physiological and nutritional parameters

The effect of infant formulas supplemented with functional ingredients on calcium (Ca), magnesium (Mg) and phosphorus (P) bioavailability was investigated in rats. Seven follow‐up infant formulas containing probiotics (Bifidobacterium bifidum and Bifidobacterium longum), prebiotics (galactooligosaccharides at 12, 50 and 100 g kg^?1) or synbiotics (bifidobacteria and galactooligosacccharides) were administered to weanling rats for 30 days. A 3 day mineral balance was performed over three periods (8–10, 18–20 and 28–30 days) to monitor mineral apparent absorption and retention ratios and physiological and nutritional parameters. Feeding rats on infant formula‐based diets showed high feed efficiency (≥0.46). It was found that infant formulas supplemented with probiotics and/or prebiotics for 30 days increased Ca, Mg and P bioavailability in rats. Mineral apparent absorption and retention ratios were higher than 90% for Ca and P and 80% for Mg during the first balance period regardless of the infant formula used, but they decreased during the next two balance periods. Although it was not possible to select one infant formula as the best to improve mineral absorption, the 100 g kg^?1 prebiotic and 50 and 100 g kg^?1 synbiotic infant formulas were the most efficient at increasing Ca, Mg and P bioavailability compared with the control group. Copyright © 2006 Society of Chemical Industry     

Prebiotic effects of fermentable carbohydrate polymers may be modulated by faecal bulking of non‐fermentable polysaccharides in the large bowel of rats

This study investigated the impact of supplementary fermentable polysaccharides inulin (a prebiotic) and barley β‐glucan on the large bowel, when consumed against a background high or low intake of mixed non‐starch polysaccharide. Rats were fed for 28 days with diets containing high (15%) and low (5%) background dietary fibre (BDF; cellulose plus sugar beet fibre), with or without 5% supplementary fermentable fibre (SFF; inulin or barley β‐glucan). High‐BDF diets unsupplemented with inulin or barley β‐glucan caused greater improvement than supplemented low‐BDF diets in several parameters linked to gut health: they increased colonic Bifidobacterium spp., butyric acid concentration in the caecum, and colonic crypt depth more than inulin and barley β‐glucan. For these parameters, inulin and barley β‐glucan added little to the effects of the high‐BDF diet alone. Furthermore, by allowing for dilution due to the greater faecal bulk induced by the mixed fibre compared with inulin or barley β‐glucan, the total quantity of butyric acid in the colon of BDF‐fed rats was greatly amplified. Interpretation of the effects of prebiotics in diets containing dietary fibre requires concurrent analysis of the multiple effects of non‐fermentable bulk.     

Effects of <Emphasis Type="Italic">cheonggukjang</Emphasis> containing arrowroot isoflavones on bone metabolism in ovariectomized rats

The effects of dietary supplementation with cheonggukjang containing arrowroot isoflavones (AIC) on bone mineral density and bone metabolism were investigated in 6-week old ovariectomized Sprague-Dawley rats divided into 4 groups: sham (sham-operation and basal diet), OVX (ovariectomy and basal diet), OVX+C (ovariectomy and basal diet with 5% cheonggukjang), and OVX+AIC (ovariectomy and basal diet with 5% AIC). Eight weeks following ovariectomy, body weight gain, and serum alkaline phosphatase activities were significantly reduced in OVX+C and OVX+AIC. Serum osteocalcin levels were significantly lower in OVX+AIC. Although urinary calcium, phosphorus, and creatinine levels increased after ovariectomy, they decreased in OVX+AIC. Bone mineral densities decreased in OVX but significantly enhanced after C and AIC supplementation. Bone mineral content did not significantly differ between OVX+AIC and sham. Thus, these results suggest that AIC may prevent bone loss in OVX rats.     

Calcium–inulin wheat bread: prebiotic effect and bone mineralisation in growing rats

The nutritional performance of wheat bread prepared with calcium carbonate and inulin was studied in growing rats fed with three diets (BD: diet containing bread with calcium and inulin, SD: diet with synergy1^® and CD: diet control‐AIN 93G‐) up to 60 days. Animals fed with BD consumed less diet and presented a caecal pH (5.5) lower than that of the CD group (7.0) with the highest amount of anaerobic micro‐organisms (1.68 × 10¹⁰ cfu g^?1) at 23 days. Microbiota profiles (DGGE) indicated that BD groups presented 66% of similarity and greater variability than the CD group, suggesting changes due to the prebiotic effect of inulin. In the BD group, calcium apparent absorption (AA_Ca: 83%), bone mineral content (18 g kg^?1), proximal tibia density (242 mg cm^?2) and bone volume (BV: 41%) were higher than in the CD group. The decrease in pH due to fermentation in the large intestine increased calcium bioavailability. Although all variables studied on animals fed with diets containing the prebiotic were improved with respect to a control without inulin, in the case of bread diet, many of them were similar to those of the positive control. Consequently, the prebiotic effect was not altered during the baking process. Results suggest that wheat bread, a highly consumed product throughout the world, is an adequate vehicle for including calcium and inulin in healthy food.     

膳食纤维对大鼠钙平衡及骨生物力学性能的影响

目的：研究不同结构的膳食纤维对钙平衡及生物力学性能的影响。方法：以大鼠作为动物模型分组饲养,分别饲喂含有50 g/kg麦麸、纤维素、木聚糖、果胶、菊粉、魔芋胶及其混合物的饲料。利用原子吸收光谱法检测饲料、粪便、尿样、股骨中钙含量;利用电解质分析仪测定血清中的总钙、游离钙、结合钙浓度;用三点弯曲法检测股骨的最大载荷。比较摄入不同膳食纤维大鼠钙吸收、血钙水平、尿钙流失、钙保留率、骨钙含量、骨的生物力学性能等参数的差异。结果：在钙吸收率方面,麦麸、纤维素组高于木聚糖、果胶、菊粉、魔芋组,其中木聚糖和魔芋组与麦麸组具有极显著差异（P<0.01）;在尿钙日排出量方面,木聚糖和纤维素组低于其余各组;在钙保留率方面,果胶组最低,处于负钙平衡;在血清钙水平方面,麦麸组血清游离钙浓度和其余实验组没有显著性差异（P>0.05）,但麦麸组结合钙和总钙浓度均高于其他各组;在骨钙含量和骨生物力学性能方面,果胶组明显低于其他各组,木聚糖组的骨最大载荷高于其他各组。结论：麦麸和纤维素等低发酵型膳食纤维的肠道钙吸收率高于木聚糖、果胶、菊粉、魔芋等高发酵型膳食纤维;木聚糖有助于提高大鼠骨生物力学性能;不同膳...     

薛荔籽果胶对去势雌性大鼠矿物质吸收的影响

目的:探讨薛荔籽果胶对去势雌性大鼠矿物质吸收的影响。方法:将30只SD成年雌鼠随机分为5组。4组大鼠做双侧卵巢切除手术,一周后分为空白组和薛荔籽果胶高、中、低剂量组;用伪切除同龄大鼠作对照(Sham组)。喂养4周后解剖,测定盲肠内容物pH值、短链脂肪酸、骨钙、骨磷含量及矿物质元素的表观吸收等指标。结果:去势雌性大鼠对钙、镁、磷、锌和铁元素的表观吸收率及骨钙和骨磷含量显著低于正常大鼠(P<0.05)。薛荔籽果胶能显著增加去势雌性大鼠短链脂肪酸含量和盲肠面积(P<0.05),降低盲肠pH值,并且在一定程度上抑制钙、镁、磷、锌和铁元素的表观吸收率。结论:薛荔籽果胶能降低去势雌性大鼠矿物质的表观吸收率。     

Short communication: Proteins in heat-processed skim milk powder have no positive effects on bone loss of ovariectomized rats

Milk has positive effects on bone growth. However, the effect of skim milk powder (SMP) on bone properties has not been reported. This study investigated the effect of SMP on bone loss in ovariectomized (OVX) rats. Forty female Sprague-Dawley rats were ovariectomized and another 10 rats received a sham operation. The OVX rats were randomly separated into 4 groups: OVX control, OVX SMP1 (SMP at 0.04 g/d), OVX SMP2 (SMP at 0.20 g/d), and OVX SMP3 (SMP at 0.40 g/d). Skim milk powder was supplied in the rat diet for 12 wk, and the rats were gavaged once per day. The effects of SMP on calcium content and bone mineral density of femur were determined by atomic absorption spectrophotometry and dual-energy x-ray absorptiometry, respectively. Compared with the control, SMP at all dose levels tested had no particular effect on weight:length, calcium content, or bone mineral density of femurs. It was demonstrated that SMP (0.04 to 0.40 g/d) had no positive effect on bone loss in OVX rats, probably because the heat treatment used during SMP processing caused a loss of biological activity in the protein.     

Maillard reaction products consumption: Magnesium bioavailability and bone mineralization in rats

The aim of this study was to analyze the influence of the consumption of Maillard reaction products (MRP), derived from glucose-lysine and glucose-methionine mixtures heated for 90 minutes, on magnesium bioavailability and tissue concentration. Magnesium balances were performed in rats. Subsequently, the animals were sacrificed and certain organs removed to analyze the magnesium contents. Glucose-methionine MRP induced increases in magnesium fractional absorption in the last week of the assay (69.2 ± 2.9%) compared with the control group (59.4 ± 1.3%), although no variations in magnesium bioavailability during the total period balance were found. The intake of both MRP assayed seemed to increase renal and hepatic magnesium, decrease calcium bone concentration and mask the positive effect of the free amino acids still present in the samples on bone magnesium. The results show that MRP dietary consumption could lead to changes in bone mineralization. The long-term effects should be more deeply studied to predict possible implications for bone health.     

Chemically modified resistant starch in breadmaking: Impact on bone,mineral metabolism and gut health of growing Wistar rats

The effect of chemically modified resistant starch (RS) included in bread formulation on bone and gut health of growing male Wistar rats was studied. In order to determine the functional properties and the prebiotic potential of RS, three groups of rats were assayed: a control group (CD), a group fed with a diet including RS (RSD) and a group fed with a diet containing bread with RS (BRSD). Rats that consumed BRSD exhibited lower daily intake indicating that more satiety is reached with this food and this group presented similar calcium absorption than control rats. In addition, an increase in bone mineral content and bone mineral density and better intestinal balance as reflected by higher lactobacilli/enterobacteria ratio was observed in rats fed with both sources of RS. Thus, these results show a prebiotic role of RS that is maintained when RS is included in a bread formulation.     

Functionality of inulin and polydextrose as sucrose replacers in sugar‐free dark chocolate manufacture – effect of fat content and bulk mixture concentration on rheological,mechanical and melting properties

Inulin and polydextrose are key bulk sugar replacers and have been utilised extensively as functional ingredients due to their fibre and prebiotic claims. This study investigated effects of fat content and bulk mixture concentrations of inulin and polydextrose on rheological properties, mechanical and melting characteristics of sugar‐free dark chocolates sweetened with steviol glycosides. Sucrose was replaced with polydextrose and inulin (0:100, 25:75, 50:50, 75:25, 100:0) at different fat contents (27%, 30% and 33%). Reducing fat content from 33% to 27% had similar effects on the sugar‐free dark chocolates as it did on reference chocolate. Increasing inulin concentrations with simultaneous reduction in polydextrose resulted in consistent increases in Casson plastic viscosity and decreases in Casson yield stress regardless of the fat content. These were explained by microstructural examination of the sugar replacers, which revealed wide variations in network structure. Understanding these factors would help reduce energy load from fat in sugar‐free chocolate confectionery.     

The prebiotic arabinogalactan of Anoectochilus formosanus prevents ovariectomy-induced osteoporosis in mice

Anoectochilus formosanus (Orchidaceae) has previously been shown to exhibit anti-osteoporosis and prebiotic properties. In this study, these bioactivities were verified and associated with an isolated type II arabinogalactan (AGAF) in ovariectomized (OVX) mice model. Female ICR mice were OVX and administrated AGAF (5 and 15 mg/kg) or inulin (400 mg/kg) orally for 3 weeks. Streptomycin was used for blocking the bioactivities of AGAF. In results, AGAF increased the level of fecal bifidobacteria, cecal soluble Ca and short chain fatty acids. Comparing to OVX control group, AGAF improved bone mineral content, trabecular bone volume, and the number of trabecular significantly. In RT-PCR analysis, AGAF reduced the expression of tartrate-resistant acid phosphatase, cathepsin K, and osteocalcin. Streptomycin inhibited both anti-osteoporosis and prebiotic effects of AGAF. In vitro experiments revealed butyrate, not AGAF could activate osteoblasts and inhibit osteoclasts differentiation. Thus, this study demonstrated that AGAF prevents bone loss in OVX mice through prebiotic effects in vivo and in vitro.     

Prebiotics as functional foods: A review

Prebiotics are short chain carbohydrates that are non-digestible by digestive enzymes in humans and selectively enhance the activity of some groups of beneficial bacteria. In the intestine, prebiotics are fermented by beneficial bacteria to produce short chain fatty acids. Prebiotics also render many other health benefits in the large intestine such as reduction of cancer risk and increase calcium and magnesium absorption. Prebiotics are found in several vegetables and fruits and are considered functional food components which present significant technological advantages. Their addition improves sensory characteristics such as taste and texture, and enhances the stability of foams, emulsions and mouthfeel in a large range of food applications like dairy products and bread. This contribution reviews bioactives from food sources with prebiotic properties. Additionally, food application of bioactive prebiotics, stimulation of the viability of probiotics, health benefits, epidemiological studies, and safety concerns of prebiotics are also reviewed.     

Prebiotics and the Bioavailability of Minerals and Trace Elements

Abstract

Promising evidence exists for a stimulatory influence of prebiotic carbohydrates (non‐digestible oligosaccharides (NDO) and lactulose) on the bioavailability of minerals and trace elements, although most information is available from rat experiments. Because the number of human studies is limited, additional research is needed, especially studies that focus on the long‐term effects of prebiotics on bone metabolism. The hypothesized mechanisms suggest that prebiotics that result in a strong pH reduction, a pronounced osmotic effect, a stimulation of the exchange of protons, an increased level of butyrate and calbindin, and an enlarged surface area in the colon may be promising candidates for increasing the absorption of minerals and trace elements. Because the place of colonic fermentation seems to be of influence in these mechanisms, the use of mixtures of different types of prebiotics is of special interest. Probiotics are involved in most prebiotic‐related mechanisms, possibly mediated in part by the production of polyamines. Therefore, the combined use of pre‐ and probiotics may yield promising results. More detailed information on the present state‐of‐the‐art concerning the effects of prebiotics on the bioavailability of minerals and trace elements in different life stages, discussed by study design and its underlying mechanisms, can be found in this review.     

Effects of probiotic,prebiotic and synbiotic follow‐up infant formulas on large intestine morphology and bone mineralisation in rats

The effects of powder functional follow‐up infant formulas on the morphology of the large intestine and the bone mineral content in rats were investigated. Infant formulas were supplemented with probiotics (Bifidobacterium bifidum and Bifidobacterium longum), prebiotics (galacto‐oligosaccharides (4′‐GOS) at 12, 50 and 100 g kg^?1) or synbiotics (bifidobacteria and 4′‐GOS) and administered to seven groups of weanling rats over 30 days. After sacrificing the animals, the caecum and colon were removed and the luminal content pH and the crypt depth and cell density within the epithelial layer were measured. Results showed that groups fed synbiotic diets had significantly (P < 0.05) lower caecal and colonic content pH values compared with the control group. However, no test diet significantly modified the crypt depth or cell density in the caecum. In contrast, all seven test diets significantly increased (P < 0.05) the crypt depth in both the proximal and distal portions of the colon. There was a high correlation (Pearson correlation coefficient 0.870) between caecal and colonic content pH values. On the other hand, colonic content pH was negatively correlated with crypt depth in both the proximal and distal colon and with cell density in the distal colon. The authors previously reported increases in calcium, magnesium and phosphorus absorption using the same infant formulas. In the present study it was concluded that the increase in calcium absorption took place in the distal colon whereas magnesium absorption increased in both the proximal and distal colon, and their contents (especially that of calcium) increased in both the femur and tibia. Copyright © 2007 Society of Chemical Industry     

The bone‐protective effect of a Taiwanese yam (Dioscorea alata L. cv. Tainung No. 2) in ovariectomised female BALB/C mice

BACKGROUND: Yam products have been marketed for treating postmenopausal syndromes. This study investigated the effects of Dioscorea alata L. cv. Tainung No. 2 (TNG yam) on the bone density of ovariectomised (OVX) female BALB/c mice and the mechanism whereby TNG yam exerted this effect. Sham and OVX control groups were fed a control diet while remaining OVX mice were randomly allocated into experimental diets, i.e. yam (630 g TNG powder kg^?1), E2 (20 mg 17β‐oestradiol kg^?1), or genistein (2 g genistein kg^?1) diet. After 12 weeks of feeding, the uterine weight, indices of bone mass and caecal short chain fatty acids were determined. RESULTS: Neither a yam nor genistein diet restored the OVX‐induced uterine atrophy as did the E2 diet. The femoral and lumbar bone mineral density (BMD) of mice fed the yam diet was greater than those of the sham group, respectively (P < 0.05 vs OVX control), while the lumbar BMD of yam and sham groups were similar (P > 0.05 vs sham). The femoral ash and calcium content in the yam group was significantly greater than that in the OVX control group, respectively (P < 0.05 vs OVX control). The total short chain fatty acid content in the caecum, only enhanced in the yam group, was not correlated with the calcium content of either bone or the plasma calcium level. CONCLUSION: TNG yam prevented loss of BMD and improved bone calcium status without stimulating uterine hypertrophy in OVX BALB/c mice. TNG yam may be beneficial for postmenopausal women for preventing bone loss. Copyright © 2008 Society of Chemical Industry     

Protective effects of bovine colostrum acid proteins on bone loss of ovariectomized rats and the ingredients identification

Scope: Milk basic proteins and bovine colostrum extracts have preventive effects on osteoporosis. However, the effects of bovine colostrum acidic proteins (BCAP) on properties of bone have not been reported. This study investigated the effect of BCAP on the prevention of bone loss in ovariectomized (OVX) rats. Methods and results: Forty‐eight 3‐month old female Sprague–Dawley rats were OVX and another 12 rats underwent a sham operation (Sham). The OVX rats were randomly separated into four groups, i.e. OVX control, OVX plus 2 mg/day BCAP, OVX plus 10 mg/day BCAP, and OVX plus 50 mg/day BCAP, and were gavaged once per day for 12 wk. The effects on bone mineral content, bone mineral density, microarchitecture and biomechanical properties were determined. The bioactive ingredients in BCAP were isolated and identified. Results showed that BCAP increased the bone mineral content and bone mineral density of the femur in a dose‐dependent manner. Scanning electron microscope observation and mechanical testing further confirmed the positive effects of BCAP. These positive effects attribute to the fact that osteopontin, lactoferrin, epidermal growth factor and insulin‐like growth factor‐2 are the dominant proteins in BCAP. Conclusions: BCAP (2–50 mg/day) could prevent osteoporosis caused by bone loss in OVX rats.     

Influence of nano-size reduction on absorption and bioavailability of calcium from fortified milk powder in rats

The present study aimed to investigate the effects of fortification and nano-size reduction on absorption and bioavailability of calcium from the fortified milk in ovariectomized (OVX) and OVX-osteoporosis rats. The main goal was to determine the effect of daily consumption of experimental diets on serum calcium, feces calcium, bone calcium, bone breaking strength and bone morphology among rats. This study was conducted to optimize the preparation of nano-fortified milk powder. Then, the calcium bioavailability in 64 female OVX rats and OVX-osteoporosis rats was investigated. The results revealed that bone breaking strength (maximum load) and bone calcium increased with consumption of nano-fortified diet compared with fortified diet. The same observations were seen for bone morphology. OVX rats exhibited higher calcium bioavailability and absorption than OVX-osteoporosis rats with regard to fortified and nano-fortified diets. The amount of calcium absorption from fortified and nano-fortified milk powders in OVX rats was 63.54% and 89.06%, respectively. The bioavailability of calcium from fortified and nano-fortified milk powders in OVX rats was 24.64% and 41.65%, respectively. Moreover, the calcium bioavailability (%) from fortified and nano-fortified milk powders in OVX-osteoporosis rats was 9.74% and 30.17%, respectively. In OVX-osteoporosis group, the absorption levels of calcium from the same experimental diets were 60.54% and 89.09%, respectively.