Selenium in Health and Nutrition


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  • Figure ___ shows how selenoproteins can be produced in the body from a variety of selenium sources. Glutathione (GSH) is considered to be the main component of the selenium metabolism pathway, taking part in the first of a series of reduction reactions that convert selenite to hydrogen selenide (H2Se), which is regarded as the precursor for supplying selenium in an active form for synthesis of selenoproteins. The further metabolism of H2Se involves sequential methylation to methylselenide (CH3SeH), dimethylselenide ([CH3]2Se), trimethylselenonium ion ((CH3)3Se+). Selenite (SeO3 2; inorganic form of selenium) crosses the plasma membrane and reacts with cytoplasmicthiols in the reduction pathway; this forms selenide, which is then methylated, giving rise to methylated selenium derivatives that are excreted in urine, expired air via the lungs, and feces
  • 2 molecules of glutathione reacts with organic hydroperoxide, when catalyzed by glutathione peroxidase (GSH–Px), yields glutathione disulfide (GSSG), an alcohol and water molecule. Hydroperoxides are toxic product of various oxidative processes and potentially harmful oxidizing agent. In erythrocytes, the unchecked buildup of peroxides results in premature cell lysis. Acts also in other organic peroxides.Heavy metal detoxification
  • interferons share several common effects; they are antiviral agents and can fight tumors.Interferons (IFNs) are proteins made and released by host cells in response to the presence of pathogens such as viruses,bacteria, parasites or tumor cells. They allow for communication between cells to trigger the protective defenses of the immune system that eradicate pathogens or tumors."interfere" with viral replication within host cellsT cells or T lymphocytes belong to a group of white blood cells known as lymphocytesT helper cells (Th cells) are a sub-group of lymphocytes, a type of white blood cell, that play an important role in the immune system, particularly in the adaptive immune system. They help the activity of other immune cells by releasing T cell cytokines. They are essential in B cell antibody class switching, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages.
  • selenoenzymes may modulate or control many aspects of thyroid hormone metabolism T4 – thyroxineT3 – triidothyronine active form of thyroid hormone
  • Serum levels reflect recent intake Erythrocyte levels are more indicative of remote exposure. Hair levels have been used in the diagnosis of deficiency
  • Selenium in Health and Nutrition

    1. 1. Selenium in Healthand DiseaseCecilia A. AlamagMS Applied NutritionInstitute of Human Nutrition and Food, College of Human Ecology,University of the Philippines,College Los Baños, LagunaCAALAMAG | Selenium in Health Disease
    2. 2. OUTLINECAALAMAG | Selenium in Health DiseaseI. INTRODUCTIONA. History and Chemical BackgroundB. SourcesC. Dietary RequirementsD. Biological Activity, Utilization and ExcretionE. FunctionsF. Laboratory AssessmentG. Deficiency and ToxicityII. SELENIUM EFFECTS TO HUMAN HEALTHA. CancerB. Cardiometabolic HealthC. ArthritisD. HIVE. Reproductive Health
    3. 3. HISTORYCAALAMAG | Selenium in Health Disease• integral part of the selenoenzymecytoplasmic glutathione peroxidase(cGPX)181719571973• discovered by Jöns Jacob Berzelius• named after the Greek Moongoddess Selene• essential nutrient for normal growthand reproduction in animals
    4. 4. CHEMICAL BACKGROUNDCAALAMAG | Selenium in Health Disease
    5. 5. PERIODIC TABLE OF ELEMENTSCAALAMAG | Selenium in Health Disease
    6. 6. SOURCESCAALAMAG | Selenium in Health DiseaseFoodMicrograms(mcg)Brazil nuts, 1 oz 543Fast food fish sandwich, 1 89Halibut, baked, 1/2 fillet 74Tuna, canned, 3oz 68Oysters, raw, 3oz 56Rice, white, long grain, 1 cup 44Chicken, breast, baked, 3 oz 39Pie crust, 1 38Egg noodles, cooked, 1 cup 38Lobster, 3 oz 36Wheat germ, toasted, 1/4 cup 28Bagel, 1, 4-inch 27Sunflower seeds, 1/4 cup 25Egg, 1 16Bread, whole wheat, 1 slice 10Asparagus, cooked, 1cup 7Milk, 2% fat, 1 cup 6Content of Selected Foods (Source: Krause’s Food and Nutrition Therapy.12th ed)
    7. 7. SOURCESCAALAMAG | Selenium in Health DiseaseThese plants grow in selenium-rich soils
    8. 8. DIETARY REQUIREMENTSCAALAMAG | Selenium in Health DiseaseNutrient ReferenceValuesMicrogramsEAR 45RDA 55RENI 31UL 400EAR 70, 60RDI 60, 50
    9. 9. BIOLOGICAL ACTIVITY & METABOLISMCAALAMAG | Selenium in Health Disease• Selenomethionine• Plant Source• Supplied with foodBIOAVAILABLE/ABSORBABLE• Selenocysteine• Selenomethionine• SeleniteFORMS
    10. 10. BIOLOGICAL ACTIVITY & METABOLISMCAALAMAG | Selenium in Health DiseaseANTAGONIST• Sulfur• Arsenic• Mercury• Guar Gum• Vitamin CENHANCER• Protein• Vitamin E• Vitamin ABODY CONCENTRATION• Red Blood Cells• Liver• Heart• Nails• Tooth Enamel• Renal Cortex• Pituitary Gland• Thyroid Gland• Adrenals• Spleen• Testes & Ovaries
    11. 11. METABOLISM & EXCRETIONCAALAMAG | Selenium in Health Disease
    12. 12. FUNCTIONSCAALAMAG | Selenium in Health DiseaseAnti-oxidant activity and glutathione synthesisHydroperoxides aretoxic product of variousoxidative processes andpotentially harmfuloxidizing agent.
    13. 13. FUNCTIONSCAALAMAG | Selenium in Health DiseaseImmune Function• increased production ofinterferon γ and other cytokines• T cell proliferation• increase in T helper cells
    14. 14. FUNCTIONSCAALAMAG | Selenium in Health DiseaseThyroid activity: deiodinasesdeiodinating T4 and T3conversion of T4 to T3Type I deiodinaseType II deiodinaseType III deiodinaseresponsible for T4 conversionto T3 in the brainresponsible for deactivating T4and T3
    15. 15. LABORATORY ASSESSMENTCAALAMAG | Selenium in Health DiseaseTypically measured in:• Plasma• Serum• Whole blood• Amniotic fluid• Urine• Hair and toenailsSerum: 50-150 μg/LWhole blood: 60-240 μg/LHair: 0.2-1.4 μg/gramUrine: 15-150 μg/LFluorometry
    16. 16. DEFICIENCY AND TOXICITYCAALAMAG | Selenium in Health DiseaseKeshan DiseaseKashin-Beck Diseasegrowth retardationcataract formationlack of spermatogenesisabnormal placental retentioncardiomyopathymuscle inflammationenhanced skin pallorDeficiency Toxicitygarlic odor on the breathgastrointestinal disordershair losssloughing of nailsFatigueIrritabilityneurological damageincreased risk of type 2 diabetes
    18. 18. CANCERCAALAMAG | Selenium in Health Disease
    19. 19. CANCERCAALAMAG | Selenium in Health Diseaseinduce DNA repair andsynthesis in damaged cellsinhibit the proliferationof cancer cellsIn 1996, Clark et al. made a double-blind, randomized,placebo-controlled trial involving 1312 patients who havehistory of squamous cell carcinoma of the skin.Individuals in the treatment arm were given 200 mg Se/dayfor a mean of 4.5 years (average daily intake in the U.S. isabout 100 mg).Patients receiving the Se-yeast supplement showed a muchlower prevalence of developing and dying from lung, colonor prostate cancer.
    20. 20. CARDIOMETABOLIC HEALTHCAALAMAG | Selenium in Health Diseaseoxidative stress from freeradicalsheart diseaseSelenium is one of a groupof antioxidants that mayhelp limit the oxidation ofLDL cholesterol andthereby help to preventcoronary artery disease.
    21. 21. CARDIOMETABOLIC HEALTHCAALAMAG | Selenium in Health DiseaseIn the Flemish Study on Environment Genes and Health Outcomes,higher blood selenium concentrations were associated with lowersystolic and diastolic BP levels at baseline and with a lower risk ofhypertension over 5.2 years of follow-up among men.In a cross-sectional study conducted in Finland, a population with lowselenium status at the time of the study, serum selenium was alsoinversely related to systolic BP levels in 722 middle-aged men.In the HDL-Atherosclerosis Treatment Study (HATS) trial, selenium(100 mg/d) was administered along with vitamin E (800 IU/d),vitamin C (1000 mg/d), and b-carotene (25 mg/d), with no effect onBP levels during three years of follow-up (Brown 2001 as cited byStranges 2010).
    22. 22. REPRODUCTIVE HEALTHCAALAMAG | Selenium in Health DiseaseTesticular tissue containshigh concentrations ofselenium.Selenium is essential fortestosterone biosynthesisand the formation andnormal development ofspermatozoa.Phospholipid hydroperoxideglutathione peroxidase(PHGPx/GPx4) andSelenoprotein P
    23. 23. REPRODUCTIVE HEALTHCAALAMAG | Selenium in Health DiseaseThe study in 1984 by Bleau et al50 reported an optimal range between50 and 60 mcg/mL in semen and a positive correlation between spermcount and semen selenium concentration in 125 men from couplesbeing investigated for infertility.In Scotland, a placebo-controlled randomized control trial (RCT) of 64men demonstrated that sperm quality and fertility improved afterselenium supplementation.Three small studies, from Poland and the United States, supplementing(200-300 mg/d) with selenite, selenium-enriched yeast, or dietsnaturally high in selenium reported that, although semen seleniumconcentrations increased, there were no positive effects on spermcharacteristics or activity.
    24. 24. CONCLUSIONCAALAMAG | Selenium in Health DiseaseAs a Nutritionist, would yousuggest SeleniumSupplementation?