Vitamin B12 is essential for DNA synthesis and for cellular energy production.This review aims to outline the metabolism of vitamin B12, and to evaluate the causes and consequences of sub-clinical vitamin B12 deficiency. Vitamin B12 deficiency is common, mainly due to limited dietary intake of animal foods or malabsorption of the vitamin. Vegetarians are at risk of vitamin B12 deficiency as are other groups with low intakes of animal foods or those with restrictive dietary patterns. Malabsorption of vitamin B12 is most commonly seen in the elderly, secondary to gastric achlorhydria. The symptoms of sub-clinical deficiency are subtle and often not recognized. The long-term consequences of sub-clinical deficiency are not fully known but may include adverse effects on pregnancy outcomes, vascular, cognitive, bone and eye health.

This research assessed the relative validity and reproducibility of the Dietary Questionnaire for Epidemiological Studies (DQESV2) over one month in young adults, given the lack of concise and convenient instruments for assessing recent dietary intake in this population. Participants were recruited from a large Australian university (N = 102; 35% male; age 18–34 years; body mass index 16–37 kg/m2). Five one-day weighed food records (WFR) were administered over one month followed by the DQESV2. Estimates for nutrients (energy, protein, total fat, saturated fat, carbohydrate, sugars, dietary fibre, and alcohol) and fruit and vegetable servings were compared between methods using correlation coefficients, 95% limits of agreement, and quintile classifications. One week later, a second DQESV2 was completed by n = 77 of the participants to assess reproducibility using intra-class correlations (ICC) and weighted kappa. Comparing methods, all nutrients and fruit and vegetable servings showed significant positive correlations (P<0.05) except protein intake in males; over 60% of participants were within one quintile classification except total fat and dietary fibre intakes in males (55% and 56%, respectively); and differences in nutrient and food intakes between methods were all within +/−20% of the mean WFR values except alcohol intake in females. Between first and second administrations of the DQESV2 all ICC coefficients were positive (P<0.01) and weighted kappa coefficients ranged from 0.54 for fruit servings (including fruit juice) in males to 0.91 for protein intake in females. Over a one month period, the DQESV2 demonstrated good reproducibility for the studied nutrients and for fruit and vegetable servings and provided a valid measure of the studied nutrients, except alcohol in females, and of fruit servings (including fruit juice) in both genders, at the group level in this young adult population.

Poor vitamin B 12 status may lead to the development of cognitive decline and dementia but there is a large variation in the quality, design of and results reported from these investigations. We have undertaken a systematic review of the evidence for the association between vitamin B 12 status and cognitive decline in older adults. A database search of the literature to 2011 was undertaken, using keywords related to vitamin B 12 and cognition. All prospective cohort studies assessing the association of serum vitamin B 12 or biomarkers were included. Quality assessment and extraction of the data were undertaken by two researchers. The quality assessment tool assigns a positive, neutral or negative rating. Of 3772 published articles, thirty-five cohort studies (n 14 325 subjects) were identified and evaluated. No association between serum vitamin B 12 concentrations and cognitive decline or dementia was found. However, four studies that used newer biomarkers of vitamin B 12 status (methylmalonic acid and holotranscobalamin (holoTC)) showed associations between poor vitamin B 12 status and the increased risk of cognitive decline or dementia diagnosis. In general, the studies were of reasonable quality (twenty-one positive, ten neutral and four negative quality) but of short duration and inadequate subject numbers to determine whether an effect exists. Future studies should be of adequate duration (at least 6 years), recruit subjects from the seventh decade, choose markers of vitamin B 12 status with adequate specificity such as holoTC and/or methylmalonic acid and employ standardised neurocognitive assessment tools and not screening tests in order to ascertain any relationship between vitamin B 12 status and cognitive decline.Key words: Vitamin B 12 : Cognition: Dementia: Systematic reviews Cognitive decline and dementia have a significant impact on the independence and quality of life of sufferers and carers, and research into modifiable risk factors is paramount.The most prevalent form of dementia is Alzheimer's disease (AD) which accounts for up to 70 % of cases (1) , with other common forms including dementia with Lewy bodies, frontotemporal dementia and vascular dementia (2) . Risk factors for dementia include advanced age, genetics, low educational level as well as CVD, and its component vascular risk factors (1,2) . The most important known genetic risk factor for the development of dementia is possession of the apoE4 allele which substantially increases the risk of AD by two to three times (3) .Poor vitamin B 12 status has been linked to cognitive decline for at least 50 years (4) but the role of vitamin B 12 in this process is not clear. Vitamin B 12 deficiency causes neurological degeneration with demyelination of the spinal cord and some initial studies have described a reversible dementia related to vitamin B 12 deficiency (5 -10) .A link between vitamin B 12 status and cognitive decline is biologically plausible. Vitamin B 12 is required for DNA and myelin synthesis, and it is a cofactor for t...

Background: Maintain Your Brain (MYB) is a randomized controlled trial of an online multi-modal lifestyle intervention targeting modifiable dementia risk factors with its primary aim being to reduce cognitive decline in an older age cohort. Methods: MYB aims to recruit 8,500 non-demented community dwelling 55 to 77 year olds from the Sax Institute's 45 and Up Study in New South Wales, Australia. Participants will be screened for risk factors related to four modules that comprise the MYB intervention: physical activity, nutrition, mental health, and cognitive training. Targeting risk factors will enable interventions to be personalized so that participants receive the most appropriate modules. MYB will run for three years and up to four modules will be delivered sequentially each quarter during year one. Upon completing a module, participants will continue to receive less frequent booster activities for their eligible modules (except for the mental health module) until the end of the trial. Discussion: MYB will be the largest internet-based trial to attempt to prevent cognitive decline and potentially dementia. If successful, MYB will provide a model for not just effective intervention among older adults, but an intervention that is scalable for broad use.

The loss of lean body mass, muscle strength and physical function causes significant problems in older adults. Protein and amino acid supplements can preserve muscle strength but the effect on function is variable. We conducted a systematic literature review and meta-analysis to investigate the effect of protein and amino acid supplementation on fat-free mass, muscle strength and physical function in malnourished, frail, sarcopenic, dependent or elderly with acute or chronic conditions, with or without rehabilitation exercise. Databases searched included Medline, BIOSIS, CINAHL, Cochrane Library, EBM Reviews, Embase, Pre-Medline, ProQuest, PubMed and Scopus. Retrieved articles were assessed by two reviewers using the Cochrane Risk of Bias (ROB) Tool. In all, thirty nine randomised controlled trails (n 4274) were included. The studies used a range of protein or essential amino acid (EAA) supplements in a variety of settings, including hospital, community and long-term care. Only seven studies had low ROB and no effect of supplementation was found on any outcomes. Analysis of all thirty-nine studies suggest protein and EAA supplements may improve fat-free mass, muscle strength and physical function (standardised mean difference 0·21-0·27, all P<0·005), but significant heterogeneity and ROB was evident. Predetermined subgroup analysis found undernourished elderly benefitted most; EAA were the most effective supplements and small beneficial effects were seen without rehabilitation exercise. The high heterogeneity and few studies with low ROB limits the conclusions and more high quality studies are needed to determine the best nutritional strategies for the maintenance of strength and function with increasing age.