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Iron and Vitamin B1 陳慧君10-21-91 Iron  The most common deficiency of a single nutrient in both the developing and the developed world  Dietary iron.

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Presentation on theme: "Iron and Vitamin B1 陳慧君10-21-91 Iron  The most common deficiency of a single nutrient in both the developing and the developed world  Dietary iron."— Presentation transcript:


2 Iron and Vitamin B1 陳慧君10-21-91

3 Iron  The most common deficiency of a single nutrient in both the developing and the developed world  Dietary iron requirements are determined by blood loss( including menstrual blood loss) and the needs of growth in children, adolescents, and pregnant women.  Reduced body iron stores may be caused by inadequate dietary iron, excessive blood loss, or both. Introduction

4  The absorption of heme iron being much less efficiently regulated. Absorption of non-heme iron is influenced by other dietary factors.  Biochemical data are a poor indication of dietary intake for individuals without substantial additional information about other dietary components, growth requirements, and blood loss. Iron

5 Serum Ferritin  Ferritin is the principal iron storage protein.  Serum ferritin level provides the best single indicator of iron stores.  Average within-subject CV% =14.5% within-assay CV% = 4.3%  Ferritin is decreased in proportion to the frequency of phlebotomy.  Ferritin is increased in proportion to supplementation and iron overload.

6  Significant correlation between total daily iron intake and serum ferritin was not significantly observed.  Meat intake was a significant predictor of serum ferritin level( a measure of heme iron). Serum Ferritin

7 Serum Iron  Serum iron level is highly variable, and changes of more than 20% have been observed within 10 minutes among healthy subjects. an unreliable long-term measure

8 Transferrin Saturation and Total Iron-Binding Capacity  Transferrin saturaiton = Serum iron TIBC  TIBC is relatively stable, transferrin saturation is determined principally by changes in the serum iron concentration and is equally subject to short-term variation.

9 Erythrocyte Protoporphyrin  Iron deficiency impaired heme synthesis and accumulation of protoporphyrin, a heme precursor, in erythrocytes.  Measurement of EP level is a sensitive indicator of iron deficiency, but provides no information about iron overload.

10  EP is good for large-scale surveys: 1. small sample size(20ul blood) 2. the relative simplicity 3. reproducibility of the measurement Erythrocyte Protoporphyrin  EP value <35 mg/dl, 88% sensitivity and 90% specificity as compared with serum ferritin. Correlation of EP with serum ferritin =0.66

11 Mean Corpuscular Volume  Microcytosis of RBC can caused by thalassemia and inflammation.  It is only a morphologic indicator of iron deficiency. Hemoglobin or Hematocrit  More severe and long-standing iron deficiency reduced Hb level.  Over hydration, hemoglobinopathies, Vit B12 deficiency and chronic diseases also caused lower Hb level.

12 Hair and Nails  The method may be a measure for patient with hemochromatosis, but gives little information about levels over the normal range of iron intake.  The biological significance of iron in hair and nails remains to be determined.

13 Other Determinants  The major determinant of iron blood loss  Blood donations and menstrual history should be considered in interpretation of iron status.  Oral contraceptive users reduced menstrual blood loss

14 Summary  The use of several biochemical indicators of iron status provides a more sensitive and specific assessment.  The appropriate cut-off values should be carefully determined to categorize subjects according to diagnostic groups.

15 Vitamin B1  5% U.S. adults over 60 years old impaired thiamin status  The prevalence among the poor, the chronically ill, the institutionalized.

16  The best method for assessing thiamine nutriture in the population is the stimulation of erythrocyte transketolase by thiamine pyrophosphate(TPP)  Transketolase activity after addition of TPP Transketolase activity before addition of TPP  Greater than 1 imply deficiency of endogenous thiamine Vitamin B1

17  Development of automated procedures make this method more applicable to large studies.  Little sample(50ul whole blood) is required for the calorimetric method.  Correlation between calorimetric method and FFQ for thiamin intake is 0.02. Vitamin B1

18  HPLC is a precise technique for measuring vitamin B1 in plasma and whole blood, but not a useful measure of thiamine status. (Thiamin deficiency does not cause a large reduction in blood level.)  Urinary thiamin level is not a good index of thiamine nutriture. Vitamin B1

19  Automatically measuring RBC transketolase stimulation provide reproducible and sensitive results.(2.7% within-run ; 4.1% between-run)  Long-term stability of RBC transketolase is uncertain. Vitamin B1

20  Measurement of Other Determinants : DM and polyneuritis low RBC transketolase activity  Pernicious anemia high activity  Heavy alcohol intake inhibit : thiamine absorption and metabolism Vitamin B1

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