Vitamin C Deficiency and the Risk of Osteoporosis in Patients with an Inflammatory Bowel Disease.

Recent research studies have shown that vitamin C (ascorbic acid) may affect bone mineral density and that a deficiency of ascorbic acid leads to the development of osteoporosis. Patients suffering from an inflammatory bowel disease are at a risk of low bone mineral density. It is vital to notice that patients with Crohn's disease and ulcerative colitis also are at risk of vitamin C deficiency which is due to factors such as reduced consumption of fresh vegetables and fruits, i.e., the main sources of ascorbic acid. Additionally, some patients follow diets which may provide an insufficient amount of vitamin C. Moreover, serum vitamin C level also is dependent on genetic factors, such as SLC23A1 and SLC23A2 genes, encoding sodium-dependent vitamin C transporters and GSTM1, GSTP1 and GSTT1 genes which encode glutathione S-transferases. Furthermore, ascorbic acid may modify the composition of gut microbiota which plays a role in the pathogenesis of an inflammatory bowel disease.

Vitamin C in Home Parenteral Nutrition: A Need for Monitoring.

To date, there are no recommendations about screening plasma vitamin C concentration and adjust its supplementation in patients on long-term home parenteral nutrition (HPN). The aim of this study was to evaluate vitamin C status and determine if a commercial multivitamin preparation (CMVP) containing 125 mg of vitamin C is sufficient in stable patients on HPN. All clinically stable patients receiving HPN or an intravenous fluid infusion at least two times per week for at least 6 months, hospitalized for nutritional assessment, were retrospectively included, for a total of 186 patients. We found that 29% of the patients had vitamin C insufficiency (i.e., <25 µmol/L). In univariate analysis, C-reactive protein (CRP) (p = 0.002) and intake of only 125 mg of vitamin C (p = 0.001) were negatively associated with vitamin C levels, and duration of follow-up in our referral center (p = 0.009) was positively associated with vitamin C levels. In multivariate analysis, only CRP (p = 0.001) and intake of 125 mg of vitamin C (p < 0.0001) were independently associated with low plasma vitamin C concentration. Patients receiving only CMVP with a low plasma vitamin C level significantly received personal compounded HPN (p = 0.008) and presented an inflammatory syndrome (p = 0.002). Vitamin C insufficiency is frequent in individuals undergoing home parenteral nutrition; therefore, there is a need to monitor plasma vitamin C levels, especially in patients on HPN with an inflammatory syndrome and only on CMVP.

Patients with Community Acquired Pneumonia Exhibit Depleted Vitamin C Status and Elevated Oxidative Stress.

Pneumonia is a severe lower respiratory tract infection that is a common complication and a major cause of mortality of the vitamin C-deficiency disease scurvy. This suggests an important link between vitamin C status and lower respiratory tract infections. Due to the paucity of information on the vitamin C status of patients with pneumonia, we assessed the vitamin C status of 50 patients with community-acquired pneumonia and compared these with 50 healthy community controls. The pneumonia cohort comprised 44 patients recruited through the Acute Medical Assessment Unit (AMAU) and 6 patients recruited through the Intensive Care Unit (ICU); mean age 68 ± 17 years, 54% male. Clinical, microbiological and hematological parameters were recorded. Blood samples were tested for vitamin C status using HPLC with electrochemical detection and protein carbonyl concentrations, an established marker of oxidative stress, using ELISA. Patients with pneumonia had depleted vitamin C status compared with healthy controls (23 ± 14 µmol/L vs. 56 ± 24 µmol/L, p < 0.001). The more severe patients in the ICU had significantly lower vitamin C status than those recruited through AMAU (11 ± 3 µmol/L vs. 24 ± 14 µmol/L, p = 0.02). The pneumonia cohort comprised 62% with hypovitaminosis C and 22% with deficiency, compared with only 8% hypovitaminosis C and no cases of deficiency in the healthy controls. The pneumonia cohort also exhibited significantly elevated protein carbonyl concentrations compared with the healthy controls (p < 0.001), indicating enhanced oxidative stress in the patients. We were able to collect subsequent samples from 28% of the cohort (mean 2.7 ± 1.7 days; range 1-7 days). These showed no significant differences in vitamin C status or protein carbonyl concentrations compared with baseline values (p = 0.6). Overall, the depleted vitamin C status and elevated oxidative stress observed in the patients with pneumonia indicates an enhanced requirement for the vitamin during their illness. Therefore, these patients would likely benefit from additional vitamin C supplementation to restore their blood and tissue levels to optimal. This may decrease excessive oxidative stress and aid in their recovery.

Adding an orange to the banana bag: vitamin C deficiency is common in alcohol use disorders.

BACKGROUND: At least a third of the world's population consumes alcohol regularly. Patients with alcohol use disorders (AUDs) are frequently hospitalized for both alcohol-related and unrelated medical conditions. It is well recognized that patients with an AUD are thiamine deficient with thiamine replacement therapy being considered the standard of care. However, the incidence of vitamin C deficiency in this patient population has been poorly defined. METHODS: In this retrospective, observational study, we recorded the admission vitamin C level in patients with an AUD admitted to our medical intensive care unit (MICU) over a 1-year period. In addition, we recorded relevant clinical and laboratory data including the day 2 and day 3 vitamin C level following empiric treatment with vitamin C. Septic patients were excluded from this study. RESULTS: Sixty-nine patients met the inclusion criteria for this study. The patients' mean age was 53 ± 14 years; 52 patients (75%) were males. Severe alcohol withdrawal syndrome was the commonest admitting diagnosis (46%). Eighteen patients (26%) had cirrhosis as the admitting diagnosis with 18 (13%) patients admitted due to alcohol/drug intoxication. Forty-six patients (67%) had evidence of acute alcoholic hepatitis. The mean admission vitamin C level was 17.0 ± 18.1 µmol/l (normal 40-60 µmol/l). Sixty-one (88%) patients had a level less than 40 µmol/l (subnormal) while 52 patients (75%) had hypovitaminosis C (level < 23 µmol/l). None of the variables recorded predicted the vitamin C level. Various vitamin C replacement dosing strategies were used. A 1.5-g loading dose, followed by 500-mg PO q 6, was effective in restoring blood levels to normal by day 2. CONCLUSION: Our results suggest that hypovitaminosis C is exceedingly common in patients with an AUD admitted to an intensive care unit and that all such patients should receive supplementation with vitamin C in addition to thiamine. Additional studies are required to confirm the findings of our observational study and to determine the optimal vitamin C dosing strategy.

Vitamin C for the critically ill: Is the evidence strong enough?

Vitamin C exhibits interesting properties in the context of critical illness, with benefits described in neurologic, cardiovascular, renal, and hematologic systems, both in in vitro and in animal models. Through direct effects on bacterial replication, immunomodulation, and antioxidant reserve of the organism, vitamin C directly affects the pathophysiological process of sepsis, trauma, burn, and systemic inflammation. Even if several observational trials have linked vitamin C deficiency to worse outcomes, the evidence is not such as to provide us with a distinction between causality effects or simple epiphenomenon, and the current focus is on interventional trials. Pharmacokinetic data suggest that a minimal supplementation of 3 g/d intravenously is required to restore normal serum values in critically ill patients with known deficiency. According to these data, only five trials, including a retrospective analysis, studied pharmacologic dose: three as an antioxidant cocktail and two as monotherapy. The largest trial, conducted in 2002, reported reduced incidence of multiorgan failure and duration of mechanical ventilation. Recently a retrospective analysis reported impressive results after administration of vitamin C, thiamine, and hydrocortisone. The two most recent trials reported improved clinical outcomes, including improved mortality, but contained significant methodological limitations. A recent systematic review did not find clinical benefits with the most-studied low-dose oral supplementation, potentially because of suboptimal or insufficient repletion. Current guidelines do not support the administration of high-dose vitamin C in critically ill patients. Future larger trials are required to support any therapy, but the low cost and safety profile can justify supplementation in the meantime. Metabolomics study will further help understand biological effect.

Making sense of early high-dose intravenous vitamin C in ischemia/reperfusion injury.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2018. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2018 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901 .

Is Vitamin C Supplementation in Patients with ß-Thalassemia Major Beneficial or Detrimental?

Globally, ß-thalassemia major (ß-TM) is one of the most common hereditary disorders. Multiple blood transfusions, that are a life-saving therapy in patients with ß-TM, is a major source of iron overload. Iron overload can lead to significant morbidity and mortality. Research evidence indicates that oxidative stress induced by iron overload, is one of the major precipitating causes of vitamin C deficiency in ß-TM patients. It has previously been shown that patients with ß-TM have significantly lower levels of vitamin C as compared to healthy individuals. It is believed that vitamin C can reduce both ferric (Fe(3+)) and ferrous (Fe(2+)) ions, and also facilitate the accessibility of iron to chelators through increase of iron release from the reticuloendothelial system. Despite the potential benefits of vitamin C in patients with ß-TM, several areas of concern exist that should be addressed by high quality research designs. Some recommendations have been provided through this study.

Vitamin D and/or calcium deficient diets may differentially affect muscle fiber neuromuscular junction innervation.

INTRODUCTION: There is evidence that supports a role for Vitamin D (Vit. D) in muscle. The exact mechanism by which Vit. D deficiency impairs muscle strength and function is not clear. METHODS: Three-week-old mice were fed diets with varied combinations of Vit. D and Ca2+ deficiency. Behavioral testing, genomic and protein analysis, and muscle histology were performed with a focus on neuromuscular junction (NMJ) -related genes. RESULTS: Vit. D and Ca2+ deficient mice performed more poorly on given behavioral tasks than animals with Vit. D deficiency alone. Genomic and protein analysis of the soleus and tibialis anterior muscles revealed changes in several Vit. D metabolic, NMJ-related, and protein chaperoning and refolding genes. CONCLUSIONS: These data suggest that detrimental effects of a Vit. D deficient or a Vit. D and Ca2+ deficient diet may be a result of differential alterations in the structure and function of the NMJ and a lack of a sustained stress response in muscles. Muscle Nerve 54: 1120-1132, 2016.

Haemodynamic instability of uncommon aetiology in Switzerland.

In Switzerland, vitamin C deficiency is a rare condition. Nonetheless, in clinical practice, there are some patients exhibiting a vitamin C deficiency as a result of an unbalanced diet or intestinal malabsorption. We report the clinical history of a 55-year-old man known for alcoholism and insufficient intake of fresh fruits and vegetables. He was admitted to the intensive care unit, for haemodynamic instability caused by blood loss due to fragile vessels (skin, gastrointestinal). Further analyses revealed a severe lack of vitamin C. The patient received a high dose of intravenous substitutive treatment, leading to a favourable clinical outcome.

Severe vitamin C deficiency in a child newly diagnosed with T-cell ALL due to nutrient gap.

A 10-year-old boy developed a perifollicular rash during interim maintenance of T-Cell acute lymphoblastic leukaemia. Differential diagnoses included drug reaction and inflammatory process. Before diagnosis, the patient had a limited diet--low in vegetables and fruits--due to selective eating, with later anorexia and taste aversions due to chemotherapy treatment. Despite nutritional counselling and starting a multivitamin, the patient incurred severe weight loss (18.5% of his usual body weight). Serum levels of ascorbic acid were non-detectable, at <5 µmol/L, indicative of vitamin C deficiency. The patient began vitamin C supplementation containing 125 mg ascorbic acid three times a day for 7 days, then 125 mg once daily for 3 months to normalise serum vitamin C. After ascorbic acid treatment was completed, the patient started a complete multivitamin and made efforts to eat fruits and vegetables rich in vitamin C. His serum ascorbic acid concentrations normalised to 52 µmol/L 3 months after receiving supplementation.

Role of vitamin C as an adjuvant therapy to different iron chelators in young ß-thalassemia major patients: efficacy and safety in relation to tissue iron overload.

BACKGROUND: Vitamin C, as antioxidant, increases the efficacy of deferoxamine (DFO). AIM: To investigate the effects of vitamin C as an adjuvant therapy to the three used iron chelators in moderately iron-overloaded young vitamin C-deficient patients with ß-thalassemia major (ß-TM) in relation to tissue iron overload. METHODS: This randomized prospective trial that included 180 ß-TM vitamin C-deficient patients were equally divided into three groups (n = 60) and received DFO, deferiprone (DFP), and deferasirox (DFX). Patients in each group were further randomized either to receive vitamin C supplementation (100 mg daily) or not (n = 30). All patients received vitamin C (group A) or no vitamin C (group B) were followed up for 1 yr with assessment of transfusion index, hemoglobin, iron profile, liver iron concentration (LIC) and cardiac magnetic resonance imaging (MRI) T2*. RESULTS: Baseline vitamin C was negatively correlated with transfusion index, serum ferritin (SF), and LIC. After vitamin C therapy, transfusion index, serum iron, SF, transferrin saturation (Tsat), and LIC were significantly decreased in group A patients, while hemoglobin and cardiac MRI T2* were elevated compared with baseline levels or those in group B without vitamin C. The same improvement was found among DFO-treated patients post-vitamin C compared with baseline data. DFO-treated patients had the highest hemoglobin with the lowest iron, SF, and Tsat compared with DFP or DFX subgroups. CONCLUSIONS: Vitamin C as an adjuvant therapy possibly potentiates the efficacy of DFO more than DFP and DFX in reducing iron burden in the moderately iron-overloaded vitamin C-deficient patients with ß-TM, with no adverse events.

The lower vitamin C plasma concentrations in elderly men compared with elderly women can partly be attributed to a volumetric dilution effect due to differences in fat-free mass.

Women show higher vitamin C plasma concentrations than men, but the reasons for this observation still require elucidation. The objective of the present study was to investigate whether sex differences in vitamin C plasma concentrations are present in elderly subjects and whether these differences are due to sex-specific lifestyles, total antioxidant status (TAOS) and/or body composition. Fasting plasma concentrations of vitamin C were assessed by photometric detection in a cross-sectional study of 181 women and eighty-nine men aged 62-92 years. Body composition was determined by bioelectrical impedance analysis. Vitamin C intake was assessed with a 3 d estimated dietary record. Stepwise multiple regression analyses were performed to investigate whether sex is an independent predictor of vitamin C plasma concentrations by controlling for age, vitamin C intake, lifestyle factors, TAOS and body composition. Women showed higher vitamin C plasma concentrations than men (76 v. 62 µmol/l, P< 0·0001). In the multiple regression analysis, male sex was a negative predictor of vitamin C plasma concentrations (ß = -0·214), as long as absolute fat-free mass (FFM) was not considered as a confounder. When absolute FFM was included, sex was no longer a predictor of vitamin C plasma concentrations, whereas absolute FFM (ß = -0·216), physical activity level (ß = 0·165), intake of vitamin C supplements (ß = 0·164), age (ß = 0·147) and smoking (ß = -0·125) affected vitamin C plasma concentrations. The results indicate that a higher absolute FFM, and thus a higher distribution volume of vitamin C, contributes to lower vitamin C plasma concentrations in men than women.

Several 'problem nutrients' are identified in complementary feeding of Guatemalan infants with continued breastfeeding using the concept of 'critical nutrient density'.

BACKGROUND/OBJECTIVES: The World Health Organization (WHO) recommends nutritionally adequate complementary feeding (CF) through the introduction of indigenous foodstuffs and local foods while breastfeeding for at least 2 years. To determine the adequacy of the contribution of CF to the diets of Guatemalan infants at the 7th-12th month of life receiving high-intensity continued breastfeeding. SUBJECTS/METHODS: Critical nutrient densities for CF were modelled using age- and sex-specific energy and protein requirements assuming children to be at the 50th weight percentile of local peers and 15th weight percentiles of the 2006 WHO standards. Nutrient requirements for the total diet were determined using the recommended nutrient intakes. Breast milk was assumed to provide 75% of total energy at the 7th-9th month and 50% at the 10th-12th month. Gaps between computed critical nutrient densities and the CF consumption of 128 Guatemalan infants based on data collected by means of three nonconsecutive 24-h quantitative intake recalls were examined. Locally consumed foods with nutrient densities above the modelled critical densities were identified. RESULTS: Observed non-breast milk complementation would result in total diets providing inadequate nutrient density for vitamin A, niacin and vitamin C in some age groups. Major gaps for calcium, iron and zinc were ubiquitous across all groups. Few foods commonly consumed among Guatemalan infants had adequate densities of 'problem nutrients'. CONCLUSIONS: The critical nutrient density concept is useful to evaluate the nutrient adequacy of the infant's diet. Fortified foods are essential sources of the main 'problem nutrients', namely calcium, iron and zinc, given that natural sources are scarce.

Análise da vitamina C sérica e ingerida e estresse oxidativo em crianças e adolescentes infectados pelo vírus da imunodeficiência humana / Analysis of serum and supplemented vitamin C and oxidative stress in HIV-infected children and adolescents

OBJETIVOS: Verificar adequação do consumo de vitamina C em crianças e adolescentes infectados pelo vírus da imunodeficiência humana (HIV), avaliar níveis séricos da vitamina e indicadores de estresse oxidativo, comparar ao grupo não infectado, correlacionar a vitamina sérica ao estresse oxidativo e associá-los segundo os valores de referência. MÉTODOS: Estudo seccional transversal comparativo. Dois grupos com 27 crianças e adolescentes cada, de 3 a 19 anos, sendo G1 infectados pelo HIV por transmissão vertical atendidos em ambulatório regional e G2 indivíduos convidados sem histórico de infecção pelo HIV. Foram pareados por sexo, idade e condição socioeconômica. Avaliou-se: antropometria (índice de massa corporal para idade), ingestão e consumo do micronutriente, análise sérica da vitamina C, proteína C reativa e albumina. RESULTADOS: Idade média encontrada de 12 anos, prevalência do sexo feminino (17 - 63%) e da classe econômica C (27 - 50%). Diagnóstico nutricional prevalente foi eutrofia em 20 (74,1%) em G1 e 21 (77,8%) em G2. O consumo de vitamina C foi significativamente maior em G1 (p = 0,006; t = 2,987) pelo método recordatório 24 horas. Houve diferença significativa da dosagem sérica de vitamina C, sendo menor em G1 (p = 0,000; t = -7,309). Em relação ao estresse oxidativo, os valores da proteína C reativa em G1 foram significativamente maiores (p = 0,007; t = 2,958). Não houve relação entre deficiência da vitamina, proteína C reativa e albumina. CONCLUSÃO: Os resultados encontrados mostram que indivíduos infectados pelo HIV apresentam baixos valores da vitamina C, não relacionados à alimentação, uma vez que o consumo desse micronutriente foi superior ao grupo comparativo, que não apresentou essa depleção. Existem peculiaridades nos indivíduos infectados que aumentam o estresse oxidativo, evidenciado pelo aumento da proteína C reativa.

OBJECTIVES: To assess adequacy of vitamin C intake in HIV-infected children and adolescents; to evaluate serum levels of vitamin C and indicators of oxidative stress; to compare with the uninfected group; to correlate serum vitamin C with oxidative stress and associate them according to the reference values. METHODS: Comparative cross-sectional study. Two groups of 27 children and adolescents each, aged between 3 to 19 years. Group 1 (G1) comprised individuals vertically infected with HIV seen at a regional outpatient clinic. Group 2 (G2) comprised invited individuals without history of HIV infection. The groups were matched for age, sex, and socioeconomic status. The following variables were analyzed: body mass index for age; micronutrient intake and consumption; and serum vitamin C, C-reactive protein (CRP), and albumin. RESULTS: The mean age was 12 years old. Most subjects were female (17, 63%), and there was prevalence of the economic class C (27, 50%). The most prevalent nutritional status was normal weight in 20 individuals (74.1%) in G1 and 21 (77.8%) in G2. The intake of vitamin C was significantly higher in G1 (p = 0.006; t = 2.987) according to the 24-hour dietary recall method. There were significant differences in serum vitamin C concentration between the groups, with a lower level in G1 (p = 0.000; t = -7.309). In relation to oxidative stress, values of CRP in G1 were significantly higher (p = 0.007; t = 2.958). There was no association between deficiency of vitamin, CRP, and albumin. CONCLUSION: Our findings show that HIV-infected individuals have low levels of vitamin C; however, this deficiency is not related to eating habits, since the intake of this nutrient was higher in this group than in the control group. HIV-infected individuals have specific characteristics that increase their oxidative stress, which is evidenced by increased CRP.

Analysis of serum and supplemented vitamin C and oxidative stress in HIV-infected children and adolescents.

OBJECTIVES: To assess adequacy of vitamin C intake in HIV-infected children and adolescents; to evaluate serum levels of vitamin C and indicators of oxidative stress; to compare with the uninfected group; to correlate serum vitamin C with oxidative stress and associate them according to the reference values. METHODS: Comparative cross-sectional study. Two groups of 27 children and adolescents each, aged between 3 to 19 years. Group 1 (G1) comprised individuals vertically infected with HIV seen at a regional outpatient clinic. Group 2 (G2) comprised invited individuals without history of HIV infection. The groups were matched for age, sex, and socioeconomic status. The following variables were analyzed: body mass index for age; micronutrient intake and consumption; and serum vitamin C, C-reactive protein (CRP), and albumin. RESULTS: The mean age was 12 years old. Most subjects were female (17, 63%), and there was prevalence of the economic class C (27, 50%). The most prevalent nutritional status was normal weight in 20 individuals (74.1%) in G1 and 21 (77.8%) in G2. The intake of vitamin C was significantly higher in G1 (p = 0.006; t = 2.987) according to the 24-hour dietary recall method. There were significant differences in serum vitamin C concentration between the groups, with a lower level in G1 (p = 0.000; t = -7.309). In relation to oxidative stress, values of CRP in G1 were significantly higher (p = 0.007; t = 2.958). There was no association between deficiency of vitamin, CRP, and albumin. CONCLUSION: Our findings show that HIV-infected individuals have low levels of vitamin C; however, this deficiency is not related to eating habits, since the intake of this nutrient was higher in this group than in the control group. HIV-infected individuals have specific characteristics that increase their oxidative stress, which is evidenced by increased CRP.

Vitamin C distribution and retention in the mouse brain.

Vitamin C (VC) is a crucial antioxidant in the brain. To assess whether different brain regions vary in their sensitivity to oxidative stress induced by VC depletion, we used the gulonolactone oxidase (gulo) knockout mouse. This mouse, like humans, cannot synthesize VC and thus its tissue VC levels can be varied by dietary VC intake. Gulo knockout mice were fed drinking water containing standard (0.33g/L), low (0.033g/L) or zero (0g/L) VC supplementation levels. After 4weeks, mice were sacrificed and different brain regions removed for assay of VC and malondialdehyde, a marker of lipid peroxidation. Compared to age-matched wild-type controls, the cerebellum, olfactory bulbs and frontal cortex had the highest VC content, whereas the pons and spinal chord had the lowest. However, in mice that did not receive VC, area differences were no longer significant as all values trended towards zero. Malondialdehyde increased in the cortex as VC supplementation was decreased. The same changes were not observed in the cerebellum or pons, suggesting that cortex is more susceptible to oxidative damage from low VC. These results suggest enhanced susceptibility of the cortex to oxidative stress induced by low VC compared to other brain regions.

Malnutrition in morbidly obese patients: fact or fiction?

Reports of nutritional deficiencies after Bariatric surgery have lead investigators to inquire about the preoperative nutritional status of morbidly obese patients. Interestingly, numerous reports demonstrated a pattern of low levels of various micronutrients among overweight and obese patients, even in comparison with normal weight population. In this article we reviewed the literature for micronutrient deficiencies in obese patients prior to weight reduction surgery.

Vitamin C deficiency and secondary hyperparathyroidism in chronic haemodialysis patients.

BACKGROUND: Maintenance haemodialysis patients often suffer from secondary hyperparathyroidism and serum parathyroid hormone levels may be influenced by nutritional variables. METHODS: We examined serum bio-intact parathyroid hormone (BiPTH) and plasma vitamin C in 117 chronic haemodialysis patients. Plasma vitamin C was measured by high-performance liquid chromatography with electrochemical detection, on samples collected before start of the dialysis treatment. RESULTS: Plasma vitamin C showed a significant positively skewed distribution, ranging from <2 microM to >300 microM. We found 15% (n = 17) of the patients with severe vitamin C deficiency (<10 microM), 66% (n = 77) in the range 10-80 microM, and 19% (n = 23) with plasma vitamin C >80 microM, the upper limit of normal for non-renal disease population. High plasma vitamin C was associated with lower plasma BiPTH (P = 0.005, one-way analysis of variance), and this association persisted after stepwise multiple regression for other factors known to influence PTH. Low vitamin C levels were also associated with increased serum alkaline phosphatase, a further indicator of the impact of vitamin C status on bone metabolism. Patients who reported dietary vitamin C intake of >or=100 mg/day had lower BiPTH (P = 0.015), consistent with findings from plasma measurements of vitamin C. This novel observation of the interaction between PTH and vitamin C may result from effects of vitamin C on cAMP-linked signalling pathways in bone and parathyroid gland. CONCLUSIONS: This finding does not yet warrant therapeutic intervention with supplemental vitamin C to remedy secondary hyperparathyroidism. However, further research may indicate a key interaction between vitamin C and the parathyroid hormone linked signalling pathways, and may uncover mechanisms of therapeutic importance.

High prevalence of ascorbate deficiency in an Australian peritoneal dialysis population.

BACKGROUND: An adequate total body pool of ascorbate is essential for optimum health in humans. Requirements for ascorbate are increased in peritoneal dialysis (PD) patients most likely due to a combination of poor nutrition and increased dialysate losses. METHODS: We measured serum ascorbate levels in 45 clinically stable PD patients to assess the prevalence of ascorbate insufficiency (level between 2 and 4 mg/L) and deficiency (level <2 mg/L). We also assessed the efficacy of subsequent supplementation and patients' adherence to the prescribed supplementation. All patients were advised on commencement of dialysis to take a multivitamin tablet containing 100-120 mg ascorbate. RESULTS: Eighteen (41%) PD patients were regularly taking ascorbate-containing multivitamins, while 27 (59%) patients did not take ascorbate supplements. Serum ascorbate levels ranged from <0.2 to 41 mg/L, with wide variations in serum ascorbate at any given intake level. Ascorbate deficiency was present in 1/3 of the current PD population (44% of patients not taking supplements and in 16% of those on supplements), although none of the patients demonstrated clinical manifestations of scurvy. Targeted supplementation of ascorbate insufficient patients increased the median serum ascorbate level from 1.7 mg/L (IQR 1.2-2.2) to 22.5 mg/L (IQR 16.7-32.9). CONCLUSION: Our results show that, in PD patients, ascorbate deficiency is common and can readily be identified with serum ascorbate measurements. Oral supplements in the form of inexpensive multivitamin preparations restore adequate serum ascorbate levels in the majority of these patients. We therefore suggest measurement of ascorbate levels in all PD patients at the commencement of dialysis with a target level in the normal range (4-14 mg/L).