Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials

Gastric Cancer Survivorship: Multidisciplinary Management, Best Practices and Opportunities

PURPOSE

Gastric cancer is the 5th most common malignancy worldwide. As early detection increases and treatments for gastric cancer improve, the number of gastric cancer survivors grows.

METHODS

Here, we review the diagnosis and management of gastric cancer and discuss important considerations for gastric cancer survivorship including cancer surveillance, weight loss, malnutrition, fatigue, specific complications related to surgery and radiation, quality of life in gastric cancer survivorship, health behavior, and models of survivorship.

RESULTS

Multimodality therapy with chemotherapy and surgery can result in chronic toxicities in multiple organ systems. This emphasizes the need for a multidisciplinary survivorship care model including cancer surveillance, management of chronic toxicities, and optimization of modifiable risk factors with long-term involvement of appropriate providers.

CONCLUSION

Adequately caring for gastric cancer survivors requires a coordinated, multidisciplinary approach.

Pathways in formulating foods for the elderly

The growth of the elderly population worldwide is posing significant challenges to human society. The progressive physical and physiological changes occur with aging, including decreased appetite, incomplete digestion, and reduced absorption of nutrients. A common feature of many elderly people's diets is a deficiency in proteins (especially easily digestible ones) and micronutrients (e.g., vitamins, zinc, iron, and calcium). One of the solutions to this problem is the incorporation of these components into suitably texture-modified foods. There is a dearth of products that meet the needs of the elderly with special medical/health conditions such as dysphagia, osteoporosis, diabetes, and cardiovascular disease, as well as those who are in hospital and palliative care. Future research and development of foods for the elderly must address specific dietary needs of different subgroups of elderly people with underlying health conditions. The existence of different physical and physiological stages of the elderly means that their specific dietary requirements must be considered. This review summarizes current knowledge on nutritional requirements including those with underlying health problems and outlines the research and innovation pathways for developing new foods considering nutrition, texture, flavor, and other sensory aspects.

Nutrition-Based Support for Osteoporosis in Postmenopausal Women: A Review of Recent Evidence

Postmenopausal osteoporosis stands as the predominant bone disorder in the developed world, posing a significant public health challenge. Nutritional factors play a crucial role in bone health and may contribute to its prevention or treatment. Calcium and vitamin D, extensively studied with robust scientific evidence, are integral components of the non-pharmacological treatment for this disorder. Nevertheless, other less-explored nutritional elements appear to influence bone metabolism. This review provides a comprehensive summary of the latest evidence concerning the relationship between various nutrients, such as phosphorus, magnesium, vitamins, phytate, and phytoestrogens; specific foods like dairy or soy, and dietary patterns such as the Mediterranean diet with bone health and osteoporosis.

Role of vitamin K2 in bone-vascular crosstalk

Vitamin K (VK) is a fat-soluble vitamin that is indispensable for the activation of vitamin K-dependent proteins (VKDPs). It has been shown to play an important role in the proper calcium deposit at the bone level, hindering that on the vascular walls. The deficiency of this vitamin in European populations is frequent and unknown. It is related to several factors, poor dietary intake, altered intestinal absorption or altered production by bacteria, indicating possible dysbiosis. For Vitamin K2 (VK2), there is currently no official reference daily intake (RDI). However, the effects of VK2 on the improvement of health in cardiovascular diseases, on bone metabolism, on chronic kidney diseases have been the subject of research in recent decades. The microbiota in the gastrointestinal tract plays an important role: Bacteroides are primarily capable of synthetizing very long chain forms of menaquinones and, in addition to the bacteria present in the intestinal flora, VK2 is also produced by bacteria used in food fermentation processes. This review provides an update on the current literature regarding the origin of VK2 and its implications in what is called the "calcium paradox", namely the lack of calcium in the bone and its storage in the wall of the vessel.

The mediation effect of vitamin A and vitamin D supplement in the association between serum vitamin K levels and musculoskeletal disorders in preschool children

Introduction

Vitamin K deficiency may elevate the incidence of musculoskeletal disorders (MSD), whereas it lacks validation for pediatric populations and has uncertain dose recommendations. In this context, we hypothesized that serum vitamin K levels are associated with MSD in preschool children, and the widely used vitamin A and vitamin D supplements may mediate these associations based on potential mechanisms, which expects to provide guidance for future practice.

Methods

A cross-sectional study was conducted in Sichuan province in southwestern China, from January 2021 to May 2022. Serum levels of vitamin K1/K2 and 25(OH)D were determined using the high-performance liquid chromatography method, and the diagnosis of MSD was executed by clinicians. Overall and stratified logistic regression analysis based on categorized 25(OH)D levels were conducted to assess association between serum vitamin K levels and MSD prevalence after adjusting for confounders. Mediation analysis was further performed and vitamin A and D supplementation was regressed as the mediator.

Results

A total of 6,368 children aged 0-6 years old were enrolled. MSD was identified in 1179 (18.51%) of the children, while 5,189 (81.49%) of them did not present such disorder. After adjusting confounders, a significant difference was found in serum vitamin K1 level between children in MSD and Non-MSD group (OR = 0.802, 95%CI 0.745-0.864). No significant difference was found in serum vitamin K2 level between the two groups (OR = 0.975, 95%CI 0.753-1.261). The association between vitamin K1 level and MSD prevalence was partly (36.8%) mediated by vitamin A and D supplementation.

Conclusions

A low serum vitamin K1 level is connected with an increased risk of MSD among children, highlighting that vitamin A and D supplementation is a helpful intervention to prevent MSD in children with vitamin K deficiency.

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

Vitamin K - a scoping review for Nordic Nutrition Recommendations 2023

Vitamin K occurs in dietary supply in two major forms: phylloquinone (vitamin K1) and menaquinones (collectively referred as vitamin K2). Phylloquinone is derived from plants. There are at least 10 forms of menaquinones varying in chain length and they are produced by bacteria except menaquinone-4. Menaquinone-4 is formed from phylloquinone or other menaquinone forms. Phylloquinone is considered to be the major contributor and menaquinones are thought to contribute less to vitamin K intake in Western diets. However, less is known about the content of menaquinones than phylloquinones in foods. Vitamin K is known to function as an enzymatic cofactor in the gamma-carboxylation of vitamin K dependent proteins (VKDPs). Hepatic VKDPs are involved in coagulation. Extrahepatic VKDPs have a role e.g. in bone health and vascular calcification. However, the amount of vitamin K needed for optimal functioning of the different VKDPs is not known.

Proceedings of the 2023 Santa Fe Bone Symposium: Progress and Controversies in the Management of Patients with Skeletal Diseases

The Santa Fe Bone Symposium (SFBS) held its 23rd annual event on August 5-6, 2023, in Santa Fe, New Mexico, USA. Attendees participated in-person and remotely, representing many states and countries. The program included plenary presentations, panel discussions, satellite symposia, a Project ECHO workshop, and a session on healthcare policy and reimbursement for fracture liaison programs. A broad range of topics were addressed, including transitions of osteoporosis treatments over a lifetime; controversies in vitamin D; update on Official Positions of the International Society for Clinical Densitometry; spine surgery and bone health; clinical applications of bone turnover markers; basic bone biology for clinicians; premenopausal-, pregnancy-, and lactation-associated osteoporosis; cancer treatment induced bone loss in patients with breast cancer and prostate cancer; genetic testing for skeletal diseases; and an update on nutrition and bone health. There were also sessions on rare bone diseases, including managing patients with hypophosphatasia; treatment of X-linked hypophosphatemia; and assessment and treatment of patients with hypoparathyroidism. There were oral presentations of abstracts by endocrinology fellows selected from those who participated in the Santa Fe Fellows Workshop on Metabolic Bone Diseases, held the 2 days prior to the SFBS. These proceedings of the 2023 SFBS present the clinical highlights and insights generated from many formal and informal discussions in Santa Fe.

[Exercise therapy and basic treatment for osteoporosis]

Physical training is an important component in the prophylaxis of osteoporosis and the prevention of fractures. Physical training not only has a direct effect on muscle strength and muscular performance, but also on the risk of falling and the fear of falling. Therefore, physical training is also an integral part of the basic treatment for osteoporosis. The recommendations for basic treatment are an adequate intake of nutrients, including protein in particular. The intake of calcium and vitamin D in sufficient quantities is also important and, in the case of specific drug therapy, also to avoid side effects and to ensure the therapeutic effect. This article summarizes the recommendations of the updated S3 guideline on the diagnosis and treatment of osteoporosis and explains the background for the recommendations included.

The additive effect of vitamin K supplementation and bisphosphonate on fracture risk in post-menopausal osteoporosis: a randomised placebo controlled trial

This study assessed whether vitamin K, given with oral bisphosphonate, calcium and/or vitamin D has an additive effect on fracture risk in post-menopausal women with osteoporosis. No difference in bone density or bone turnover was observed although vitamin K1 supplementation led to a modest effect on parameters of hip geometry.

PURPOSE

Some clinical studies have suggested that vitamin K prevents bone loss and may improve fracture risk. The aim was to assess whether vitamin K supplementation has an additive effect on bone mineral density (BMD), hip geometry and bone turnover markers (BTMs) in post-menopausal women with osteoporosis (PMO) and sub-optimum vitamin K status receiving bisphosphonate, calcium and/or vitamin D treatment.

METHODS

We conducted a trial in 105 women aged 68.7[12.3] years with PMO and serum vitamin K1 ≤ 0.4 µg/L. They were randomised to 3 treatment arms; vitamin K1 (1 mg/day) arm, vitamin K2 arm (MK-4; 45 mg/day) or placebo for 18 months. They were on oral bisphosphonate and calcium and/or vitamin D. We measured BMD by DXA, hip geometry parameters using hip structural analysis (HSA) software and BTMs. Vitamin K1 or MK-4 supplementation was each compared to placebo. Intention to treat (ITT) and per protocol (PP) analyses were performed.

RESULTS

Changes in BMD at the total hip, femoral neck and lumbar spine and BTMs; CTX and P1NP did not differ significantly following either K1 or MK-4 supplementation compared to placebo. Following PP analysis and correction for covariates, there were significant differences in some of the HSA parameters at the intertrochanter (IT) and femoral shaft (FS): IT endocortical diameter (ED) (% change placebo:1.5 [4.1], K1 arm: -1.02 [5.07], p = 0.04), FS subperiosteal/outer diameter (OD) (placebo: 1.78 [5.3], K1 arm: 0.46 [2.23] p = 0.04), FS cross sectional area (CSA) (placebo:1.47 [4.09],K1 arm: -1.02[5.07], p = 0.03).

CONCLUSION

The addition of vitamin K1 to oral bisphosphonate with calcium and/or vitamin D treatment in PMO has a modest effect on parameters of hip geometry. Further confirmatory studies are needed.

TRIAL REGISTRATION

The study was registered at Clinicaltrial.gov:NCT01232647.

Study protocol of the InterVitaminK trial: a Danish population-based randomised double-blinded placebo-controlled trial of the effects of vitamin K (menaquinone-7) supplementation on cardiovascular, metabolic and bone health

INTRODUCTION

Vitamin K has been suggested to have protective effects against progression of vascular calcification and development of cardiovascular disease (CVD). However, few well-powered randomised controlled trials have examined whether vitamin K prevents progression of vascular calcification in individuals from the general population. The aim of the InterVitaminK trial is to investigate the effects of vitamin K supplementation (menaquinone-7, MK-7) on cardiovascular, metabolic, respiratory and bone health in a general ageing population with detectable vascular calcification.

METHODS AND ANALYSIS

The InterVitaminK trial is a randomised, double-blinded, placebo-controlled, trial. A total of 450 men and women aged 52-82 years with detectable coronary artery calcification (CAC), but without manifest CVD, will be randomised (1:1) to receive daily MK-7 (333 µg/day) or placebo tablets for 3 years. Health examinations are scheduled at baseline, and after 1, 2 and 3 years of intervention. Health examinations include cardiac CT scans, measurements of arterial stiffness, blood pressure, lung function, physical function, muscle strength, anthropometric measures, questionnaires on general health and dietary intake, and blood and urine sampling. The primary outcome is progression of CAC from baseline to 3-year follow-up. The trial has 89% power to detect a between-group difference of at least 15%. Secondary outcomes are bone mineral density, pulmonary function and biomarkers of insulin resistance.

ETHICS AND DISSEMINATION

Oral MK-7 supplementation is considered safe and has not been found to cause severe adverse events. The Ethical Committee of the Capital Region (H-21033114) approved the protocol. Written informed consent is obtained from all participants and the trial is conducted in accordance with the Declaration of Helsinki II. Both negative and positive findings will be reported.

TRIAL REGISTRATION NUMBER

NCT05259046.

The Pleiotropic Role of Vitamin K in Multimorbidity of Chronic Obstructive Pulmonary Disease

Although defined by the presence of airflow obstruction and respiratory symptoms, patients with chronic obstructive pulmonary disease (COPD) are characterized by multimorbidity. Numerous co-occurring conditions and systemic manifestations contribute to the clinical presentation and progression of COPD; however, underlying mechanisms for multimorbidity are currently not fully elucidated. Vitamin A and vitamin D have been related to COPD pathogenesis. Another fat-soluble vitamin, vitamin K, has been put forward to exert protective roles in COPD. Vitamin K is an unequivocal cofactor for the carboxylation of coagulation factors, but also for extra-hepatic proteins including the soft tissue calcification inhibitor matrix Gla-protein and the bone protein osteocalcin. Additionally, vitamin K has been shown to have anti-oxidant and anti-ferroptosis properties. In this review, we discuss the potential role of vitamin K in the systemic manifestations of COPD. We will elaborate on the effect of vitamin K on prevalent co-occurring chronic conditions in COPD including cardiovascular disorders, chronic kidney disease, osteoporosis, and sarcopenia. Finally, we link these conditions to COPD with vitamin K as a connecting factor and provide recommendations for future clinical studies.

Role of Vitamin K in Bone and Muscle Metabolism

Vitamin K, a cofactor for the γ-glutamyl carboxylase enzyme, is required for the post-translational activation of osteocalcin and matrix Gla protein, which play a key role in bone and muscle homeostasis. In vivo and in vitro models for osteoporosis and sarcopenia suggest the vitamin K could exert a positive effect in both conditions. In bone, it increases osteoblastogenesis, whilst decreases osteoclast formation and function. In muscle, it is associated with increased satellite cell proliferation and migration and might play a role in energy metabolism. Observational trials suggest that high levels of vitamin K are associated with increased bone mineral density and reduced fracture risk. However, interventional studies for vitamin K supplementation yielded conflicting results. Clinical trials in sarcopenia suggest that vitamin K supplementation could improve muscle mass and function. One of the main limitations on the vitamin K studies are the technical challenges to measure its levels in serum. Thus, they are obtained from indirect sources like food questionnaires, or levels of undercarboxylated proteins, which can be affected by other environmental or biological processes. Although current research appoints to a beneficial effect of vitamin K in bone and muscle, further studies overcoming the current limitations are required in order to incorporate this supplementation in the clinical management of patients with osteosarcopenia.

Bone fragility during the COVID-19 pandemic: the role of macro- and micronutrients

Bone fragility is the susceptibility to fracture due to poor bone strength. This condition is usually associated with aging, comorbidities, disability, poor quality of life, and increased mortality. International guidelines for the management of patients with bone fragility include a nutritional approach, mainly aiming at optimal protein, calcium, and vitamin D intakes. Several biomechanical features of the skeleton, such as bone mineral density (BMD), trabecular and cortical microarchitecture, seem to be positively influenced by micro- and macronutrient intake. Patients with major fragility fractures are usually poor consumers of dairy products, fruit, and vegetables as well as of nutrients modulating gut microbiota. The COVID-19 pandemic has further aggravated the health status of patients with skeletal fragility, also in terms of unhealthy dietary patterns that might adversely affect bone health. In this narrative review, we discuss the role of macro- and micronutrients in patients with bone fragility during the COVID-19 pandemic.

Dietary recommendations in the prevention and treatment of osteoporosis

INTRODUCTION

This article presents the initial recommendations of the French Rheumatology Society (Société Française de Rhumatologie - SFR) and the Osteoporosis Research and Information Group (Groupe de Recherche et d'Informations sur les Ostéoporoses - GRIO) on the role of diet in the prevention and treatment of osteoporosis.

METHODS

The recommendations were produced by a working group composed of rheumatologists, physician nutrition specialists and a geriatrician. Fifteen (15) questions pertaining to "daily practices" were preselected by the working group. For the literature review, the working group focussed mainly on the effects of diet on bone mineral density (BMD) and fractures, and primarily on meta-analyses of longitudinal studies and dietary intervention studies.

RESULTS

A Mediterranean-type diet and the daily consumption of 2 to 3 dairy products are recommended. Together, these provide the calcium and "high quality" protein required to maintain a normal calcium-phosphorus balance and bone metabolism, and are associated with lower fracture risk. Conversely, unbalanced Western diets, vegan diets, weight-loss diets in non-overweight individuals, alcohol consumption and daily consumption of sodas are advised against. In terms of the beneficial effects on bone mineral density and fracture risk, current scientific data are either insufficient or too divergent to recommend increasing or restricting the consumption of tea or coffee, vitamins other than vitamin D, vitamin D-enriched or phytoestrogen-rich foods, calcium-enriched plant-based beverages, oral nutritional supplements, or dietary sources of prebiotics and probiotics.

CONCLUSIONS

These are the first set of recommendations addressing the role of diet in the prevention and treatment of osteoporosis. More research is necessary to direct and support guidelines.

Exclusively breastmilk-fed preterm infants are at high risk of developing subclinical vitamin K deficiency despite intramuscular prophylaxis at birth

BACKGROUND

There is near-global consensus that all newborns be given parenteral vitamin K1 (VK1 ) at birth as prophylaxis against VK deficiency bleeding (VKDB). Breastmilk has a low VK content and cases of late VKDB are reported in exclusively breastmilk-fed preterm infants despite VK prophylaxis at birth.

OBJECTIVES

To assess the prevalence of functional VK insufficiency in preterm infants based on elevated under-γ-carboxylated (Glu) species of Gla proteins, factor II (PIVKA-II), and osteocalcin (GluOC), synthesized by liver and bone, respectively.

PATIENTS/METHODS

Prospective, multicenter, observational study in preterm infants born <33 weeks' gestation. Blood samples and dietary history were collected before hospital discharge, and after discharge at 2-3 months' corrected age. Outcome measures were serum VK1 , PIVKA-II, and %GluOC (GluOC as a percentage of the sum of GluOC plus GlaOC) compared between exclusively breastmilk-fed and formula/mixed-fed infants after discharge.

RESULTS

After discharge, breastmilk-fed babies had significantly lower serum VK1 (0.15 vs. 1.81 μg/L), higher PIVKA-II (0.10 vs. 0.02 AU/ml) and higher %GluOC (63.6% vs. 8.1%) than those receiving a formula/mixed-feed diet. Pre-discharge (based on elevated PIVKA-II), only one (2%) of 45 breastmilk-fed infants was VK insufficient. After discharge, eight (67%) of 12 exclusively breastmilk-fed babies were VK insufficient versus only one (4%) of 25 formula/mixed-fed babies.

CONCLUSIONS

Preterm infants who remain exclusively or predominantly human breastmilk-fed after neonatal unit discharge are at high risk of developing subclinical VK deficiency in early infancy. Routine postdischarge VK1 supplementation of breastfed infants to provide intakes comparable to those from formula milks should prevent this deficiency.

Efficacy and safety of vitamin K2 for postmenopausal women with osteoporosis at a long-term follow-up: meta-analysis and systematic review

INTRODUCTION

Vitamin K2 supplementation has been revealed to be effective in the prevention and treatment of osteoporosis in Japan, but further proof for the effectiveness of this practice is still needed.

OBJECTIVE

To investigate whether vitamin K2 supplementation plays a role in maintaining bone mineral density (BMD) and reducing the incidence of fractures for postmenopausal women with osteoporosis at a long-term follow-up.

MATERIALS AND METHODS

We searched systematically throughout the databases of PubMed, Cochrane library, and EMBASE from the dates of their inception to November 16 2021 in this meta-analysis and systematic review, using keywords vitamin K2 and osteoporosis.

RESULTS

Nine RCTs with 6853 participants met the inclusion criteria. Vitamin K2 was associated with a significantly increased percentage change of lumbar BMD and forearm BMD (WMD 2.17, 95% CI [1.59-2.76] and WMD 1.57, 95% CI [1.15-1.99]). There were significant differences in undercarboxylated osteocalcin (uc-OC) reduction (WMD -0.96, 95% CI [-0.70 to 0.21]) and osteocalcin (OC) increment (WMD 26.52, 95% CI [17.06-35.98]). Adverse reaction analysis showed that there seemed to be higher adverse reaction rates in the vitamin K2 group (RR = 1.33, 95% CI [1.11-1.59]), but no serious adverse events related to vitamin K2 supplementation.

CONCLUSION

This meta-analysis and systematic review seemed to support the hypothesis that vitamin K2 plays an important role in the maintenance and improvement of BMD, and it decreases uc-OC and increases OC significantly at a long-term follow-up. Vitamin K2 supplementation is beneficial and safe in the treatment of osteoporosis for postmenopausal women.

Effect of Vitamin K on Bone Mineral Density and Fracture Risk in Adults: Systematic Review and Meta-Analysis

Summary: Recent studies have proposed that adequate intake of Vitamin K (VK) is associated with a low risk of fracture and high bone mineral density (BMD) to improve skeletal health in adults. This systematic review was designed to summarize the most relevant and updated evidence discussing the relationship between VK and bone. It explores the effect of VK deficiency and its supplementation on various bone parameters. Methods: The distinct databases such as PubMed, the Cochrane Library, Google Scholar, National Clinical Trials, Current Controlled Trials, and Clinical Trials were searched up to Jan 2020 to identify eligible trials. All relevant randomized controlled trial studies with any oral dosage form of VK supplement administered for at least six months and assessing BMD or fracture in adults were extracted. Finally, two independent reviewers identified 20 relevant citations for the systematic review and extracted data in tabular form. Results: The meta-analysis was performed with all studies, including postmenopausal and osteoporotic females, for both total clinical and vertebral fracture outcomes. The quantitative analysis showed that the odds ratios (OR) of any fracture were lower for VK as compared to control [OR 0.42 (95% CI 0.27 to 0.66)] for vertebral fractures and OR of 0.44 (95% CI 0.23 to 0.88) for clinical fracture. For the BMD, a meta-analysis of the pooled effect of interventional studies suggested a non-significant association between the use of VK and improvement in femoral BMD (CI 95%, p = 0.08 [−0.03–0.20]). Conclusion: VK decreases general fracture risk, and it can be an option to counter bone loss disorders. However, insufficient evidence is available regarding the significant impact of VK on femoral neck BMD. Therefore, further studies are required to establish the therapeutic value of VK as a treatment for osteoporosis.

The Effects of Osteoporotic and Non-osteoporotic Medications on Fracture Risk and Bone Mineral Density

Osteoporosis is a highly prevalent bone disease affecting more than 37.5 million individuals in the European Union (EU) and the  United States of America (USA). It is characterized by low bone mineral density (BMD), impaired bone quality, and loss of structural and biomechanical properties, resulting in reduced bone strength. An increase in morbidity and mortality is seen in patients with osteoporosis, caused by the approximately 3.5 million new osteoporotic fractures occurring every year in the EU. Currently, different medications are available for the treatment of osteoporosis, including anti-resorptive and osteoanabolic medications. Bisphosphonates, which belong to the anti-resorptive medications, are the standard treatment for osteoporosis based on their positive effects on bone, long-term experience, and low costs. However, not only medications used for the treatment of osteoporosis can affect bone: several other medications are suggested to have an effect on bone as well, especially on fracture risk and BMD. Knowledge about the positive and negative effects of different medications on both fracture risk and BMD is important, as it can contribute to an improvement in osteoporosis prevention and treatment in general, and, even more importantly, to the individual's health. In this review, we therefore discuss the effects of both osteoporotic and non-osteoporotic medications on fracture risk and BMD. In addition, we discuss the underlying mechanisms of action.

The combined effect of vitamin K and calcium on bone mineral density in humans: a meta-analysis of randomized controlled trials

Background

With the increasing incidence of osteoporosis, vitamin K and calcium have been linked to bone mineral density (BMD) and undercarboxylated osteocalcin (UcOC) in many studies, but the results of studies of the combined effect of vitamin K and calcium on BMD and UcOC in humans have been inconsistent. We conducted a systematic review of randomized controlled trials to assess the effect of this combination treatment on BMD and UcOC in humans.

Methods

A search for articles was conducted using PubMed, Embase, and the Cochrane Library database up to March 2021 (no language restrictions). We also reviewed the reference lists of the relevant publications and reviews to locate additional publications. The standard mean difference (SMD) was used as the primary measure of effect size. Our main endpoints were lumbar BMD, femoral neck BMD, hip BMD, total femoral BMD, and UcOC from baseline to end point. We performed subgroup analysis, heterogeneity testing, and assessment of publication bias.

Results

A total of 1346 patients from 10 randomized controlled trials were included in the meta-analysis. The forest plot analysis revealed that vitamin K combined with calcium was associated with a higher lumbar spine BMD compared to controls. The SMD was 0.20 [95% confidence interval (CI): 0.07 to 0.32]. Vitamin K and calcium supplementation led to a significant decrease in UcOC (SMD: − 1.71, 95% CI: − 2.45 to − 0.96). Subgroup analysis showed that vitamin K2 and vitamin K1 had SMDs of 0.30 (95% CI: 0.10 to 0.51) and SMDs of 0.14 (95% CI: − 0.02 to 0.29), and calcium dosages of ≤ 1000 mg/d or > 1000 mg/d had SMDs of 0.19 (95% CI: 0.05 to 0.32) and 0.26 (95% CI: − 0.04 to 0.55).

Conclusion

The combination of vitamin K and calcium has a positive effect on lumbar BMD and decreases the level of UcOC.

Registration: The protocol for this meta-analysis was registered at the International Prospective Register of Systematic Reviews (CRD42021251825).

The ViKTORIES trial: A randomized, double-blind, placebo-controlled trial of vitamin K supplementation to improve vascular health in kidney transplant recipients

Premature cardiovascular disease and death with a functioning graft are leading causes of death and graft loss, respectively, in kidney transplant recipients (KTRs). Vascular stiffness and calcification are markers of cardiovascular disease that are prevalent in KTR and associated with subclinical vitamin K deficiency. We performed a single-center, phase II, parallel-group, randomized, double-blind, placebo-controlled trial (ISRCTN22012044) to test whether vitamin K supplementation reduced vascular stiffness (MRI-based aortic distensibility) or calcification (coronary artery calcium score on computed tomography) in KTR over 1 year of treatment. The primary outcome was between-group difference in vascular stiffness (ascending aortic distensibility). KTRs were recruited between September 2017 and June 2018, and randomized 1:1 to vitamin K (menadiol diphosphate 5 mg; n = 45) or placebo (n = 45) thrice weekly. Baseline demographics, clinical history, and immunosuppression regimens were similar between groups. There was no impact of vitamin K on vascular stiffness (treatment effect -0.23 [95% CI -0.75 to 0.29] × 10^-3  mmHg^-1 ; p = .377), vascular calcification (treatment effect -141 [95% CI - 320 to 38] units; p = .124), nor any other outcome measure. In this heterogeneous cohort of prevalent KTR, vitamin K supplementation did not reduce vascular stiffness or calcification over 1 year. Improving vascular health in KTR is likely to require a multifaceted approach.

Vitamin K - sources, physiological role, kinetics, deficiency, detection, therapeutic use, and toxicity

Vitamin K is traditionally connected with blood coagulation, since it is needed for the posttranslational modification of 7 proteins involved in this cascade. However, it is also involved in the maturation of another 11 or 12 proteins that play different roles, encompassing in particular the modulation of the calcification of connective tissues. Since this process is physiologically needed in bones, but is pathological in arteries, a great deal of research has been devoted to finding a possible link between vitamin K and the prevention of osteoporosis and cardiovascular diseases. Unfortunately, the current knowledge does not allow us to make a decisive conclusion about such a link. One possible explanation for this is the diversity of the biological activity of vitamin K, which is not a single compound but a general term covering natural plant and animal forms of vitamin K (K₁ and K₂) as well as their synthetic congeners (K₃ and K₄). Vitamin K₁ (phylloquinone) is found in several vegetables. Menaquinones (MK₄–MK₁₃, a series of compounds known as vitamin K₂) are mostly of a bacterial origin and are introduced into the human diet mainly through fermented cheeses. Current knowledge about the kinetics of different forms of vitamin K, their detection, and their toxicity are discussed in this review.

Management of osteoporosis in postmenopausal women: the 2021 position statement of The North American Menopause Society

OBJECTIVE

To review evidence regarding osteoporosis screening, prevention, diagnosis, and management in the past decade and update the position statement published by The North American Menopause Society (NAMS) in 2010 regarding the management of osteoporosis in postmenopausal women as new therapies and paradigms have become available.

DESIGN

NAMS enlisted a panel of clinician experts in the field of metabolic bone diseases and/or women's health to review and update the 2010 NAMS position statement and recommendations on the basis of new evidence and clinical judgement. The panel's recommendations were reviewed and approved by the NAMS Board of Trustees.

RESULTS

Osteoporosis, especially prevalent in older postmenopausal women, increases the risk of fractures that can be associated with significant morbidity and mortality. Postmenopausal bone loss, related to estrogen deficiency, is the primary contributor to osteoporosis. Other important risk factors for postmenopausal osteoporosis include advanced age, genetics, smoking, thinness, and many diseases and drugs that impair bone health. An evaluation of these risk factors to identify candidates for osteoporosis screening and recommending nonpharmacologic measures such as good nutrition (especially adequate intake of protein, calcium, and vitamin D), regular physical activity, and avoiding smoking and excessive alcohol consumption are appropriate for all postmenopausal women. For women at high risk for osteoporosis, especially perimenopausal women with low bone density and other risk factors, estrogen or other therapies are available to prevent bone loss. For women with osteoporosis and/or other risk factors for fracture, including advanced age and previous fractures, the primary goal of therapy is to prevent new fractures. This is accomplished by combining nonpharmacologic measures, drugs to increase bone density and to improve bone strength, and strategies to reduce fall risk. If pharmacologic therapy is indicated, government-approved options include estrogen agonists/antagonists, bisphosphonates, RANK ligand inhibitors, parathyroid hormone-receptor agonists, and inhibitors of sclerostin.

CONCLUSIONS

Osteoporosis is a common disorder in postmenopausal women. Management of skeletal health in postmenopausal women involves assessing risk factors for fracture, reducing modifiable risk factors through dietary and lifestyle changes, and the use of pharmacologic therapy for patients at significant risk of osteoporosis or fracture. For women with osteoporosis, lifelong management is necessary. Treatment decisions occur continuously over the lifespan of a postmenopausal woman. Decisions must be individualized and should include the patient in the process of shared decision-making.

Nutritional intake and bone health

Osteoporotic or fragility fractures affect one in two women and one in five men who are older than 50. These events are associated with substantial morbidity, increased mortality, and an impaired quality of life. Recommended general measures for fragility fracture prevention include a balanced diet with an optimal protein and calcium intake and vitamin D sufficiency, together with regular weight-bearing physical exercise. In this narrative Review, we discuss the role of nutrients, foods, and dietary patterns in maintaining bone health. Much of this information comes from observational studies. Bone mineral density, microstructure-estimated bone strength, and trabecular and cortical microstructure are positively associated with total protein intake. Several studies indicate that fracture risk might be lower with a higher dietary protein intake, provided that the calcium supply is sufficient. Dairy products are a valuable source of these two nutrients. Hip fracture risk appears to be lower in consumers of dairy products, particularly fermented dairy products. Consuming less than five servings per day of fruit and vegetables is associated with a higher hip fracture risk. Adherence to a Mediterranean diet or to a prudent diet is associated with a lower fracture risk. These various nutrients and dietary patterns influence gut microbiota composition or function, or both. The conclusions of this Review emphasise the importance of a balanced diet including minerals, protein, and fruit and vegetables for bone health and in the prevention of fragility fractures.

Three-Dimensional Co-Culture System of Human Osteoblasts and Osteoclast Precursors from Osteoporotic Patients as an Innovative Model to Study the Role of Nutrients: Focus on Vitamin K2

Several natural compounds, such as vitamin K2, have been highlighted for their positive effects on bone metabolism. It has been proposed that skeletal disorders, such as osteoporosis, may benefit from vitamin K2-based therapies or its regular intake. However, further studies are needed to better clarify the effects of vitamin K2 in bone disorders. To this aim, we developed in vitro a three-dimensional (3D) cell culture system one step closer to the bone microenvironment based on co-culturing osteoblasts and osteoclasts precursors obtained from bone specimens and peripheral blood of the same osteoporotic patient, respectively. Such a 3-D co-culture system was more informative than the traditional 2-D cell cultures when responsiveness to vitamin K2 was analyzed, paving the way for data interpretation on single patients. Following this approach, the anabolic effects of vitamin K2 on the osteoblast counterpart were found to be correlated with bone turnover markers measured in osteoporotic patients’ sera. Overall, our data suggest that co-cultured osteoblasts and osteoclast precursors from the same osteoporotic patient may be suitable to generate an in vitro 3-D experimental model that potentially reflects the individual’s bone metabolism and may be useful to predict personal responsiveness to nutraceutical or drug molecules designed to positively affect bone health.

Circulating Alpha-Tocopherol Levels, Bone Mineral Density, and Fracture: Mendelian Randomization Study

Recent cohort studies indicate a potential role of the antioxidant α-tocopherol in reducing bone loss and risk of fractures, especially hip fractures. We performed a Mendelian randomization investigation of the associations of circulating α-tocopherol with estimated bone mineral density (eBMD) using heel ultrasound and fractures, identified from hospital records or by self-reports and excluding minor fractures. Circulating α-tocopherol was instrumented by three genetic variants associated with α-tocopherol levels at p < 5 × 10^-8 in a genome-wide association meta-analysis of 7781 participants of European ancestry. Summary-level data for the genetic associations with eBMD in 426,824 individuals and with fracture (53,184 cases and 373,611 non-cases) were acquired from the UK Biobank. Two of the three genetic variants were strongly associated with eBMD. In inverse-variance weighted analysis, a genetically predicted one-standard-deviation increase of circulating α-tocopherol was associated with 0.07 (95% confidence interval, 0.05 to 0.09) g/cm² increase in BMD, which corresponds to a >10% higher BMD. Genetically predicted circulating α-tocopherol was not associated with odds of any fracture (odds ratio 0.97, 95% confidence interval, 0.91 to 1.05). In conclusion, our results strongly strengthen a causal link between increased circulating α-tocopherol and greater BMD. Both an intervention study in those with a low dietary intake of α-tocopherol is warranted and a Mendelian randomization study with fragility fractures as an outcome.

The Dual Role of Vitamin K2 in "Bone-Vascular Crosstalk": Opposite Effects on Bone Loss and Vascular Calcification

Osteoporosis (OP) and vascular calcification (VC) represent relevant health problems that frequently coexist in the elderly population. Traditionally, they have been considered independent processes, and mainly age-related. However, an increasing number of studies have reported their possible direct correlation, commonly defined as “bone-vascular crosstalk”. Vitamin K2 (VitK2), a family of several natural isoforms also known as menaquinones (MK), has recently received particular attention for its role in maintaining calcium homeostasis. In particular, VitK2 deficiency seems to be responsible of the so-called “calcium paradox” phenomenon, characterized by low calcium deposition in the bone and its accumulation in the vessel wall. Since these events may have important clinical consequences, and the role of VitK2 in bone-vascular crosstalk has only partially been explained, this review focuses on its effects on the bone and vascular system by providing a more recent literature update. Overall, the findings reported here propose the VitK2 family as natural bioactive molecules that could be able to play an important role in the prevention of bone loss and vascular calcification, thus encouraging further in-depth studies to achieve its use as a dietary food supplement.

Functional vitamin K insufficiency, vascular calcification and mortality in advanced chronic kidney disease: A cohort study

Patients with chronic kidney disease (CKD) suffer from vitamin K deficiency and are at high risk of vascular calcification (VC) and premature death. We investigated the association of functional vitamin K deficiency with all-cause mortality and whether this association is modified by the presence of VC in CKD stage 5 (CKD G5). Plasma dephosphorylated-uncarboxylated matrix Gla-protein (dp-ucMGP), a circulating marker of functional vitamin K deficiency, and other laboratory and clinical data were determined in 493 CKD G5 patients. VC was assessed in subgroups by Agatston scoring of coronary artery calcium (CAC) and aortic valve calcium (AVC). Backward stepwise regression did not identify dp-ucMGP as an independent determinant of VC. During a median follow-up of 42 months, 93 patients died. Each one standard deviation increment in dp-ucMGP was associated with increased risk of all-cause mortality (sub-hazard ratio (sHR) 1.17; 95% confidence interval, 1.01-1.37) adjusted for age, sex, cardiovascular disease, diabetes, body mass index, inflammation, and dialysis treatment. The association remained significant when further adjusted for CAC and AVC in sub-analyses (sHR 1.22, 1.01-1.48 and 1.27, 1.01-1.60, respectively). In conclusion, functional vitamin K deficiency associates with increased mortality risk that is independent of the presence of VC in patients with CKD G5.

Associations of serum vitamins levels with bone mineral density in the different race-ethnicities US adults

BACKGROUND

The conclusions on the associations of specific vitamin levels with bone mineral density (BMD) were controversial. Therefore, the aims of this study were to examine the associations of serum vitamins levels with BMD and the modified effect of race/ ethnicity on these associations in the US adults.

METHODS

This study was from the third National Health and Nutrition Examination Survey. All participants aged ≥18 years with complete data were eligible. Serum vitamins A, B9, B12, C, and E levels were assayed using the Quantaphase II Radioassay Kit (Bio-Rad). Dual-energy X-ray absorptiometry was employed to measure BMD, including femur neck and the total hip.

RESULTS

There were 6023 participants included in the final analysis. Serum folate, vitamins A and C levels were positively associated with BMD. No significant associations of serum vitamins B12 and E levels with BMD were observed. There were positive associations of serum folate level (β = 0.00027 and 0.00032; and 95% CI: 0.00002-0.00057 and 0.00002-0.00063, respectively), vitamin A level (β = 0.01132 and 0.01115; and 95% CI: 0.00478-0.01787 and 0.00430-0.01799, respectively), and vitamin C level (β = 0.00027 and 0.00029; and 95% CI: 0.00012-0.00042 and 0.00013-0.00045, respectively) with BMD at femur neck and the total hip only in the Not Hispanic participants.

CONCLUSION

Elevated serum folate, vitamins A and C levels were associated with a higher BMD. Furthermore, sex and race/ ethnicity modified the associations of serum vitamins levels with BMD.

Nutritional Supplements and Skeletal Health

PURPOSE OF REVIEW

Nutrition influences skeletal health throughout the lifespan, from the impact of maternal intakes during development, through the development of peak bone mass, to the rate of bone loss during aging. However, there are limited data available on the effects of nutritional supplements on bone density, let alone fracture risk. This review will assess the current literature, focusing on human studies, and emphasizing nutrients where bone density or fracture data are available.

RECENT FINDINGS

Calcium and vitamin D supplements, in combination, reduce fracture risk, particularly in populations with low intakes. Extensive recent analyses have supported the safety of these interventions at recommended intakes. There is growing evidence that specific isoflavones may improve bone density although fracture data are lacking. Multiple other nutrient supplements may benefit skeletal health, but data are limited. The effect size of nutrient interventions are relatively small, requiring large sample sizes for trials with bone outcomes, may be difficult to blind, and the impact of supplementation may depend on baseline intake. However, nutrition is the only intervention that can be implemented life long and on a population wide basis. Further investigation is needed into the potential benefits of nutritional supplements to determine in which settings supplements may add benefit in addition to dietary intakes.

Serum vitamin K1 (phylloquinone) is associated with fracture risk and hip strength in post-menopausal osteoporosis: A cross-sectional study

PURPOSE

Vitamin K may play a potential role in bone metabolism, although further evidence is needed. The mechanisms behind its skeletal effects and optimum intake for maintaining bone health remain poorly defined. To elucidate these two issues, we investigated the association between circulating vitamin K₁ (phylloquinone) concentrations with fracture risk, bone mineral density (BMD), hip geometry and plasma dephospho-uncarboxylated-Matrix Gla Protein (dp-ucMGP), an extra-hepatic vitamin K dependent protein (VKDP), in post-menopausal osteoporosis (PMO).

METHODS

We studied 374 women aged (mean [SD]) 68.7[12.3] years with PMO. Information including demographics, lifestyle habits and previous fractures was captured through a questionnaire. Serum was analysed for vitamin K₁. BMD at the lumbar spine (LS), total hip (TH) and femoral neck (FN) (n = 277) and hip structural analysis (HSA) parameters (n = 263) were derived from DXA scans. VKDPs including undercarboxylated prothrombin (PIVKA-II) and dp-ucMGP were measured in a sub-group (n = 130).

RESULTS

Serum vitamin K₁ was significantly lower in the group with fractures (prevalent fractures: 0.53 [0.41], no fractures; 0.65 [0.66] μg/L, p = 0.04) and independently associated with fracture risk. The adjusted odds ratio (95% CI) per μg/L increase in vitamin K₁ was 0.550 (0.310-0.978, p = 0.042). Among the HSA parameters, serum vitamin K₁ was positively associated with cross-sectional area (CSA) (p = 0.02), cross sectional moment of inertia (CSMI) (p = 0.028) and section modulus (Z) (p = 0.02) at the narrow neck (NN) of femur. Dp-ucMGP was detectable in 97 (75%) participants with serum vitamin K₁ of 0.26 [0.15] μg/L, whilst PIVKA-II was above the clinical threshold in only 3.8%.

CONCLUSIONS

Our data suggest that the positive effect of vitamin K on fracture risk may be related to its effects on bone strength. Higher concentrations of serum vitamin K₁ may be required for vitamin K's skeletal effects compared to coagulation. Further prospective or interventional studies are needed for confirmation and should include measures of bone quality.

Cheung A. Vitamin K and Osteoporosis

Vitamin K acts as a coenzyme of carboxylase, catalyzing the carboxylation of several vitamin K dependent proteins. Beyond its well-known effects on blood coagulation, it also exerts relevant effects on bone and the vascular system. In this review, we point out the relevance of an adequate vitamin K intake to obtain sufficient levels of carboxylated (active form) vitamin K dependent proteins (such as Osteocalcin and matrix Gla protein) to prevent bone health. Another bone-related action of Vitamin K is being a ligand of the nuclear steroid and xenobiotic receptor (SXR). We also discuss the recommended intake, deficiency, and assessment of vitamin K. Furthermore, we review the few available studies that have as pre-specified outcome bone fractures, indicating that we need more clinical studies to confirm that vitamin K is a potential therapeutic agent for bone fractures.

Correction to Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials

Following the work of Avenell et al. that has raised concerns about the integrity of the Yamaguchi Osteoporosis Prevention Study (YOPS) conducted by Ishida and Kawai we issue here an adjustment to all meta-analysis estimates that contained this work within our systematic review.

Six months vitamin K treatment does not affect systemic arterial calcification or bone mineral density in diabetes mellitus 2

PURPOSE

Vitamin K-dependent proteins are involved in (patho)physiological calcification of the vasculature and the bones. Type 2 diabetes mellitus (DM2) is associated with increased arterial calcification and increased fractures. This study investigates the effect of 6 months vitamin K2 supplementation on systemic arterial calcification and bone mineral density (BMD) in DM2 patients with a history of cardiovascular disease (CVD).

METHODS

In this pre-specified, post hoc analysis of a double-blind, randomized, controlled clinical trial, patients with DM2 and CVD were randomized to a daily, oral dose of 360 µg vitamin K2 or placebo for 6 months. CT scans were made at baseline and follow-up. Arterial calcification mass was quantified in several large arterial beds and a total arterial calcification mass score was calculated. BMD was assessed in all non-fractured thoracic and lumbar vertebrae.

RESULTS

68 participants were randomized, 35 to vitamin K2 (33 completed follow-up) and 33 to placebo (27 completed follow-up). The vitamin K group had higher arterial calcification mass at baseline [median (IQR): 1694 (812-3584) vs 1182 (235-2445)] for the total arterial calcification mass). Six months vitamin K supplementation did not reduce arterial calcification progression (β [95% CI]: - 0.02 [- 0.10; 0.06] for the total arterial calcification mass) or slow BMD decline (β [95% CI]: - 2.06 [- 11.26; 7.30] Hounsfield units for all vertebrae) when compared to placebo.

CONCLUSION

Six months vitamin K supplementation did not halt progression of arterial calcification or decline of BMD in patients with DM2 and CVD. Future clinical trials may want to pre-select patients with very low vitamin K status and longer follow-up time might be warranted. This trial was registered at clinicaltrials.gov as NCT02839044.

Vitamin K and Kidney Transplantation

The assessment of the vitamin K status and its effects on clinical outcomes in kidney transplantation (KT) patients has sparked interest, but it is still largely unfulfilled. In part, this is due to difficulties in laboratory measurements of vitamin K, especially K2 vitamers. Vitamin K status is currently best assessed by measuring undercarboxylated vitamin-K-dependent proteins. The relative contribution of vitamin K1 and K2 to the health status of the general population and CKD (chronic kidney disease) patients, including KT patients, is also poorly studied. Through a complete and first review of the existing literature, we summarize the current knowledge of vitamin K pathophysiology and its potential role in preventing KT complications and improving organ survival. A specific focus is placed on cardiovascular complications, bone fractures, and the relationship between vitamin K and cancer. Vitamin K deficiency could determine adverse outcomes, and KT patients should be better studied for vitamin K assessment and modalities of effective therapeutic approaches.

Hip Fracture Patients in Geriatric Rehabilitation Show Poor Nutritional Status, Dietary Intake and Muscle Health

The aim of this study was to gain insight into the nutritional status, dietary intake and muscle health of older Dutch hip fracture patients to prevent recurrent fractures and to underpin rehabilitation programs. This cross-sectional study enrolled 40 hip fracture patients (mean ± SD age 82 ± 8.0 years) from geriatric rehabilitation wards of two nursing homes in the Netherlands. Assessments included nutritional status (Mini Nutritional Assessment), dietary intake on three non-consecutive days which were compared with Dietary Reference Intake values, and handgrip strength. Muscle mass was measured using Bioelectrical Impedance Analysis and ultrasound scans of the rectus femoris. Malnutrition or risk of malnutrition was present in 73% of participants. Mean energy, protein, fibre and polyunsaturated fat intakes were significantly below the recommendations, while saturated fat was significantly above the UL. Protein intake was <0.8 in 46% and <1.2 g/(kg·day) in 92%. Regarding micronutrients, mean intakes of calcium, vitamin D, potassium, magnesium and selenium were significantly below the recommendations. The prevalence of low muscle mass, low handgrip strength and sarcopenia were 35, 27 and 10%, respectively. In conclusion, a poor nutritional status, dietary intake and muscle health are common in older hip fracture patients in geriatric rehabilitation wards.

Vitamin K Supplementation to Improve Vascular Stiffness in CKD: The K4Kidneys Randomized Controlled Trial

BACKGROUND

Vascular calcification, a risk factor for cardiovascular disease, is common among patients with CKD and is an independent contributor to increased vascular stiffness and vascular risk in this patient group. Vitamin K is a cofactor for proteins involved in prevention of vascular calcification. Whether or not vitamin K supplementation could improve arterial stiffness in patients with CKD is unknown.

METHODS

To determine if vitamin K supplementation might improve arterial stiffness in patients in CKD, we conducted a parallel-group, double-blind, randomized trial in participants aged 18 or older with CKD stage 3b or 4 (eGFR 15-45 ml/min per 1.73 m²). We randomly assigned participants to receive 400 μg oral vitamin K2 or matching placebo once daily for a year. The primary outcome was the adjusted between-group difference in carotid-femoral pulse wave velocity at 12 months. Secondary outcomes included augmentation index, abdominal aortic calcification, BP, physical function, and blood markers of mineral metabolism and vascular health. We also updated a recently published meta-analysis of trials to include the findings of this study.

RESULTS

We included 159 randomized participants in the modified intention-to-treat analysis, with 80 allocated to receive vitamin K and 79 to receive placebo. Mean age was 66 years, 62 (39%) were female, and 87 (55%) had CKD stage 4. We found no differences in pulse wave velocity at 12 months, augmentation index at 12 months, BP, B-type natriuretic peptide, or physical function. The updated meta-analysis showed no effect of vitamin K supplementation on vascular stiffness or vascular calcification measures.

CONCLUSIONS

Vitamin K2 supplementation did not improve vascular stiffness or other measures of vascular health in this trial involving individuals with CKD.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Vitamin K therapy to improve vascular health in patients with chronic kidney disease, ISRCTN21444964 (www.isrctn.com).

Nutrients and Dietary Patterns Related to Osteoporosis

Osteoporosis is a common chronic disease characterized by a decrease in bone mineral density, impaired bone strength, and an increased risk of fragility fractures. Fragility fractures are associated with significant morbidity, mortality and disability and are a major public health problem worldwide. The influence of nutritional factors on the development and progression of this disease can be significant and is not yet well established. Calcium intake and vitamin D status are considered to be essential for bone metabolism homeostasis. However, some recent studies have questioned the usefulness of calcium and vitamin D supplements in decreasing the risk of fractures. The adequate intake of protein, vegetables and other nutrients is also of interest, and recommendations have been established by expert consensus and clinical practice guidelines. It is important to understand the influence of nutrients not only in isolation but also in the context of a dietary pattern, which is a complex mixture of nutrients. In this review, we evaluate the available scientific evidence for the effects of the main dietary patterns on bone health. Although some dietary patterns seem to have beneficial effects, more studies are needed to fully elucidate the true influence of diet on bone fragility.

Calcium, vitamin D, vitamin K2, and magnesium supplementation and skeletal health

Supplementation with calcium (Ca) and/or vitamin D (vitD) is key to the management of osteoporosis. Other supplements like vitamin K2 (VitK2) and magnesium (Mg) could contribute to the maintenance of skeletal health. This narrative review summarizes the most recent data on Ca, vitD, vitK2 and Mg supplementation and age-related bone and muscle loss. Ca supplementation alone is not recommended for fracture prevention in the general postmenopausal population. Patients at risk of fracture with insufficient dietary intake and absorption could benefit from calcium supplementation, but it needs to be customized, taking into account possible side-effects and degree of adherence. VitD supplementation is essential in patients at risk of fracture and/or vitD deficiency. VitK2 and Mg both appear to be involved in bone metabolism. Data suggest that VitK2 supplementation might improve bone quality and reduce fracture risk in osteoporotic patients, potentially enhancing the efficacy of Ca ± vitD. Mg deficiency could negatively influence bone and muscle health. However, data regarding the efficacy of vitK2 and Mg supplementation on bone are inconclusive.

The effects of vitamin K-rich green leafy vegetables on bone metabolism: A 4-week randomised controlled trial in middle-aged and older individuals

Background

High vegetable intake is associated with beneficial effects on bone. However, the mechanisms remain uncertain. Green leafy vegetables are a rich source of vitamin K1, which is known to have large effects on osteoblasts and osteocalcin (OC) metabolism.

Objective

To examine the effects of consumption of two to three extra serves of green leafy vegetables daily on bone metabolism.

Methods

Thirty individuals (mean age 61.8 ± 9.9 years, 67% male) completed three experimental phases in a randomised controlled crossover design, each lasting four weeks, with a washout period of four weeks between phases (clinical trial registration: ACTRN12615000194561). The three experimental phases were: (i) increased dietary vitamin K1 by consuming green leafy vegetables (H-K; ~200 g/d containing 164.3 [99.5-384.7] μg/d of vitamin K1); (ii) low vitamin K1 by consuming vitamin K1-poor vegetables (L-K; ~200 g/d containing 9.4 [7.7-11.6] μg/d of vitamin K1); and (iii) control (CON) where participants consumed an energy-matched non-vegetable control. OC forms, total OC (tOC), carboxylated OC (cOC) and undercarboxylated OC (ucOC), were measured in serum pre- and post-intervention for each experimental phase using a sandwich-electrochemiluminescence immunoassay.

Results

Pre-intervention tOC, ucOC and ucOC:tOC levels were similar between phases (P > .05). Following H-K, but not L-K, tOC, ucOC and ucOC:tOC levels were significantly lower compared to pre-intervention levels (P ≤ .001) and compared to CON (~14%, 31% and 19%, respectively, all P < .05), while cOC remained unchanged.

Conclusions

In middle-aged healthy men and women, an easily achieved increase in dietary intake of vitamin K1-rich green leafy vegetables substantially reduces serum tOC and ucOC suggesting increased entry of OC into bone matrix, where it may improve the material property of bone. In conjunction with previous epidemiological and randomised controlled trial data, these findings suggest that interventions to increase vegetable intake over extended periods should include bone end points including fracture risk.

Early vascular ageing in chronic kidney disease: impact of inflammation, vitamin K, senescence and genomic damage

Chronic kidney disease (CKD) is a clinical model of premature ageing characterized by cardiovascular disease, persistent uraemic inflammation, osteoporosis muscle wasting and frailty. The accelerated early vascular ageing (EVA) process mediated by medial vascular calcification (VC) is a hallmark of senescence as well as a strong predictor of cardiovascular morbidity and mortality in the CKD population. Current clinical therapeutic strategies and novel treatments for VC have not yet been proven to prevent or reverse VC progression in patients with CKD. Knowledge of the fundamental mechanism underlying EVA is urgently needed to identify and develop novel and efficient therapeutic targets for VC and EVA. An accumulating body of evidence indicates that deoxyribonucleic acid (DNA) damage-induced cellular senescence and 'inflammaging' may largely contribute to such pathological conditions characterized by accelerated EVA. Growing evidence shows that nuclear factor erythroid 2-related factor 2 (NRF2) signalling and vitamin K play a crucial role in counteracting oxidative stress, DNA damage, senescence and inflammaging, whereby NRF2 activation and vitamin K supplementation may provide a novel treatment target for EVA. In this review we discuss the link between senescence and EVA in the context of CKD, with a focus on the role of NRF2 and vitamin K in DNA damage signalling, senescence and inflammaging.

Vitamin K as a Powerful Micronutrient in Aging and Age-Related Diseases: Pros and Cons from Clinical Studies

Vitamin K is a multifunctional micronutrient implicated in age-related diseases such as cardiovascular diseases, osteoarthritis and osteoporosis. Although vitamin K-dependent proteins (VKDPs) are described to have a crucial role in the pathogenesis of these diseases, novel roles have emerged for vitamin K, independently of its role in VKDPs carboxylation. Vitamin K has been shown to act as an anti-inflammatory by suppressing nuclear factor κB (NF-κB) signal transduction and to exert a protective effect against oxidative stress by blocking the generation of reactive oxygen species. Available clinical evidences indicate that a high vitamin K status can exert a protective role in the inflammatory and mineralization processes associated with the onset and progression of age-related diseases. Also, vitamin K involvement as a protective super-micronutrient in aging and ‘inflammaging’ is arising, highlighting its future use in clinical practice. In this review we summarize current knowledge regarding clinical data on vitamin K in skeletal and cardiovascular health, and discuss the potential of vitamin K supplementation as a health benefit. We describe the clinical evidence and explore molecular aspects of vitamin K protective role in aging and age-related diseases, and its involvement as a modulator in the interplay between pathological calcification and inflammation processes.

Multiple Modes of Vitamin K Actions in Aging-Related Musculoskeletal Disorders

Vitamin K is a fat-soluble vitamin that was originally found as an essential factor for blood coagulation. With the discovery of its role as a co-factor for γ-glutamyl carboxylase (GGCX), its function for blood coagulation was understood as the activation of several blood coagulation factors by their γ-carboxylation. Over the last two decades, other modes of vitamin K actions have been discovered, such as the regulation of transcription by activating the steroid and xenobiotic receptor (SXR), physical association to 17β-Hydroxysteroid dehydrogenase type 4 (17β-HSD4), covalent modification of Bcl-2 antagonist killer 1 (Bak), and the modulation of protein kinase A (PKA) activity. In addition, several epidemiological studies have revealed that vitamin K status is associated with some aging-related diseases including osteoporosis, osteoarthritis, and sarcopenia. Clinical studies on single nucleotide polymorphisms of GGCX suggested an association between higher GGCX activity and bone protective effect, while recent findings using conditional knockout mice implied that a contribution in protective effect for bone loss by GGCX in osteoblastic lineage was unclear. GGCX in other cell lineages or in other tissues might play a protective role for osteoporosis. Meanwhile, animal experiments by our groups among others revealed that SXR, a putative receptor for vitamin K, could be important in the bone metabolism. In terms of the cartilage protective effect of vitamin K, both GGCX- and SXR-dependent mechanisms have been suggested. In clinical studies on osteoarthritis, the γ-carboxylation of matrix Gla protein (MGP) and gla-rich protein (GRP) may have a protective role for the disease. It is also suggested that SXR signaling has protective role for cartilage by inducing family with sequence similarity 20a (Fam20a) expression in chondrocytes. In the case of sarcopenia, a high vitamin K status in plasma was associated with muscle strength, large muscle mass, and high physical performance in some observational studies. However, the basic studies explaining the effects of vitamin K on muscular tissue are limited. Further research on vitamin K will clarify new biological mechanisms which contribute to human longevity and health through the prevention and treatment of aging-related musculoskeletal disorders.