More than healthy bones: a review of vitamin D in muscle health

Evaluating the effectiveness and risks of bread fortification programs in the middle eastern region: a comprehensive review

Fortification of staple foods such as bread has been implemented as a public health strategy to address nutrient deficiencies. Currently, 11 out of 22 Middle Eastern countries have mandatory wheat flour fortification, primarily with iron and folic acid, while others have voluntary initiatives. Despite progress in bread fortification efforts across the Middle East the long-term effectiveness and safety of these programs remain unclear. We assess the historical context, existing policies, and standards of fortification, focusing on public health outcomes, implementation challenges, and potential risks. A comprehensive search in PubMed, MEDLINE, Cochrane, and ProQuest databases, and relevant studies from the inception of the fortification efforts till 2024 were selected. Our search included Bread or flour fortification and their effectiveness and potential risks specific to Middle Eastern Regions. Findings from the literature indicate that fortification was effective in combating micronutrient deficiencies without causing the harmful effects of overload. However, ongoing research is needed to monitor potential risks, such as micronutrient overload. Most studies are concentrated in Egypt and Iran, with limited data from Saudi Arabia, Turkey, and Jordan, and a notable absence of research from other Middle Eastern countries. This highlights the need for further studies across a wider range of countries to provide a more comprehensive understanding of the regional impact and effectiveness of fortification policies. Addressing the challenges of inadequate coverage, compliance issues, and infrastructure limitations could provide a more comprehensive understanding of the region's fortification policies and their effectiveness.

The Prevalence of Low Vitamin D in Elite Para-Athletes: A Systematic Review

BACKGROUND

Vitamin D insufficiency (25OHD, 50-75 nmolˑl- 1) is a common issue within healthy adults and elite athletes and is associated with decreased musculoskeletal health and performance. However, few studies have identified the prevalence and risk factors associated with vitamin D insufficiency within elite Para-Athletes.

METHODS

An electronic search was completed on the 5th January 2023 and updated on the 21st June 2024, searching Web of Science, PubMed, Scopus, Cochrane Library and EASY (originally OpenGrey). To meet the eligibility criteria, retrieved studies were required to include at least one baseline measure of a vitamin D biomarker from elite Para-Athletes performing at national or international levels and therefore all quantitative study designs could be included. Risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Checklist (8-item) for analytical cross-sectional studies. Data from the eligible studies was extracted and charted, with a supporting narrative synthesis.

RESULTS

The search strategy retrieved 3083 articles, of which ten studies met the inclusion criteria. In total there were n = 355 Para-Athletes, 69.6% of which comprised of males in the included studies. Across the ten included studies, n = 546 samples were taken from n = 355 Para-Athletes across different seasons and based upon the 25(OH)D insufficiency and deficiency thresholds set by each individual study 43.2% of the samples were considered insufficient and 28.1% deficient. During the winter months vitamin D insufficiency was at its most prevalent at 74.1%, compared to 57.1% in summer of the 25(OH)D samples measured in Para-Athletes. Wheelchair athletes who competed in indoor sports were also more susceptible to low vitamin D.

CONCLUSION

This review has highlighted that vitamin D insufficiency and deficiency is highly prevalent in elite level Para-Athletes, all year, across both summer and winter months. Therefore, this review highlights the need for education, treatment, and preventative measures in elite Para-Athletes throughout the year.

REGISTRATION

The following systematic review was prospectively registered through PROSPERO International prospective register of systematic reviews (PROSPERO registration ID number: CRD42022362149).

Effects of vitamin D supplementation on muscle strength in middle-aged and elderly individuals: a retrospective, propensity score-matched study

Introduction

The aim of this study is to investigate the impact of vitamin D supplementation on the muscle strength of the elderly.

Methods

This retrospective, propensity score-matched study included 160 middle-aged and elderly individuals from a community in Beijing, China. The control group (n=110) received health education and lifestyle guidance, while the intervention group (n=50) was given oral vitamin D supplementation in addition to health education and lifestyle guidance. All participants underwent laboratory tests, muscle function, and physical function at baseline and follow-up.

Results

In the propensity score-matched cohort of 41 patients per group, the levels of serum calcium and 25-hydroxyvitamin D in both groups were improved significantly by the end of the study (p<0.05), with the intervention group showing a more significant improvement. The muscle strength of the left lower limb in the intervention group significantly increased after the intervention (p<0.05). The results also showed that the grip strength and pinch strength of the patients in both groups increased after the intervention, and the difference between the two groups was statistically significant (p<0.05).

Discussion

The findings of this study suggest that vitamin D supplementation, in conjunction with lifestyle guidance and health education, is beneficial for enhancing the upper and lower limb strength of patients.

Vitamin D and Muscle Status in Inflammatory and Autoimmune Rheumatic Diseases: An Update

Background and Objectives: Vitamin D is a secosteroid hormone essential for calcium homeostasis and skeletal health, but established evidence highlights its significant roles also in muscle health and in the modulation of immune response. This review aims to explore the impact of impaired vitamin D status on outcomes of muscle function and involvement in inflammatory and autoimmune rheumatic diseases damaging the skeletal muscle efficiency both with direct immune-mediated mechanisms and indirect processes such as sarcopenia. Methods: A comprehensive literature search was conducted on PubMed and Medline using Medical Subject Headings (MeSH) terms: "vitamin D, muscle, rheumatic diseases." Additionally, conference abstracts from The European Alliance of Associations for Rheumatology (EULAR) and the American College of Rheumatology (ACR) (2020-2023) were reviewed, and reference lists of included papers were scanned. The review emphasizes the evidence published in the last five years, while also incorporating significant studies from earlier years, structured by the extent of evidence linking vitamin D to muscle health in the most commonly inflammatory and autoimmune rheumatic diseases encountered in clinical practice. Results: Observational studies indicate a high prevalence of vitamin D serum deficiency (mean serum concentrations < 10 ng/mL) or insufficiency (<30 ng/mL) in patients with idiopathic inflammatory myopathies (IIMs) and polymyalgia rheumatica, as well as other autoimmune connective tissue diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and systemic sclerosis (SSc). Of note, vitamin D insufficiency may be associated with reduced muscle strength (2 studies on RA, 2 in SLE and 1 in SSc), increased pain (1 study on SLE), fatigue (2 studies on SLE), and higher disease activity (3 studies on IIMs and 1 on SLE) although there is much heterogeneity in the quality of evidence and different associations for the different investigated diseases. Therefore, linked to the multilevel biological intervention exerted by vitamin D, several translational and clinical studies suggest that active metabolites of this secosteroid hormone, play a role both in reducing inflammation, but also in enhancing muscle regeneration, intra-cellular metabolism and mitochondrial function, although interventional studies are limited. Conclusions: Altered serum vitamin D status is commonly observed in inflammatory and autoimmune rheumatic diseases and seems to be associated with adverse muscle health outcomes. While maintaining adequate serum vitamin D concentrations may confer muscle-protective effects, further research is needed to confirm these findings and establish optimal supplementation strategies to obtain a safe and efficient serum threshold.

Has a High Dose of Vitamin D3 Impacted Health Conditions in Older Adults?-A Systematic Review and Meta-Analysis Focusing on Dose 100,000 IU

BACKGROUND

Older adults are prone to vitamin D3 (VD3) deficiency, which may impair their health. A high dose of VD3 (HDVD3 = 100,000 IU) could improve their 25-hydroxyvitamin D3 [25(OH)D] level and health outcomes. However, evidence for such a beneficial effect of HDVD3 in older adults coming from clinical trials is mixed.

OBJECTIVE

To review the literature on the efficacy of a single dose of 100,000 IU of VD3 in older people.

METHODS

We searched PubMed/Medline, Science Direct, and NIH's clinical trials registry for clinical studies on the effect of a single high dose of VD3 on various health outcomes in older people. We also performed a meta-analysis using the standardized mean difference to assess the effect of VD3 on its blood level. Due to expected high heterogeneity, its amount (i.e., tau2) was estimated using the DerSimonian-Laird estimator. To estimate tau2, the Q-test for heterogeneity and the I2 statistic were calculated.

RESULTS

Search results identify 13 studies that reported diverse health outcomes, such as lung and cardiovascular function, skin cancer progression, intensive care unit mortality, immune system response, and bone density. The meta-analysis showed a significant increase in 25(OH)D blood levels after treatment in 10 studies, with an average standardized mean difference of 2.60 ng/mL (95% CI: 2.07 to 3.13). Their results suggested that a single high dose of VD3 may benefit intensive care unit patients and skin cancer patients in remission. However, evidence for other beneficial health effects of HDVD3 was mixed due to high heterogeneity among studies.

CONCLUSIONS

A single high dose of VD3 may positively affect some health outcomes in older people, possibly due to its pleiotropic and immunomodulatory effects. However, the evidence needs to be more extensive and consistent, and more rigorous studies are required to confirm the benefits and safety of VD3 high doses in older patients.

Association of eating behavior with symptoms of pelvic floor disorders in middle-aged women: An observational study

BACKGROUND

Estrogen deficiency during menopause, aging, reproductive history, and factors increasing intra-abdominal pressure may lead to structural and functional failure in the pelvic floor. Lifestyle choices, such as eating behavior, may contribute to pelvic floor disorders.

OBJECTIVES

The objective of the study was to investigate associations of eating behavior with symptoms of pelvic floor disorders, that is, stress urinary incontinence, urgency urinary incontinence, fecal incontinence, and constipation or defecation difficulties among middle-aged women.

DESIGN

A cross-sectional, observational study was performed using a population sample of 1098 Finnish women aged 47-55 years.

METHODS

Eating behavior, food consumption frequency, demographical, gynecological, and physical activity variables were assessed using self-report questionnaires. Logistic regression models were used to assess the associations of eating behavior, food frequency, and symptoms of pelvic floor disorders. Models were adjusted with demographical, gynecological, and physical activity variables.

RESULTS

In adjusted models, middle-aged women with disordered eating style were more likely to experience the symptoms of stress urinary incontinence (odds ratio (OR) 1.5, p = 0.002), and constipation or defecation difficulties (OR 1.4, p = 0.041). Adding body mass index into the models abolished associations. Of the studied food items, more frequent consumption of ready-made, highly processed foods (OR 1.5, p = 0.001), and fast foods (OR 1.5, p = 0.005) were independently associated with symptoms of stress urinary incontinence regardless of eating style, whereas consuming ready-made foods (OR 1.4, p = 0.048) was associated with symptoms of urgency urinary incontinence. Daily consumption of fruits (OR 0.8, p = 0.034) was independently associated with symptoms of stress urinary incontinence. Furthermore, we observed that daily consumption of porridge was associated with symptoms of constipation or defecation difficulties (OR 1.7, p = 0.010) independently of eating style. Alcohol consumption (OR 0.9, p = 0.015) was inversely associated with constipation and defecation difficulties. Women with overall higher quality diet had lower odds for stress urinary incontinence (OR 0.9, p = 0.002).

CONCLUSION

This study provides proof-of-concept evidence to the hypothesis that eating behavior and consuming certain food items are associated with perceived pelvic floor disorders. As a preventive action, eating behavior of women with the risk of these symptoms should be assessed, and guidance toward healthy eating patterns should be provided.

Gastric Cancer with Sarcopenia: an Area Worth Focusing On

OPINION STATEMENT

Gastric cancer (GC) is the fifth most common cancer and the third leading cause of cancer death worldwide, which seriously endangers human health. A number of studies have shown that sarcopenia occurs more frequently in patients with gastric cancer than in the general population and can significantly affect the disease status and survival of patients, which is of great significance in predicting the prognosis of gastric cancer. Patients with gastric cancer may suffer sarcopenia no matter before or after surgery, and the pathogenesis is complex. Abnormal nutrient metabolism and reduced exercise are the leading causes. In addition, surgical treatment and chemotherapy for gastric cancer might participate in the physiological and pathological mechanism of sarcopenia. Generally speaking, exercise and nutritional therapy are the main prevention and treatment methods for sarcopenia. But more prospective evidence is needed to establish reasonable interventions, and other drug treatments are in their infancy. For the diagnostic criteria of sarcopenia, the cut-off values of the skeletal muscle mass index obtained from CT images vary widely and need to be standardized and unified. We also need to explore simple predictors to facilitate sarcopenia risk assessment. More research is needed to formulate more appropriate treatments for gastric cancer patients with sarcopenia.

Whey protein and vitamin D supplementation in institutionalized older adults: A randomized trial

Background: The increase in life expectancy and in the number of individuals over 60 years old brings new demands to health professionals and services based on the physiological changes that occur in this population. The aging process results in changes in body composition, increasing body fat and reducing muscle mass, in addition to a reduction in bone mass. Aim: The aim of this study was to examine the effect of whey protein and vitamin D supplementation on body composition and skeletal muscle in older adults living in long-term care facilities. Methods: This study is a double-blind randomized controlled trial. Thirty older adults (>60 years old) were randomized and allocated in three groups: group receiving resistance training and supplementation receiving resistance training, whey protein and vitamin D; group received resistance and placebo training receiving resistance training and placebo, and control group without any intervention. Body composition was measured by dual-energy X-ray absorptiometry at baseline, 12 weeks, and 24 weeks. Results: The mean age was 74.87 (± 8.14) years. A significant difference (p = 0.042) was observed between the group receiving resistance training and supplementation and control groups in relation to lean mass increase (kg) at 24 weeks. After 24 weeks of intervention, there was a significant increase in Relative index of muscle mass for the two groups that underwent resistance training, group received resistance and placebo training (p = 0.042) and group receiving resistance training and supplementation (p = 0.045), in relation to the control. Conclusion: Combined supplementation of whey protein and vitamin D with resistance training can significantly improve lean mass, total mass, and relative index of muscle mass in institutionalized older adults.

The lack of association between dietary antioxidant quality score with handgrip strength and handgrip endurance amongst Tehranian adults: A cross-sectional study from a Middle East country

OBJECTIVE

The association between dietary antioxidant quality score (DAQS) and handgrip strength (HS) and handgrip endurance (HE) is still unclear. We aimed to investigate whether adherence to dietary antioxidant quality score (DAQS) is associated with handgrip strength (HS) and handgrip endurance (HE) amongst adults in Tehran.

METHODS

This cross-sectional study was conducted on 270 (43.7% males, mean age 37 years and 56.3% females, mean age 35 years) apparently healthy adult subjects (53.2% were married) selected from different parts of Tehran, Iran. Dietary intake was assessed using a 168-item validated food frequency questionnaire. DAQS was calculated using antioxidant-nutrient intake. Body composition was measured using a body composition analyser. Handgrip strength and endurance were measured by a digital handgrip dynamometer. Relative muscle strength was expressed as the ratio of handgrip strength by body mass index (BMI).

RESULTS

The results showed that DAQs had no significant association with HS (P = .67, adjusted R2  = .60) and HE (P = .19, adjusted R2  = .08) after adjusting for potential confounders. However, a significant positive association was found between selenium intake and HE even after adjusting for potential confounders (P = .01, adjusted R2  = .10). After controlling for potential confounders no differences in the mean of HS (P = .29) and also HE (P = .61) amongst tertiles of DAQS was found. Positive linear association was found between vitamin C (P = .02, adjusted R2  = .53) and vitamin E (P = .03, adjusted R2  = .55) intake with relative muscle strength.

CONCLUSION

Our results revealed that no significant association between DAQS and HE and HS. It was found that more intake of selenium was positively linked to HE. Dietary intake of vitamin C and vitamin E are associated with higher relative muscle strength. It is evident that more prospective studies are needed to confirm the veracity of our results.

Calcium prescription by Indian orthopaedic surgeons: A survey and a review of literature

BACKGROUND

Orthopaedic surgeons prefer calcium supplement for various pathologies like fracture, osteoporosis, chronic musculoskeletal pain, yet there is no proper evidence to support the benefits of taking them regularly. The average requirement for calcium is around 500-1000 mg/day for a healthy adult, this amount of calcium is not achieved by diet, especially in developing countries like India. Despite this, the serum calcium level remains unaltered, due to the well-controlled absorption and excretion of calcium by the human body. As there is no clarity over the dose, duration and the prefered calcium salts, we constructed a survey to find the preferred dose, duration, the preferred calcium salts among orthopaedic surgeons, and to give an in-depth review of literature about dose, duration, timing, preferred calcium salt and various other calcium-related queries.

MATERIALS AND METHOD

The survey included 15 pre-structured questionnaires; these questions were formatted and validated by senior surgeons and other specialists after a through a review of calcium-related literature. These questionnaires were used in a pilot study conducted within the department and were later modified and separated into 7 sections. Data were collected by both online survey (google forms) and direct interviews.

RESULT AND CONCLUSION

128 Orthopedic surgeons responded. The total number of response obtained was 2355. Unanswered questions were 152. From the survey, it was found that most orthopaedic surgeons prefer to prescribe calcium routinely (55.46%). The commonly used calcium salt was calcium carbonate (47.65%), followed by citrate (32.8%). 42.18% were not aware of the efficiency of prescribing calcium in divided doses. Most responded that calcium is not to be given for patients with renal stones, but literature shows that calcium prescribed reduces the recurrence of commonest kidney stones, calcium oxalate stones.

Effects of Different Vitamin D Supplementation Schemes in Post-Menopausal Women: A Monocentric Open-Label Randomized Study

BACKGROUND

The improvement of muscular strength is a well-known extra-skeletal effect of Vitamin D. The aim of the study was to evaluate the effectiveness of the calcifediol supplementation compared to various cholecalciferol administration schedules in increasing 25(OH)D serum levels and improving muscular function.

METHODS

107 post-menopausal women with hypovitaminosis D were assigned to receive Vitamin D supplementation according to four different regimens: colecalciferol single, monthly, or weekly oral dose and calcifediol weekly oral dose. Serum levels of 25(OH)D and muscular function of lower limbs (Sit-to-Stand test and Timed-Up-and-Go test) were evaluated at baseline and during 6 months follow-up.

RESULTS

Calcifediol and weekly cholecalciferol induced a greater and faster increase of serum 25(OH)D, compared to monthly or single-dose cholecalciferol administration. The 25(OH)D increase was associated with an improvement of muscle function of lower limbs. The larger increase of serum 25(OH)D observed with calcifediol and with weekly cholecalciferol was associated with a concomitant greater improvement of muscle strength.

CONCLUSIONS

Supplementation with calcifediol is more effective and faster compared to cholecalciferol in increasing 25(OH)D serum levels and is associated with a greater improvement of muscular function, thus representing a therapeutic alternative for treatment of hypovitaminosis D.

Nutrients to mitigate osteosarcopenia: the role of protein, vitamin D and calcium

PURPOSE OF REVIEW

Osteosarcopenia (the joint loss of bone density and muscle mass and function) is an emerging geriatric syndrome, which associates with poor health outcomes. Several nutrients including protein, vitamin D and calcium interact (directly or through absorption properties) to regulate muscle and bone metabolism. We provided an update on the efficacy of these nutrients on musculoskeletal outcomes in older adults with, or at risk of, osteosarcopenia.

RECENT FINDINGS

Randomized trials show that correcting vitamin D and calcium deficiencies to meet the recommended dietary allowance (RDA) increases bone density and reduces fracture (but not falls) risk. Supplementing above the RDA with protein supports gains in lean mass and lumbar-spine bone density; however, there is inconclusive evidence for muscle strength, physical function or other bone density sites. A likely explanation for this relates to the significant heterogeneity between trials regarding protein dose, type and timing, as well as baseline protein intake. Further high-quality trials are needed in older osteosarcopenic adults to investigate the effects of protein (while correcting vitamin D and calcium deficiencies) on clinically meaningful outcomes such as activities of daily living, falls and fractures.

SUMMARY

An adequate intake of protein (1.2-1.5 g/kg/day), vitamin D (800 IU/day) and calcium (1000-1200 mg/day), is well tolerated and effective at mitigating some aspects of osteosarcopenia such as lean mass, bone density and fracture risk.

Differences and determinants of vitamin D deficiency among UK biobank participants: A cross-ethnic and socioeconomic study

BACKGROUND

The public health relevance of true vitamin D deficiency is undisputed, although controversy remains regarding optimal vitamin D status. Few contemporary cross-ethnic studies have investigated the prevalence and determinants of very low 25-hydroxyvitamin D [25(OH)D] concentrations.

METHODS

We conducted cross-ethnic analyses on the prevalence and determinants of vitamin D deficiency (25(OH)D ≤ 25 nmol/L) using data from 440,581 UK Biobank participants, of which 415,903 identified as White European, 7880 Asian, 7602 Black African, 1383 Chinese, and 6473 of mixed ancestry. Determinants of vitamin D deficiency were examined by logistic regression.

RESULTS

The prevalence of vitamin D deficiency was highest among participants of Asian ancestry (57.2% in winter/spring and 50.8% in summer/autumn) followed by those of Black African ancestry (38.5% and 30.8%, respectively), mixed (36.5%, 22.5%), Chinese (33.1%, 20.7%) and White European ancestry (17.5%, 5.9%). Participants with higher socioeconomic deprivation were more likely to have 25(OH)D deficiency compared to less deprived participants (P = <1 × 10^-300); this pattern was more apparent among those of White European ancestry and in summer (P_interaction ≤6.4 × 10^-5 for both). In fully-adjusted analyses, regular consumption of oily fish was associated with reduced odds of vitamin D deficiency across all ethnicities, while outdoor-time in summer was less effective for Black Africans (OR 0.89, 95% CI 0.70, 1.12) than White Europeans (OR 0.40, 95% CI 0.38, 0.42).

CONCLUSIONS

Severe vitamin D deficiency remains an issue throughout the UK, particularly in lower socioeconomic areas. In some groups, levels of deficiency are alarmingly high with one-half of Asian and one-third of Black African ancestry populations affected across seasons.

KEY MESSAGES

The prevalence of vitamin D deficiency in the UK is alarming, with certain ethnic and socioeconomic groups considered particularly vulnerable.

Sleep duration is associated with vitamin D deficiency in older women living in Macao, China: A pilot cross-sectional study

Chinese women are known to have both a high prevalence of metabolic syndrome (MetS) and vitamin D deficiency (serum 25-hydroxyvitamin D (25OHD) <50 nmol/l). Associations between sleep duration and circulating 25OHD have recently been reported but, to our knowledge, these associations have not been studied in older Chinese populations. We thus investigated whether sleep duration was associated with vitamin D status in a population from Macao, China, and whether sleep duration modified the association between MetS and vitamin D deficiency. In 207 older (>55 years) Macanese, anthropometry, blood samples and validated questionnaires, including sleep duration and cardiovascular risk factors, were simultaneously collected. On multivariable categorical analyses, those women, not men, who had short sleep duration (≤6 hours (h)) were at a 2-fold risk for vitamin D deficiency (both <50 nmol/L and <37 nmol/L; OR = 1.94, 95%CI 1.29–2.92; OR = 2.05, 95%CI 1.06–3.98, respectively) and those who had longer sleep duration (>8 h) were 3-fold more likely to have vitamin D deficiency (OR = 3.07, 95%CI 1.47–6.39; OR = 2.75, 95%CI 1.08–7.00, respectively) compared to those with normal sleep duration (6–8 h). Both women and men with MetS were 2-fold more likely to have vitamin D deficiency (women: OR = 2.04, 95%CI 1.31–3.17; OR = 2.15, 95%CI 1.11–4.17, respectively; men: OR = 2.01, 95%CI 1.23–3.28; OR = 2.04, 95%CI 1.00–4.29, respectively). Moreover, women with both short sleep duration and MetS had an increased risk of vitamin D deficiency (OR = 3.26, 95%CI 1.10–9.64). These associations were not found in those with longer sleep. Men with longer sleep and MetS had a 5-fold risk of vitamin D deficiency (OR = 5.22; 95%CI 2.70–10.12). This association was non-significant for men with shorter sleep. We conclude that both short and long sleep duration were associated with vitamin D deficiency in older Chinese women. Further research is needed in larger cohorts or with intervention studies to further examine the associations between reduced sleep, metabolic syndrome and vitamin D deficiency.

The relationship between serum vitamin D and fracture risk in the elderly: a meta-analysis

BACKGROUND

The incidence of osteoporotic fractures has increased rapidly, and because of the poor prognosis and high mortality associated with osteoporotic fractures, they remain a prospective research area globally. One way to reduce their incidence is to investigate their intervention risk factors in the elderly. Hence, this study explores the correlation between serum 25-hydroxyvitamin D [25(OH)D] levels and osteoporotic fractures in elderly patients through a meta-analysis.

METHODS

We conducted our literature search mainly in PubMed and Embase for identifying studies that investigated the relationship between serum 25(OH)D levels and the risk for osteoporotic fractures. We performed categorical analysis, heterogeneity checks, publication bias analysis, and subgroup analyses.

RESULTS

In total, 20 studies were included, of which 4 were case-cohort studies and 16 were cohort studies. A total of 41,738 patients from 20 studies were included in the meta-analysis, of which 5916 had fractures, including 3237 hip fractures. By combining the lowest and highest categories of relative risks (RRs) and 95% confidence intervals (CIs), it was suggested that lower serum 25-hydroxyvitamin D levels may be a risk factor for fractures. RR (95% CI) for total and hip fractures were 1.11 (0.99, 1.24) and 0.89 (0.80, 0.98) after adjustments.

CONCLUSIONS

Our study showed that compared to low serum 25(OH)D levels, high serum 25(OH)D levels reduce the risk of hip fractures in the patients aged 60 years or older. In contrast, serum 25(OH)D has no significant relationship with total fracture risk.

Relative D3 vitamin deficiency and consequent cognitive impairment in an animal model of Alzheimer's disease: Potential involvement of collapsin response mediator protein-2

Alzheimer's disease (AD) starts with memory impairments that can be observed before the appearance of significant neuropathology; thus, identifying mechanisms to stop AD progression is an urgent priority. Epidemiological and clinical data show that the consequences of vitamin D deficiency are relevant to disease risk and can be observed in the progression of many diseases, especially AD, whereas higher serum levels of vitamin D are associated with better cognitive test performance. However, the potential therapeutic strategy and underlying mechanisms of vitamin D supplementation against AD still need to be further investigated. In the present study, we found that 3xTg-AD mice with vitamin D supplementation exhibited an increase in serum vitamin D concentrations and improved cognition. We measured serum vitamin D binding protein (VDBP) concentrations and found that serum VDBP levels were increased in 3xTg-AD mice compared to B6129S control mice, but there was no significant difference between control- and vitamin D-treated 3xTg-AD groups. The vitamin D-mediated memory improvement may be accompanied by the suppression of increased hippocampal collapsin response mediator protein-2 (CRMP2) phosphorylation, and the restoration of CRMP2 phosphorylation by okadaic acid (OA) could abolish the beneficial effects of vitamin D. In addition, we found that CRMP2 was associated with NR2B and PSD-95 in 3xTg-AD mice with vitamin D supplementation. This CRMP2-NR2B interaction could be disrupted by a TAT-CBD3 peptide or OA, leading to attenuated memory protection in vitamin D-treated 3xTg-AD mice. Therefore, CRMP2 may be involved in vitamin D-mediated memory improvement in AD.

Nutritional strategies for maintaining muscle mass and strength from middle age to later life: A narrative review

Progressive age-related reductions in muscle mass and strength (sarcopenia) can cause substantial morbidity. This narrative review summarizes evidence of nutritional interventions for maintaining muscle mass and strength from midlife through old age. PubMed and Cochrane databases were searched to identify studies of dietary intake and nutritional interventions for sustaining muscle mass and strength. The benefits of progressive resistance training with and without dietary interventions are well documented. Protein and amino acid (particularly leucine) intake should be considered, and supplementation may be warranted for those not meeting recommended intakes. Vitamin D receptors are expressed in muscle tissue; meta-analyses have shown that vitamin D benefits muscle strength. Data suggest that milk and other dairy products containing different bioactive compounds (i.e. protein, leucine) can enhance muscle protein synthesis, particularly when combined with resistance exercise. Omega-3 s can improve muscle mass and strength by mediating cell signaling and inflammation-related oxidative damage; no studies were specifically conducted in sarcopenia. Low-dose antioxidants (e.g. vitamins C and E) can protect muscle tissue from oxidative damage, but relevant studies are limited. Magnesium is involved with muscle contraction processes, and data have shown benefits to muscle strength. Acidogenic diets increase muscle protein breakdown, which is exacerbated by aging. Alkalizing compounds (e.g. bicarbonates) can promote muscle strength. Small studies of probiotics and plant extracts have generated interest, but few large studies have been conducted. Based on available data, dietary and supplemental interventions may add to the benefits of exercise on muscle mass and strength; effects independent of exercise have not been consistently shown.

The role of parathyroid hormone (PTH) and vitamin D in falls and hip fracture type

BACKGROUND

Fragility fractures of the hip are associated with high morbidity and mortality, and represent a rather devastating consequence of osteoporosis. Hip fractures are traditionally investigated as a whole, although it has been recently implied that distinct pathogenic mechanisms may lead either to trochanteric or subcapital fractures.

AIMS

To investigate whether differences exist by hip fracture type with respect to serum 25(OH)D (vitamin D) and parathyroid hormone (PTH) levels, in addition to epidemiological and demographic data, including history of falls.

METHODS

The inclusion criteria were met by 116 patients [48 men and 68 women; mean age 80.8 ± 8.5 (range 62-94) years]. Patients were analyzed according to hip fracture type, history of falls, and vitamin D and PTH status.

RESULTS

Older age, recurrent falls, serum levels of PTH > 65 pg/ml, and severe vitamin D deficiency were found to be associated with trochanteric fractures. Additionally, older age, female gender, PTH > 65 pg/ml, and severe vitamin D deficiency were related to recurrent falls. Meanwhile, patients with absence of PTH response to low vitamin D levels, were not repeated fallers and suffered mostly from subcapital fractures.

DISCUSSION AND CONCLUSION

Elevated PTH levels predispose both to falls and trochanteric fractures, while vitamin D-deficient patients with normal PTH levels are mostly related to subcapital fractures. It is thereby indicated that different pathophysiological processes lie behind subcapital and trochanteric fractures. A better understanding of these mechanisms may assist in the development of prevention strategies for individuals recognized at risk for falls and either type of hip fracture.

No effect of 25-hydroxyvitamin D supplementation on the skeletal muscle transcriptome in vitamin D deficient frail older adults

Objective

Vitamin D deficiency is common among older adults and has been linked to muscle weakness. Vitamin D supplementation has been proposed as a strategy to improve muscle function in older adults. The aim of this study was to investigate the effect of calcifediol (25-hydroxycholecalciferol) on whole genome gene expression in skeletal muscle of vitamin D deficient frail older adults.

Methods

A double-blind placebo-controlled trial was conducted in vitamin D deficient frail older adults (aged above 65), characterized by blood 25-hydroxycholecalciferol concentrations between 20 and 50 nmol/L. Subjects were randomized across the placebo group and the calcifediol group (10 μg per day). Muscle biopsies were obtained before and after 6 months of calcifediol (n = 10) or placebo (n = 12) supplementation and subjected to whole genome gene expression profiling using Affymetrix HuGene 2.1ST arrays.

Results

Expression of the vitamin D receptor gene was virtually undetectable in human skeletal muscle biopsies, with Ct values exceeding 30. Blood 25-hydroxycholecalciferol levels were significantly higher after calcifediol supplementation (87.3 ± 20.6 nmol/L) than after placebo (43.8 ± 14.1 nmol/L). No significant difference between treatment groups was observed on strength outcomes. The whole transcriptome effects of calcifediol and placebo were very weak, as indicated by the fact that correcting for multiple testing using false discovery rate did not yield any differentially expressed genes using any reasonable cut-offs (all q-values ~ 1). P-values were uniformly distributed across all genes, suggesting that low p-values are likely to be false positives. Partial least squares-discriminant analysis and principle component analysis was unable to separate treatment groups.

Conclusion

Calcifediol supplementation did not significantly affect the skeletal muscle transcriptome in frail older adults. Our findings indicate that vitamin D supplementation has no effects on skeletal muscle gene expression, suggesting that skeletal muscle may not be a direct target of vitamin D in older adults.

Trial registration

This study was registered at clinicaltrials.gov as NCT02349282 on January 28, 2015.

Vitamin D Receptor in Muscle Atrophy of Elderly Patients: A Key Element of Osteoporosis-Sarcopenia Connection

In this study, we investigated the relationship between sarcopenia (evaluated in term of fibers atrophy), vitamin d receptor protein expression and TaqI/Cdx2/FokI VDR genotypes in an Italian cohort of osteoporosis(n=44) and osteoarthritis (n=55) patients. Muscle biopsies were fixed and investigated by both immunohistochemistry (vitamin d receptor expression) and transmission electron microscopy (satellite stem cells niches). Vitamin d receptor polymorphisms were studied on DNA extracted from muscle paraffin sections. For the first time, we reported that aging differently affects the VDR activation in OA and OP patients. In particular, while in OP patients we observed a significant reduction of VDR positive myonuclei with age, no “age effect” was observed in OA patients. The frequent activation of VDR could explain the lower number of atrophic fiber that we observed in OA patients respect to OP. From genetic point of view, we showed a putative association among polymorphisms FokI and Cdx2 of VDR gene, vitamin d receptor activation and the occurrence of sarcopenia. Altogether these data open new prospective for the prevention and cure of age-related muscle disorders.

Vitamin D is associated with lower limb muscle strength and grip strength in Middle Eastern- and African-born immigrants in Sweden

There is increasing evidence that vitamin D status is associated with muscle function. Vitamin D deficiency is common in immigrants. We hypothesized that there was a positive association between vitamin D status and muscle strength in immigrants. The aim of this study was to examine associations between vitamin D status and muscle strength in an immigrant population in Sweden. All immigrants aged 25-65 years, born in 9 African or Middle East countries, and living in a district in Umeå (n = 1306) were invited. A total of 111 men and 105 women (16.5%) completed the study. Lower limb muscle strength was examined using a standardized muscle function indices of muscle strength. Grip strength was examined using a JAMAR hand dynamometer. Serum 25-hydroxyvitamin D [25(OH)D] was measured using liquid chromatography-tandem mass spectrometry. The analyses were adjusted for sex, age, height, body mass index, years since immigration, 25(OH)D, vitamin D deficiency, physical activity, and medical and socioeconomic factors. Twelve percent of the immigrants had vitamin D deficiency [25(OH)D levels <25 nmol/L]. In multivariable analyses, reduced lower limb muscle strength remained linearly associated with lower 25(OH)D concentrations (P = .008) and weaker grip strength remained associated with vitamin D deficiency (P = .022) after adjustments. The association between vitamin D deficiency and reduced lower limb muscle strength did not reach statistical significance (P = .052). The results demonstrate that vitamin D deficiency and low 25(OH)D concentrations were associated with muscle weakness in immigrants.

Normal/high-fat milk consumption is associated with higher lean body and muscle mass in Japanese women aged between 40 and 60 years: a cross-sectional study

Background

Milk is known to contain various nutrients that may have health benefits for postmenopausal women who are at an increased risk of cardiovascular and musculoskeletal diseases. We investigated the association between normal/high- and low-fat milk consumption and body composition in Japanese women aged 40 to 60 years.

Methods

This cross-sectional study used the baseline data collected in a previous study that examined the effects of a dietary supplement on a variety of health parameters in 85 Japanese women aged 40 to 60 years. Participants had been assessed for age, menopausal status, lifestyle factors, and body composition. We estimated the consumption of normal/high- and low-fat milk using a brief-type self-administered diet history questionnaire (BDHQ). Normal/high- and low-fat milk intake were classified as consumer (drank milk at least twice a week) or non-consumer (drank milk at most once a week), in order to identify the parameters that were independently associated with the consumption of normal/high- and low-fat milk.

Results

Of the 85 participants who completed the BDHQ, 27 were categorized as non-consumers, 18 as exclusive low-fat milk consumers, and 29 as exclusive normal/high-fat milk consumers. 11 women who consumed both low-fat and normal/high-fat milk were excluded from the analysis. Compared with non-consumers and exclusive low-fat milk consumers, exclusive high-fat milk consumers had significantly higher lean body mass (mean ± standard deviation [SD], 39.4 ± 2.7 kg vs. 37.9 ± 2.2 kg and 37.6 ± 2.9 kg, P < 0.05) and muscle mass (mean ± SD, 37.2 ± 2.5 kg vs. 35.8 ± 2.0 kg and 35.5 ± 2.7 kg, P < 0.05). Both lean body and muscle masses were significantly correlated with vitamin D intake from milk (Pearson r = 0.29, P = 0.008, and Pearson r = 0.29, P = 0.008, respectively).

Conclusion

Normal/high-fat milk consumption was associated with higher lean body and muscle mass in middle-aged Japanese women presumably through high vitamin D intake.

Raising awareness on the therapeutic role of cholecalciferol in CKD: a multidisciplinary-based opinion

Vitamin D is recognized to play an essential role in health and disease. In kidney disease, vitamin D analogs have gained recognition for their involvement and potential therapeutic importance. Nephrologists are aware of the use of oral native vitamin D supplementation, however, uncertainty still exists with regard to the use of this treatment option in chronic kidney disease as well as clinical settings related to chronic kidney disease, where vitamin D supplementation may be an appropriate therapeutic choice. Two consecutive meetings were held in Florence in July and November 2016 comprising six experts in kidney disease (N = 3) and bone mineral metabolism (N = 3) to discuss a range of unresolved issues related to the use of cholecalciferol in chronic kidney disease. The panel focused on the following six key areas where issues relating to the use of oral vitamin D remain controversial: (1) vitamin D and parathyroid hormone levels in the general population, (2) cholecalciferol in chronic kidney disease, (3) vitamin D in cardiovascular disease, (4) vitamin D and renal bone disease, (5) vitamin D in rheumatological diseases affecting the kidney, (6) vitamin D and kidney transplantation.

A mechanism based approach to management of children with end-stage liver disease

Due to parallel advances in surgical and acute care disciplines, liver transplantation (LT) has revolutionized the outlook for children with end-stage liver disease (ESLD). Contrary to advances in technical aspects of LT and the peri-operative care, pre-transplant management of ESLD remains quite a formidable challenge. Areas covered: This review provides mechanisms based management strategies to address common complications of ESLD including malnutrition, amended metabolic pathways, gastrointestinal dysfunction, and development of ascites. Clinically relevant discussion of each paradigm is followed by an account of high impact therapeutic interventions which can be used as guides for formulating management plans. A tabulated summary of the suggested interventions is also provided. Indeed, execution of a dynamic plan tailored to the evolution of pathophysiologic derangements can further enhance outcomes of pediatric LT. Expert commentary: LT has evolved as a dependable therapeutic option for a variety of fatal pediatric liver diseases. However, relative organ shortage remains a formidable challenge. Similarly, consumer expectations continue to grow for sustained improvement of graft and patient survival after LT. In this environment, the level of sophistication applied to the management ESLD before LT stands out as a major opportunity with lasting impact on the future of pediatric LT.

Skeletal muscle vitamin D in patients with end stage osteoarthritis of the knee

Muscle function is often impaired in patients with knee osteoarthritis (OA), with reduced strength and increased pain. The role of vitamin D and the vitamin D-endocrine pathway in muscle health has recently been placed in the spotlight, with various groups reporting positive effects on muscle development, function and health. Recently, it has been shown that uptake into muscle of the specialized vitamin D binding protein (DBP) is dependent on the endocytic receptor, megalin. Here we analyse circulating vitamin D, and muscle DBP, megalin and the cognate vitamin D receptor (VDR) in patients with knee OA and compare them to asymptomatic controls. Muscle and blood samples were collected from 19 patients with end-stage OA of the knee and 10 age-matched controls. Muscle biopsies from the OA group were performed during knee replacement surgery and a needle biopsy was used on control volunteers. Immunoblots performed with specific antibodies were used to detect the presence of DBP, megalin, VDR (using the specific D-6 antibody) and albumin in the muscle biopsies. Results were correlated with FoxO1, a key regulator of the ubiquitin-proteasome degradation pathway in muscle. There were no differences in circulating levels of 25 (OH) vitamin D3 between the groups, and no subjects were vitamin D deficient. We found increased VDR, DBP and albumin protein in the muscle from patients with OA compared to controls, with no change in muscle megalin expression. Furthermore, DBP levels in the muscle correlated with FoxO1, suggesting an association between muscle protein breakdown and the activation of the vitamin D-endocrine pathway in muscle surrounding an OA affected joint. We show, for the first time, that the factors involved in the vitamin D-endocrine-pathway are present at higher levels in muscles from OA patients compared to asymptomatic controls. This is despite no differences in circulating 25 (OH) vitamin D levels between the groups. These findings indicate the activation of vitamin D pathway in these muscles that may provide a beneficial compensatory stimulation of the repair process in muscles that are subject to inflammatory and proteolytic processes.

Vitamin D, a modulator of musculoskeletal health in chronic kidney disease

The spectrum of activity of vitamin D goes beyond calcium and bone homeostasis, and growing evidence suggests that vitamin D contributes to maintain musculoskeletal health in healthy subjects as well as in patients with chronic kidney disease (CKD), who display the combination of bone metabolism disorder, muscle wasting, and weakness. Here, we review how vitamin D represents a pathway in which bone and muscle may interact. In vitro studies have confirmed that the vitamin D receptor is present on muscle, describing the mechanisms whereby vitamin D directly affects skeletal muscle. These include genomic and non-genomic (rapid) effects, regulating cellular differentiation and proliferation. Observational studies have shown that circulating 25-hydroxyvitamin D levels correlate with the clinical symptoms and muscle morphological changes observed in CKD patients. Vitamin D deficiency has been linked to low bone formation rate and bone mineral density, with an increased risk of skeletal fractures. The impact of low vitamin D status on skeletal muscle may also affect muscle metabolic pathways, including its sensitivity to insulin. Although some interventional studies have shown that vitamin D may improve physical performance and protect against the development of histological and radiological signs of hyperparathyroidism, evidence is still insufficient to draw definitive conclusions.

Potential Benefits of Ameliorating Metabolic and Nutritional Abnormalities in People With Profound Developmental Disabilities

Background:

People with profound developmental disabilities have some of the most severe neurological impairments seen in society, have accelerated mortality due to huge medical challenges, and yet are often excluded from scientific studies. They actually have at least 2 layers of conditions: (1) the original disability and (2) multiple under-recognized and underexplored metabolic and nutritional imbalances involving minerals (calcium, zinc, and selenium), amino acids (taurine, tryptophan), fatty acids (linoleic acid, docosahexaenoic acid, arachidonic acid, adrenic acid, Mead acid, plasmalogens), carnitine, hormones (insulinlike growth factor 1), measures of oxidative stress, and likely other substances and systems.

Summary:

This review provides the first list of metabolic and nutritional abnormalities commonly found in people with profound developmental disabilities and, based on the quality of life effects of similar abnormalities in neurotypical people, indicates the potential effects of these abnormalities in this population which often cannot communicate symptoms.

Key messages:

We propose that improved understanding and management of these disturbed mechanisms would enhance the quality of life of people with profound developmental disabilities. Such insights may also apply to people with other conditions associated with disability, including some diseases requiring stem cell implantation and living in microgravity.

Vitamin D Deficiency in Patients With Chronic Tension-Type Headache: A Case-Control Study

OBJECTIVE

To see the interrelation between chronic tension-type headache (CTTH) and serum vitamin D levels.

BACKGROUND

Several studies have suggested an association between chronic pain and vitamin D deficiency. Anecdotal evidence suggests that vitamin D deficiency may be associated with tension-type headache and migraine.

METHODS

This case-control study was carried out to examine the association between CTTH and serum 25-hydroxy vitamin (25(OH) D) levels. One hundred consecutive adult (>18 years) patients with CTTH and 100 matched healthy controls were enrolled.

RESULTS

The serum 25(OH) D levels were significantly lower in CTTH patients than in the controls (14.7 vs 27.4 ng/mL). The prevalence of vitamin D deficiency (serum 25 (OH) D < 20 ng/mL) was greater in patients with CTTH (71% vs 25%). CTTH patients had a significantly high prevalence of musculoskeletal pain (79% vs 57%), muscle weakness (29%vs 10%), muscle tenderness score (7.5 vs 1.9), and bone tenderness score (3.0 vs 0.8) in comparison to controls. CTTH patients with vitamin D deficient group (<20 ng/mL) had a higher prevalence of musculoskeletal pain (58% vs 31%), muscle weakness (38%vs 7%), muscle and bone tenderness score, associated fatigue (44% vs 17%) and more prolonged course (15.5 months vs 11.2 months). A strong positive correlation was noted between serum vitamin D levels and total muscle tenderness score (R²  = 0. 7365) and total bone tenderness score (R²  = 0. 6293).

CONCLUSION

Decreased serum 25(OHD) concentration was associated with CTTH. Intervention studies are required to find out if supplementation of vitamin D is effective in patients with CTTH.

The associations between serum 25-hydroxyvitamin D level and the risk of total fracture and hip fracture

In this meta-analysis, we evaluated the association between serum 25-hydroxyvitamin D (25(OH) vitamin D) level and the risk of total fractures and hip fractures. Low serum 25(OH) vitamin D level is associated with an increased risk of total and hip fractures.

INTRODUCTION

Data on the association between serum 25(OH) vitamin D level and the risk of fractures are conflicting. This study aimed to provide a summary of prospective cohort or nested case-control studies on the association between serum 25(OH) vitamin D level and the risk of total fractures and hip fractures.

METHODS

We identified relevant studies by searching the PubMed, EMBASE, and OVID databases from their inception to June 1, 2016. We included published prospective cohort or nested case-control studies evaluating the associations of serum 25(OH) vitamin D level with the fracture risk. Two reviewers abstracted the data independently. Relative risks (RRs) with 95% confidence intervals (CIs) were derived throughout the whole analysis.

RESULTS

Sixteen prospective cohort studies and three nested case-control studies were included. We found that low serum 25(OH) vitamin D level was significantly associated with the risk of total fractures (RR 1.25, 95% CI 1.06-1.43; I ² = 31.3%, p for heterogeneity = 0.15) and hip fractures (RR 1.48, 95% CI 1.29-1.68; I ² = 0%, p for heterogeneity = 0.51). The hip fracture risk was increased by 40% for each SD decrease in serum 25(OH) vitamin D level (RR 1.40, 95% CI 1.20-1.61; I ² = 0%, p for heterogeneity = 0.51). The per SD decrease in serum 25(OH) vitamin D level was not associated with the increased risk of total fractures (RR 1.14, 95% CI 0.93-1.35; I ² = 63.2%, p for heterogeneity = 0.04).

CONCLUSIONS

Our study suggests that low serum 25(OH) vitamin D level is associated with increased risks of total and hip fractures. In the analyzed studies, the per SD decrease in serum 25(OH) vitamin D level was associated with the hip fracture risk but not with the total fracture risk.

Chronic Osteoporotic Pain in Mice: Cutaneous and Deep Musculoskeletal Pain Are Partially Independent of Bone Resorption and Differentially Sensitive to Pharmacological Interventions

Although the pathological changes in osteoporotic bones are well established, the characterization of the osteoporotic pain and its appropriate treatment are not fully elucidated. We investigated the behavioral signs of cutaneous and deep musculoskeletal pain and physical function; time-dependent changes in bone mineral density (BMD) and the emergence of the behavioral phenotype; and the effects of pharmacological interventions having different mechanisms of action (chronic intraperitoneal administration of pamidronate [0.25 mg/kg, 5x/week for 5 weeks] versus acute treatment with intraperitoneal morphine [10 mg/kg] and pregabalin [100 mg/kg]) in a mouse model of ovariectomized or sham-operated mice 6 months following surgery. We observed reduced BMD associated with weight gain, referred cutaneous hypersensitivity, and deep musculoskeletal pain that persisted for 6 months. Chronic bisphosphonate treatment, 6 months after ovariectomy, reversed bone loss and hypersensitivity to cold, but other behavioral indices of osteoporotic pain were unchanged. While the efficacy of acute morphine on cutaneous pain was weak, pregabalin was highly effective; deep musculoskeletal pain was intractable. In conclusion, the reversal of bone loss alone is insufficient to manage pain in chronic osteoporosis. Additional treatments, both pharmacological and nonpharmacological, should be implemented to improve quality of life for osteoporosis patients.

Factors Associated with the Serum Myostatin Level in Patients Undergoing Peritoneal Dialysis: Potential Effects of Skeletal Muscle Mass and Vitamin D Receptor Activator Use

Myostatin is a member of the transforming growth factor-β family, which regulates synthesis and degradation of skeletal muscle proteins and is associated with the development of sarcopenia. It is up-regulated in the skeletal muscle of chronic kidney disease patients and is considered to be involved in the development of uremic sarcopenia. However, serum myostatin levels have rarely been determined, and the relationship between serum myostatin levels with clinical and metabolic factors remains unknown. This cross-sectional study investigated the association between serum myostatin level and clinical factors in 69 outpatients undergoing peritoneal dialysis. Serum myostatin level was determined by commercially available enzyme-linked immunosorbent assay (ELISA). Univariable and multivariable analysis were conducted to determine factors associated with serum myostatin levels. The factors included age, sex, diabetes mellitus, dialysis history, body mass index, residual kidney function, peritoneal dialysate volume, serum biochemistries, and the use of vitamin D receptor activators (VDRAs). Mean serum myostatin level was 7.59 ± 3.37 ng/mL. There was no association between serum myostatin level and residual kidney function. Serum myostatin levels were significantly and positively associated with lean body mass measured by the creatinine kinetic method and negatively associated with the use of VDRAs after adjustment for potential confounding factors. Our study indicated that serum myostatin levels are associated with skeletal muscle mass and are lower in patients treated with VDRAs. Further studies are necessary to determine the significance of measuring serum myostatin level in patients undergoing peritoneal dialysis.

Nutrition for Sarcopenia

Aging-related sarcopenia means that muscle mass, strength, and physical performance tend to decline with age, and malnutrition is associated with sarcopenia. Therefore, nutritional interventions may make an important contribution to prevent the development of sarcopenia. Here I reviewed published articles about the effects of nutritional factors on sarcopenia in elderly people. A growing body of evidence suggests that metabolic factors associated with obesity and diabetes induce the progression of sarcopenia. However, the effectiveness and safety of caloric restriction for sarcopenia remained unclear. Protein intake and physical activity are the main anabolic stimuli for muscle protein synthesis. As optimal dietary protein intake, 1.0 - 1.2 g/kg (body weight)/day with an optimal repartition over each daily meal or 25 - 30 g of high quality protein per meal were recommended to prevent sarcopenia, which was supported by some observational studies. Protein supplementation using cheese and milk protein, essential amino acids, leucine, beta-hydroxy-beta-methylbutyrate and vitamin D has been investigated as a potential supplement to improve muscle quality in sarcopenic elderly people.