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More trace minerals
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Zinc, copper, iodine, fluoride, and selenium
Zinc
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A relatively recent addition to mineral requirements
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Zinc supplementation reversed defects
1961--researchers in Iran found young men who were growth retarded,
anemic, and some had night blindness
Zinc’s functions in body
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Required in over 300 enzymes (text says only 80)
Essential for proper immune function
Needed for DNA replication and protein synthesis
Zinc finger proteins can interact with hormones and influence their function
Zinc absorption
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As with iron, small intestinal cells act as security guards to avoid
absorbing
too much
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Factors inhibiting zinc absorption--phytates, fiber, iron supplements
The protein metallothionein in gut cells binds zinc and slows its transport
into
blood
Transport, distribution, etc.
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Zinc is bound to albumin and alpha-macroglobulin in blood
Muscle and bone contain 90% of body’s zinc
Some recycling of zinc occurs, but body does not hold on to it as tightly or
store it the way it does iron
RDA’s
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Men 11 mg/day; women 8 mg/day
Pregnancy 11 mg/day; lactation 12 mg/day
UL 40 mg/day
Sources of Zinc
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Oysters--154 mg/3 ounces!!!
Crab
Beef
Liver
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Fortified cereals
Zinc deficiency--who’s at risk
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Vegans
Burn patients
Persons with intestinal diseases
Persons with diabetes, kidney disease, chronic diarrhea, sickle cell disease
Zinc toxicity is rare
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Very high intakes for long periods can depress immune function
Increases LDL and decreases HDL
High zinc intake can cause a copper deficiency
Copper
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Iron and zinc’s partner
Copper deficiency not a serious public health problem
Copper’s functions
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Required with zinc for the enzyme superoxide dismutase (quenches a free
radical)
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Required for an enzyme in electron transfer chain
In ceruloplasmin, helps change Fe charge
Also required for collagen, melanin, and norepinephrine synthesis
Copper absorption, etc.
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Absorbed in upper small intestine
Gut cells also protect against overload
Amino acid histidine increases absorption
Iron and zinc supplements can reduce absorption
Bound to albumin in blood until it gets to liver; then circulates bound to
ceruloplasmin
Dietary Copper Sources
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Oysters--6.4 mg/3 ounces
Liver, other seafood
Nuts
Chocolate
Tofu, beans
RDA for Copper
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Men and women: 900 micrograms (µg)/day
UL: 10 mg/day
Typical US diet contains 1000-1600 µg Cu
Copper deficiency
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Causes microcytic anemia
Bone disease in children
Menkes’ disease--rare inherited disorder in which copper cannot get delivered
into blood from gut or into brain
Wilson’s Disease
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A genetic copper storage disease analogous to hemochromatosis
Can also cause liver failure
Patients can be treated with high dose zinc (to reduce Cu absorption) and/or
metal chelating agents
Iodine
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Iodized salt was the first fortified food
Iodine’s function
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As constituent of two thyroid hormones
– Triiodothyronine (T3)-most active
– Thyroxine (T4)
Sources of dietary iodine
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Fish and seafood
Milk
Iodized salt
DRI’s for Iodine
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RDA 150 µg/day for adult men and women
UL 1100 µg/day
Iodine deficiency--goiter
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Thyroid grows in volume in response to stimulus from thyroid stimulating
hormone
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Person with goiter has low metabolic rate, cold intolerance, weight gain, and
decreased body temperature
Maternal iodine deficiency causes cretinism in offspring
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Child has irreparable mental retardation
Stunted growth
Often deafness as well
Iodine toxicity can also cause goiter
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BUT thyroid hormone production is also reduced by excess iodine
Selenium
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A fairly new mineral to worry about
Selenium’s functions
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Part of selenocysteine and selenomethionine, where Se takes place of sulfur
Required for glutathione peroxidase
Works in concert with vitamin E as an antioxidant
Also needed for thyroid function--deiodinase enzymes
Absorption, etc.
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Mostly absorbed from food as selenocysteine or selenomethionine
Can be absorbed as inorganic (non-carbon) selenium salts
Control of Se status is at level of kidneys--excess is excreted in urine
Selenium Deficiency
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Keshan disease-in China
– Children died of heart disease secondary to viral infection
– Selenium deficiency predisposed them to the problem
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Heart problems and muscle weakness in patients who have been on IV
nutrition without Se for long periods
Sources of Selenium
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Oysters, other seafood
Liver, pork
Oatmeal
Egg
DRI’s for selenium
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RDA 55 µg/day
UL 400 µg/day
Fluoride
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Good for your teeth--up to a point
Fluoridation of water began in late 1940’s
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Studies from areas with high fluoride in ground water showed fewer dental
caries (cavities) in residents
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Fluoride may also prevent osteoporosis
Fluoride absorption
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Only nutrient absorbed mostly from stomach
Circulates free in plasma
> 99% found in bones and teeth
Excess excreted in urine
Function
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Combines with Ca and P to form stronger crystal in bones and teethfluorapatite
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Fluorapatite less easily reabsorbed than hydroxyapatite
DRI’s for Fluoride
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AI: 4 mg men, 3 mg women
No RDA
UL 10 mg/day
Sources
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Fluoridated water in some areas
Toothpastes
Mouthwashes
Fluorosis
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Mottling of teeth--unsightly, but not hazardous
Too much fluoride in supplement--headache, gastritis, stiff joints
Download
1. Science
2. Biology
3. Nutrition
More trace minerals.doc
Minerals Chapter 7
The Trace Minerals
Water and Minerals: The Ocean Within
Minerals
Trace Minerals
The Trace Minerals
Trace Minerals
The Major Minerals (Found in “major” amounts
Minerals Iva Řehová
Eggs
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