Magnesium
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We don’t get enough of it
Magnesium’s roles
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Required for ATP synthesis and utilization
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Blood clotting
Bone-assists in mineralization
– 50-60% of body’s Mg in bone
Muscle function
RDA’s for magnesium
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Ages 19-30: 400 mg men, 310 mg women
Ages 31-70: 420 mg men, 320 mg women
BUT average US diet contains only about 75% of RDA
UL: 350 mg/day from supplements
Magnesium sources
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Whole grains
Green vegetables (chlorophyll contains Mg)
Oysters
Crab
Peanut butter
Cooked dried beans
Overt Primary Mg Deficiency is Rare
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Can cause hypocalcemia because of depressed PTH secretion
Also causes hypokalemia
Also muscle weakness, loss of appetite, heart arrhythmias (irregular heart
beat)
Trace Elements
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Required in quantities < 100 mg per day
Iron
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Too little or too much of this good thing is hazardous to your health
Iron’s functions
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Part of hemoglobin (in the humble RBC’s) and myoglobin (in muscle)
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Myelination of nerves
Required for several enzymes
– Cytochromes in electron transport chain
– Catalase--breaks down peroxides (free radicals)
Iron and copper are transition metals
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Iron can exist as +2 charge (ferrous) and +3 charge (ferric)
Copper exists as +1 (cuprous) and +2 (cupric)
This quality influences the way the body handles both nutrients
How iron chemistry influences biology
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Ferrous (+2) iron supplements are better absorbed by the body
BUT most of functional iron in body is in the 3+ form
A copper-containing enzyme can convert iron between forms
Iron absorption
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The gut is the main control point of iron status in the body
If someone has adequate iron, less will be absorbed into blood
– Intestinal cell can turn it away, OR
– Store iron until cell is sloughed off
Influences on iron absorption
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Normal g-i function
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Other dietary factors
– Increase-Vitamin C, “meat factor”
– Decrease-Dietary fiber, tannins, oxalate
Amount and form of iron in food
– Heme iron better absorbed than nonheme
– Fe2+ absorbed over Fe3+
Iron-binding proteins
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Transferrin--transports iron in blood
– Delivers iron to cells by binding to transferrin receptor
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Ferritin--storage protein
Hemosiderin--another storage protein
Once it’s in your body, iron is guarded greedily
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Iron from dead RBC’s is recycled into new RBC’s
Men and postmenopausal women need less iron per day than women of
childbearing age
RDA for iron
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Men and postmenopausal women: RDA 9 mg/day
Women of childbearing age: RDA 18 mg/day
Pregnancy: RDA 27 mg/day
UL: 45 mg/day
Iron Deficiency
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A worldwide problem
The most common nutrient deficiency
Causes of iron deficiency
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Low intake
Increased losses (bleeding in g-i tract)
Increased needs (pregnancy)
Premature infants
Lead poisoning
Stages of iron deficiency
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Decreased stores
Decreased transport
Decreased hemoglobin synthesis
Iron deficiency anemia--microcytic, hypochromic
You need not have anemia to have consequences of deficiency
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Reduced work capacity/fatigue can occur before anemia is obvious
How to measure iron status
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Hemoglobin and hematocrit--only changes in full anemia
Transferrin saturation
RBC protoporphyrin levels
Iron toxicity
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A major cause of poisoning in children
– Keep ALL supplements out of reach of children
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Hemochromatosis--hereditary iron storage disease