Dietary fibre modulates the gut microbiota

peer-reviewedDietary fibre has long been established as a nutritionally important, health-promoting food ingredient. Modern dietary practices have seen a significant reduction in fibre consumption compared with ancestral habits. This is related to the emergence of low-fibre “Western diets” associated with industrialised nations, and is linked to an increased prevalence of gut diseases such as inflammatory bowel disease, obesity, type II diabetes mellitus and metabolic syndrome. The characteristic metabolic parameters of these individuals include insulin resistance, high fasting and postprandial glucose, as well as high plasma cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Gut microbial signatures are also altered significantly in these cohorts, suggesting a causative link between diet, microbes and disease. Dietary fibre consumption has been hypothesised to reverse these changes through microbial fermentation and the subsequent production of short-chain fatty acids (SCFA), which improves glucose and lipid parameters in individuals who harbour diseases associated with dysfunctional metabolism. This review article examines how different types of dietary fibre can differentially alter glucose and lipid metabolism through changes in gut microbiota composition and function

Gut microbiota in older subjects: variation, health consequences and dietary intervention prospects

peer-reviewedAlterations in intestinal microbiota composition and function have been linked to conditions including functional gastrointestinal disorders, obesity and diabetes. The gut microbiome encodes metabolic capability in excess of that encoded by the human genome, and bacterially produced enzymes are important for releasing nutrients from complex dietary ingredients. Previous culture-based studies had indicated that the gut microbiota of older people was different from that of younger adults, but the detailed findings were contradictory. Small-scale studies had also shown that the microbiota composition could be altered by dietary intervention or supplementation. We showed that the core microbiota and aggregate composition in 161 seniors was distinct from that of younger persons. To further investigate the reasons for this variation, we analysed the microbiota composition of 178 elderly subjects for whom the dietary intake data were available. The data revealed distinct microbiota composition groups, which overlapped with distinct dietary patterns that were governed by where people lived: at home, in rehabilitation or in long-term residential care. These diet-microbiota separations correlated with cluster analysis of NMR-derived faecal metabolites and shotgun metagenomic data. Major separations in the microbiota correlated with selected clinical measurements. It should thus be possible to programme the microbiota to enrich bacterial species and activities that promote healthier ageing. A number of other studies have investigated the effect of certain dietary components and their ability to modulate the microbiota composition to promote health. This review will discuss dietary interventions conducted thus far, especially those in elderly populations and highlight their impact on the intestinal microbiota.PUBLISHEDpeer-reviewe

The effect of vitamin K1 supplemention for 12 months on bone mineral density and indices of vitamin K status and bone turnover in adult Crohn s disease patients

peer-reviewedAdult patients with Crohn’s disease (CD), even those in remission, have been shown to have higher circulating under-g-carboxylated osteocalcin (ucOC) concentrations, a sensitive marker of vitamin K nutritional status(1), compared to age- and sex-matched healthy control subjects(2,3). Increased concentrations of ucOC in CD patients in these studies appear to be positively and negatively associated with the rate of bone turnover(3) and bone mineral density (BMD) at some sites(2), respectively. The aim of our study was to investigate whether supplementation with vitamin K1 (1000 mg/d) for 12 months had a positive effect on the rate of bone turnover and BMD in CD patients. We have previously shown that this level of supplementation maximally suppresses the degree of ucOC in CD patients(4).PUBLISHEDpeer-reviewe

Effect of phylloquinone (vitamin K1) supplementation for 12 months on the indices of vitamin K status and bone health in adult patients with Crohn's disease.

peer-reviewedAlthough epidemiological findings support a role for vitamin K status in the improvement of bone indices in adult patients with Crohn's disease (CD), this needs to be confirmed in double-blind, randomised controlled trials (RCT) with phylloquinone (vitamin K1). By conducting two RCT, the present study aimed to first establish whether supplementation with 1000 μg of phylloquinone daily near-maximally suppresses the percentage of undercarboxylated osteocalcin in serum (%ucOC; marker of vitamin K status) in adult patients with CD currently in remission as it does in healthy adults and second determine the effect of supplementation with phylloquinone at this dose for 12 months on the indices of bone turnover and bone mass. The initial dose-ranging RCT was conducted in adult patients with CD (n 10 per group) using 0 (placebo), 1000 or 2000 μg of phylloquinone daily for 2 weeks. In the main RCT, the effect of placebo v. 1000 μg vitamin K/d (both co-administered with Ca (500 mg/d) and vitamin D3 (10 μg/d)) for 12 months (n 43 per group) on the biochemical indices of bone turnover (determined by enzyme immunoassay) and bone mass (determined by dual-energy X-ray absorptiometry) were investigated. At baseline, the mean %ucOC was 47 %, and this was suppressed upon supplementation with 1000 μg of phylloquinone daily ( - 81 %; P0·1) on bone turnover markers or on the bone mass of the lumbar spine or femur, but modestly increased (P< 0·05) the bone mass of the total radius. Despite near maximal suppression of serum %ucOC, supplementation with 1000 μg of phylloquinone daily (with Ca and vitamin D3) had no effect on the indices of bone health in adult CD patients with likely vitamin K insufficiency.PUBLISHEDpeer-reviewe

Analysis of vitamin K status, and its correlation with inflammation and cognition, in a well-phenotyped cohort of older Irish people

peer-reviewedHistorically, vitamin K is known for its role in blood clotting; however in recent years additional functions have been identified including a role in sphingolipid metabolism and as an anti-inflammatory agent. Studies have shown correlations between low vitamin K status and poor cognitive function while several biomarkers of inflammation are inversely correlated with cognition. The ELDERMET cohort, a group of well characterised subjects aged ≥ 64 years, were used in this study. The aim of this study was to identify potential associations between vitamin K status and cognition as well as any correlations between biomarkers of inflammation and cognition using a subgroup of the ELDERMET cohort. In addition the study aimed to ascertain significant differences in variables across living stratification i.e. the community dwelling subjects versus those in long term care. Subjects were divided into 4 groups based on their Mini Mental State Exam (MMSE) score. Vitamin K status was determined by measuring dietary and serum phylloquinone (vitamin K) status. Percent undercarboxylated osteocalcin (% ucOC) was also measured in serum as a long-term indicator of functional vitamin K status. Biomarkers of inflammation including high sensitivity C-reactive protein (hsCRP), Interleukin 6 (IL-6), Interleukin 8 (IL-8) and Tumour Necrosis Factor alpha (TNFα) were measured. Analysis of variance (ANOVA) revealed significant differences between markers of vitamin K status and inflammation and MMSE categories. Positive correlations were found between MMSE and serum and dietary phylloquinone. Inverse correlations were found between MMSE and other variables including %ucOC, hsCRP, IL-6, IL-8 and TNFα. Similarly, significant differences were found across living stratification for biomarkers of inflammation. Analysis of covariance (ANCOVA) showed a significant difference in dietary phylloquinone intake between those with severe cognitive impairment and those with normal cognitive function, and between those with moderate cognitive impairment and normal functionality. In addition, a significant difference between IL-6, TNFα and hsCRP was found especially between those with poor cognitive function and those with normal cognitive ability. This study adds to the growing body of evidence which suggests a role for vitamin K in cognitive function. Findings from this study have the potential to help inform public health policy and dietary recommendations aimed at promoting healthy aging

Osteocalcin: The extra-skeletal role of a vitamin K-dependent protein in glucose metabolism

The role of vitamin K in the body has long been associated with blood clotting and coagulation. In more recent times, its role in a range of physiological processes has been described including the regulation of bone and soft tissue calcification, cell growth and proliferation, cognition, inflammation, various oxidative processes and fertility, where osteocalcin is thought to up-regulate the synthesis of the enzymes needed for the biosynthesis of testosterone thereby increasing male fertility. Vitamin K dependent proteins (VKDP) contain γ-carboxyglutamic acid residues which require post-translational, gamma-glutamyl carboxylation by the vitamin K-dependent (VKD) gamma-glutamyl carboxylase enzyme for full functionality. These proteins are present both hepatically and extrahepatically. The role of bone-derived osteocalcin has many physiological roles including, maintenance of bone mass with more recent links to energy metabolism due to the role of the skeleton as an endocrine organ. It has been proposed that insulin binds to bone forming cells (osteoblasts) promoting osteocalcin production which in turn promotes β-cell proliferation, insulin secretion and glucose control. However much of this research has been conducted in animal models with equivocal findings in human studies. This review will discuss the role of osteocalcin in relation to its role in human health, focusing specifically on glucose metabolism

Gender differences in folate status are associated with cognition in healthy Irish elderly adults

In elderly populations, cognitive impairment and incident dementia may be related to inadequate vitamin B status, predominantly folate and vitamin B12. Folate deficiency has been associated with Alzheimer’s disease as well as preceding the onset of other dementia(1), while low folate and vitamin B12 have been associated with depressive symptoms(2). Functional deterioration may also increase with folate deficiency(3). The aim of this study was to examine associations between B vitamins (serum folate and vitamin B12) and measures of cognition in a sample of healthy Irish adults

Compliance with Irish food based dietary guidelines in elderly subjects recruited from rehabilitation wards and out-patient clinics in Southern region hospitals (The ELDERMET project)

The elderly population are an “at-risk” group for under-nutrition which is associated with longer duration in hospitalised care as well as increased prevalence of morbidity and mortality(1). Identifying food consumption patterns and the contribution of the main food groups to nutritional status is essential to identify those at risk of under- or over-nutrition. The aim of this study was to establish the frequency of consumption of the major food groups in two groups of elderly Irish subjects, who participated in the ELDERMET project, and to explore their compliance with the recently revised Irish food based dietary recommendations(2)

Gender differences in food intake among Irish community-dwelling elderly subjects: The ELDERMET project

The proportion of citizens older than 65 years of age in Western populations is increasing. It is therefore important to investigate the fundamental role of diet in the prevention of age-associated chronic disease(1). In addition, gender differences in food consumption and nutrient intakes are well recognised(2), and need to be further explored and addressed

Vitamin D–vitamin K interaction: effect of vitamin D supplementation on serum percentage undercarboxylated osteocalcin, a sensitive measure of vitamin K status, in Danish girls

There is some evidence for a nutritional interaction between vitamin D and vitamin K status. We have recently reported that serum percentage undercarboxylated osteocalcin (%ucOC; a marker of vitamin K status) was inversely correlated with serum 25-hydroxyvitamin D (25(OH)D) concentration (reflective of vitamin D status) in healthy Danish girls (aged 11–12 years), in line with a similar relationship reported in elderly women. While the causal nature of the relationship between vitamin D status and serum %ucOC has been tested in studies of elderly women, it has not been investigated in children. The objective of the present study was to test the hypothesis that improving vitamin D status significantly lowers serum %ucOC. Serum samples from sixty-seven healthy Danish girls (aged 11–12 years), who participated in a 12-month double-blind, placebo-controlled, vitamin D3 intervention trial were used for the present study. These girls were a subset of subjects which began and finished the intervention during wintertime, thus avoiding the influence of seasonality on vitamin D status. A total of thirty-three and thirty-four of the girls had been randomised to treatment with 10 mg vitamin D3 per d and placebo, respectively, for 12 months. Total osteocalcin and the fraction of ucOC in serum (via enzyme-immunoassay) as well as serum 25(OH)D (via HPLC) were assessed at baseline and end-point. Vitamin D3 supplementation significantly increased serum 25(OH)D (21·6 %; P,0·002) but had no effect on serum %ucOC (P.0·8). In conclusion, the findings of the present intervention study in young girls suggest that vitamin D supplementation does not affect serum %ucOC, a marker of vitamin K status