2009 cengage-wadsworth chapter 13 ultratrace elements

2009 Cengage-Wadsworth

Chapter 13

Ultratrace Elements


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


Arsenic

• Sources– Content depends on soil & pollution– Foods of marine origin– Most toxic: inorganic arsenite,

trivalent organoarsenicals– Less toxic: pentavalent, methylated

arsenic compounds


Arsenic

• Absorption– Simple diffusion

• Transport• Metabolism

– Organic - little or none in liver– Inorganic - reduced, methylated or

both in liver– Concentrates in skin, hair, nails


Arsenic

• Functions– Formation & utilization of methyl

groups generated in methionine metabolism to S-adenosylmethionine

• Deficiency– Impairs methionine metabolism


Arsenic

• Excretion– Mostly via kidneys in urine

• Recommended intake– Suggested: 12-25 µg

• Toxicity– Fatal at intakes of 70-300 mg


Arsenic

• Assessment of nutriture– Hair analysis– Atomic absorption spectrometry

preferred– Other methods:

• Mass spectrometry• Neutron activation analysis• Emission spectroscopy


Boron

• Sources– Fruits, vegetables, nuts, legumes

• Especially avocado, peanuts, peanut butter, pecans, raisins, grapes

– Wine, cider, beer

• Absorption– Passive diffusion


Boron

• Transport– In blood as boric acid, orthoboric acid,

borate monovalent anion B(OH)4-

– Boron transporter

• Storage– Bones, teeth, nails, hair


Boron

• Excretion– Mostly urine, also feces, sweat

• Functions– Embryogenesis– Bone development– Cell membrane function & stability– Metabolic regulation– Immune response


Boron

• Deficiency– Studied in animals– Symptoms related to suspected

functions

• Recommended intake– Not established


Boron

• Toxicity– UL = 20 mg

• Assessment of nutriture– Inductively coupled plasma emission

spectrometry


Nickel

• Sources– Nuts, legumes, grains, chocolate

• Absorption– Carrier & passive diffusion

• Transport– In blood: binds mainly to albumin,

also amino acids, other proteins


Nickel

• Storage– Throughout body in low

concentrations– Highest in thyroid, adrenal glands,

hair, bone

• Functions– Undefined


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


Nickel

• Excretion– Mostly urine, also sweat, bile

• Recommended intake– Suggested: <100 µg/day

• Toxicity– UL = 1.0 mg soluble Ni salts


Nickel

• Assessment of nutriture– Flameless atomic absorption

spectrophotometry– No valid method for assessing human

status available


Silicon

• Sources– Plants contain more than animals

• Absorption– Not well understood

• Transport– Bound

– Free - orthosilicic acid, Si(OH)4


Silicon

• Storage– Concentrates in connective tissues

• Excretion– Mostly in urine

• Functions– Metabolic & structural role – Bone, connective tissue & cartilage

formation, growth & development


Silicon

• Deficiency– Smaller, less flexible long bones &

skull deformation

• Recommended intake– Suggestions range from ~5-35

mg/day


Silicon

• Toxicity– Suggested maximum: 1,750 mg/day– Kidney stones

• Assessment of nutriture– Serum/plasma– Mass spectrometry, emission

spectroscopy, atomic absorption spectrophotometry (preferred), etc.


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


Vanadium

• Transport– Converted to vanadyl in fluids– Vanadyl binds to albumin & iron-

containing proteins– Enters cells as vanadate using

phosphate transport systems


Vanadium

• Storage– Concentrates in bones, teeth, lungs,

thyroid gland

• Functions– Many pharmacological effects– No specific biochemical function

identified


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


Vanadium

• Excretion– Mostly urine, also bile

• Recommended intake– Suggested: 10 µg/day

• Toxicity– UL = 1.8 mg/day elemental vanadium


Vanadium

• Assessment of nutriture– Neutron activation analysis– Flameless atomic absorption

spectrophotometry (preferred)


Cobalt

• Part of vitamin B12

• Can substitute for other metals in metalloenzymes in vitro– In vivo? No evidence of this

• Little evidence that ionic cobalt is essential in humans

2009 cengage-wadsworth chapter 13 ultratrace elements

Documents

orthoboric acid

blood glucose changes

depressed growth

hairboronexcretionmostly

albumin iron

thyroid glandfun

fish sticks

inorganic arsenite