HTHSCI 3BB3 - F2023 - 8B - Trace Elements

Good sources of iron include

meat, fish, leafy greens, lentils and whole grains

Who requires more dietary iron because the iron in plant foods is less more difficult to absorb?

vegans

Which iron is better absorbed?

- part of the heme-group is better absorbed (heme-iron)

- Found in meat (hemoglobin in blood and myoglobin in muscle)

non-heme irone

- not bound to the heme group (e.g. plant-based iron).

• This is more difficult to absorb

which form is iron absorbed

directly in its Fe2+ (ferrous) form or as Heme-bound iron

What helps convert the Fe3+ (ferric) form to the Fe2+?

Acidic foods, stomach acid and Vitamin C can enhance absorption in this way

What can prevent iron absorption?

Fibre, phytates, tannins, oxalates, calcium can bind iron and prevent its absorption

where is iron stored?

mucosal cells, liver

How is iron transported as part of the protein transferrin:

Body cells for use in iron-containing proteins like myoglobin

Bone marrow for production of RBCs

RBCs as hemoglobin for transport of O2

Liver for storage as Ferritin

RBCs are recycled in the spleen, marrow and liver, allowing the iron to be reused

When is iron lost?

When mucosal cells containing ferritin die

When blood is lost, results in loss of transferrin and hemoglobin in RBCs

In the body iron is used for:

- Hemoglobin- delivery of O2 and removal of CO2

- Myoglobin- storage of O2 in muscle cells

- Citric Acid Cycle and Electron Transport Chain Proteins

- Drug Metabolism- Cytochrome P450 (contains a Heme group)

- Immune Function

- Catalase-Protein that protects from oxidative stress by converting H2O2 to water and oxygen

iron deficiency symptoms

"fatigue, weakness, headache, decreased work capacity, an inability to maintain body temperature in a cold environment, changes in behavior, decreased resistance to infection, adverse pregnancy outcomes, impaired development in infants, and an increased risk of lead poisoning in young children, [pica]"

Iron toxicity

Leads increased oxidative stress

Acute-one of the most common forms of poising in children

Chronic - Iron Overload or hemochromatosis

iron supplementation

- Iron cookware

- Iron consumed with acidic foods and foods with vitamin C (e.g. orange juice) is more readily absorbed

- Avoid consumption with diary (calcium, Ca2+ can interfere with absorption)

- supplements can interfere with intake of Copper (Cu2+) and Zinc (Zn2+)

Jon is a 36-year-old male with no health concerns. He is an executive and recently completed an annual physical exam as required by his employer. Blood collected for screening purposes revealed random elevated transferrin saturation of 82% (normal is 15-50%). What do you think the diagnosis for Jon is?

Iron overload from increased iron absorption

Zinc sources

- animal sources better absorbed

- Phytates in vegetables can bind zinc and prevent its absorption

How is zinc lost?

lost in grain processing and not added back as enrichment

zinc in the body

transport proteins regulate the amount of zinc absorbed in the small intestine

Metallothione in proteins regulates the amount of zinc that moves into the blood from the mucosal cells

How is zinc excreted?

Zinc can be excreted in the pancreatic and intestinal juices, allowing excess zinc to be removed from the body

ziinc as a cofactor

- for over 300 enzymes

- Helps reduce oxidative stress as a cofactor in superoxide dismutase

How is zinc part of DNA binding proteins?

Zinc-fingers

Many hormones bind to proteins with zinc fingers

This means deficiency can have wide-spread effects in the body

Zinc deficiency

• Can occur in those with amutation in a zinc transporter and,

• those consuming diets low in protein or high in phytates

Copper in diet

Organ meats, seafood, nuts and seeds, whole grains are good sources

Soil content will impact levels in food

Copper in the body

Free copper can lead to oxidative damage, so transported in the blood with albumin

Secreted in the bile, allowing it to be excreted in the feces

iron transport

Super oxide dismutase-prevention of oxidative stress

Copper deficiency

anemia (poor iron transport) and

connective tissue defects (similar to scurvy due to its role in collagen cross- linking)

Manganese in the body

Absorption is inversely associated with intake

- eliminated in bile

- enzymes involved in amino acid, carbohydrate, and cholesterol metabolism, cartilage formation, urea synthesis, and antioxidant protection.

Part of mitochondrial superoxide dismutase

Manganese sources

whole grains, legumes, nuts

Selenium sources

soil, grains, meat, fish, poultry, dairy

Selenium in the body

- Part of selenoproteins (proteins with selenium)

- Glutathione peroxidase is an example

• Protects from oxidative stress by neutralizing peroxides

• Neededforthesynthesisofthyroid hormones

Selenium deficiency

- Muscular discomfort and weakness

- Keshen disease

• Enlarged heart and poor heart function

selenium toxicity

Changes in fingernail structure and hair loss

Iodine in the body

- used in the synthesis of thyroid hormones

- Thyroid hormones are synthesized from the amino acid tyrosine

• Thyroid hormones regulate gene expression of proteins involved in:

• protein synthesis

• basal metabolic rate

• growth and development

Iodine deficiency

goiter (causes the thyroid gland to synthesis more TSH, enlarging it and taking in more iodine)

Goitrogens

substances that interfere with the utilization of iodine or the function of the thyroid gland

Fluoride in the body

- associates with calcium and helps protect teeth from cavities by making the enamel more resistant to acids

- Deficiency increases the risk of tooth decay

iodine sources

- present in low amount in almost all soil, water, plants and animals

- tea

- water and tooth paste is fortified with fluoride to prevent dental cavities