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(Nutrition) Ch. 13: The Trace Minerals

Terms in this set (61)

(13.1) The Trace Minerals - An Overview
- body requires trace minerals in small quantities
Food Sources
- trace mineral contents of foods depend on soil and water composition and on how foods are processed
- many factors in diet and within the body affect the minerals' bioavailability
Deficiencies
- assessing trace mineral status is challenging
- severe deficiencies of better-known minerals are easy to recognize but deficiencies of others may be harder to diagnose
- bc minerals are active in many body systems, deficiencies can have wide reaching effects and can affect people at all ages
- most common result of deficiency in children is failure to grow and thrive
Toxicities
- most of trace minerals are toxic at intakes only 2 1/2 to 11 times above current recommendations
- imp not to exceed UL
- many supplements contain trace minerals, making it easy for users to exceed their needs
- to avoid dangers, select supplements that contain no more than 100% of daily value
Interactions
- interactions among the trace minerals are common and often are coordinated to meet the body's needs
- several of the trace minerals support the insulin's work, influencing its synthesis, storage, release, and action
- interactions can lead to nutrient imbalances - excess of one can cause deficiency of another
- deficiency of one may interfere with work of another
- deficiency of trace mineral may even open way for contaminant mineral to cause a toxic reaction
- supplementation can easily create imbalances
Nonessential Trace Minerals
- research to determine whether other trace minerals are essential is challenging bc quantities in body are so small and also bc human deficiencies are unknown
- research is currently insufficient to determine DRI for nickel, bromine, vanadium, cobalt, and boron even though they play beneficial roles in body
- arsenic may be useful in small quantities- useful in treatment of some types of leukemia
(13.2) The Trace Minerals
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IRON
- is an essential nutrient, vital to many of cell's activities but poses a problem for millions of people
- some don't get enough in diet and some have too much that it threatens their health
- both too little and too much can be harmful
- body has several ways to maintain iron balance, protecting against both deficiency and toxicity
Iron Roles in the Body
- switches back and forth between two ionic states - in reduced state, iron has lost 2 electrons and has a net positive charge of 2 (ferrous iron, Fe++); in oxidized state, iron has lost a third electron, has a net positive charge of 3, and is known as ferric iron
- by doing so, iron can serve as a cofactor to enzymes involved in the numerous oxidation-reduction reactions that commonly occur in cells
- enzymes involved in making amino acids, collagen, hormones, and neurotransmitters all require iron
- iron forms a part of the electron carriers that participate in ETC - these carriers transfer hydrogens and electrons to oxygen, forming water, and in the process, make ATP for the cells' energy use
- most of body's iron found in 2 proteins: hemoglobin in RBC and myoglobin in muscle cells - in both, iron helps accept, carry, and then release oxygen
Iron Absorption
- body conserves iron - bc it's difficult to excrete iron once in body, balance is maintained primarily through absorption
- more iron is absorbed when stores are empty and less is absorbed when stores are full
- special proteins help body absorb iron from food - ferritin captures iron from food and stores it in cells of small intestine; when body needs iron, ferritin releases some iron to iron transport protein transferrin
- if body doesn't need iron, it's carried out when intestinal cells are shed and excreted in feces; intestinal cells replaced every 3-5 days
- by holding iron temporarily, these cells control iron absorption by either delivering iron when the day's intake falls short or disposing of it when intakes exceed needs
- iron occurs in 2 forms in foods: as heme iron which is only found in flesh of animals and as nonheme iron, found in both plant derived and animal derived food
- on avg, heme iron represents about 10% of iron a person consumes in a day - it is so well absorbed it contributes significant iron
- about 25% of heme iron and 17% of nonheme iron is absorbed, depending on dietary factors and body's iron stores
- in iron deficiency, absorption increases and in overload, absorption declines
- heme iron has high availability and is not influenced by dietary factors but several dietary factors influence nonheme iron absorption
- figure 13-3 (p. 411)
- meat, fish, poultry contain heme iron and a peptide (MFP factor) that promotes absorption of nonheme iron
- vitamin c also enhances nonheme iron absorption
- some acids and sugars also enhance absorption
- some dietary factors bind w nonheme iron, inhibiting absorption - phytates in legumes, whole grains, and rice; veggie proteins in soybeans, other legumes, and nuts; calcium in milk; polyphenols in tea, coffee, grain products, oregano, and red wine
- enhancers, inhibitors, and combined effects make it difficult to estimate iron absorption - most factors exert strong influence individually but not combined in meals - impact of combined effects diminishes when a diet is evaluated over several days
- when multiple meals are analyzed together, 3 factors appear to be most relevant: MFP factor and vitamin c as enhancers and phytates as inhibitors
- 18% of dietary iron absorbed from mixed diets and 10% from vegetarian diets
- iron absorption also depends on an individual's health, stage in life cycle, and iron status
- body makes more ferritin to absorb more iron from small intestine and more transferrin to carry more iron around body
Iron Transport and Storage
- transferrin delivers iron to bone marrow and other tissues- bone marrow uses large quantities of iron to make new RBCs while other tissues use less
- surplus iron is stored in ferritin, primarily in the liver, but also in bone marrow and spleen
- when dietary iron has been plentiful, ferritin is constantly and rapidly made and broken down, providing an ever-ready supply of iron
- when iron concentrations become abnormally high, the liver converts some ferritin into another storage protein called hemosiderin - it releases iron more slowly than ferritin does
- storing excess iron in hemosiderin protects body against damage that free iron can cause - free iron acts as a free radical, attacking cell lipids, DNA, and protein
- avg RBC lives 4 months then spleen and liver remove it from the blood, take it apart, and prepare the degradation products for excretion or recycling
- the iron is salvaged: liver attaches it to transferrin, which transports it back to bone marrow to be reused in making new RBCs - even though RBCs only live for 4 months, iron recycles through each new generation of cells
- figure 13-5 (p. 412)
- body loses some iron daily via Gi tract and through blood if bleeding occurs
- tiny amounts of iron lose in urine, sweat, and shed skin
- women and men lose about 1 milligram of iron per day with women losing addition iron in menses; menstrual losses vary but over a month, they average about 0.5 mg per day
- central to regulation of iron balance is hormone hepcidin (produced by liver) - helps to maintain blood iron within normal range by limiting absorption from small intestine and controlling release from liver, spleen, and bone marrow - production increases in iron overload and decreases in deficiency
Iron Deficiency
- iron deficiency is most common nutrient deficiency w iron-deficiency anemia affecting 1.5-2 billion people - mostly preschool children and pregnant women
- affects 10% of toddlers i, adolescent girls and women of childbearing age in US
- deficiency also common in overweight people - increased production of hepcidin in obesity
- women in reproductive years prone to iron deficiency bc of repeated blood losses during periods
- pregnancy demands additional iron to support the added blood volume, growth of fetus, and blood loss during childbirth
- infants and young children receive little iron from high milk diets yet need extra iron to support rapid growth and brain development
- deficiency in toddlers in US is common
- adequate iron intake imp in rapid growth of adolescence esp for males and menstrual losses of females
- bleeding from any site incurs iron losses
- in developing countries, blood loss is brought on by malaria and parasitic infections of GI tract
- people who donate blood incur losses
Assessment of Iron Deficiency
- deficiency develops in stages
- first stage, iron stores diminish - measures of serum ferritin in blood reflect iron stores and are most valuable in assessing iron status at this earliest stage
- second stage is characterized by decrease in transport iron: serum iron falls and iron-carrying protein transferrin increases - measurements of serum iron and transferrin can determine severity of deficiency - the more transferrin and less iron in the blood, the more advanced the deficiency is; transferrin saturation (% of transferrin that is saturated w iron) decreases as iron stores decline
- third stage occurs when lack of iron limits hemoglobin production - hemoglobin precursor, erythrocyte protoporphyrin begins to accumulate as hemoglobin and hematocrit values decline - hematocrit and hemoglobin tests most commonly used in evaluating iron status but they are late indicators
Iron Deficiency and Anemia
- deficiency and anemia are different
- iron deficiency: depleted body stores without regard to degree of depletion or to presence of anemia
- iron-deficiency anemia: severe depletion of iron stores that results in low hemoglobin concentration
- in iron deficiency anemia, hemoglobin synthesis decreases, resulting in RBCs that are pale, and small
- without adequate iron, these cells can't carry enough oxygen from lungs to tissues
- energy metabolism in cells falters - result is fatigue, weakness, headaches, apathy, pallor, and poor resistance to cold temperatures
- skin is pale and in dark skinner person, tongue and eyelining is pale
- people with anemia feel fatigue only when they exert themselves - work productivity, voluntary activities, and athletic performance declune
Iron Deficiency and Behavior
- developing iron deficiency affects behavior
- even at slightly lowered iron levels, energy metabolism is impaired and neurotransmitter synthesis is altered, reducing physical work capacity and mental productivity
- no deficiency symptoms, they just appear unmotivated and apathetic
- many of symptoms associated with iron deficiency easily mistaken for behavioral or motivational probs
Iron Deficiency and Pica
- a curious behavior seen in some iron-deficient people, esp in women and children of low income groups is pica - the craving and consumption of ice, chalk, starch, and other nonfood substances - these substances contain no iron and can't remedy a deficiency
- poorly understood, its cause is unknown - may be motivated by hunger, nutrient deficiencies, or an attempt to protect against toxins or microbes
- a consequence is anemia
Iron Overload
- some individuals vulnerable to excess iron
- once considered rare, iron overload has emerged as an imp disorder of iron metabolism and regulation
- iron overload disorder - hemochromatosis is caused by a genetic failure to prevent unneeded iron in diet from being absorbed - hormone hepcidin supports iron homeostasis and its deficiency or resistance causes hemochromatosis
- other causes of iron overload - repeated blood transfusions, massive doses of supplementary iron, and other rare metabolic disorders
- symptoms of iron overload: apathy, lethargy, and fatigue
- iron overload assessment tests measure transferrin saturation and serum ferritin
- iron overload characterized by toxic accumulation of iron in liver, heart, joints, and other tissues
- excess iron in these tissues causes free-radical damage
- infections are likely bc viruses and bacteria thrive on iron-rich blood
- symptoms most severe in alcoholics bc alcohol damages small intestine, further impairing its defenses against absorbing excess iron
- if overload is untreated, it increases the risks of diabetes, liver cancer, heart diseases, and arthritis - treatment includes phlebotomy and chelation therapy
- more common in men than women and is twice as prevalent among men as iron deficiency
- vitamin c enhances iron absorption and releases iron from ferritin, allowing free iron to wreak the damage typical of free radicals - vitamin c as a prooxidant when taken in high doses
Iron and Chronic Diseases
- heart disease and excess iron
- limited evidence on iron and some cancers
- iron can be involved in contributing to these chronic diseases focus on its free radical activity
- one of the benefits of high fiber diet may be that the accompanying phytates bind iron, making it less available for such reactions
Iron Poisoning
- large doses of supplements cause GI distress, including constipation, nausea, vomiting, and diarrhea
- UL of 45 mg a day for adults
- ingestion of iron containing supplements is a common cause of accidental poisoning in children - symptoms of toxicity: nausea, vomiting, diarrhea, rapid heartbeat, weak pulse, dizziness, shock, and confusion
- as few as 5 tables (200 mg) have caused death
- excessive free radical damage is thought to play a role in heart failure and respiratory distress
Iron Recommendations
- usual diet in US provides about 6-7 mg of iron for every 1000 kcal
- recommended daily intake for men is 8 mg bc men eat more than 2000 kcal day
- women need 18 mg a day - bc women have higher iron needs and lower energy needs, they sometimes have trouble obtaining enough iron
- on avg, women receive only 12-13 mg a day
- vegetarians need 1.8x as much iron to make up for low bioavailability typical of their diets- good vegetarian food sources: legumes, nuts, seeds, cereals, dried fruit, veggies, black strap molasses
Iron Food Sources
- meats, fish, poultry contribute most iron per serving
- legumes and eggs
- milk group poor in iron
- dark green and dried fruits contribute some iron
- most states require manufacturers to enrich flour and grain products w iron
- iron added to foods is nonheme iron which is not absorbed as well as heme iron, but when eaten with absorption enhancing foods, enrichment iron can increase iron stores and reduce iron deficiency
- bioavailabilty of iron is high in meats, fish and poultry, intermediate in grains and legumes, and low in most veggies esp those with oxalates such as spinach
- for max absorption of nonheme iron, eat meat for the MFP factor and fruits or veggies for vitamin c
Iron Contamination
- contamination iron from nonfood sources of inorganic iron salts can contribute to day's intakes
- foods cooked in iron cookware take up in iron salts
- the more acidic the food and the longer it's cooked in iron cookware, the higher the iron content - iron content of eggs can triple in time it takes to scramble them in an iron plan
Iron Supplementation
- those who are iron deficient
- for pregnant women, infants, and young children
- iron from supplements is less well absorbed than that from food so the doses must be high
- absorption of iron taken as ferrous sulfate is better than that from other iron supplements
- absorption also improves when supplements are taken between meals, at bedtime on an empty stomach, and with liquids
- taking iron supplements in a single dose instead of several doses per day is equally effective and may improve a person's willingness to take it regularly
- vitamin c doesn't enhance absorption from supplements like it does for food
- constipation is side effect to supplements - drink a lot of water
- best strategy is to ensure compliance is to individualize the dose, formulation, and schedule
ZINC
- required for numerous metabolic reactions
- highest concentrations found in muscle and bone
Zinc Roles in the Body
- supports the work of hundreds of proteins in the body such as metalloenzymes, which participate in a variety of metabolic processes, and transcription factors, which regulate gene expression
- zinc stabilizes cell membranes and DNA, helping to strengthen antioxidant defenses against free-radical attacks
- assists in immune function and in growth and development
- participates in synthesis, storage, and release of insulin in pancreas but doesn't play a direct role in insulin's action
- interacts with platelets in blood clotting, affects thyroid hormone function, influences behavior and learning performance
- needed to produce active form of vitamin a (Retinal) in visual pigments and retinol-binding protein that transports vitamin a
- essential to normal taste perception, wound healing, sperm production, and fetal development
- deficiency would impair all these functions
Zinc Absorption
- circular passage of zinc from small intestine to body and back again
- rate of zinc absorption varies from 15-40%, depending on amount consumed - as zinc intake increases, rate of absorption decreases and vice versa
- dietary factors such as phytates influence absorption, limiting its bioavailability
- when zinc is absorbed into intestinal cell, it has 2 options - can participate in metabolic functions of the intestinal cell itself or it may be retained within the intestinal cells by metallothionein until body needs zinc- metallothionein plays key role in storing and distributing zinc throughout body
Zinc Transport
- after being absorbed, some zing goes to pancreas where it's incorporated into many of the digestive enzymes that the pancreas releases into the small intestine at mealtimes - small intestine receives 2 doses of zinc w each meal, one from foods and other from rich pancreatic juices
- enteropancreatic circulation: recycling of zinc in body from pancreas to small intestine and back to pancreas
- when zinc circulates through small intestine, it may be excreted in shed intestinal cells or reabsorbed into the body - body loses most zinc in feces and smaller losses in urine, shed skin, hair, sweat, menstrual fluids, and semen
- zinc's main transport vehicle in the blood is the protein albumin - some zinc also binds to transferrin
Zinc Deficiency
- nearly 2 billion deficient
- children have esp high zinc needs bc they're growing and synthesizing many zinc-containing proteins
- middle eastern diets esp low in zinc-rich diets, meat - staple foods are legumes, unleavened bread, and other whole grain foods that are high in fiber and phytates, which inhibit zinc absorption
- deficiency causes severe growth retardation and immature sexual development
- deficiency also hinders digestion and absorption, causing diarrhea, which worsens malnutrition for zinc and other nutrients
- impairs the immune response- pneumonia and GI tract infections which worsen in malnutrition
- chronic deficiency damages nervous system and brain and may lead to poor motor development and cognitive performance
- vitamin a deficiency symptoms appear
- disturbs thyroid function and metabolic rate
- alters taste, causes lack of appetite, slows wound healing
- generalized malnutrition and sickness more likely to be diagnosis than simple zinc deficiency since its symptoms are so pervasive
Zinc Toxicity
- high doses (50 mg) may cause vomiting, diarrhea, headaches, exhaustion
- UL is 40 mg based on zinc's interference in copper metabolism
Zinc Recommendations and Sources
- highest in protein-rich foods like shellfish, meats, poultry, milk, and cheese
- legumes and whole grains good sources if eating in large quantities
- phytate in grains in US not enough to impair zinc absorption
- veggies vary in zinc content depending on soil they're grown in
- avg intake usually higher than recommendation
ZINC SUPPLEMENTATION
-in developing countries, supplementation plays a major role in effectively reducing the incidence of disease and death associated with diarrhea and pneumonia
- zinc lozenges may shorten duration, but not severity of cold
- consumers need to take relatively high doses (75 mg) of the lozenges within 24 hours of the onset of symptoms and continue daily throughout the duration of the cold - common side effects are nausea and bad taste reactions
IODINE
- in the GI tract, iodine from foods becomes iodide, which is readily absorbed
Iodide Roles in the Body
- is an integral part of the thyroid hormones that regulate body temp, metabolic rate, reproduction, growth, blood cell production, nerve and muscle function, and more
- by controlling rate at which cells use oxygen, these hormones influence the amount of energy expended during basal metabolism
Iodine Deficiency
- with deficiency, thyroid hormone production declines and body response by secreting more TSH in attempt to accelerate iodide uptake by the thyroid gland - if deficiency persists, cells of thyroid gland enlarge to trap as much iodide as possible - sometimes gland enlarges until it makes a visible lump in neck, a goiter
- goiter - cause is mainly iodine deficiency but other 4% have it bc they eat excessive amounts of foods that contain an antithyroid substance (goitrogen) whose effect is not counteracted by dietary iodine - foods w goitrogen: veggies like cabbage spinach radishes, legumes like peanuts and soy, fruits like peaches and strawberries
- goiter may be earliest and most obvious sign of iodine deficiency but most tragic and prevalent damage occurs in brain
- deficiency is most common cause of preventable mental retardation and brain damage - 1/3 of children have iron deficiency
- severe deficiency during pregnancy causes the extreme and irreversible mental and physical retardation known as cretinism - can be averted by early diagnosis and treatment of maternal iodine deficiency
- giving people iodized salt - dual fortification w both iron and iodine may be most beneficial
Iodine Toxicity
- excessive intake can interfere with thyroid function and enlarge the gland
- during pregnancy, excessive exposure from food, supplements, or meds is damaging to developing infant- baby may develop goiter so severe as to block airways and cause suffocation
- UL is 1100 mg a day for adults -most foods provide 3-75 micrograms of iodine per serving
Iodine Recommendations and Sources
- ocean is world's major source of iodine
- in coastal areas, kelp, seafood, water, and iodine containing sea mist
- inland: amount of iodine in foods is variable and generally reflects the amount present in the soil in which plants are grown or on which animals graze - flood prone areas prone in iodine and landmasses once under ocean rich in iodine
- 60 micrograms of iodine for every grain of salt - some developing countries w/o salt put it in bread, fish paste, or drinking water instead
- processed foods use regular salt, not iodized salt
- intakes usually below toxic level
- 1/2 teaspoon meets RDA for iodine
SELENIUM
- can substitute for sulfur in amino acids, methionine, cysteine, and cystine
Selenium Roles in Body
- is one of body's antioxidant nutrients, working primarily as part of proteins - glutathione peroxidase enzymes - works w vitamin E in tandem
- glutathione peroxidase prevents free radical formation, blocking the chain reaction before it begins but if it does form, vitamin e stops it
- other selenium-containing enzymes selectively activate or inactivate thyroid hormones
Selenium Deficiency
- associated with Keshan disease - heart disease prevalent in regions of China where soil and foods lack selenium - cause is probably a virus or toxin but selenium deficiency predisposes people to it and adequate selenium prevents it
- symptoms: impaired cognition and poor immunity
Selenium and Cancer
- antioxidant action of selenium may protect against some types of cancers but supplements don't help - may in fact damage DNA and cause harm
Selenium Recommendations and Sources
- is found in soil and therefore in the crops grown for consumption
- avg in takes in US exceed RDA, which is based on the amount needed to maximize glutathione peroxidase activity
Selenium Toxicity
- UL is set bc high doses can be toxic
- causes loss and brittleness of hair and nails, garlic breath odor, and nervous system abnormalities
COPPER
- body contains about 100 mg of copper in a variety of cells and tissues
- copper balance and transport depend on system of proteins
Copper Roles in the Body
- serves as constituent of several enzymes - all have diverse metabolic roles w one common characteristic: all involve reactions that consume oxygen or oxygen radicals
- role in iron metabolism makes it a key factor in hemoglobin synthesis
- copper and zinc-containing enzymes participate in body's natural defenses against oxidative damage of free radicals but other copper enzymes help to manufacture collage, inactive histamine, and degrade serotonin
- is needed in many of the reactions involved in energy metabolism
Copper Deficiency and Toxicity
- deficiency is rare
- in animals, copper deficiency raises blood cholesterol and damages blood vessels, raising questions about whether low dietary copper might contribute to cardiovascular disease in humans
- some genetic disorders create copper toxicity
- excessive intakes from supplements- liver damage
- UL SET
- menkes disease: intestinal cells absorb copper but can't release it into circulation, causing deficiency- treatment: intravenous copper
- wilson's disease: copper accumulates in liver and brain, creating toxicity - can be controlled by reducing copper intake, using chelating agents, and taking zinc supplements which interfere w copper absorption
Copper Recommendations and Sources
- legumes, whole grains, nuts, shellfish, and seeds
- more than half of copper from food is absorbed and major route of elimination is bile
- water provides copper, depending on type of plumbing pipe and hardness of water
MANGANESE
- human body contains 20 mg of manganese - most can be found in bones and metabolically active organs like liver, kidneys, and pancreas
Manganese Roles in Body
- acts as cofactor for many enzymes that facilitate the metabolism of carbs, lipids, and amino acids
- manganese-containing metalloenymes assist in bone formation and conversion of pyruvate to TCA cycle compound
Manganese Deficiency and Toxicity
- requirements are low and many plant foods contain significant amounts of manganese so deficiencies are rare
- phytates inhibit its absorption
- high intakes of iron and calcium limit manganese absorption so people who use supplements many impair their manganese status
- toxicity more likely to occur from contaminated environment than from excessive dietary intake
- exposed exposure (miners) - brain disease and abnormalities in appearance and behavior
- UL established based on intakes from food, water, and supplements
Manganese Recommendations and Sources
- grain products
- AI set based on average intakes
FLUORIDE
- present in all soils, water supplies, plants, and animals
- body only contains small amount but crystalline deposits in teeth are larger and more perfectly formed
Fluoride Roles in Body
- fluoride replaces the hydroxyl portions of hydroxyapatite crystal, forming fluorapatite, which makes teeth stronger and more resistant to decay
- when fluoride is lacking, dental decay is common
- drinking water is best source of fluoride
- fluoridation of drinking water (to 0.7 milligrams per liter of water) protects against dental caries and supports oral health
- most bottled water lacks fluoride
Fluoride Toxicity
- too much can damage teeth, causing fluorosis
- UL has been estbalished
- in mild cases, teeth develop small white flecks and in sever cases, enamel becomes pitted and permanently stained
- fluorosis occurs in only during tooth development and can't be reverse - making its prevention during first 3 years of life a high priority
- to limit fluoride ingestion, take care not to swallow fluoride containing dental products and don't use fluoride supplements unless advised to
Fluoride Recommendations and Sources
- water delivers about 1 milligram per person per day
- fish and most teas
CHROMIUM
- participates in carb and lipid metabolism
- like iron, it assumes different charges
- Cr+++ ion is most stable and most commonly found in foods
Chromium Roles in Body
- helps maintain glucose homeostasis by enhancing activity of hormone insulin
- when chromium is lacking, a diabetes-like condition may develop, w elevated blood glucose and impaired glucose tolerance, insulin response, and glucagon response
Chromium Recommendations and Sources
- present in a variety of foods
- best sources are unrefined foods, particularly liver, brewer's yeast, and whole grains
- the more refined foods people eat, the less chromium they ingest
Chromium Supplements
- ads tell consumers that chromium supplements can help people lose fat and build muscle - controversial
MOLYBDENUM
- acts as working part of several metalloenzymes
deficiencies are unknown bc needed amounts are tiny- 0.1 part per million parts of body tissue
- legumes, breads, other grain products, leafy green veggies, milk, liver
- toxicity is rare
- toxicity include kidney damage and reproductive abnormalities
(13.3) Contaminant Minerals
- impair the body's growth, work capacity, and general health
- include heavy metals- lead, mercury, cadmium, which enter food supply by soil, water and air pollusion
Lead Poisoning
- lead is indestructible, body can't change its chemistry
- lead displaces nutrients from some of the metabolic sites they normally occupy so they're unable to perform their roles
- competes w calcium in the brain but can't signal messages from nerve cells
- excess lead in blood deranges the structure of RBC membranes, making them leaky and fragile - interacts w WBCs also, impairing their ability to fight infection and it binds to antibodies, thwarting their effort to resist disease
- children w iron deficiency esp vulnerable to lead toxicity
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