Vitamin D toxicity redefined: vitamin K and the molecular mechanism

Interaction between Dietary Vitamin D3 and Vitamin K3 in Gilthead Seabream Larvae (Sparus aurata) in Relation to Growth and Expression of Bone Development-Related Genes

Vitamins D and K are essential fat-soluble nutrients that intervene in bone development processes among other biological functions. The present study is aimed at investigating the potential combined effect of dietary supplementation with vitamin D₃ (cholecalciferol) and vitamin K₃ (menadione) in gilthead seabream (Sparus aurata) larvae. For that purpose, seabream diets were supplemented with different combinations of vitamin D₃/vitamin K₃ (mg/kg diet) as follows: 0.00/0, 0.06/70, 0.06/170, 0.13/70, 0.13/170, 0.40/70, and 0.40/170. Feeding gilthead seabream larvae (22 days post hatch) for 21 days with the diets supplemented with 0.06-0.13 mg/kg vitamin D₃ and 70 mg/kg vitamin K₃ (diets 0.06/70 and 0.13/70) led to the highest larval growth and survival and the highest expression of important biomarkers of both bone development and health, such as bmp2, osx, and mgp, and calcium homeostasis, such as pthrp and casr. However, the increased supplementation with both vitamins at 0.40 mg/kg vitamin D₃ and 170 mg/kg vitamin K₃ (diet 0.40/170) reduced larval growth and survival, downregulated bmp2 and pthrp expressions, and upregulated osx and mgp, causing an unbalance in the relative expression of these genes. The results of the present study have shown the interaction between vitamin D₃ supplementation and vitamin K₃ supplementation in larval performance and gene expression related to bone development and calcium homeostasis, denoting the significance of a correct balance between both vitamins in larval diets.

Vitamin D and neurodegenerative diseases

Neurodegenerative diseases, featured by progressive loss of structure or function of neurons, are considered incurable at present. Movement disorders like tremor and postural instability, cognitive or behavioral disorders such as memory impairment are the most common symptoms of them and the growing patient population of neurodegenerative diseases poses a serious threat to public health and a burden on economic development. Hence, it is vital to prevent the occurrence of the diseases and delay their progress. Vitamin D can be transformed into a hormone in vivo with both genomic and non-genomic actions, exerting diverse physiological effects. Cumulative evidence indicates that vitamin D can ameliorate neurodegeneration by regulating pertinent molecules and signaling pathways including maintaining Ca²⁺ homeostasis, reducing oxidative stress, inhibiting inflammation, suppressing the formation and aggregation of the pathogenic protein, etc. This review updates discoveries of molecular mechanisms underlying biological functions of vitamin D in neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and vascular dementia. Clinical trials investigating the influence of vitamin D supplementation in patients with neurodegenerative diseases are also summarized. The synthesized information will probably provoke an enhanced understanding of the neuroprotective roles of vitamin D in the nervous system and provide therapeutic options for patients with neurodegenerative diseases in the future.

Vitamin D and Stress Fractures in Sport: Preventive and Therapeutic Measures-A Narrative Review

There are numerous risk factors for stress fractures that have been identified in literature. Among different risk factors, a prolonged lack of vitamin D (25(OH)D) can lead to stress fractures in athletes since 25(OH)D insufficiency is associated with an increased incidence of a fracture. A 25(OH)D value of <75.8 nmol/L is a risk factor for a stress fracture. 25(OH)D deficiency is, however, only one of several potential risk factors. Well-documented risk factors for a stress fracture include female sex, white ethnicity, older age, taller stature, lower aerobic fitness, prior physical inactivity, greater amounts of current physical training, thinner bones, 25(OH)D deficiency, iron deficiency, menstrual disturbances, and inadequate intake of 25(OH)D and/or calcium. Stress fractures are not uncommon in athletes and affect around 20% of all competitors. Most athletes with a stress fracture are under 25 years of age. Stress fractures can affect every sporty person, from weekend athletes to top athletes. Stress fractures are common in certain sports disciplines such as basketball, baseball, athletics, rowing, soccer, aerobics, and classical ballet. The lower extremity is increasingly affected for stress fractures with the locations of the tibia, metatarsalia and pelvis. Regarding prevention and therapy, 25(OH)D seems to play an important role. Athletes should have an evaluation of 25(OH)D -dependent calcium homeostasis based on laboratory tests of 25-OH-D3, calcium, creatinine, and parathyroid hormone. In case of a deficiency of 25(OH)D, normal blood levels of ≥30 ng/mL may be restored by optimizing the athlete's lifestyle and, if appropriate, an oral substitution of 25(OH)D. Very recent studies suggested that the prevalence of stress fractures decreased when athletes are supplemented daily with 800 IU 25(OH)D and 2000 mg calcium. Recommendations of daily 25(OH)D intake may go up to 2000 IU of 25(OH)D per day.

Vitamin D - current stage of knowledge about analysis and supplementation

Nowadays, topics related to the proper nutrition of the body, which requires a complex of compounds and supplementation of these ingredients have undoubtedly gained popularity, so it should come as no surprise that there is a widespread interest in vitamin D in science, medicine, analytics and nutrition. In the world of developing technologies, new directions of physiological action of this vitamin on the body are being discovered. Issues related to the demand for vitamin D in various populations and its sources in food, the appropriate form of supplementation, safety and toxicity are extremely important. The present manuscript focuses on the concise evaluation of key data in the field of vitamin D. Structure and physicochemical properties, demand and delivery trails, deficiency and its diagnosis, supplementation, interactions of vitamin D with supplements and drugs are discussed. Attention has also been paid to the methods of vitamin D analysis in various matrices, which allow for an accurate and precise quality assessment of dietary supplements, drugs and food products. The presented information allows deeper understanding of the mechanisms responsible for the development of many diseases in the context of vitamin D levels.

Application of nutrient essentiality criteria to dietary carbohydrates

The purpose of the present review is to describe how human physiology at very low carbohydrate intakes relates to the criteria for nutritional essentiality. Although we did not limit ourselves to one particular type or function of carbohydrates, we did primarily focus on glucose utilisation as that function was used to determine the recommended daily allowance. In the general population, the human body is able to endogenously synthesise carbohydrates, and does not show signs of deficiency in the absence of dietary carbohydrates. However, in certain genetic defects, such as glycogen storage disease type I, absence of dietary carbohydrates causes abnormalities that are resolved with dietary supplementation of carbohydrates. Therefore, dietary carbohydrates may be defined as conditionally essential nutrients because they are nutrients that are not required in the diet for the general population but are required for specific subpopulations. Ketosis may be considered a physiological normal state due to its occurrence in infants in addition to at very low carbohydrate intakes. Although sources of dietary carbohydrates can provide beneficial micronutrients, no signs of micronutrient deficiencies have been reported in clinical trials of low-carbohydrate ketogenic diets. Nonetheless, more research is needed on how micronutrient requirements can change depending on the dietary and metabolic context. More research is also needed on the role of dietary fibre during a low-carbohydrate ketogenic diet as the beneficial effects of dietary fibre were determined on a standard diet and several studies have shown beneficial effects of decreasing non-digestible carbohydrates.

Joint Association of Low Vitamin D and Vitamin K Status With Blood Pressure and Hypertension

Low vitamin D and K status are both associated with an increased cardiovascular risk. New evidence from experimental studies on bone health suggest an interaction between vitamin D and K; however, a joint association with vascular health outcomes is largely unknown. To prospectively investigate whether the combination of low vitamin D and K status is associated with higher systolic and diastolic blood pressure in 402 participants and with incident hypertension in 231 participants free of hypertension at baseline. We used data from a subsample of the Longitudinal Aging Study Amsterdam, a population-based cohort of Dutch participants aged 55 to 65 years. Vitamin D and K status were assessed by 25-hydroxyvitamin D and dp-ucMGP (dephosphorylated uncarboxylated matrix gla protein) concentrations (high dp-ucMGP is indicative for low vitamin K status) in stored samples from 2002 to 2003. Vitamin D and K status were categorized into 25-hydroxyvitamin D <50/≥50 mmol/L and median dp-ucMGP <323/≥323 pmol/L. During a median follow-up of 6.4 years, 62% of the participants (n=143) developed hypertension. The combination of low vitamin D and K status was associated with increased systolic 4.8 mm Hg (95% confidence interval, 0.1–9.5) and diastolic 3.1 mm Hg (95% confidence interval, 0.5–5.7) blood pressure compared with high vitamin D and K status ( P for interaction =0.013 for systolic blood pressure and 0.068 for diastolic blood pressure). A similar trend was seen for incident hypertension: hazard ratio=1.62 (95% confidence interval, 0.96–2.73) for the low vitamin D and K group. The combination of low vitamin D and K status was associated with increased blood pressure and a trend for greater hypertension risk.

Severe hypercalcaemia in a child secondary to use of alternative therapies

We describe a case of a 4-year-old boy who presented with acute vomiting, weight loss, loss of appetite, polyuria and polydipsia. Initial investigations revealed a very elevated corrected calcium level which peaked at 4.46 mmol/L. He had a prior diagnosis of autism and his mother had consulted an alternative therapist who had recommended many supplements, including calcium and vitamin D. He required treatment with hyperhydration, calcitonin, furosemide and several doses of pamindronate before his calcium level returned to the normal range 2 weeks later.

Non-linear contribution of serum vitamin D to symptomatic diabetic neuropathy: A case-control study

AIMS

Vitamin D deficiency has recently been speculated to be associated with increased risk of diabetes neuropathy (DN). The aim of this study was to evaluate the odds of symptomatic DN across serum vitamin D levels.

METHODS

All patients with DM were assessed using diabetic neuropathy symptoms and diabetic neuropathy examination score. Overall, 150 cases with DN and 600 controls were included. Serum 25-hydroxyvitamin D (25-OH-D) was measured to determine vitamin D status.

RESULTS

A non-linear association between 25-OH-D and suffering from symptomatic DN was observed which was extracted after stratifying the ORs across different serum 25-OH-D levels. When compared to individuals with 25-OH-D of 30-40 ng/mL, patients with deficient (<20 ng/mL) vitamin D levels had higher odds of having symptomatic DN (OR: 2.04, 95%CI: 0.99-4.02, P=0.054). Participants with vitamin D values of greater than 40 ng/mL were also more likely to exhibit symptomatic DN (fully adjusted OR: 4.29, 95%CI: 1.59-11.55).

CONCLUSIONS

We hypothesize a non-linear contribution of serum vitamin D to symptomatic DN occurrence, which emphasizes that administration of vitamin D should be monitored and evaluated more carefully, especially in patients with diabetes.

Plausible ergogenic effects of vitamin D on athletic performance and recovery

The purpose of this review is to examine vitamin D in the context of sport nutrition and its potential role in optimizing athletic performance. Vitamin D receptors (VDR) and vitamin D response elements (VDREs) are located in almost every tissue within the human body including skeletal muscle. The hormonally-active form of vitamin D, 1,25-dihydroxyvitamin D, has been shown to play critical roles in the human body and regulates over 900 gene variants. Based on the literature presented, it is plausible that vitamin D levels above the normal reference range (up to 100 nmol/L) might increase skeletal muscle function, decrease recovery time from training, increase both force and power production, and increase testosterone production, each of which could potentiate athletic performance. Therefore, maintaining higher levels of vitamin D could prove beneficial for athletic performance. Despite this situation, large portions of athletic populations are vitamin D deficient. Currently, the research is inconclusive with regards to the optimal intake of vitamin D, the specific forms of vitamin D one should ingest, and the distinct nutrient-nutrient interactions of vitamin D with vitamin K that affect arterial calcification and hypervitaminosis. Furthermore, it is possible that dosages exceeding the recommendations for vitamin D (i.e. dosages up to 4000-5000 IU/day), in combination with 50 to 1000 mcg/day of vitamin K₁ and K₂ could aid athletic performance. This review will investigate these topics, and specifically their relevance to athletic performance.

The trials and tribulations of vitamin D: time for the 'sunshine' vitamin to come in out of the cold - or just more broken promises?

We are presently faced with the competing notions of modern life being a 'state of vitamin D depletion', implying a widespread need to supplement with vitamin D, or, the opposite view, which is that the present evidence can only support at best selective targeted vitamin D intervention. This is important as there is evidence that over the last 40-50 years there were downwards global trends in serum 25(OH)D concentrations, while individual consumption of vitamin D as supplements rose. For this reason and many others, a large population-based interventional study, the VITAL trial, was designed to try to establish the health value of vitamin D supplementation. VITAL is a huge primary prevention trial looking at the effects of vitamin D repletion in preventing cancer and cardiovascular disease in a fundamentally healthy population. This may seem an unusual approach given that what we mostly know about vitamin D is that is has some effects on the skeleton. This review looks to explore current knowledge about vitamin D in health and disease, and at how this is now undergoing significant reappraisal and revision. We will carefully critique the VITAL study design to see if it will allow for the construction of the detailed portfolio of clinical evidence so urgently needed to allow us better to understand role of vitamin D supplementation in health and disease.

Vitamin D therapy and related metabolomics: is the calciferol dose and form the only requirements for successful clinical therapeutics?

A nutraceutical that has exploded onto the prescription pad in recent years is the fat soluble vitamin, vitamin D. This is due to an increasing medical interest in the utility of the vitamin in the treatment and prevention of an array of diseases and ailments. Despite the continued debate over the correct dose, form and serum levels, many clinicians fail to achieve intended therapeutic responses with their patients and deficiencies still exist. This may be due to medical professionals being less aware of the multitude of factors that can influence treatment when dosing a product. In this paper we explore the magnitude of interactions that exist between the host physiology and the vitamin and cite such points as a reason for confounding treatment end points. Aspects that are proposed to influence treatment success more critically than dose and molecular form prescribed are: organ pathology, intracellular states, the endocrine system, concomitant products, genetics, lifestyle, quality of product, and modern delivery systems.

Role of Fat-Soluble Vitamins A and D in the Pathogenesis of Influenza: A New Perspective

Reduced exposure to solar radiation, leading to a deficiency of vitamin D and hence impaired innate immunity, has been suggested as a trigger for influenza viral replication and as an explanation of seasonal influenza. Although this hypothesis accounts for many unexplained facts about the epidemiology of influenza, gaps remain in understanding the pathogenesis and manifestations of the disease. Several observations suggest a role for vitamin A compounds (retinoids) in the disease. This paper presents a new model of the etiopathogenesis of influenza, suggesting that host resistance and susceptibility depend importantly on the ratio of vitamin D to vitamin A activity. Retinoid concentrations within normal physiological limits appear to inhibit influenza pathogenesis whereas higher background concentrations (i.e., very low vitamin D : A ratios) increase the risk of severe complications of the disease. There is also evidence that influenza-induced or preexisting liver disease, diabetes, and obesity worsen the severity of infection, possibly via liver dysfunction and alterations in retinoid metabolism. The model could be tested by determining the presence of retinoids in the secretions of patients with influenza and by studies of retinoid profiles in patients and controls. Potential strategies for prevention and treatment are discussed.

Vitamin D supplementation during pregnancy: safety considerations in the design and interpretation of clinical trials

Maternal-child health benefits of optimizing vitamin D status during pregnancy may include a reduced risk of pre-eclampsia, improved fetal growth and beneficial effects on infant immune function. These hypotheses require evaluation by randomized controlled antenatal vitamin D supplementation trials using doses that are high enough to elevate serum 25-hydroxyvitamin D concentrations into the range believed to be associated with improved health outcomes. Such doses may be considerably higher than the current recommended dietary allowance (600 IU day(-1)) or standard prenatal supplement dose (400 IU day(-1)), and may even be higher than the tolerable upper intake level (4000 IU day(-1)) advised by the Institute of Medicine (2010). A critical review of the published literature yielded limited data regarding the safety of antenatal vitamin D regimens. There have been no published reports of the teratogenic effects of vitamin D on humans. Some animal studies have suggested the potential for dose-dependent fetal toxicities (for example, growth impairment, skeletal malformations and cardiovascular anomalies), but the relevance of these observations to humans is unknown. Antenatal vitamin D supplementation trials should incorporate a range of methods for objectively establishing maternal and fetal safety, and aim to identify the lowest doses of vitamin D required to achieve target outcomes.