Blood Health Flashcards
What is blood?
- only fluid tissue in body
- transports nutrients to cells
- removes waste products from cells
- need appropriate quantity and healthy quality
- micronutrients are important to blood health
What are the basic components of blood?
- plasma ~55% of volume, contributes to blood volume
- red blood cells ~45% of volume, transport oxygen
- white blood cells <1% of volume, contribute to immune function
- platelets <1% of volume, contribute to blood clotting
What increases absorption of iron and zinc?
- **high demand by body (e.g., growth), low body stores
- Iron Heme-type; zinc from animal sources have increased bioavailability
- stomach acid
- Vitamin C (primarily boosts non-heme iron absorption)
- Meat protein factor
What decreases absorption of iron and zinc in the body?
- full body stores
- binders: phytic acid & oxalic acid found in plant foods
- decreased stomach acid
- polyphenols (eg - tannins in tea, caffeine in coffee)
- high dietary fibre (>50g day)
- supplemental intakes of other minterals
What are the two oxidation states of iron?
- 2+ (ferrous)
- 3+ (ferric)
What is the primary oxidation state of zinc?
2+
Where is iron found in the body?
80% found in hemoglobin (RBC) & myoglobin (muscle)
What is the mucosal block?
The mucosal block describes the ability of an initial dose of ingested iron (or zinc) to block absorption of a second dose given 2-4 h later. This has a protective effect against toxicity.
There is a blockage of Iron absorption at the level of the mucosal cells (also known as intestinal cells, absorptive cells, or enterocytes)
Once Fe enters the intestinal cells, it induces the synthesis of a protein called FERRITIN (or metallothionein for zinc), a storage form of Fe
When iron body pools are full, absorptive cells in the small intestine capture incoming iron, hold it there in the form of ferritin preventing its absorption, and then it is sloughed off when the intestinal cells die (2-3 day life span) and are shed in the feces
How is iron transported?
Iron packaged in mucosal transferrin (a transport protein), and transported in blood
How is iron stored?
- excess Iron is stored in the proteins FERRITIN & HEMOSIDERIN in liver, spleen, intestinal, bone marrow and red blood cells (RBC)
How does the body access iron when stores are low?
- as Iron is needed, it is transferred from mucosal ferritin to mucosal transferrin in the intestinal cells then on to a different molecule in the blood called blood transferrin for transport to other cells and to bone marrow for incorporation of Iron into hemoglobin (Hb) during RBC synthesis
What is enteropancreatic circulation?
If Zinc is needed by the body, Zinc in the bloodstream (where it is bound to blood transport proteins such as albumin and blood transferrin), circulates through the body (cells taking what they need) to the pancreas where Zinc can enter the lumen of the small intestine via pancreatic digestive juices and can re- enter the absorptive cells or not be re-absorbed and excreted in the feces
-this loop is called ENTEROPANCREATIC CIRCULATION (‘entero’ means ‘gut’ or ‘intestine’) -pancreas > intestine > blood > pancreas…
What are the three main roles of iron?
- *Release of Energy from the Macronutrients**
- Iron is required for release of energy at the end of energy-producing cycle in cells (electron transport chain)
- *Hemoglobin (Hb) and Myoglobin (Mb)**
- Iron is an integral part of both hemoglobin and myoglobin
- Iron binds oxygen in Hb and Mb making it available for energy production inside cells
- *Enzyme Synthesis**
- Iron needed as a cofactor for the synthesis of many enzymes found in all cells that oxidize compounds (eg - cytochromes in Electron Transport Chain, catalase antioxidant enzyme – degrades hydrogen peroxide)
What are the main roles of zinc?
- *Enzymes**
- >100 enzymes need Zinc as a cofactor
- needed for synthesis of hemoglobin
- component of superoxide dismutase – aids in the breakdown of free radicals that cause damage to cell membranes
- needed for pancreatic secretion of Zinc
- aids in the release of vitamin A from the liver, in production of the active form of vitamin A (retinal) in the retina for vision, and in the transport of vitamin A through the action of retinol-binding protein
- required for DNA synthesis
- *Many Body Functions Need Zinc**
- growth, protein metabolism, wound healing (platelet production)
- sexual development
- sperm production
- taste sensation
- gene regulation
- thyroid function
What is iron depletion?
Stage 1
Depleted body stores (ferritin) of iron; levels still in normal range
What populations are at risk of iron-deficiency anemia?
- all people, except healthy adult males
- newborns are born with ~6 month stores (dependent upon mother’s status)
- infants/preschoolers have a high demand for Iron due to growth
- children become restless, irritable and are unable to concentrate
- adolescents: males -rapid growth
- females - onset of menses
- women of child-bearing years due to menstrual losses
- pregnant women due to increased blood volume, muscle mass and growth needs
- athletes have increased iron losses through RBC destruction (esp. runners), increased blood volume, decreased Iron intake from heme sources (vegetarian??)
- blood donors
- elderly, usually due to lower intake of Iron and poorer absorption
What is the prevalence and cause of iron-deficiency anemia?
What are foods with high, moderate, and low bioavailability of iron and zinc?
high bioavailability –meat, fish, poultry
moderate bioavailability –grains, legumes
low bioavailability –vegetables
Iron-poor foods - milk & milk products, breastmilk has low amounts but high bioavailability
What are the iron intake recommendations?
- assumes ~18% absorption
- vegetarians: recommended 1.8x RDA intake –mostly grains, vegetables, legumes, small amounts of meat, fish
- adult diet contains ~5-7 mg Fe/1000 kcal
What are the zinc intake recommendations?
Assumes ~20% absorption
typical intakes slightly higher than RDA
What are food sources of copper?
Protein rich foods or water from copper pipes.
