Absorption of vitamin D3-3H in control subjects and patients with intestinal malabsorption

[Vitamin D role in oral cavity diseases]

The purpose of this scientific article is to analyze the scientific literature aimed at identifying the relationship between vitamin D levels in the body and diseases of the oral organs, in order to determine the potential impact of vitamin D deficiency on their development. Special attention is paid to the development of recommendations for maintaining optimal vitamin D levels for various population groups in order to strengthen both general health and prevent diseases of the oral cavity.

Comparative bioavailability of vitamins in human foods sourced from animals and plants

Vitamins are essential components of enzyme systems involved in normal growth and function. The quantitative estimation of the proportion of dietary vitamins, that is in a form available for utilization by the human body, is limited and fragmentary. This review provides the current state of knowledge on the bioavailability of thirteen vitamins and choline, to evaluate whether there are differences in vitamin bioavailability when human foods are sourced from animals or plants. The bioavailability of naturally occurring choline, vitamin D, vitamin E, and vitamin K in food awaits further studies. Animal-sourced foods are the almost exclusive natural sources of dietary vitamin B-12 (65% bioavailable) and preformed vitamin A retinol (74% bioavailable), and contain highly bioavailable biotin (89%), folate (67%), niacin (67%), pantothenic acid (80%), riboflavin (61%), thiamin (82%), and vitamin B-6 (83%). Plant-based foods are the main natural sources of vitamin C (76% bioavailable), provitamin A carotenoid β-carotene (15.6% bioavailable), riboflavin (65% bioavailable), thiamin (81% bioavailable), and vitamin K (16.5% bioavailable). The overview of studies showed that in general, vitamins in foods originating from animals are more bioavailable than vitamins in foods sourced from plants.

Vitamin D beyond the blood: Tissue distribution of vitamin D metabolites after supplementation

Vitamin D3's role in mineral homeostasis through its endocrine function, associated with the main circulating metabolite 25-hydroxyvitamin D3, is well characterized. However, the increasing recognition of vitamin D3's paracrine and autocrine functions-such as cell growth, immune function, and hormone regulation-necessitates examining vitamin D3 levels across different tissues post-supplementation. Hence, this review explores the biodistribution of vitamin D3 in blood and key tissues following oral supplementation in humans and animal models, highlighting the biologically active metabolite, 1,25-dihydroxyvitamin D3, and the primary clearance metabolite, 24,25-dihydroxyvitamin D3. While our findings indicate significant progress in understanding how circulating metabolite levels respond to supplementation, comprehensive insight into their tissue concentrations remains limited. The gap is particularly significant during pregnancy, a period of drastically increased vitamin D3 needs and metabolic alterations, where data remains sparse. Within the examined dosage ranges, both human and animal studies indicate that vitamin D3 and its metabolites are retained in tissues selectively. Notably, vitamin D3 concentrations in tissues show greater variability in response to administered doses. In contrast, its metabolites maintain a more consistent concentration range, albeit different among tissues, reflecting their tighter regulatory mechanisms following supplementation. These observations suggest that serum 25-hydroxyvitamin D3 levels may not adequately reflect vitamin D3 and its metabolite concentrations in different tissues. Therefore, future research should aim to generate robust human data on the tissue distribution of vitamin D3 and its principal metabolites post-supplementation. Relating this data to clinically appropriate exposure metrics will enhance our understanding of vitamin D3's cellular effects and guide refinement of clinical trial methodologies.

Scientific opinion on the tolerable upper intake level for vitamin D, including the derivation of a conversion factor for calcidiol monohydrate

Following two requests from the European Commission (EC), the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the revision of the tolerable upper intake level (UL) for vitamin D and to propose a conversion factor (CF) for calcidiol monohydrate into vitamin D3 for labelling purposes. Vitamin D refers to ergocalciferol (vitamin D2), cholecalciferol (vitamin D3), and calcidiol monohydrate. Systematic reviews of the literature were conducted to assess the relative bioavailability of calcidiol monohydrate versus vitamin D3 on serum 25(OH)D concentrations, and for priority adverse health effects of excess vitamin D intake, namely persistent hypercalcaemia/hypercalciuria and endpoints related to musculoskeletal health (i.e. falls, bone fractures, bone mass/density and indices thereof). Based on the available evidence, the Panel proposes a CF for calcidiol monohydrates of 2.5 for labelling purposes. Persistent hypercalciuria, which may be an earlier sign of excess vitamin D than persistent hypercalcaemia, is selected as the critical endpoint on which to base the UL for vitamin D. A lowest-observed-adverse-effect-level (LOAEL) of 250 μg/day is identified from two randomised controlled trials in humans, to which an uncertainty factor of 2.5 is applied to account for the absence of a no-observed-adverse-effect-level (NOAEL). A UL of 100 μg vitamin D equivalents (VDE)/day is established for adults (including pregnant and lactating women) and for adolescents aged 11-17 years, as there is no reason to believe that adolescents in the phase of rapid bone formation and growth have a lower tolerance for vitamin D compared to adults. For children aged 1-10 years, a UL of 50 μg VDE/day is established by considering their smaller body size. Based on available intake data, European populations are unlikely to exceed the UL, except for regular users of food supplements containing high doses of vitamin D.

Calcifediol: a review of its pharmacological characteristics and clinical use in correcting vitamin D deficiency

BACKGROUND

In addition to the role of vitamin D in bone mineralization, calcium and phosphate homeostasis, and skeletal health, evidence suggests an association between vitamin D deficiency and a wide range of chronic conditions. This is of clinical concern given the substantial global prevalence of vitamin D deficiency. Vitamin D deficiency has traditionally been treated with vitamin D₃ (cholecalciferol) or vitamin D₂ (ergocalciferol). Calcifediol (25-hydroxyvitamin D₃) has recently become available more widely.

METHODS

By means of targeted literature searches of PubMed, this narrative review overviews the physiological functions and metabolic pathways of vitamin D, examines the differences between calcifediol and vitamin D₃, and highlights clinical trials conducted with calcifediol in patients with bone disease or other conditions.

RESULTS

For supplemental use in the healthy population, calcifediol can be used at doses of up to 10 µg per day for children ≥ 11 years and adults and up to 5 µg/day in children 3-10 years. For therapeutic use of calcifediol under medical supervision, the dose, frequency and duration of treatment is determined according to serum 25(OH)D concentrations, condition, type of patient and comorbidities. Calcifediol differs pharmacokinetically from vitamin D₃ in several ways. It is independent of hepatic 25-hydroxylation and thus is one step closer in the metabolic pathway to active vitamin D. At comparable doses to vitamin D₃, calcifediol achieves target serum 25(OH)D concentrations more rapidly and in contrast to vitamin D₃, it has a predictable and linear dose-response curve irrespective of baseline serum 25(OH)D concentrations. The intestinal absorption of calcifediol is relatively preserved in patients with fat malabsorption and it is more hydrophilic than vitamin D₃ and thus is less prone to sequestration in adipose tissue.

CONCLUSION

Calcifediol is suitable for use in all patients with vitamin D deficiency and may be preferable to vitamin D₃ for patients with obesity, liver disease, malabsorption and those who require a rapid increase in 25(OH)D concentrations.

Proteins involved in fat-soluble vitamin and carotenoid transport across the intestinal cells: New insights from the past decade

It is now well established that vitamins D, E, and K and carotenoids are not absorbed solely through passive diffusion. Broad-specificity membrane transporters such as SR-BI (scavenger receptor class B type I), CD36 (CD36 molecule), NPC1L1 (Niemann Pick C1-like 1) or ABCA1 (ATP-binding cassette A1) are involved in the uptake of these micronutrients from the lumen to the enterocyte cytosol and in their secretion into the bloodstream. Recently, the existence of efflux pathways from the enterocyte back to the lumen or from the bloodstream to the lumen, involving ABCB1 (P-glycoprotein/MDR1) or the ABCG5/ABCG8 complex, has also been evidenced for vitamins D and K. Surprisingly, no membrane proteins have been involved in dietary vitamin A uptake so far. After an overview of the metabolism of fat-soluble vitamins and carotenoids along the gastrointestinal tract (from the mouth to the colon where interactions with microbiota may occur), a focus is placed on the identified and candidate proteins participating in the apical uptake, intracellular transport, basolateral secretion and efflux back to the lumen of fat-soluble vitamins and carotenoids in enterocytes. This review also highlights the mechanisms that remain to be identified to fully unravel the pathways involved in fat-soluble vitamin and carotenoid intestinal absorption.

Calcifediol for Use in Treatment of Respiratory Disease

Calcifediol is the prohormone of the vitamin D endocrine system (VDES). It requires hydroxylation to move to 1,25(OH)2D3 or calcitriol, the active form that exerts its functions by activating the vitamin D receptor (VDR) that is expressed in many organs, including the lungs. Due to its rapid oral absorption and because it does not require first hepatic hydroxylation, it is a good option to replace the prevalent deficiency of vitamin D (25 hydroxyvitamin D; 25OHD), to which patients with respiratory pathologies are no strangers. Correcting 25OHD deficiency can decrease the risk of upper respiratory infections and thus improve asthma and COPD control. The same happens with other respiratory pathologies and, in particular, COVID-19. Calcifediol may be a good option for raising 25OHD serum levels quickly because the profile of inflammatory cytokines exhibited by patients with inflammatory respiratory diseases, such as asthma, COPD or COVID-19, can increase the degradation of the active metabolites of the VDES. The aim of this narrative revision is to report the current evidence on the role of calcifediol in main respiratory diseases. In conclusion, good 25OHD status may have beneficial effects on the clinical course of respiratory diseases, including COVID-19. This hypothesis should be confirmed in large, randomized trials. Otherwise, a rapid correction of 25(OH)D deficiency can be useful for patients with respiratory disease.

Vitamin D as therapeutic modulator in cerebrovascular diseases: a mechanistic perspectives

Vitamin D deficiency has been linked to several major chronic diseases, such as cardiovascular and neurodegenerative diseases, diabetes, and cancer, linked to oxidative stress, inflammation, and aging. Vitamin D deficiency appears to be particularly harmful to the cardiovascular system, as it can cause endothelial dysfunctioning and vascular abnormalities through the modulation of various downstream mechanisms. As a result, new research indicates that therapeutic approaches targeting vitamin D inadequacies or its significant downstream effects, such as impaired autophagy, abnormal pro-inflammatory and pro-oxidant reactions, may delay the onset and severity of major cerebrovascular disorders such as stroke and neurologic malformations. Vitamin D modulates the various molecular pathways, i.e., Nitric Oxide, PI3K-Akt Pathway, cAMP pathway, NF-kB Pathway, Sirtuin 1, Nrf2, FOXO, in cerebrovascular disorder. The current review shows evidence for vitamin D's mitigating or slowing the progression of these cerebrovascular disorders, which are significant causes of disability and death worldwide.

Vitamin D kinetics in nonpregnant and pregnant women after a single oral dose of trideuterated vitamin D3

The plasma pool of the hormone 1,25-dihydroxyvitamin D (1,25(OH)₂D) is increased throughout most of human pregnancy. Mechanisms behind this adaptation are unclear, in part due to limited data on vitamin D kinetics during pregnancy. Stable isotopes make it possible to study vitamin D kinetics in vulnerable study populations like pregnant women. We conducted a pilot study of vitamin D kinetics in nonpregnant and pregnant women. We evaluated a clinical protocol and developed analytical methods to assess the serum appearance and disappearance of trideuterated vitamin D₃ (d3-vitamin D₃) and trideuterated 25-hydroxyvitamin D₃ (d3-25(OH)D₃) after a single oral dose of 25 μg of [6,19,19-²H]-vitamin D₃ (d3-vitamin D₃). Blood was collected at baseline and 2, 4, 6, 24, 168, 264, and 456 hours post-dosing. We then described the serum kinetic profiles of d3-vitamin D₃ and d3-25(OH)D₃ in nonpregnant and pregnant women. Serum kinetic profiles of d3-vitamin D₃ and d3-25(OH)D₃ followed a time course in line with previous pharmacokinetic studies. There was marked variability between participants in the area under the concentration-time curve (AUC) of d3-25(OH)D₃ over the 20-day study period. This AUC of d3-25(OH)D₃ was positively correlated with the serum vitamin D binding protein (DBP) concentration, which was higher in pregnant compared with nonpregnant women. The mean serum half-life of 25(OH)D₃ was longer but not significantly different in pregnant women (18.8 days) compared with nonpregnant women (13.6 days). Our pilot study demonstrated that a single oral dose of 25 μg of d3-vitamin D₃ can be used to study vitamin D kinetics. Serum DBP concentration is an important predictor of vitamin D kinetics, and more research is needed to fully understand the significance of elevated DBP concentration during pregnancy.

A Randomized, Open-Label Study to Assess Efficacy of Weekly Assumption of Cholecalciferol versus Calcifediol in Older Patients with Hypovitaminosis D

The aim of this single-center, open-label, randomized controlled study was to evaluate which formulation of vitamin D—between cholecalciferol and calcifediol—is most effective in the treatment of hypovitaminosis D in older adults. Demographic characteristics, clinical history, and comprehensive geriatric assessment were recorded at admission. Eligible patients were randomly assigned an equivalent vitamin D supplement, either with cholecalciferol or calcifediol, from the time of hospital admission to three months after discharge. Among the 140 older patients included (mean age 83 ± 6.6 years, 57.8% females), 69 received cholecalciferol and 71 received calcifediol. The mean plasma values of 25-hydroxyvitamin D3 (25OH-vitamin D3) found at the time of enrollment were 16.8 ± 9.9 ng/mL in patients receiving cholecalciferol and 18.8 ± 13.3 ng/mL in those treated with calcifediol (p = 0.31). At the three month follow-up, the mean concentration of 25OH-vitamin D3 was significantly higher in patients treated with calcifediol than in those receiving cholecalciferol (30.7 ± 8.4 vs. 45.4 ± 9.8 ng/mL, respectively; p < 0.001). Supplementation with either cholecalciferol or calcifediol effectively results in reaching the optimal circulating values of 25OH-vitamin D3 in older patients suffering from hypovitaminosis D. However, supplementation with calcifediol led to average circulating values of 25OH-vitamin D3 that were significantly higher (over 50%) than those obtained with cholecalciferol.

A pilot-randomized, double-blind crossover trial to evaluate the pharmacokinetics of orally administered 25-hydroxyvitamin D3 and vitamin D3 in healthy adults with differing BMI and in adults with intestinal malabsorption

BACKGROUND

Obese and malabsorptive patients have difficulty increasing serum 25-hydroxyvitamin D [25(OH)D] after taking vitamin D supplementation. Since 25(OH)D is more hydrophilic than vitamin D, we hypothesized that oral 25(OH)D supplementation is more effective in increasing serum 25(OH)D concentrations in these patients.

OBJECTIVES

We aimed to investigate the pharmacokinetics of oral 25-hydroxyvitamin D3 [25(OH)D3] and oral vitamin D3 in healthy participants with differing BMI and malabsorptive patients.

METHODS

A randomized, double-blind crossover trial was performed in 6 malabsorptive patients and 10 healthy participants who were given 900 µg of either vitamin D3 or 25(OH)D3 orally followed by a pharmacokinetic study (PKS). After ≥28 d from the first dosing, each participant returned to receive the other form of vitamin D and undergo another PKS. For each PKS, serum vitamin D3 and 25(OH)D3 were measured at baseline and at 2, 4, 6, 8, and 12 h and days 1, 2, 3, 7, and 14. Pharmacokinetic parameters were calculated.

RESULTS

Data were expressed as means ± SEMs. The PKS of 900 µg vitamin D3 revealed that malabsorptive patients had 64% lower AUC than healthy participants (1177 ± 425 vs. 3258 ± 496 ng · h/mL; P < 0.05). AUCs of 900 µg 25(OH)D3 were not significantly different between the 2 groups (P = 0.540). The 10 healthy participants were ranked by BMI and categorized into higher/lower BMI groups (5/group). The PKS of 900 µg vitamin D3 showed that the higher BMI group had 53% lower AUC than the lower BMI group (2089 ± 490 vs. 4427 ± 313 ng · h/mL; P < 0.05), whereas AUCs of 900 µg 25(OH)D3 were not significantly different between the 2 groups (P = 0.500).

CONCLUSIONS

Oral 25(OH)D3 may be a good choice for managing vitamin D deficiency in malabsorption and obesity. This trial was registered at clinicaltrials.gov as (NCT03401541.

Vitamin D Sources, Metabolism, and Deficiency: Available Compounds and Guidelines for Its Treatment

Studies on vitamin/hormone D deficiency have received a vast amount of attention in recent years, particularly concerning recommendations, guidelines, and treatments. Moreover, vitamin D's role as a hormone has been confirmed in various enzymatic, metabolic, physiological, and pathophysiological processes related to many organs and systems in the human body. This growing interest is mostly due to the evidence that modest-to-severe vitamin D deficiency is widely prevalent around the world. There is broad agreement that optimal vitamin D status is necessary for bones, muscles, and one's general health, as well as for the efficacy of antiresorptive and anabolic bone-forming treatments. Food supplementation with vitamin D, or the use of vitamin D supplements, are current strategies to improve vitamin D levels and treat deficiency. This article reviews consolidated and emerging concepts about vitamin D/hormone D metabolism, food sources, deficiency, as well as the different vitamin D supplements available, and current recommendations on the proper use of these compounds.

Vitamin A and D Absorption in Adults with Metabolic Syndrome versus Healthy Controls: A Pilot Study Utilizing Targeted and Untargeted LC-MS Lipidomics

SCOPE

Persons with metabolic syndrome (MetS) absorb less vitamin E than healthy controls. It is hypothesized that absorption of fat-soluble vitamins (FSV) A and D2 would also decrease with MetS status and that trends would be reflected in lipidomic responses between groups.

METHODS AND RESULTS

Following soymilk consumption (501 IU vitamin A, 119 IU vitamin D2 ), the triglyceride-rich lipoprotein fractions (TRL) from MetS and healthy subjects (n = 10 age- and gender-matched subjects/group) are assessed using LC-MS/MS. Absorption is calculated using area under the time-concentration curves (AUC) from samples collected at 0, 3, and 6 h post-ingestion. MetS subjects have ≈6.4-fold higher median vitamin A AUC (retinyl palmitate) versus healthy controls (P = 0.07). Vitamin D2 AUC is unaffected by MetS status (P = 0.48). Untargeted LC-MS lipidomics reveals six phospholipids and one cholesterol ester with concentrations correlating (r = 0.53-0.68; P < 0.001) with vitamin A concentration.

CONCLUSIONS

The vitamin A-phospholipid association suggests increased hydrolysis by PLB, PLRP2, and/or PLA2 IB may be involved in the trend in higher vitamin A bioavailability in MetS subjects. Previously observed differences in circulating levels of these vitamins are likely not due to absorption. Alternate strategies should be investigated to improve FSV status in MetS.

Functional effects of vitamin D: From nutrient to immunomodulator

Vitamin D can be obtained from the endogenous synthesis in the epidermis by exposure to UVB light, and from foods and supplements in the form of ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). The main metabolite used to measure vitamin D serum status is calcidiol [25(OH)D]. However, its active metabolite calcitriol [1α,25(OH)₂D] performs pleiotropic effects in the cardiovascular, neurological, and adipose tissue as well as immune cells. Calcitriol exerts its effects through genomic mechanisms modulated by the nuclear vitamin D receptor (VDR)/retinoid X receptor (RXR) complex, to bind to vitamin D response elements (VDRE) in target genes of several cells such as activated T and B lymphocytes, neutrophils, macrophages, and dendritic cells; besides of its genomic mechanisms, VDR performs novel non-genomic mechanisms that involve its membrane expression and soluble form; highlighting that vitamin D could be an immunomodulatory nutrient that plays a key role during physiological and pathological events. Therefore, the aim of this comprehensive literature review was to describe the most relevant findings of vitamin D dietary sources, absorption, synthesis, metabolism, and factors that influence its serum status, signaling pathways, and biological effects of this immunonutrient in the health and disease.

Vitamin D3 Supplementation in Drinking Water Prior to Slaughter Improves Oxidative Status, Physiological Stress, and Quality of Pork

The aims of this study were to investigate the effect of vitamin D₃ administration in drinking water during lairage time prior to slaughter on physiological stress, oxidative status, and pork quality characteristics. Two experiments were carried out. The first one was performed to examine the effect of vitamin D₃ supplementation in drinking water, and the second one to check the effect of supplementation dose (500,000 IU/L vs. 700,000 IU/L). Serum calcium concentration was greater in pigs receiving vitamin D₃ in water when compared to the control group. In experiment 1, a 40% α-tocopherol increase in meat from the group supplemented with vitamin D₃ (500,000 IU/animal) was observed, that resulted in a tendency of decreased meat malondialdehyde (MDA) values at days 5 and 8 after refrigerated storage. In experiment 2, since water intake was higher (800,000 IU and 1,120,000 IU/animal of vitamin D₃ consumption) effects on oxidative status were more profound and vitamin D₃ supplementation increased serum α-tocopherol and decreased cortisol and serum TBARS. These effects were also observed in meat; TBARS levels were decreased after 3 days of refrigerated storage. In both experiments meat from pigs that received vitamin D₃ in drinking water had a lower proportion of total free-polyunsaturated fatty acids (mainly n-6) when compared to the unsupplemented pigs, and these were positively correlated with TBARS production at day 5 of refrigerated storage (r = 0.53 and 0.38 for experiments 1 and 2, respectively). Meat from pigs receiving vitamin D₃ in water showed reduced cohesiveness, gumminess, and chewiness values compared to the control group. The magnetic resonance imaging study of muscle confirmed the effects on water retention with lesser transverse relaxation time in pigs supplemented with vitamin D₃. No vitamin D₃ dose effect was observed, apart from muscle α-tocopherol concentration that was higher in pigs supplemented with 700,000 compared to those supplemented with 500,000 UI/L.

The correlation between vitamin D levels and demographics in patients with gastrointestinal disorders; a cross-sectional study

AIM

The aim of the present study was to evaluate vitamin D levels, in correlation with age, body mass index (BMI), gender and ethnicity, in patients with gastrointestinal disorders (GID).

BACKGROUND

Vitamin D deficiency (VDD) is a global health issue, affecting over 1 billion people. A great body of evidence has shown that it can lead to increased morbidity and mortality. Furthermore, latitude, sedentary lifestyle, limited sunlight exposure, ageing and the presence of comorbidities and chronic illnesses, places patients at an increased risk of VDD.

METHODS

305 consecutive patients, with GID, were assessed for vitamin D levels, using a two-step competitive binding immunoenzymatic assay. Patients were then classified as adequate (50-150nmol/l), insufficient (25-50nmol/l) and deficient (<25nmol/l).

RESULTS

62% of the investigated subjects had low vitamin D levels. From this group, 132 patients (43.3%) had insufficient vitamin D levels, 57 (18.7%) had deficient levels and 116 (38%) had adequate levels. Age was not significantly different in the 3 groups (p=0.29). Interestingly, vitamin D levels were significantly lower in men (39.23±23.62) compared to women (50.68±24.46) (p=0.0001). The BMI was significantly higher in patients with insufficient vitamin D levels. Being of Asian ethnicity had a positive influence on vitamin D levels (B=0.076) (p<0.0001). 71.4% of patients, with IBD, and 60% of patients, with abnormal liver function, had low vitamin D levels.

CONCLUSION

VDD has a high prevalence in patients with GID in particular IBD and liver disease in the United Kingdom. Routine vitamin D testing and supplementations in the case of deficiency and suboptimal level of vitamin D for patients with hepatobiliary, pancreatic, kidney, malabsorptive and restrictive diseases/surgeries is recommended.

Intestinal absorption of vitamin D: a systematic review

Context

Vitamin D is frequently prescribed as a supplement, yet its absorption remains poorly understood.

Objective

This systematic review was performed to evaluate data on mechanisms involved in the intestinal absorption of vitamin D.

Data Sources

PubMed, Embase, and Cochrane Library databases were searched.

Study Selection

The following studies were included: experimental laboratory studies of vitamin D absorption through the enterocyte brush-border membrane; absorption tests that used radiolabeled vitamin D; and clinical trials in adults that investigated a single dose of cholecalciferol or ergocalciferol and reported at least 2 measurements of serum cholecalciferol, ergocalciferol, or 25-hydroxyvitamin D.

Data Extraction

From 2069 articles identified, 46 met the inclusion criteria.

Results

Different methods were employed to evaluate vitamin D absorption. Recent research suggests that vitamin D absorption is not an exclusive simple diffusion process. Vitamin D was better absorbed when it was consumed with fat-containing meals, but absorption also occurred without fat or oily vehicles. Factors that modified cholesterol absorption also altered vitamin D absorption.

Conclusion

Vitamin D is probably absorbed through passive diffusion and a mechanism involving membrane carriers, especially cholesterol transporters, although data remain scarce. Some data suggest that fat, when consumed concomitantly with vitamin D, improves vitamin D absorption.

Comparative effectiveness of vitamin D supplementation via buccal spray versus oral supplements on serum 25-hydroxyvitamin D concentrations in humans: a systematic review protocol

REVIEW QUESTIONS

The questions of this review are.

The value and significance of 25(OH) and 1,25(OH) vitamin D serum levels in adult coeliac patients: A review of the literature

Within the wide spectrum of symptoms and alteration of systems that characterizes CeD, several studies indicate a low-level of vitamin D, therefore recent guidelines suggest its evaluation at the time of diagnosis. This review examines the data from existing studies in which vitamin D has been assessed in CeD patients. Our review indicates that most of the studies on vitamin D in adult CeD report a 25 (OH) vitamin D deficiency at diagnosis that disappears when the patient goes on a gluten-free diet, independently of any supplementation. Instead, when the calcitriol, the active 1,25 (OH) vitamin D form, was evaluated, it resulted in the normal range at the time of CeD diagnosis. A strict and lifelong gluten-free diet can help recover vitamin D level without any supplementation.

Is calcifediol better than cholecalciferol for vitamin D supplementation?

Modest and even severe vitamin D deficiency is widely prevalent around the world. There is consensus that a good vitamin D status is necessary for bone and general health. Similarly, a better vitamin D status is essential for optimal efficacy of antiresorptive treatments. Supplementation of food with vitamin D or using vitamin D supplements is the most widely used strategy to improve the vitamin status. Cholecalciferol (vitamin D₃) and ergocalciferol (vitamin D₂) are the most widely used compounds and the relative use of both products depends on historical or practical reasons. Oral intake of calcifediol (25OHD₃) rather than vitamin D itself should also be considered for oral supplementation. We reviewed all publications dealing with a comparison of oral cholecalciferol with oral calcifediol as to define the relative efficacy of both compounds for improving the vitamin D status. First, oral calcifediol results in a more rapid increase in serum 25OHD compared to oral cholecalciferol. Second, oral calcifediol is more potent than cholecalciferol, so that lower dosages are needed. Based on the results of nine RCTs comparing physiologic doses of oral cholecalciferol with oral calcifediol, calcifediol was 3.2-fold more potent than oral cholecalciferol. Indeed, when using dosages ≤ 25 μg/day, serum 25OHD increased by 1.5 ± 0.9 nmol/l for each 1 μg cholecalciferol, whereas this was 4.8 ± 1.2 nmol/l for oral calcifediol_. Third, oral calcifediol has a higher rate of intestinal absorption and this may have important advantages in case of decreased intestinal absorption capacity due to a variety of diseases. A potential additional advantage of oral calcifediol is a linear dose-response curve, irrespective of baseline serum 25OHD, whereas the rise in serum 25OHD is lower after oral cholecalciferol, when baseline serum 25OHD is higher. Finally, intermittent intake of calcifediol results in fairly stable serum 25OHD compared with greater fluctuations after intermittent oral cholecalciferol.

Update of the tolerable upper intake level for vitamin D for infants

Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to revise the tolerable upper intake level (UL) for vitamin D for infants (≤ 1 year) set in 2012. From its literature review, the Panel concluded that the available evidence on daily vitamin D intake and the risk of adverse health outcomes (hypercalciuria, hypercalcaemia, nephrocalcinosis and abnormal growth patterns) cannot be used alone for deriving the UL for infants. The Panel conducted a meta-regression analysis of collected data, to derive a dose-response relationship between daily supplemental intake of vitamin D and mean achieved serum 25(OH)D concentrations. Considering that a serum 25(OH)D concentration of 200 nmol/L or below is unlikely to pose a risk of adverse health outcomes in infants, the Panel estimated the percentage of infants reaching a concentration above this value at different intakes of vitamin D. Based on the overall evidence, the Panel kept the UL of 25 μg/day for infants aged up to 6 months and set a UL of 35 μg/day for infants 6-12 months. The Panel was also asked to advise on the safety of the consumption of infant formulae with an increased maximum vitamin D content of 3 μg/100 kcal (Commission Delegated Regulation (EU) 2016/127 repealing Directive 2006/141/EC in 2020). For infants aged up to 4 months, the intake assessment showed that the use of infant formulae containing vitamin D at 3 μg/100 kcal may lead some infants to receive an intake above the UL of 25 μg/day from formulae alone without considering vitamin D supplemental intake. For infants aged 4-12 months, the 95th percentile of vitamin D intake (high consumers) estimated from formulae and foods fortified or not with vitamin D does not exceed the ULs, without considering vitamin D supplemental intake.

Comparison of the Micellar Incorporation and the Intestinal Cell Uptake of Cholecalciferol, 25-Hydroxycholecalciferol and 1-α-Hydroxycholecalciferol

In the context of the global prevalence of vitamin D insufficiency, we compared two key determinants of the bioavailability of 3 vitamin D forms with significant biopotencies: cholecalciferol, 25-hydroxycholecalciferol and 1-α-hydroxycholecalciferol. To this aim, we studied their incorporation into synthetic mixed micelles and their uptake by intestinal cells in culture. Our results show that 1-α-hydroxycholecalciferol was significantly more solubilized into mixed micelles compared to the other forms (1.6-fold and 2.9-fold improvement compared to cholecalciferol and 25-hydroxycholecalciferol, respectively). In Caco-2 TC7 cells, the hydroxylated forms were taken up more efficiently than cholecalciferol (p < 0.05), and conversely to cholecalciferol, their uptake was neither SR-BI(Scavenger-Receptor class B type I)- nor NPC1L1 (NPC1 like intracellular cholesterol transporter 1)-dependent. Besides, the apical membrane sodium–bile acid transporter ASBT (Apical Sodium-dependent Bile acid Transporter) was not involved, at least in vitro, in the uptake of any of the three vitamin D forms. Further investigations are needed to identify the uptake pathways of both 1-α-hydroxycholecalciferol and 25-hydroxycholecalciferol. However, considering its high bioavailability, our results suggest the potential interest of using 1-α-hydroxycholecalciferol in the treatment of severe vitamin D deficiency.

Role of Vitamin D in Rheumatoid Arthritis

Vitamin D is a fat soluble hormone, with a well described role in bone health and calcium/phosphate metabolism. Recent evidences have related vitamin D to other physiological functions and pathological conditions. Specifically, vitamin D has widely proven activities on immune system and evidences suggest that it may be implicated in the pathogenesis of rheumatoid arthritis (RA). The relationship between vitamin D and RA is complex, also because a deficitary vitamin D status, which is very common in RA patients, can contribute to the increased risk of osteoporosis typical of RA. In this chapter, will be described and discussed the main aspects of the relationship between RA and vitamin D.

Vitamin D bioavailability: state of the art

There has been renewed interest in vitamin D since numerous recent studies have suggested that besides its well-established roles in bone metabolism and immunity, vitamin D status is inversely associated with the incidence of several diseases, e.g., cancers, cardio-vascular diseases, and neurodegenerative diseases. Surprisingly, there is very little data on factors that affect absorption of this fat-soluble vitamin, although it is acknowledged that dietary vitamin D could help to fight against the subdeficient vitamin D status that is common in several populations. This review describes the state of the art concerning the fate of vitamin D in the human upper gastrointestinal tract and on the factors assumed to affect its absorption efficiency. The main conclusions are: (i) ergocalciferol (vitamin D2), the form mostly used in supplements and fortified foods, is apparently absorbed with similar efficiency to cholecalciferol (vitamin D3, the main dietary form), (ii) 25-hydroxyvitamin D (25OHD), the metabolite produced in the liver, and which can be found in foods, is better absorbed than the nonhydroxy vitamin D forms cholecalciferol and ergocalciferol, (iii) the amount of fat with which vitamin D is ingested does not seem to significantly modify the bioavailability of vitamin D3, (iv) the food matrix has apparently little effect on vitamin D bioavailability, (v) sucrose polyesters (Olestra) and tetrahydrolipstatin (orlistat) probably diminish vitamin D absorption, and (vi) there is apparently no effect of aging on vitamin D absorption efficiency. We also find that there is insufficient, or even no data on the following factors suspected of affecting vitamin D bioavailability: (i) effect of type and amount of dietary fiber, (ii) effect of vitamin D status, and (iii) effect of genetic variation in proteins involved in its intestinal absorption. In conclusion, further studies are needed to improve our knowledge of factors affecting vitamin D absorption efficiency. Clinical studies with labeled vitamin D, e.g., deuterated or (13)C, are needed to accurately and definitively assess the effect of various factors on its bioavailability.

Intestinal absorption of vitamin D: from the meal to the enterocyte

Vitamin D plays key roles in bone, infectious, inflammatory and metabolic diseases. As most people get inadequate sun exposure for sufficient vitamin D status, they need adequate intake of dietary vitamin D. Many studies see optimizing vitamin D status as a public health priority. It is thus vital to gain deeper insight into vitamin D intestinal absorption. It was long assumed that vitamin D intestinal absorption is a passive process, but new data from our laboratory showed that it is actually far more complex than previously thought. This review describes the fate of vitamin D in the human upper gastrointestinal lumen during digestion and focuses on the proteins involved in the intestinal membrane and cellular transport of vitamin D across the enterocyte. Although recent data significantly improve our understanding of vitamin D intestinal absorption, further studies are still needed to increase our knowledge of the molecular mechanisms underlying this phenomenon.

Vitamin D deficiency in patients with intestinal malabsorption syndromes--think in and outside the gut

There is a very high prevalence of vitamin D deficiency, which is defined by a serum level of 25-hydroxyvitamin D [25(OH)D] of lower than 20 ng/mL, in all populations of the world. Unfortunately, the prevalence of vitamin D deficiency in patients with intestinal malabsorption syndromes, including cystic fibrosis (CF), celiac disease (CD), short bowel syndrome and inflammatory bowel disease (IBD), is higher than that in the general population, indicating the presence of disease-specific causative factors. In this review, we aimed to present clinical findings to highlight the roles of insufficient exposure to sunlight and inflammation in the development of vitamin D deficiency in patients with intestinal malabsorption syndromes. Furthermore, we aimed to present experimental evidence that supported a role of vitamin D deficiency in the pathogenesis of IBD. Finally, we reviewed clinical intervention strategies aiming to normalize vitamin D status in and even to improve the conditions of patients and to discuss certain issues that needed to be addressed in future research.

A randomized two way cross over study for comparison of absorption of vitamin D3 buccal spray and soft gelatin capsule formulation in healthy subjects and in patients with intestinal malabsorption

BACKGROUND

Vitamin D deficiency has been proposed to contribute to the development of malabsorption diseases. Despite this, the vitamin D status of these patients is often neglected. The objective of the present work was to compare the absorption of vitamin D3 through the oral route by comparing a 1000 IU soft gelatin capsule and a 500 IU buccal spray (delivering 1000 IU in two spray shots) in healthy subjects and in patients with malabsorption disease.

METHODS

An open label, randomized, two-periods, two-way cross over study was conducted, first in healthy subjects (n = 20) and then in patients with malabsorption syndrome (n = 20). The study participants were equally divided and received either of the treatments (buccal spray, n = 7; soft gelatin capsule, n = 7; control, n = 6) in Period I for 30 days. After washout of another 30 days, the treatments were changed in crossover fashion in Period II. Fasting blood samples were collected to measure baseline 25-hydroxyvitamin D [25(OH)D] levels in all participants at day 0 (Screening visit), day 30 (completion of period I), day 60 (end of wash out and initiation of period II) and day 90 (completion of period II). Safety was evaluated by hematology and biochemistry analyses. Statistical analyses was performed using differences of mean and percentage change from baseline of 25(OH)D levels between two formulation by two tailed Paired t-test with 95% confidence interval.

RESULTS

In healthy subjects, the mean increase in serum 25(OH)D concentration was 4.06 (95% CI 3.41, 4.71) ng/ml in soft gelatin capsule group and 8.0 (95% CI 6.86, 9.13) ng/ml in buccal spray group after 30 days treatment (p < 0.0001). In patients with malabsorption disease, the mean increase in serum 25(OH)D concentration was 3.96 (95% CI 2.37, 5.56) ng/ml in soft gelatin capsule group and 10.46 (95% CI 6.89, 14.03) ng/ml in buccal spray group (p < 0.0001).

CONCLUSION

It can be concluded from the results that the buccal spray produced a significantly higher mean serum 25(OH)D concentration as compared to the soft gelatin capsule, in both healthy subjects as well as in patients with malabsorption syndrome over a period of 30 days administration in a two way cross over study. Treatments were well tolerated by both subject groups

TRIAL REGISTRATION

CTRI/2013/06/003770.

Can vitamin D metabolite measurements facilitate a "treat-to-target" paradigm to guide vitamin D supplementation?

Substantial variability exists in the serum 25(OH)D increase observed in response to vitamin D supplementation. Measurement of circulating cholecalciferol and 24,25(OH)₂D, as indicators of vitamin D absorption and degradation, respectively, account for approximately half of the variation in serum 25(OH)D observed following supplementation.

INTRODUCTION

Vitamin D supplementation produces a variable response in serum 25(OH)D. This variability likely reflects, in part, differences in vitamin D absorption and/or degradation. Despite this variation in response, virtually all expert recommendations endorse a fixed vitamin D supplementation dose, an approach also used in most prospective studies. Such utilization of a single vitamin D dose does not assure attaining any pre-specified target 25(OH)D level, thereby compromising clinical care and prospective supplementation trials. This study begins addressing this weakness by exploring the feasibility of vitamin D metabolite measurements to predict serum 25(OH)D level attained following supplementation.

METHODS

Ninety-one community-dwelling postmenopausal women with baseline 25(OH)D of 10-30 ng/mL received oral vitamin D₃, 2300 or 2500 IU, daily for 4-6 months. Serum 25(OH)D, cholecalciferol (D₃), and 24,25(OH)₂D were measured before and at the end of supplementation to determine if metabolite concentrations allow prediction of the 25(OH)D level attained.

RESULTS

From baseline and follow-up data, we derived a multiple linear regression model predicting posttreatment 25(OH)D as follows: final 25(OH)D = 8.3 + (1.05*initial 25(OH)D) - (7.7*initial 24,25(OH)₂D) + (0.53*final D₃) + (4.2*final 24,25(OH)₂D). This model has an adjusted R(2) = 0.55, thus accounting for approximately half of the observed variance in the final 25(OH)D level.

CONCLUSIONS

The contributions of circulating cholecalciferol and 24,25(OH)₂D to this predictive model can be considered as indicators of intestinal absorption and clearance, respectively. This paradigm requires further study; it may allow efficient "treat-to-25(OH)D-target" strategies useful in optimizing prospective studies and clinical practice.

Postprandial lipid and insulin responses among healthy, overweight men to mixed meals served with baked herring, pickled herring or baked, minced beef

PURPOSE

The aim was to compare postprandial lipid, insulin and vitamin D responses after consumption of three otherwise identical meals served either with baked herring, pickled herring or with baked, minced beef.

METHODS

Seventeen healthy, overweight men (mean age 58 years, BMI 26.4-29.5 kg/m(2)) consumed standardized lunches together with baked herring, pickled herring or baked, minced beef on three occasions in a crossover design. Blood samples were taken just before and up to 7 h after the meal. The postprandial response was measured as serum concentrations of triglycerides (TG), total cholesterol and lipoproteins (LDL, HDL and VLDL), insulin, 25-OH vitamin D and plasma fatty acid composition.

RESULTS

There was no difference in postprandial lipid responses between the two herring meals, whereas a slower TG clearance was observed after the baked, minced beef meal. The 150 g servings of baked and pickled herring provided 3.3 and 2.8 g of long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), respectively, which was reflected in a substantial postprandial increase in plasma LC n-3 PUFA levels. The pickled herring contained 22% sugar and consequently gave a higher insulin response compared with the other two meals.

CONCLUSIONS

Both pickled and baked herring are good sources of LC n-3 PUFA in the diet, but the presence of sugar in pickled herring should be taken into consideration, especially if large amounts are consumed. The faster postprandial TG clearance after a meal with baked herring compared with baked beef supports previous studies on the beneficial effects of herring on cardiovascular health.

What you and your patients need to know about vitamin D

"Vitamin D" is the term commonly used to denote the lipid-soluble hormone critical for calcium homeostasis and skeletal maintenance. A precursor to the active compound is found in many plants and animal tissues and can be absorbed from the gut; it can also be derived from cell membranes in the epidermis during ultraviolet B irradiation. This compound is then hydroxylated sequentially in the liver and kidney to produce the active hormone 1,25(OH)(2)D that binds its nuclear receptor to modulate gene expression. Recently, vitamin D hydroxylases and the nuclear receptor have been identified in many tissues, suggesting previously unrecognized roles for vitamin D. Some epidemiologic studies have also correlated low levels of the inactive storage form 25(OH)D with an increased incidence or prevalence of a variety of diseases, suggesting that large oral supplements and/or increased ultraviolet (UV) exposure might therefore improve individual health. However, randomized, prospective controlled trials comparing vitamin D supplements with placebo have not supported this belief. Moreover, current evidence supports the conclusion that protection from UV radiation does not compromise vitamin D status or lead to iatrogenic disease. In contrast, high vitamin D levels appear to incur a risk of kidney stones and other adverse effects. In the case of true vitamin D deficiency, supplements are a more reliable and quantifiable source of the vitamin than UV exposure.

Gastric acid, calcium absorption, and their impact on bone health

Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.

Oxidative stress and antioxidant capacity in patients with chronic pancreatitis with and without diabetes mellitus

AIM

To determine oxidant stress and antioxidant capacity in chronic pancreatitis (CP) patients with and without diabetes mellitus.

METHODS

This study is a secondary data analysis of our earlier study on 127 (male = 86) patients with CP, grouped as those with diabetes (case; n = 23) and those without diabetes (control). Markers of antioxidant status included vitamins A and E, total antioxidant capacity (TAC; measured as ferric-reducing ability of plasma [FRAP]), and total glutathione (T-GSH). Markers for oxidative stress included lipid peroxidation, measured as thiobarbituric acid reactive substances (TBARS) and serum superoxide dismutase (s-SOD).

RESULTS

Patients with diabetes were older (mean [SD] age 36.4 [9.7] vs. 29.3 [10.0] years; p = 0.032), had longer duration of CP [4 (0.3-21) vs. 3 (0.3-24) years; p = 0.07), and had a lower TAC (269.8 [92.4] vs. 355.5 [128.6] μmoles Fe(+2) liberated; p = 0.003) compared to those without diabetes. In multiple logistic regression analysis taking all exploratory variables, FRAP (<270 μmoles Fe(+2) liberated) was associated with diabetes independent of duration of CP, age of patients, and TBARS levels. However, oxidative stress levels were not different between diabetic and nondiabetic patients.

CONCLUSIONS

Diabetes was found to be associated with longer duration of CP and with low antioxidant capacity. Further studies will be needed to evaluate a causal association.

Plasma appearance and disappearance of an oral dose of 25-hydroxyvitamin D2 in healthy adults

25-Hydroxyvitamin D (25(OH)D) half-life is a potential biomarker for investigating vitamin D metabolism and requirements. We performed a pilot study to assess the approach and practical feasibility of measuring 25(OH)D half-life after an oral dose. A total of twelve healthy Gambian men aged 18–23 years were divided into two groups to investigate the rate and timing of (1) absorption and (2) plasma disappearance after an 80 nmol oral dose of 25(OH)D₂. Fasting blood samples were collected at baseline and, in the first group, every 2 h post-dose for 12 h, at 24 h, 48 h and on day 15. In the second group, fasting blood samples were collected on days 3, 4, 5, 6, 9, 12, 15, 18 and 21. Urine was collected for 2 h after the first morning void at baseline and on day 15. 25(OH)D₂ plasma concentration was measured by ultra-performance liquid chromatography-tandem MS/MS and corrected for baseline. Biomarkers of vitamin D, Ca and P metabolism were measured at baseline and on day 15. The peak plasma concentration of 25(OH)D₂ was 9·6 (sd 0·9) nmol/l at 4·4 (sd 1·8) h. The terminal slope of 25(OH)D₂ disappearance was identified to commence from day 6. The terminal half-life of plasma 25(OH)D₂ was 13·4 (sd 2·7) d. There were no significant differences in plasma 25(OH)D₃, total 1,25(OH)₂D, parathyroid hormone, P, Ca and ionised Ca and urinary Ca and P between baseline and day 15 and between the two groups. The present study provides data on the plasma response to oral 25(OH)D₂ that will underpin and contribute to the further development of studies to investigate 25(OH)D half-life.

The hepatic conversion of vitamin D in alcoholics with varying degrees of liver affection

The seasonal variations in circulating 25-hydroxycholecalciferol (25-HCC) were studied in 102 alcoholics with fatty liver disease without histologic signs of cirrhosis and in 35 patients with alcoholic cirrhosis. The mean levels were compared with those of normal persons. Alcoholics had generally lower 25-HCC values than the controls, particularly in the summer. This was primarily explained by insufficient diet and reduced exposure to sunshine. The ability of the liver to hydroxylate in the 25-position was studied in three groups of alcoholics with 1) fatty liver disease without cirrhosis, 2) compensated cirrhosis, 3) severely incompensated liver cirrhosis. All three groups exhibited a significant increase in serum 25-HCC following the peroral administration of cholecalciferol at a dose of 1 200 U daily for 7 days. Similar rises were seen 7 days after a single injection of 10 000 U cholecalciferol. This indicates a normal intestinal absorption of vitamin D, even in advanced alcoholic liver disease, and is inconsistent with a severely damaged 25-hydroxylation capacity in these patients. Osteomalacia due to impaired liver hydroxylation of vitamin D can hardly explain the increased fracture rate and the decreased bone mass, which have been described in alcoholics.

Impairment of vitamin D and bone metabolism in patients with bypass operation for obesity

Thirty-four patients were studied 2--6 years after jejunoileal bypass for morbid obesity. The serum concentration of 25-hydroxyvitamin D (25-OHD) were reduced and related to the frequency fo stools and to the weight reduction. Fifteen patients were not able to normalize serum 25-OHD following a long-term regular vitamin D intake. The serum immunoreactive parathyroid hormone concentration (iPTH) and the alkaline phosphatase levels were elevated in this group, indicating a secondary hyperparathyroidism. The mean bone mineral content of the forearm was reduced 3--6 years after the operation, most severely in those with elevated serum iPTH. The desired weight reduction by jejunoileal shunt was obtained at the expense of a severely disturbed vitamin D metabolism. We suggest, that all patients with an intestinal bypass for obesity should receive regular vitamin D supplement, and serum 25-OHD should be measured in order to monitor the effect of therapy.

Vitamin D insufficiency/deficiency in gastrointestinal disorders

Vitamin D and calcium are critical for skeletal health. Their absorption from the intestine is negatively impacted by a number of gastrointestinal diseases and surgical procedures, leading to osteoporosis and/or osteomalacia. Diseases of the liver can impact the metabolism of vitamin D to its circulating form, 25(OH)D, as well as the production of carrier proteins, albumin and vitamin D-binding protein, that may alter the delivery of 25(OH)D and its active metabolite 1,25(OH)(2)D to target tissues, including the skeleton, again leading to bone disease. The clinician evaluating a patient with apparent osteoporosis and vitamin D deficiency/ insufficiency needs to consider a gastrointestinal etiology. Similarly, the clinician evaluating a patient with a gastrointestinal disorder needs to evaluate that patient for vitamin D deficiency and bone disease. Treatment involves adequate vitamin D and calcium supplementation to achieve normal serum 25(OH)D, PTH, and serum and urine calcium levels.

Diabetes mellitus worsens antioxidant status in patients with chronic pancreatitis

BACKGROUND

Patients with chronic pancreatitis (CP) are at high risk of antioxidant deficiencies. Furthermore, this disease can lead to diabetes mellitus (DM) that could exacerbate the severity of oxidative stress. Oxidative stress and the resulting LDL oxidation are a major cause of atherosclerosis.

OBJECTIVE

The objective of the study was to ascertain whether diabetes significantly modifies oxidative status in patients with CP.

DESIGN

CP patients with or without DM were compared with type 1 DM patients and healthy control subjects.

RESULTS

Two-way factorial analyses showed that a decrease in the plasma concentrations of vitamin A, vitamin E, and carotenoids accompanied both CP and DM, and CP was also associated with lower plasma concentrations of selenium and zinc, lower catalase activity, and higher plasma concentrations of copper. The lag phase of LDL oxidation was lower in CP patients with or without DM than in the control subjects, whereas there was no significant difference between type 1 DM patients and control subjects. Multivariate analysis showed that LDL vitamin E (R2 = 0.24, P < 0.0001) and fasting plasma glucose (R2 = 0.32, P < 0.0001) concentrations were the main determinants of the lag phase of LDL oxidation.

CONCLUSIONS

Antioxidant status is altered in CP patients, particularly in those who also have DM. In these patients, a vitamin E deficiency and an elevated plasma glucose concentration were associated with significantly higher LDL oxidizability.

Factors affecting intestinal absorption of highly lipophilic food microconstituents (fat-soluble vitamins, carotenoids and phytosterols)

Highly lipophilic food microconstituents (HLFMs) with octanol-water partition coefficients log10 P(c) > 8 include the fat-soluble vitamins (A, E, D and K) and phytochemicals with potential health benefits, the carotenoids and phytosterols. It has been assumed that these compounds have the same metabolism in the human upper gastrointestinal tract and that they follow the same fate as lipids. However, a literature review shows that the metabolism of HLFMs in the upper gastrointestinal tract depends on each HLFM species. For example, some HLFM esters are hydrolyzed mainly by pancreatic lipase, others by bile salt-stimulated lipase; some HLFMs are apparently absorbed by passive diffusion, others by a transporter. Also, although some factors (HLFM molecular species, fat, food matrix) affect absorption efficiency of most HLFMs, other factors (fibers, microconstituents) apparently affect absorption only of some HLFMs. The mnemonic acronym SLAMENGHI, previously proposed to list the factors affecting the bioavailability of carotenoids, was used here to review current knowledge of the factors suspected to affect the intestinal absorption of HLFMs. The available data reveal numerous gaps in the knowledge of the metabolism of HLFMs and the factors that affect their absorption. These gaps need to be filled to be able to formulate HLFMs so as to promote greater absorption efficiency.

Plasma vitamin D and 25OHD responses of young and old men to supplementation with vitamin D3

OBJECTIVES

This study was conducted to determine whether there are age differences in the plasma parent vitamin D and 25-hydroxyvitamin D (25OHD) responses to eight weeks of supplementation with 20 microg/day of vitamin D3.

METHODS

Twenty-five healthy young men (age 18-35) and 25 healthy older men (62-79) were randomly assigned to supplementation with 20 microg/day of vitamin D3 or to no intervention and followed for eight weeks. Plasma vitamin D3 was measured by high performance liquid chromatography and 25OHD was measured by competitive protein binding.

RESULTS

Both young and old men in the supplemented group had pronounced, rapid and similar increases in plasma vitamin D3, whereas vitamin D3 concentrations were stable in the control group. By the end of the eight-week adaptation period, plasma vitamin D3 of young and old men had increased by 4.3 and 6.2 nmol/L respectively. In the supplemented group, mean 25OHD concentrations of both the young and old men increased during the study, and the magnitude of the change after eight weeks was nearly identical in the two age groups (22.5 and 22.1 nmol/L in the young and the old men, respectively). In the control group there was a modest decrease in 25OHD of both the young and old men.

CONCLUSIONS

There appears to be no age-related impairment among men in the absorption or metabolism of 20 microg/day of vitamin D3 taken orally for at least eight weeks.

Absorption of calcium and magnesium in patients with intestinal resections treated with medium chain fatty acids

BACKGROUND

Steatorrhoea is associated with increased faecal loss of calcium and magnesium. Medium chain C8-C10 triglycerides (MCTs) improve fat absorption in patients with small bowel resections but the effects on intestinal absorption of divalent cations are not clear.

AIM

To assess the effect of dietary replacement of long chain triglycerides (LCTs) with MCTs on calcium and magnesium absorption in patients with small bowel resections.

PATIENTS

Nineteen adult patients with a remaining small intestine averaging 171 cm (range 50-300).

METHODS

In a crossover design, patients were randomised to two high fat diets (10 MJ/day, 50% as fat) for four days each separated by one day of washout. Diets were prepared in duplicate and were based on either LCT (LCT period) or equal quantities of LCT and MCT (L/MCT period). Metabolic balances were calculated during the last three days of each period.

RESULTS

Mean stool volume increased significantly with the L/MCT diet and was 336 ml more than that with the LCT diet (95% confidence interval of mean difference, 26-649 ml). There was no significant change in the net absorption of calcium and magnesium between the two diets. On average, percentage calcium absorption was 8.6% with the LCT diet and 12.5% with the L/MCT diet. Mean percentage magnesium absorption was 5.4% with the LCT diet and 2.9% with the L/MCT diet.

CONCLUSIONS

Dietary replacement of 50% long chain triglycerides with medium chain triglycerides in small bowel resected patients increased faecal volume significantly. No changes in the intestinal net absorption of calcium and magnesium were demonstrated.

Bioavailability of vitamin D from wild edible mushrooms (Cantharellus tubaeformis) as measured with a human bioassay

BACKGROUND

The bioavailability of vitamin D from mushrooms in humans is unknown.

OBJECTIVE

We investigated the bioavailability of vitamin D from wild edible mushrooms (Cantharellus tubaeformis) using the increase in serum 25-hydroxyvitamin D concentrations as a measure of vitamin D bioavailability.

DESIGN

Twenty-seven volunteers with serum 25-hydroxyvitamin D concentrations <60 nmol/L (mean : 38.5 nmol/L; range: 15-60 nmol/L) were randomly divided into 3 groups of 9 persons each. For 3 wk, excluding Saturdays and Sundays, group 1 received mushrooms (C. tubaeformis) providing 14 microg ergocalciferol/d with their lunch, group 2 (control) received an ergocalciferol supplement providing 14 microg/d, and group 3 (also a control) received no supplementation.

RESULTS

At the beginning of the study, mean serum 25-hydroxyvitamin D concentrations did not differ significantly among the groups (P = 0.280). When all 3 groups were considered, serum 25-hydroxyvitamin D concentrations showed different time-related changes among the groups during the study: group (P = 0.388), time (P = 0.000), and group x time (P = 0.001). When groups 1 and 2 were compared with group 3, serum 25-hydroxyvitamin D concentrations at 3 wk differed significantly between groups 1 and 3 (P = 0.032) as well as between groups 2 and 3 (P = 0.004). Serum 25-hydroxyvitamin D concentrations at 3 wk did not differ significantly between groups 1 and 2 (P = 0.317).

CONCLUSIONS

We showed for the first time that ergocalciferol was well absorbed from lyophilized and homogenized mushrooms in humans and that vitamin D bioavailability can be studied in humans with such an experimental protocol.

Vitamin D deficiency in veterans with chronic spinal cord injury

Chronic spinal cord injury (SCI) is associated with osteopenia, increasing the prevalence of long-bone fractures. Although disuse may be the primary cause of osteopenia, identification of any additional mechanisms of bone loss may lead to potential therapeutic interventions. We investigated the relationships of serum calcium (Ca), phosphorus (PO4), albumin, alkaline phosphatase (Alk P), and parathyroid hormone (PTH) with serum 25-hydroxyvitamin D [25(OH)D] in 100 subjects with chronic SCI and 50 control subjects. in a subgroup of 50 subjects with SCI and 50 control subjects, we correlated these parameters with serum 1,25-dihydroxyvitamin D [1,25(OH)2D]. Mean ages for the group with SCI and the controls were the same. In subjects with SCI, the duration of injury was 20 +/- 1 years (mean +/- SD). Thirty-two of 100 subjects with SCI, as compared with eight of 50 controls, had serum 25(OH)D levels less than the normal range (chi2 = 4.36, P < .05). In subjects with SCI, a negative correlation was demonstrated between serum 25(OH)D and PTH (r = .29, P < .005). Mean serum 1.25(OH)2D levels were significantly elevated in subjects with SCI as compared with controls (61 +/- 21 v 46 +/- 18 pg/mL, P < .0005). Twenty of 50 subjects with SCI had serum 1.25(OH)2D levels greater than 62 pg/mL, as compared with 10 of 50 controls (chi2 = 4.76 P < .05). A positive correlation was found between serum PTH and 1,25(OH)2D in subjects with SCI and controls (r = .41, P < .005 and r = .30, P < .05, respectively). Twelve subjects with SCI had serum PTH levels greater than the normal range. In this high-serum PTH subgroup, serum 15(OH)D concentration was significantly lower (P < .05) and serum 1,25(OH)2D and Alk P concentrations were significantly higher (P < .005 and P < .05, respectively) as compared with the subgroup with serum PTH values within the normal range. In subjects with SCI, 17 had a serum Ca concentration less than 8.5 mg/dL. In persons with SCI, depressed levels of serum 25(OH)D, as well as other factors, may result in forces inclined to reduce the serum calcium concentration. A state of mild secondary hyperparathyroidism may result, thus increasing the conversion of serum 25(OH)D to 1.25(OH)2D. These data suggest that in chronic SCI subjects, as in the general population, secretion of PTH and the increase of circulating 1.25(OH)2D are subject to control by negative-feedback mechanisms. Higher levels of serum PTH would be expected to accelerate bone resorption of a skeleton already regionally osteoporotic as a consequence of the bone mineral loss due to acute immobilization.

Coeliac disease and bone mineral density in adult female patients

A cross sectional study was undertaken to examine the relationship between coeliac disease and bone mineral density. The 135 female coeliac patients registered on the database of the Department of Gastroenterology at Hull Royal Infirmary were approached by letter, advising them of a potential risk of osteoporosis and inviting them to undergo bone densitometry. A total of 81 registered women (60%) attended the Osteoporosis Laboratory, Princess Royal Hospital and underwent dual energy x ray absorptiometry at the lumbar spine (L2-L4) and femoral neck. Historical data relating to the time of diagnosis and adherence to a gluten free diet were obtained. A control group was selected from the local normal population and was first matched for height, weight, and menopausal status. Postmenopausal patients were then further matched to controls of equivalent menopausal age. In coeliac patients, bone mineral density expressed in g/cm2 as mean (SD) was significantly lower at the lumbar spine (1.076 (0.186)) than in the control group (1.155 (0.143), p < 0.001). This was also the case at the femoral neck (0.887 (0.142) versus 0.965 (0.127), p < 0.001). When the coeliac patients were stratified by menopausal status, it was found that femoral neck bone mineral density was significantly below control values in both premenopausal and postmenopausal women. Spinal bone mineral density exhibited a significant decrement only in the postmenopausal group. The age at diagnosis of coeliac disease and adherence to a gluten free diet did not influence bone mineral density at either hip or spine. These results confirm coeliac patients' higher risk of osteopenia. Coeliac disease should be added to the list of medical conditions which constitute an indication for bone densitometry in order that the individual risk of osteoporosis related fracture may be determined.