Soluble maize fibre affects short-term calcium absorption in adolescent boys and girls: a randomised controlled trial using dual stable isotopic tracers

Abstract

Soluble maize fibre (SCF) has been found to significantly improve bone mineral density and strength in growing rats compared with several other novel prebiotic fibres. The objective of the present study was to investigate the effect of SCF on Ca absorption and retention in pubertal children by studying the potential absorption mechanisms of the intestinal microbiota. A total of twenty-four adolescent boys and girls (12 -15 years) participated in two 3-week metabolic balance studies testing 0 g/d SCF (control (CON) treatment) and 12 g/d SCF (SCF treatment) in a random order by inclusion in a low-Ca diet (600 mg/d). Fractional Ca absorption was measured at the end of the two intervention periods using a dual-stable isotope method. Diet composites and faecal and urine samples were collected daily and analysed for Ca content. Ca retention was calculated as dietary Ca intake minus Ca excretion in faeces and urine over the last 2 weeks. Microbial community composition in the faecal samples collected at the beginning and end of each session was determined by 454 pyrosequencing of the PCR-amplified 16S ribosomal RNA gene. Fractional Ca absorption was 12 % higher (41 mg/d) after the SCF treatment compared with that after the CON treatment (0·664 (SD 0·129) and 0·595 (SD 0·142), respectively; P¼0·02), but Ca retention was unaffected. The average proportion of bacteria of the phylum Bacteroidetes was significantly greater in the participants after the SCF treatment than after the CON treatment. These results suggest that moderate daily intake of SCF, a well-tolerated prebiotic fibre, increases short-term Ca absorption in adolescents consuming less than the recommended amounts of Ca.Key words: Prebiotics: Calcium absorption: Microbiota: Soluble maize fibre Adolescence is an important stage of life for bone health that provides a unique opportunity to maximise mineral retention and prevent the risk of osteoporosis-related fractures later in life. Because Ca is becoming increasingly deficient in the diet due to a decrease in milk consumption (1,2) , there is strong interest in functional food ingredients for enhancing Ca utilisation. Non-digestible oligosaccharides, including fructo-oligosaccharides (3,4) and galacto-oligosaccharides (5) , have been reported to be associated with increased Ca absorption. In animal studies, these carbohydrate compounds have been found to be associated with increases in bone mineral density (BMD) (6 -8) as well as improved bone geometry and strength (7,9,10) . The increase in Ca absorption and subsequent improvements in bone health are possibly mediated by microbial fermentation. Bongers & Van den Heuvel (11) suggested that SCFA produced by microbial fermentation can produce an acidic intestinal environment ideal for increasing the solubility and transcellular absorption of Ca.We had compared eight novel fibres for their effects on Ca utilisation and bone properties in a growing rat model (12) . Soluble maize fibre (SCF) was found to have effects similar to those of soluble fibre dextr...

New Frontiers in Fibers: Innovative and Emerging Research on the Gut Microbiome and Bone Health

“…During growth, intake of fructo-oligosaccharides, galacto-oligosaccharides (GOS), SCF, and other prebiotic fibers have resulted in increased calcium absorption in both humans and rats [28][29][30][31]. A landmark clinical study in this area showed that pubertal adolescents assigned to 8 g/d mixed short-and long-chain inulin-type fructans increased calcium absorption at 8 weeks and whole-body bone mineral density at 1 year [28].…”

“…SCF improved peak breaking force by 8.8%, total body mineral content (g) by 7.6%, total body bone mineral density (g/m 2 ) by 2.9%, and distal femoral cortical thickness (mm) by 22.4% [32]. When tested in adolescent boys and girls, SCF increased calcium absorption in the lower gut by 12% in both efficacy (0 and 12 g fiber/d) [30] and effectiveness (0, 10, and 20 g fiber/d) [31] studies. Prebiotic fiber consumption has been associated with shifts in gut microbial communities, typically in fiber fermenters [29,30,34].…”

“…Prebiotic fiber consumption has been associated with shifts in gut microbial communities, typically in fiber fermenters [29,30,34]. These shifts are significantly positively associated with increases in calcium absorption [30,31]. SCF treatment increases amounts of specific nonpathogenic bacteria (such as Lachnospiraceae and Bacteroides) that have been shown to be positively correlated with increased calcium absorption.…”

“…SCF treatment increases amounts of specific nonpathogenic bacteria (such as Lachnospiraceae and Bacteroides) that have been shown to be positively correlated with increased calcium absorption. Correlations between bacterial changes and calcium absorption suggest that SCF may be acting through SCFA mechanisms [30,31]. To put this into context, an increase in peak bone mass by 10% has been estimated to delay osteoporosis by 13 years [33].…”

Review of Ca Metabolic Studies and a Model for Optimizing Gastrointestinal Ca Absorption and Peak Bone Mass in Adolescents

“…There are available data reporting the effects of dietary treatment on human intestinal microbial community composition (Whisner et al, 2014;Whisner et al, 2013) and high-throughput pyrosequencing data regarding Figure 3. Complete model schematic including IGF-1 action, microbial community, and dietary effect (prebiotics and proteins).…”