The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Julie A. Ross - One of the best experts on this subject based on the ideXlab platform.
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Periconceptional maternal Vitamin Supplementation and childhood leukaemia : an uncertainty analysis. Commentary
Journal of Epidemiology and Community Health, 2009Co-Authors: Matthew P. Fox, Anne M. Jurek, George Maldonado, Logan G. Spector, Julie A. RossAbstract:Background: Recent studies in childhood cancer suggest that maternal Vitamin Supplementation may reduce the risk of leukaemia, neuroblastoma and certain types of childhood brain tumours. For example, a previous study found a significantly reduced risk of acute lymphoblastic leukaemia (ALL) but not acute myeloid leukaemia (AML) in children with Down syndrome whose mothers reported any Vitamin supplement use prior to knowledge of pregnancy (ALL OR adjusted for confounders 0.51, 95% confidence limits (CL): 0.30, 0.89; AML OR adjusted for confounders 0.92, 95% CL 0.48, 1.76). Recall of exposures, including maternal Vitamin supplement use, however, may be difficult and subject to error. Epidemiologists are encouraged to quantitatively adjust for systematic error in study results, but often do not. Methods: The impact that misclassification of maternal Vitamin supplement use may have had on the observed ORs in this study was quantified. Uncertainty analysis was used to calculate ORs adjusted for inaccurate reporting of Vitamin supplement use under assumed probability distributions for exposure misclassification parameters. Results: Given our assumptions, adjustment for exposure misclassification yielded ORs that were predominantly more protective for ALL than the crude OR. Conclusions: Uncertainty analysis can give important insights into the magnitude and direction of error in study results due to exposure misclassification.
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Periconceptional maternal Vitamin Supplementation and childhood leukaemia: an uncertainty analysis
Journal of epidemiology and community health, 2008Co-Authors: Anne M. Jurek, George Maldonado, Logan G. Spector, Julie A. RossAbstract:Background: Recent studies in childhood cancer suggest that maternal Vitamin Supplementation may reduce the risk of leukaemia, neuroblastoma and certain types of childhood brain tumours. For example, a previous study found a significantly reduced risk of acute lymphoblastic leukaemia (ALL) but not acute myeloid leukaemia (AML) in children with Down syndrome whose mothers reported any Vitamin supplement use prior to knowledge of pregnancy (ALL OR adjusted for confounders 0.51, 95% confidence limits (CL): 0.30, 0.89; AML OR adjusted for confounders 0.92, 95% CL 0.48, 1.76). Recall of exposures, including maternal Vitamin supplement use, however, may be difficult and subject to error. Epidemiologists are encouraged to quantitatively adjust for systematic error in study results, but often do not. Methods: The impact that misclassification of maternal Vitamin supplement use may have had on the observed ORs in this study was quantified. Uncertainty analysis was used to calculate ORs adjusted for inaccurate reporting of Vitamin supplement use under assumed probability distributions for exposure misclassification parameters. Results: Given our assumptions, adjustment for exposure misclassification yielded ORs that were predominantly more protective for ALL than the crude OR. Conclusions: Uncertainty analysis can give important insights into the magnitude and direction of error in study results due to exposure misclassification.
Arshag D. Mooradian - One of the best experts on this subject based on the ideXlab platform.
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Vitamin Supplementation Therapy in the Elderly
Drugs & Aging, 1997Co-Authors: Jerome E. Thurman, Arshag D. MooradianAbstract:Vitamin Supplementation in large dosages is increasingly common in the older population. Often, such Supplementation is used in an attempt to improve an individual’s health status. There have been claims that the effects of Vitamins halt the normal aging process or prevent and cure disease. However, several recent studies have failed to demonstrate the efficacy of Vitamin Supplementation in preventing several types of cancer. In moderate dosages, Supplementation with Vitamin E (tocopherols) shows promise as a lipid antioxidant, and may reduce the risk of coronary heart disease. However, before Vitamin E becomes an accepted medical therapy, further long term studies must be undertaken to examine the safety and efficacy of such therapy. An adequate intake of Vitamins should be ensured by adherence to a well balanced diet. However, the elderly are prone to circumstances that may prevent them from eating a balanced diet. In addition, there are several age-related medical conditions that may predispose individuals to dietary and Vitamin deficiencies. To prevent Vitamin deficiency diseases and their associated morbidity, modest Vitamin Supplementation may be necessary. However, Supplementation should be reserved for individuals with documented deficiency or who are at risk of developing such deficiencies, especially those who are homebound or institutionalised. Vitamins taken in large dosages should be considered as drugs. These medicines, which are obtainable over-the-counter, should be carefully regulated to prevent toxicity.
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Vitamin Supplementation Therapy in the Elderly
Drugs & aging, 1997Co-Authors: Jerome E. Thurman, Arshag D. MooradianAbstract:Vitamin Supplementation in large dosages is increasingly common in the older population. Often, such Supplementation is used in an attempt to improve an individual’s health status. There have been claims that the effects of Vitamins halt the normal aging process or prevent and cure disease.
Martin Den Heijer - One of the best experts on this subject based on the ideXlab platform.
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The effect of homocysteine reduction by B-Vitamin Supplementation on inflammatory markers.
Clinical chemistry and laboratory medicine, 2007Co-Authors: Anita C.t.m. Peeters, Henk J Blom, Benien E. Van Aken, Pieter H. Reitsma, Martin Den HeijerAbstract:BACKGROUND: Hyperhomocysteinemia has been associated with vascular disease in many epidemiological studies. However, the pathophysiology is unclear. It is postulated that increased levels of homocysteine induce an inflammatory response in endothelial cells, mediated by pro-inflammatory cytokines and chemokines. The aim of this study was to investigate whether plasma concentrations of interleukin-6, interleukin-8, C-reactive protein, and monocyte chemoattractant protein-1 are increased with higher plasma homocysteine concentrations and whether decreasing homocysteine by Vitamin Supplementation decreases the concentration of these markers. METHODS: Plasma homocysteine, interleukin-6, interleukin-8, C-reactive protein, and monocyte chemoattractant protein-1 concentrations were measured in 230 volunteers before and after 8 weeks of multiVitamin Supplementation (folic acid, B(6), and B(12)). RESULTS: At baseline, plasma homocysteine concentration was weakly associated with interleukin-8, but not with interleukin-6, C-reactive protein or monocyte chemoattractant protein-1. Vitamin Supplementation resulted in a significant decrease in homocysteine concentration, but no effect on interleukin-6, interleukin-8, C-reactive protein or monocyte chemoattractant protein-1 was observed. CONCLUSIONS: At baseline homocysteine was only weakly correlated with interleukin-8, but not with interleukin-6, C-reactive protein or monocyte chemoattractant protein-1. Vitamin Supplementation affected homocysteine concentration, but not cytokine levels. The hypothesis that hyperhomocysteinemia increases arteriosclerotic or thrombotic risk through vascular inflammation was not supported by this study.
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The effect of homocysteine reduction by B-Vitamin Supplementation on markers of endothelial dysfunction.
Thrombosis and Haemostasis, 2004Co-Authors: Anita C.t.m. Peeters, Els F Van Der Molen, Henk J Blom, Martin Den HeijerAbstract:Hyperhomocysteinemia is a risk factor for arterial vascular disease and venous thrombosis. The pathophysiology of this relation is unclear, but several studies suggest that hyperhomocysteinemia impairs endothelial function. We examined the effect of homocysteine lowering by B-Vitamin Supplementation on tissue plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI) and von Willebrand factor (vWf) - markers of endothelial dysfunction - in hyperhomocysteinemic and normohomocysteinemic volunteers. A total of 123 healthy volunteers were randomized to placebo or B-Vitamins (5 mg folic acid, 0.4 mg hydroxycobalamin and 50 mg pyridoxine) daily for 8 weeks. Before and after the intervention period, blood samples were taken for measurements of homocysteine, tPA, PAI and vWf.There was no evident association between homocysteine concentration and concentrations of markers of endothelial dysfunction at baseline.The mean reduction of homocysteine concentration was 31% (95%CI 22.7 to 39.1) in the B-Vitamin group compared to 3% reduction in the placebo group. Concentrations of tPA, PAI and vWf did not change after Supplementation of B-Vitamins. In conclusion, the results of our study show that homocysteine reduction by B-Vitamin Supplementation has no effect on markers of endothelial dysfunction in healthy volunteers.
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Effect of homocysteine reduction by B-Vitamin Supplementation on markers of clotting activation.
Thrombosis and haemostasis, 2002Co-Authors: Mariska Klerk, Henk J Blom, G. M. J. Bos, Petra Verhoef, Bert Verbruggen, Evert G. Schouten, Martin Den HeijerAbstract:Homocysteine may have an effect on risk of cardiovascular disease by stimulating procoagulant factors and/or impair anti-coagulant mechanisms or fibrinolysis. However, data in humans of such effects are sparse. In this intervention study, we examined the effect of homocysteine lowering by B-Vitamin Supplementation on prothrombin fragments 1 and 2 (F1 + 2), thrombin-antithrombin complex (TAT), and fibrin degradation products (D-dimer). The study comprised 118 healthy volunteers, 50 with homocysteine > 16 mumol/L and 68 with homocysteine < or = 16 mumol/L, who were randomized to placebo or high-dose B-Vitamin supplements (5 mg folic acid, 0.4 mg hydroxycobalamin, and 50 mg pyridoxine) daily for 8 weeks. Although homocysteine concentrations were 27.7% (p < 0.0001) reduced in the B-Vitamin group compared to the placebo group, no effect on F1 + 2 and TAT concentrations was observed. A 10.4% reduction was observed for D-dimer (p = 0.08). In conclusion, it appears that in healthy subjects homocysteine reduction by B-Vitamin Supplementation has a modest beneficial effect on clotting activation.
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Vitamin Supplementation reduces blood homocysteine levels a controlled trial in patients with venous thrombosis and healthy volunteers
Arteriosclerosis Thrombosis and Vascular Biology, 1998Co-Authors: Martin Den Heijer, Anja P Spaans, Hans L. Haak, Pierre W. Wijermans, Ingeborg A Brouwer, Henk J Blom, Christopher M. Thomas, Frits R. Rosendaal, W B J GerritsAbstract:Abstract —Hyperhomocysteinemia is a risk factor for atherosclerosis and thrombosis and is inversely related to plasma folate and Vitamin B12 levels. We assessed the effects of Vitamin Supplementation on plasma homocysteine levels in 89 patients with a history of recurrent venous thrombosis and 227 healthy volunteers. Patients and hyperhomocysteinemic (homocysteine level >16 μmol/L) volunteers were randomized to placebo or high-dose multiVitamin supplements containing 5 mg folic acid, 0.4 mg hydroxycobalamin, and 50 mg pyridoxine. A subgroup of volunteers without hyperhomocysteinemia was also randomized into three additional regimens of 5 mg folic acid, 0.5 mg folic acid, or 0.4 mg hydroxycobalamin. Before and after the intervention period, blood samples were taken for measurements of homocysteine, folate, cobalamin, and pyridoxal-5′-phosphate levels. Supplementation with high-dose multiVitamin preparations normalized plasma homocysteine levels (≤16 μmol/L) in 26 of 30 individuals compared with 7 of 30 in the placebo group. Also in normohomocysteinemic subjects, multiVitamin Supplementation strongly reduced homocysteine levels (median reduction, 30%; range, −22% to 55%). In this subgroup the effect of folic acid alone was similar to that of multiVitamin: median reduction, 26%; range, −2% to 52% for 5 mg folic acid and 25%; range, −54% to 40% for 0.5 mg folic acid. Cobalamin Supplementation had only a slight effect on homocysteine lowering (median reduction, 10%; range, −21% to 41%). Our study shows that combined Vitamin Supplementation reduces homocysteine levels effectively in patients with venous thrombosis and in healthy volunteers, either with or without hyperhomocysteinemia. Even Supplementation with 0.5 mg of folic acid led to a substantial reduction of blood homocysteine levels.
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Will a decrease of blood homocysteine by Vitamin Supplementation reduce the risk for vascular disease
Fibrinolysis, 1994Co-Authors: Martin Den Heijer, W B J Gerrits, G. M. J. Bos, Henk J BlomAbstract:Abstract Several studies have demonstrated a relationship between blood homocysteine and arterial vascular disease. Furthermore blood homocysteine can he lowered by means of Vitamin Supplementation. However in studies on the relation between blood homocysteine and vascular disease, no clear difference in Vitamin level between cases and controls could be observed. We discuss this finding and argue that this may indicate an objection to beneficial effects of Vitamin Supplementation with respect to vascular disease. Also a hypothetical explanation for this phenomenon is discussed.
A. Vinet - One of the best experts on this subject based on the ideXlab platform.
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Effect of antioxidant Vitamin Supplementation on endothelial function in type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials
Obesity Reviews, 2014Co-Authors: D. Montero, G. Walther, C. D. A. Stehouwer, A. J. H. M. Houben, J. A. Beckman, A. VinetAbstract:Controversy exists among trials assessing whether prolonged antioxidant Vitamin Supplementation improves endothelial function in type 2 diabetes mellitus (T2DM) subjects. The aim of this study was to systematically review and quantify the effect of antioxidant Vitamin Supplementation on endothelial function in T2DM subjects. MEDLINE, Cochrane, Scopus and Web of Science were searched up to February 2013 for randomized controlled trials assessing the effect of antioxidant Vitamin E and/or C Supplementation on endothelial function in T2DM subjects. Ten randomized controlled trials comparing antioxidant Vitamin-supplemented and control groups (overall n = 296) met the inclusion criteria. Post-intervention standardized mean difference (SMD) in endothelial function did not reach statistical significance between groups (0.35; 95% confidence interval = −0.17, 0.88; P = 0.18). In subgroup analysis, post-intervention endothelial function was significantly improved by antioxidant Vitamin Supplementation in T2DM subgroups with body mass index (BMI) ≤ 29.45 kg m−2 (SMD = 1.02; P 29.45 kg m−2 (SMD = −0.07; P = 0.70). In meta-regression, an inverse association was found between BMI and post-intervention SMD in endothelial function (B = −0.024, P = 0.02). Prolonged antioxidant Vitamin E and/or C Supplementation could be effective to improve endothelial function in non-obese T2DM subjects.
Jerome E. Thurman - One of the best experts on this subject based on the ideXlab platform.
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Vitamin Supplementation Therapy in the Elderly
Drugs & Aging, 1997Co-Authors: Jerome E. Thurman, Arshag D. MooradianAbstract:Vitamin Supplementation in large dosages is increasingly common in the older population. Often, such Supplementation is used in an attempt to improve an individual’s health status. There have been claims that the effects of Vitamins halt the normal aging process or prevent and cure disease. However, several recent studies have failed to demonstrate the efficacy of Vitamin Supplementation in preventing several types of cancer. In moderate dosages, Supplementation with Vitamin E (tocopherols) shows promise as a lipid antioxidant, and may reduce the risk of coronary heart disease. However, before Vitamin E becomes an accepted medical therapy, further long term studies must be undertaken to examine the safety and efficacy of such therapy. An adequate intake of Vitamins should be ensured by adherence to a well balanced diet. However, the elderly are prone to circumstances that may prevent them from eating a balanced diet. In addition, there are several age-related medical conditions that may predispose individuals to dietary and Vitamin deficiencies. To prevent Vitamin deficiency diseases and their associated morbidity, modest Vitamin Supplementation may be necessary. However, Supplementation should be reserved for individuals with documented deficiency or who are at risk of developing such deficiencies, especially those who are homebound or institutionalised. Vitamins taken in large dosages should be considered as drugs. These medicines, which are obtainable over-the-counter, should be carefully regulated to prevent toxicity.
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Vitamin Supplementation Therapy in the Elderly
Drugs & aging, 1997Co-Authors: Jerome E. Thurman, Arshag D. MooradianAbstract:Vitamin Supplementation in large dosages is increasingly common in the older population. Often, such Supplementation is used in an attempt to improve an individual’s health status. There have been claims that the effects of Vitamins halt the normal aging process or prevent and cure disease.
