Trace Minerals Lecture 18 Readings: Chapter 13: pages 429 – 453 (Omit “Molybdenum”, “Other Trace Minerals” and “Contaminant Minerals” on pages 450 and 451) Next lectures: Highlights 10, 11, and 13

Overview trace minerals required only in miniscule amounts content contained in foods dependant on soil content, water composition, and processing of foods interactions among trace minerals are common include: –iron –zinc –iodine –selenium –copper –fluoride –chromium

Iron exists in two forms: –“reduced” or ferrous iron (Fe 2+ ) –“oxidized” or ferric iron (Fe 3+ ) Functions forms part of electron carriers called ______________ in the electron transport chain forms part of proteins ________________ and ________________ enabling these proteins to accept, carry and release oxygen required by enzymes that synthesize collagen, hormones, neurotransmitters, and amino acids

Iron Absorption and Metabolism iron is not readily excreted from the body iron balance is maintained by adjusting absorption Types of Iron a) _____ from food derived from animal food sources 25% absorption b) _________ from both animal and plant derived foods only 10% is absorbed

Iron Sources

Iron Sources Others broccoli, spinach, dried fruits, eggs, legumes, enriched grains and cereals Contamination Iron iron found in foods as the result of contamination by inorganic iron salts form iron cookware or iron containing soils Recommendations Men: Women:

Iron Factors Enhancing Absorption Factors Inhibiting Absorption

Iron Transport and Storage the intestine absorbs iron and stores it in protein called –iron that is not needed is lost when intestinal cells are shed when body needs iron, it is moved to another protein called transferrin transports iron to the rest of the body where it is needed e.g. bone marrow where red blood cells are synthesized Figure 13-1, page 431

Iron Transport and Storage surplus is stored in ___________ in the liver, bone marrow and spleen even greater concentrations of iron lead to storage of iron in another protein called ______________ storage is important to: Figure 13-1, page 431

Iron Deficiency most common nutrient deficiency world wide prevalence is higher in less developed countries greatest risk for women in reproductive years, pregnant women, infants and young children, and teenagers Ways Iron is Lost from the Body… some iron is lost daily from the digestive tract only tiny amounts lost through feces, urine, sweat and shedding skin lost with ___________

Iron Deficiency cont. Stages in the Development of Deficiency 1. –measured by assessing serum ferritin 2. –decreased serum iron –levels of serum transferrin  to enhance absorption 3. –insufficient iron to produce hemoglobin –accumulation of erythrocyte protoporphyrin –decrease in hematocrit

Iron Deficiency cont. Symptoms a) red blood cells are small and pale results in fatigue, weakness, headaches, pallor, poor resistance to cold b) appear first unmotivated, apathetic, physically unfit “pica” = appetite for ice, clay, paste and non-food substances

Iron Toxicity extra dietary consumption generally poses no extra risk because iron absorption decreases when body needs decrease excess iron is referred to as “iron overload” hereditary disorder characterized by enhanced iron absorption results from long-term overconsumption of iron characterized by deposits of hemosiderin in tissues

Iron Toxicity cont. Symptoms & Consequences tissue damage, deposits of iron apathy, lethargy and fatigue increased risk of infections increased risk of heart disease: –free iron acts as an oxidant –may oxidize LDL and contribute to the development of atherosclerosis increased risk of cancer –increased free radical formation may contribute to DNA damage poisoning in children if ingest supplements

Zinc Functions acts as a cofactor for many enzymes Example: assists in important for growth and development –required for DNA and RNA synthesis synthesis of heme in hemoglobin releases Vitamin A from stores and converts to its active form (retinal) in the retina forms part of an antioxidant enzyme that protects from free radicals

Zinc Functions cont. stabilizes cell membranes and helps protect them from free radical attack interacts with platelets in blood clotting required for the synthesis, storage, and release of the hormone insulin regulates thyroid hormone function influences behaviour and learning performance plays important role in protein synthesis participates in carbohydrate, fatty acids and alcohol metabolism others: sperm production, fetal development, taste

Zinc Absorption and Metabolism absorption rate varies between % –dependant on zinc status –absorption inhibited by fibers and phytates after absorption may be stored by the protein transported in the blood by two proteins: –albumin –transferrin

Zinc Interactions an excess of dietary iron may reduce zinc absorption –a dietary iron : zinc ratio > 2 : 1 decreases zinc absorption large doses of zinc: –inhibit iron absorption –interferes with copper absorption

Zinc Sources richest sources are protein rich foods Examples Recommendations Men = 11 mg/day Women = 8 mg/day

Zinc Deficiency most vulnerable are pregnant women, young children, the elderly, and the poor Symptoms severe growth retardation and arrested sexual development during growth

Zinc Deficiency Symptoms cont. diarrhea symptoms of a Vitamin A deficiency impaired thyroid function altered taste perception anorexia impaired glucose tolerance slowed wound healing impaired immune function

Zinc Toxicity excessive doses may result in vomiting, diarrhea, headaches may interfere with ______ and _________ absorption and metabolism

Iodine iodine in foods is converted to its ionic form iodide by the body Functions an integral part of ________________ thyroid hormone has many important functions including: –regulation of _______ –regulation of body temperature –necessary for reproduction and growth

Iodine Sources iodized salt, ocean fish, plants grown in iodine rich soil average intake of North Americans is above recommendation but below toxic levels

Iodine Deficiency results in hypothyroidism and causes an enlargement of the thyroid gland called a ____________ maternal iodine deficiency during pregnancy leads to _____________ in the developing fetus –affects 6 million people worldwide –characterized by severe physical and mental retardation

Iodine Toxicity also enlarges the thyroid gland causing a __________ poses risk of suffocation for a fetus is excess consumed during pregnancy –goiter may block airways upper limit is 1000  g per day Note a goiter may also develop from excess consumption of ___________, an anti-thyroid substance found in plants of the cabbage family

Selenium Functions forms part of the enzyme _______________________ –acts as an ___________ Deficiency associated with a predisposition to a type of heart disease –Keshan disease, also linked to a viral infection may be associated with an increased incidence of some cancers Toxicity high doses produce vomiting, diarrhea, hair loss, skin lesions and neurological problems

Copper Functions forms part of several enzymes including __________ ______________ –an _________________ important for the synthesis of ____________ Sources legumes, whole grains, nuts, shellfish, organ meats, seeds, water

Copper Deficiency rare, may be associated with excess Vitamin C which interferes with absorption symptoms include _________________ in animals leads to increased blood cholesterol and damage to blood vessels Toxicity rare may interfere with iron and zinc metabolism

Fluoride Functions forms ____________________ in teeth –replaces the hydroxyl (OH) in hydroxyapatite crystals Deficiency associated with _____________ _______________________________ confers best protection against dental caries primary source of fluoride is drinking water; also in tea and seafood

Fluoride Toxicity ____________ –damage to teeth that pits and stains the enamel also leads to nausea, vomiting, diarrhea, chest pain, and itching

Chromium Functions regulates carbohydrate and lipid metabolism enhances _______________ Sources present in a wide variety of foods rich sources include liver, brewer’s yeast, whole grains, nuts and seeds Deficiency produces a ____________________ marked by an inability to use glucose normally