 2009 Cengage-Wadsworth Chapter 13 Ultratrace Elements

 2009 Cengage-Wadsworth Introduction Definition –Estimated, established or suspected requirements of <1 mg/day –Some of these were covered in Chapter 12 because an RDA/AI has been set

 2009 Cengage-Wadsworth Arsenic Sources –Content depends on soil & pollution –Foods of marine origin –Most toxic: inorganic arsenite, trivalent organoarsenicals –Less toxic: pentavalent, methylated arsenic compounds

 2009 Cengage-Wadsworth Arsenic Absorption –Simple diffusion Transport Metabolism –Organic - little or none in liver –Inorganic - reduced, methylated or both in liver –Concentrates in skin, hair, nails

 2009 Cengage-Wadsworth Arsenic Functions –Formation & utilization of methyl groups generated in methionine metabolism to S-adenosylmethionine Deficiency –Impairs methionine metabolism

 2009 Cengage-Wadsworth Arsenic Excretion –Mostly via kidneys in urine Recommended intake –Suggested: µg Toxicity –Fatal at intakes of mg

 2009 Cengage-Wadsworth Arsenic Assessment of nutriture –Hair analysis –Atomic absorption spectrometry preferred –Other methods: Mass spectrometry Neutron activation analysis Emission spectroscopy

 2009 Cengage-Wadsworth Boron Sources –Fruits, vegetables, nuts, legumes Especially avocado, peanuts, peanut butter, pecans, raisins, grapes –Wine, cider, beer Absorption –Passive diffusion

 2009 Cengage-Wadsworth Boron Transport –In blood as boric acid, orthoboric acid, borate monovalent anion B(OH) 4 - –Boron transporter Storage –Bones, teeth, nails, hair

 2009 Cengage-Wadsworth Boron Excretion –Mostly urine, also feces, sweat Functions –Embryogenesis –Bone development –Cell membrane function & stability –Metabolic regulation –Immune response

 2009 Cengage-Wadsworth Boron Deficiency –Studied in animals –Symptoms related to suspected functions Recommended intake –Not established

 2009 Cengage-Wadsworth Boron Toxicity –UL = 20 mg Assessment of nutriture –Inductively coupled plasma emission spectrometry

 2009 Cengage-Wadsworth Nickel Sources –Nuts, legumes, grains, chocolate Absorption –Carrier & passive diffusion Transport –In blood: binds mainly to albumin, also amino acids, other proteins

 2009 Cengage-Wadsworth Nickel Storage –Throughout body in low concentrations –Highest in thyroid, adrenal glands, hair, bone Functions –Undefined

 2009 Cengage-Wadsworth Nickel Deficiency –Animals: depressed growth, altered mineral distribution, blood glucose changes, impaired hematopoiesis Interactions with other nutrients –Competes with other metal ions for ligand sites Iron, copper, zinc

 2009 Cengage-Wadsworth Nickel Excretion –Mostly urine, also sweat, bile Recommended intake –Suggested: <100 µg/day Toxicity –UL = 1.0 mg soluble Ni salts

 2009 Cengage-Wadsworth Nickel Assessment of nutriture –Flameless atomic absorption spectrophotometry –No valid method for assessing human status available

 2009 Cengage-Wadsworth Silicon Sources –Plants contain more than animals Absorption –Not well understood Transport –Bound –Free - orthosilicic acid, Si(OH) 4

 2009 Cengage-Wadsworth Silicon Storage –Concentrates in connective tissues Excretion –Mostly in urine Functions –Metabolic & structural role –Bone, connective tissue & cartilage formation, growth & development

 2009 Cengage-Wadsworth Silicon Deficiency –Smaller, less flexible long bones & skull deformation Recommended intake –Suggestions range from ~5-35 mg/day

 2009 Cengage-Wadsworth Silicon Toxicity –Suggested maximum: 1,750 mg/day –Kidney stones Assessment of nutriture –Serum/plasma –Mass spectrometry, emission spectroscopy, atomic absorption spectrophotometry (preferred), etc.

 2009 Cengage-Wadsworth Vanadium Sources –Black pepper, parsley, dill seed, canned apple juice, fish sticks, mushrooms Absorption –Varies with oxidation states –Vanadate mimics phosphate & uses its transport system

 2009 Cengage-Wadsworth Vanadium Transport –Converted to vanadyl in fluids –Vanadyl binds to albumin & iron- containing proteins –Enters cells as vanadate using phosphate transport systems

 2009 Cengage-Wadsworth Vanadium Storage –Concentrates in bones, teeth, lungs, thyroid gland Functions –Many pharmacological effects –No specific biochemical function identified

 2009 Cengage-Wadsworth Vanadium –Pharmacological effects: Inhibits Na + /K + -ATPase Stimulates adenylate cyclase These together affect transport of amino acids across the intestinal mucosa Mimics the action of insulin (as vanadate & vanadyl) –Can substitute for zinc, copper, iron in metalloenzyme activity

 2009 Cengage-Wadsworth Vanadium Excretion –Mostly urine, also bile Recommended intake –Suggested: 10 µg/day Toxicity –UL = 1.8 mg/day elemental vanadium

 2009 Cengage-Wadsworth Vanadium Assessment of nutriture –Neutron activation analysis –Flameless atomic absorption spectrophotometry (preferred)

 2009 Cengage-Wadsworth Cobalt Part of vitamin B 12 Can substitute for other metals in metalloenzymes in vitro –In vivo? No evidence of this Little evidence that ionic cobalt is essential in humans