Trace Minerals Lecture 18

1
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

2
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

3
Iron

• exists in two forms
• reduced or ferrous iron (Fe2)
• oxidized or ferric iron (Fe3)
• 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

4
Iron

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

5
Iron

• Sources

6
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

7
Iron
Factors Enhancing Absorption Factors Inhibiting Absorption

8
Iron
Figure 13-1, page 431

• 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

9
Iron
Figure 13-1, page 431

• 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

10
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 ___________

11
Iron

• Deficiency cont.
• Stages in the Development of Deficiency
• measured by assessing serum ferritin
• decreased serum iron
• levels of serum transferrin ? to enhance
  absorption
• insufficient iron to produce hemoglobin
• accumulation of erythrocyte protoporphyrin
• decrease in hematocrit

12
Iron

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

13
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

14
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

15
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

16
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

17
Zinc

• Absorption and Metabolism
• absorption rate varies between 15 - 40
• 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

18
Zinc

• Interactions
• an excess of dietary iron may reduce zinc
  absorption
• a dietary iron zinc ratio gt 2 1 decreases
  zinc absorption
• large doses of zinc
• inhibit iron absorption
• interferes with copper absorption

19
Zinc

• Sources
• richest sources are protein rich foods

Examples Recommendations Men 11
mg/day Women 8 mg/day
20
Zinc

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

21
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

22
Zinc

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

23
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

24
Iodine

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

25
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

26
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 mg per day
• Note
• a goiter may also develop from excess consumption
  of ___________, an anti-thyroid substance found
  in plants of the cabbage family

27
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

28
Copper

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

29
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

30
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

31
Fluoride

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

32
Chromium

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