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At least 775 records · Page 43Linked to original sources
PubMed2006

The impact of over-the-counter vitamin D supplements on vitamin D and parathyroid hormone levels in chronic kidney disease.

BACKGROUND: In addition to the known disturbances in mineral metabolism and vitamin D activation, the majority of patients with chronic kidney disease (CKD) do not have sufficient vitamin D stores. The impact of supplementation with low-dose, nonactive forms of vitamin D (calciferol) on parathyroid hormone (PTH) levels in this population is unknown, however. METHODS: A cross-sectional evaluation of vitamin D levels, intact parathyroid hormone (iPTH) and other laboratory results in 108 stage 3 and stage 4 CKD patients according to their intake of over-the-counter vitamin D. RESULTS: 37 patients took 400 IU of vitamin D daily with supplemental calcium and 71 did not. Compared to subjects who did not take it, patients who were on the supplement had higher 25(OH)D (31 +/- 15 vs. 17 +/- 9) ng/ml, higher 1,25(OH)D (21 +/- 12 vs. 16 +/- 9) pg/ml, lower iPTH (75 +/- 48 vs. 144 +/- 100) pg/ml and were more likely to meet K-DOQI PTH guidelines. However, these subjects were more likely to have oversuppressed iPTH values. The groups did not differ with regard to demographics, glomerular filtration rate and calcium and phosphorus levels. CONCLUSIONS: Vitamin D supplements may be a valuable tool in the prevention and treatment of hyperparathyroidism in patients with stages 3 and 4 CKD. CKD patients who have oversuppressed PTH need to be asked about their vitamin supplement intake.

Aged↗
PubMed1999

Effects of vitamin E and vitamin C supplementation on plasma lipid peroxidation and on oxidation of apolipoprotein B-containing lipoproteins in experimental hyperthyroidism.

Increasing numbers of experimental and epidemiological studies suggest the involvement of free radicals in the pathogenesis of various disease entities. Similarly, oxidative processes have been implicated as playing roles in the genesis of hyperthyroidism-induced damage. In this study, we investigated the effects of vitamin E and vitamin C on plasma lipid peroxidation and the susceptibility of apolipoprotein B (apo B)-containing lipoproteins to oxidation in experimental hyperthyroidism. The study animals were initially divided into a control group (Group C) and a hyperthyroid group. The latter was further re-grouped later according to their vitamin supplementation status: Hyperthyroid group without vitamin supplementation (Group H), hyperthyroid group with vitamin E supplementation (Group H+E) and hyperthyroid group with vitamin C supplementation (Group H+C). Malondialdehyde (MDA) level was measured as an indicator of plasma lipid peroxidation. The apo B-containing lipoproteins were separated by precipitation and incubated with copper sulphate. The MDA levels of this non-HDL fraction were measured prior to and after 1, 2 and 3 hours of incubation. Plasma MDA levels showed no significant differences among groups. Whereas MDA levels measured in non-HDL fraction were significantly higher in Group H than Group C. Group H+E and Group H+C had significantly lower MDA levels than Group H in all these measurements. This finding strongly indicates an increased susceptibility of apo B-containing lipoproteins to oxidation in hyperthyroidism, and that vitamin E as well as vitamin C supplementation protect these lipoproteins from copper-induced oxidation.

Animals↗
PubMed2000

The effects of vitamin C and vitamin E on oxidative DNA damage: results from a randomized controlled trial.

Oxidative DNA damage may be important in mutagenic, carcinogenic, and aging processes. Although it is plausible that antioxidant vitamins may reduce oxidative DNA damage, evidence from human studies has been sparse and inconsistent. We determined the short-term effects of vitamin C (500 mg/day) and vitamin E (400 IU d-alpha-tocopheryl acetate/day) supplements on oxidative DNA damage in a double-masked, placebo-controlled, 2x2 factorial trial in 184 nonsmoking adults. Mean duration of supplementation was 2 months. Oxidative DNA damage was measured by 24-h urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG). At baseline, urinary 8-OHdG (mean +/- SE; ng/mg creatinine) was associated with race (15.6 +/- 0.8 in African Americans versus 20.3 +/- 1.2 in Caucasians, P = 0.001), prior antioxidant supplement use (18.6 +/- 0.8 in users versus 13.8 +/- 1.5 in non-users, P = 0.007), and regular exercise (19.2 +/- 1.1 in exercisers versus 16.6 +/- 0.9 in non-exercisers, P = 0.04). Fruit and vegetable intake and serum ascorbic acid were inversely associated with urinary 8-OHdG (P-trend = 0.02 and 0.016, respectively). The benefits of fruit and vegetable intake became evident with the consumption being at least three servings/day. At the end of supplementation, change from baseline in urinary 8-OHdG (mean +/- SE; ng/mg creatinine) was -0.6 +/- 1.4 (P = 0.61), 0.6 +/- 1.1 (P = 0.59), 0.5 +/- 1.0 (P = 0.61), and 1.6 +/- 1.4 (P = 0.27) in the placebo, vitamin C alone, vitamin E alone, and combined vitamins C and E groups, respectively. In overall and subgroup analyses, there was no significant main effect or interaction effect of the supplements on urinary 8-OHdG. In conclusion, supplementation of diet with vitamin C (500 mg/day) and vitamin E (400 IU d-alpha-tocopheryl acetate/day) had no significant main effect or interaction effect on oxidative DNA damage as measured by urinary 8-OHdG in nonsmoking adults. However, several aspects of a healthy lifestyle were associated with lower oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Vitamin C and vitamin E supplement use and colorectal cancer mortality in a large American Cancer Society cohort.

Some recent epidemiological studies have suggested that use of vitamin C or vitamin E supplements, both of which are important antioxidants, may substantially reduce the risk of colon or colorectal cancer. We examined the association between colorectal cancer mortality and use of individual vitamin C and E supplements in the American Cancer Society's Cancer Prevention Study II cohort. We used proportional hazards modeling to estimate rate ratios among 711,891 men and women in the United States who completed a self-administered questionnaire at study enrollment in 1982, had no history of cancer, and were followed for mortality through 1996. During the 14 years of follow-up, 4404 deaths from colorectal cancer occurred. After adjustment for multiple colorectal cancer risk factors, regular use of vitamin C or E supplements, even long-term use, was not associated with colorectal cancer mortality. The combined-sex rate ratios were 0.89 [95% confidence interval (CI), 0.73-1.09] for 10 or more years of vitamin C use and 1.08 (95% CI, 0.85-1.38) for 10 or more years of vitamin E use. In subgroup analyses, use of vitamin C supplements for 10 or more years was associated with decreased risk of colorectal cancer mortality before age 65 years (rate ratio = 0.48; 95% CI, 0.28-0.81) and decreased risk of rectal cancer mortality at any age (rate ratio = 0.40; 95% CI, 0.20-0.80). Our results do not support a substantial effect of vitamin C or E supplement use on overall colorectal cancer mortality.

Adult↗
PubMed2001

Vitamin D, calcium, and vitamin D receptor polymorphism in colorectal adenomas.

Experimental studies suggest that vitamin D and calcium protect against cancer by reducing proliferation and inducing differentiation. The effects of vitamin D and calcium may be mediated by the vitamin D receptor (VDR), which is encoded by the VDR gene. The present study investigated whether calcium intake and serum vitamin D, as an integrated measure of intake and endogenous production, were associated with risk of colorectal adenoma, known precursors of invasive colorectal cancer. In addition, the interrelation among vitamin D, calcium, and FokI polymorphism of the VDR gene was investigated. Persons (239) with histologically confirmed colorectal adenomas and 228 control individuals without colorectal adenomas confirmed by sigmoidoscopy were enrolled in this case control study conducted at the National Naval Medical Center, Bethesda, MD. We observed an inverse association of serum 25-OH vitamin D [25-(OH)D] with colorectal adenoma. With each 10 ng/ml increase of serum 25-(OH)D, the risk of colorectal adenoma decreased by 26% (odds ratio 0.74, 95% confidence interval 0.60-0.92). The results provided limited evidence for a weak association between calcium intake and colorectal adenoma (odds ratio 0.97, 95% confidence interval 0.93-1.01 per each 100-mg calcium intake). However, the inverse association of serum 25-(OH)D with colorectal adenoma is suggested to be stronger in subjects with calcium intake above the median (P for multiplicative interaction 0.13). The VDR FokI polymorphism was not significantly associated with colorectal adenoma and did not modify the effect of vitamin D or calcium. In conclusion, the study results suggested a protective effect for vitamin D on colorectal adenoma.

Adenoma↗
PubMed2002

Vitamin C, vitamin E, and multivitamin supplement use and stomach cancer mortality in the Cancer Prevention Study II cohort.

Supplementation with antioxidant vitamins has been associated with decreased risk of stomach cancer or regression of precancerous lesions in high-risk areas of China and Colombia. We examined the association between stomach cancer mortality and regular use (> or =15 times per month) of individual vitamin C supplements, individual vitamin E supplements, and multivitamins among 1,045,923 United States adults in the Cancer Prevention Study II (CPS-II) cohort. CPS-II participants completed a questionnaire at enrollment in 1982 and were followed for mortality through 1998. During follow-up, there were 1,725 stomach cancer deaths (1,127 in men and 598 in women). After adjustment for multiple potential stomach cancer risk factors, vitamin C use at enrollment was associated with reduced risk of stomach cancer mortality [rate ratio (RR), 0.83; 95% confidence interval (CI), 0.68-1.01]. However, this reduction in risk was observed only among participants with short duration use at enrollment (RR, 0.68; 95% CI, 0.51-0.91 for <10 years of use; RR, 1.00; 95% CI, 0.73-1.38 for > or =10 years of use). There was no association between stomach cancer mortality and regular use of vitamin E (RR, 1.02; 95% CI, 0.82-1.27) or multivitamins (RR, 0.89; 95% CI, 0.77-1.03), regardless of duration of use. Our results suggest that the use of vitamin C, vitamin E, or multivitamin supplements may not substantially reduce risk of stomach cancer mortality in North American populations in which stomach cancer rates are relatively low. Our results do not rule out effects of vitamin supplementation in areas in which stomach cancer rates are high and stomach cancer etiology may differ.

Adult↗
PubMed2003

Vitamin D analogs--drug design based on proteins involved in vitamin D signal transduction.

Vitamin D analogs have proven to be very valuable tools for the treatment of calcium-related diseases and certain hyperproliferative conditions such as renal osteodystrophy, psoriasis and cancer. In general, vitamin D analogs exploit the enzymic and receptor machinery of the 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) signal transduction pathway. Key proteins in this cascade include the vitamin D receptor (VDR), the vitamin D-binding protein (DBP) and three cytochrome P450s (CYP27A, CYP27B and CYP24) which effect the synthesis and breakdown of the natural hormone, 1alpha,25(OH)(2)D(3). Analogs have been designed which reduce or enhance the importance of each of these proteins in the signal transduction pathway. Vitamin D prodrugs require one or more steps of activation and overcome congenital or acquired blocks in the 1alpha-hydroxylation step. By far the biggest class of vitamin D analogs are the VDR agonists which directly mimic 1alpha,25(OH)(2)D(3) and trigger protein conformational changes in the receptor which lead to changes in the transcriptional machinery at vitamin D-responsive genes. Other emerging classes of molecules include the VDR antagonists and CYP24 inhibitors which target different events in the cascade. This review assesses the relative importance of each of the proteins of the vitamin D cascade, evaluates the success of these modifications in tailoring drugs in all classes for selected disease states and contemplates future directions for the field.

Animals↗
PubMed1992

Retinol (vitamin A) and riboflavin (vitamin B2) administration and metabolism in very low birth weight infants.

The combination of marginal hepatic retinol stores at delivery and the reduction of daily retinol dose due to complications with the delivery system places the VLBW infant receiving parenteral nutrition at high risk for retinol deficiency during the first month of life. This has serious health implications because retinol is essential during this period for normal growth and repair of the pulmonary tissue in VLBW infants. Enterally fed VLBW infants, on the other hand, receive relatively higher doses of retinol from vitamin-supplemented premature infant formula and fortified breast milk. Equally serious is the problem of monitoring vitamin A status in infants receiving supplemental doses of vitamin A. It seems clear that while plasma vitamin A levels are the most easily available method of monitoring vitamin A status, further studies are necessary to determine if these levels correlate with hepatic content. This is of particular concern since liver disease is common in VLBW infants and vitamin A hepatotoxicity has been described in a cohort of 41 patients receiving therapeutic doses of the vitamin. While further research of daily enteral and parenteral retinol requirements of VLBW infants should continue, formulation of a specific VLBW parenteral vitamin supplement should also be developed.

Delivery, Obstetric↗
PubMed1986

Serum concentration of vitamin D metabolites during treatment with vitamin D2 and D3 in normal premenopausal women.

Serum concentrations of vitamin D metabolites were measured in 19 healthy premenopausal women before and during treatment with 4000 IU per day of either vitamin D2 or vitamin D3 for 8 weeks. Vitamin D2 treatment increased the serum concentration of 25(OH)D2, but a corresponding decrease in 25(OH)D3 resulted in an unchanged value for total 25(OH)D. The serum concentration of the D3 dihydroxy metabolites was also significantly decreased. Vitamin D3 treatment increased the serum concentrations of 25(OH)D3 and D3 dihydroxy metabolites. The serum concentration of 1,25(OH)2D did not change in either of the treatment groups. We conclude that vitamin D2 and vitamin D3 given in the same doses in international units have a different effect on the serum concentration of vitamin D metabolites and biochemical indices of calcium metabolism.

Adult↗
PubMed1988

Multiple vitamins and vitamins with iron: accidental poisoning in children.

To insure adequate nutrition, parents and pediatricians often advocate vitamin and mineral supplementation in young children. A retrospective review of 275 pediatric cases (6 mo-6 yr) involving multiple vitamins and vitamins with iron was conducted. Six cases with co-ingestants were excluded. The product ingested was the child's own dietary supplement in 93% of the cases. Fifty-six percent were children's multiple vitamins and 44% were children's multiple vitamins with iron. Adult vitamin preparations accounted for 7% of the ingestions. The average amount of vitamin A ingested by history was 43,300 IU (1,500-225,000) while the mean ingestion of iron was 16.8 mg/kg (0.9-77.5 mg/kg). Fifty ingestions (18.2%) involved more than one child. The mean time since ingestion was 15.8 min (0-150 min). Management data showed 246 (89.5%) being treated in the home setting with dilution (83%) or syrup of ipecac induced-emesis (10%). Medical intervention including emesis, serum iron/TIBC, and oral complexation was needed in 10.5% of the cases. The mean serum iron levels were 204.6 mcg/dl (81-414 mcg/dl). No patient needed admission. This review revealed 100% of patients showed no significant toxic effects. We conclude that early recognition and prompt treatment of pediatric overdoses involving multiple vitamins with and without iron significantly reduces morbidity.

Child↗
PubMed1984

Intraventricular hemorrhage and vitamin E in the very low-birth-weight infant: evidence for efficacy of early intramuscular vitamin E administration.

To determine whether early intramuscular vitamin E supplementation influences the incidence of intraventricular hemorrhage (IVH) in infants with birth weight less than or equal to 1,500 g, data were analyzed from 134 infants enrolled on a protocol to evaluate the efficacy of intramuscular plus oral vitamin E v oral supplementation alone in the treatment of retrolental fibroplasia. All 134 infants received, via nasogastric tube, 100 mg/kg/d of vitamin E daily (dl-alpha-tocopheryl acetate in MCT [medium-chain triglyceride] oil; 150 mosM) for at least 8 weeks with the first dose administered within the first eight hours of life. Sixty-four patients received, in addition, intramuscular vitamin E on days 1, 2, 4, and 6 of life and 70 patients received placebo injections in a randomized double-blind fashion. In the first week, vitamin E plasma levels were significantly higher in the 64 patients given intramuscular vitamin E. In spite of this difference no change in the incidence of sepsis or necrotizing enterocolitis was observed. Both the incidence and severity of intraventricular hemorrhage were reduced significantly in the patients given intramuscular vitamin E as compared to the patients given placebo (P = .013 and P = .04, respectively). The data suggest that vitamin E, a natural antioxidant, may play an important role in protecting the CNS microcirculation from the effects of hypoxic/ischemic injury.

Administration, Oral↗
PubMed1994

Vitamin K status and parenteral nutrition; the effect of Intralipid on plasma vitamin K1 levels.

Parenteral nutrition may affect the patient's vitamin K status. This imposes a risk when using drugs that interfere with the vitamin K-dependent clotting factor synthesis, such as N-methyl-thiotetrazole-containing cephalosporins. Intravenous lipid emulsions based on plant oils may contain phylloquinone (vitamin K1). We estimated the vitamin K1 content of the intravenous lipid emulsion product Intralipid (20%), an emulsion based on soybean oil, and estimated the vitamin K1 status of recipient patients. The emulsion was found to contain 0.6-0.7 micrograms/ml of the vitamin. Patients supplied with the product per continuous intravenous infusion, showed a steady increase of their plasma vitamin K1 levels, 3-30-fold over 4 days of infusion. In conclusion, the study shows that fat emulsions prepared from plant oils may contain vitamin K1 in sufficient amounts to meet the daily requirement.

Clinical Protocols↗
PubMed1994

Vitamin activities in human portal, hepatic and femoral blood after vitamin ingestion.

The dynamics of intestinal absorption, blood concentration and distribution of thiamin, biotin, nicotinate, riboflavin, pantothenate, various folates (folic acid, folinic acid, pteroyltriglutamate), vitamins A, E, C, B12, and B6 were monitored in 12 patients by multiple simultaneous sampling of blood obtained by combined catheterization of portal vein, hepatic vein, and femoral artery after vitamin ingestion. All water-soluble vitamins proved elevated after vitamin ingestion principally in portal blood within 10 minutes as compared with hepatic and femoral blood. Elevated vitamin levels in portal blood--compared to hepatic and femoral blood--remained high even after 120 min. indicating that absorption from the gut was still progressing. In contrast, ingestion of the fat-soluble vitamins A and E evoked no elevated vitamin activity in portal blood. Within 10 min. after vitamin ingestion, all folates were converted into reduced and methylated 5-methyltetrahydrofolate (5-CH3THF) on passage through the gut. At this time, portal blood elevation of 5-CH3THF persisted before its elevation in hepatic or femoral blood. Presumably, the elevation was not due to the flushing of stored 5-CH5THF from tissues but rather of folate conversion to 5-CH3THF upon gut passage. The significance of these findings is discussed.

Administration, Oral↗
PubMedDate not supplied

Chronically increased vitamin intake and vitamin status of healthy men.

The effects of an 8-wk chronically increased vitamin intake on the biochemical parameters of vitamin status in 498 healthy men were estimated. A control group of 520 volunteers, given a placebo instead of vitamins, was also examined to control the changes that occur in biochemical vitamin supply parameters. Comparison of the measurements between the groups showed that plasma concentrations of folate, vitamin B12, and tocopherol; the urine concentrations of thiamine and riboflavin; and the activities of measured vitamin-related enzymes increased linearly and independently to the baseline vitamin status by the absolute value. Plasma concentrations of ascorbic acid, activity coefficients, and urinary excretion of 4-pyridoxic acid increased more in men with lower baseline values. The plasma retinol concentration did not change despite doubling the vitamin A intake.

Adolescent↗
PubMed1996

Effect of vitamin K2 on experimental calcinosis induced by vitamin D2 in rat soft tissue.

The effect of vitamin K2 on calcium (Ca) and inorganic phosphorus (P) levels in the aorta and kidney obtained from experimental calcinosis induced by vitamin D2(2.5 x 10(5) I.U./ kg b.w.) of male rats was investigated. A high dose of vitamin K2 (100 mg/kg b.w.) inhibited the increase in the aortic Ca and P or in the renal Ca and P induced by vitamin D2, and a low dose of vitamin K2 (10 mg/kg b.w.) showed the same tendency, but the degree of the efficacy was small. It may be suggested that a high dose of vitamin K2 suppressed experimental calcification of soft tissues induced by vitamin D2. Therefore, a pharmacological dose of vitamin K2 might have a usefulness for the prevention and treatment of arteriosclerosis with calcification.

Animals↗
PubMed2001

Vitamin K administration to elderly patients with osteoporosis induces no hemostatic activation, even in those with suspected vitamin K deficiency.

The administration of menaquinone-4 (MK-4), one of subclasses of vitamin K2, significantly reduces bone loss in postmenopausal osteoporotic women. However, concerns have been raised about whether vitamin K administration alters the hemostatic balance by inducing a thrombotic tendency. We investigated were whether the administration of vitamin K in the form of MK-4 induced a thrombotic tendency in 29 elderly patients with osteoporosis (5 men, 24 women; age range 78.7+/-5.1 years). Patients were administered 45 mg/day (three times a day, 30 min after each meal) of MK-4 for 12 weeks. Blood samples were obtained from the patients at 0, 4 and 12 weeks after the start of MK-4 administration. A number of hemostatic parameters remained stable under the markedly increased plasma levels of MK-4. However, in patients with suspected vitamin K deficiency, whose plasma levels of vitamin K or factor VII were low, vitamin-K-dependent clotting factors such as factor VII and prothrombin were gradually increased after administration of MK-4. No changes in the sensitive molecular markers such as TAT and F1+2, which reflect the amount of thrombin generated in the blood stream, were observed, even in those patients with suspected vitamin K deficiency. These results indicate that MK-4 can be administered safely, with regard to maintaining the hemostatic balance, to osteoporotic patients receiving no anticoagulant therapy.

Aged↗
PubMed2003

Vitamin E prevents changes in the cornea and conjunctiva due to vitamin A deficiency.

PURPOSE: To determine whether vitamin E can prevent changes in the cornea and conjunctiva due to vitamin A deficiency. METHODS: Male infant rats from normal mothers were weaned at 20 days of age and divided into three groups: in group 1, A(-), rats were fed a vitamin A-deficient diet; in group 2, A(-)E(+), rats were fed a vitamin A-deficient diet and injected intraperitoneally with 15 mg of vitamin E per week; group 3 rats were normal controls. At 13 weeks of age, the corneal and conjunctival changes were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). RESULTS: SEM showed more fine microvilli and clear cells in the most superficial epithelial layer of the cornea and conjunctiva in A(-)E(+) rats than in that of A(-) rats. Numerous secretory granules were seen in the goblet cells of the conjunctiva of A(-)E(+) rats, but in A(-) rats there was a total absence of conjunctival goblet cells. TEM showed a severely keratinized corneal surface in A(-) rats. On the other hand, the corneas of A(-)E(+) rats were almost normal in appearance. The conjunctivae of A(-) rats had superficial epithelial keratinization, scarce goblet cells, and many keratohyalin granules in the epithelium and dark cells, while in the conjunctivae of A(-)E(+) rats there were numerous secretory granules in goblet cells and some dark cells. CONCLUSION: The present study suggests that vitamin E has a protective effect against the corneal and conjunctival damage caused by vitamin A deficiency.

Animals↗
PubMed2002

Use of vitamin D(4) analogs to investigate differences in hepatic and target cell metabolism of vitamins D(2) and D(3).

In this study, we used molecules with either of the structural differences in the side chains of vitamin D(2) and vitamin D(3) to investigate which feature is responsible for the significant differences in their respective metabolism, pharmacokinetics and toxicity. We used two cell model systems-HepG2 and HPK1A-ras-to study hepatic and target cell metabolism, respectively. Studies with HepG2 revealed that the pattern of 24- and 26-hydroxylation of the side chain reported for 1alpha-hydroxyvitamin D(2) (1alpha-OH-D(2)) but not for 1alpha-OH-D(3) is also observed in both 1alpha-OH-D(4) and Delta(22)-1alpha-OH-D(3) metabolism. This suggests that the structural feature responsible for targeting the enzyme to the C24 or C26 site could be either the C24 methyl group or the 22-23 double bond. In HPK1A-ras cells, the pattern of metabolism observed for the 24-methylated derivative, 1alpha,25-(OH)(2)D(4), was the same pattern of multiple hydroxylations at C24, C26 and C28 seen for vitamin D(2) compounds without evidence of side chain cleavage observed for vitamin D(3) derivatives, suggesting that the C24 methyl group plays a major role in this difference in target cell metabolism of D(2) and D(3) compounds. Novel vitamin D(4) compounds were tested and found to be active in a variety of in vitro biological assays. We conclude that vitamin D(4) analogs and their metabolites offer valuable insights into vitamin D analog design, metabolic enzymes and maybe useful clinically.

Cholecalciferol↗