Folate, Vitamin B12 and Vitamin K Flashcards
Name 2 functions of folate.
- DNA synthesis and repair
- Plays important role in cell division and growth
Which cells are most vulnerable to folate deficiency?
+ rapidly dividing cells (RBCs and cells of GI tract)
What is folate?
Vitamin B9
Name some sources of folate.
- Leafy green vegetables
- Fresh, uncooked vegetables & fruits
- Eggs
- Orange juice & legumes
Which vitamin is most likely to interact with medications? Which kinds of medications?
- Folate, drugs will limit the absorption of folate
• Aspirin, antacids
• Oral contraceptives
• Anticonvulsant medications
In foods, how does folate naturally occur?
Polyglutamate (multiple glutamates)
What is the chemical structure of folate?
3 rings and a glutamate
In enriched foods and supplements, how does folate naturally occur?
Monoglutamate
Absorbed 2x as efficienctly
What happens in the intestine in terms of folate?
Digestion breaks glutamate off and adds a methyl group. Folate is absorbed and delivered to cells
In what form is folate in in the cells?
Folate is trapped in its inactive form
How do you activate folate in the cells?
Vitamin B12 removes and keeps the methyl group, which activates both the folate and the vitamin B12
They are both available for DNA synthesis
What is the DRI unit for folate?
Dietary Folate Equivalent
What produces the intrinsic factor?
Stomach
How long does the storage of vitamin B12 last?
3 years
Can you absorb vitamin B12 without intrinsic factor?
No, this would cause a secondary deficiency
- Elderly have less production of intrinsic factor
What can stop folate from being recycled?
Folate cannot be recycled unless b12 takes it out of its trapped inactive form
How do red blood cells during folate OR vitamin B12 deficiency?
- DNA strands break and cell division diminishes
- RNA synthesis continues, resulting in a large cell and large nucleus
- Megaloblastic anemia: large, immature, nucleated cells
Why does megaloblastic B12 and folate anemia look the same?
Since the methyl group transfer is the issue
How can folate affect birth defects? What is the neural tube?
Neural tube will not develop properly with low folate
The neural tube is the embryonic tissue that forms the brain and the spinal cord
How much folate does Health Canada fortify their grains with? What are the results?
- 0.15 mg folate/100 g of flour
- 1.13 defects/1000 to 0.58/1000 in Ontario
What happens with neural tube defect?
- Improper development at the level where it is developed
- Opening in the spinal cord or brain remains from early in human development
- Outpouching of nerves, can cause paralysis or can be relatively minor (Spina bifida)
What is anencephaly?
Absence of a major portion of the head that results when the neural tube fails to close
Infant will die
How can we predict in a child has anencephaly?
Amniotic fluid sample from mom about alpha-fetoprotein, high quantity of this protein will say if there is a neural tube defect
Why are all pregnancies at risk for neural tube defects?
95% of pregnancies with it have no previous histories
Name 3 risk factors for folate deficiency during pregnancy.
1) Diet-Preconceptional Folate status
2) Genetic Link (family history with NTD on either side)
3) Ethnic Background (northern European and Hungarian ancestry)
What did Health Canada suggest pregnant women do to avoid NTD? What did they opt for instead?
- Multivitamin contain 0.4 mg of folate to take starting BEFORE pregnant = unrealistic
- Fortify food supply instead
Name 3 reasons why you would fortify the food supply.
1) To correct or prevent widespread nutrient deficiency
2) To restore nutrients lost in processing
3) To add nutrients normally supplied in the food the product replaces (soy beverage)
Name 2 fortification controversies.
- Targeting the at-risk population
* Optimal intake (fix problem without endangering others)
How can folate supplements mask B12 deficiency?
- Additional folate will erase megaloblastic anemia
- Does not fix neurological problem of B12 deficiency
- High intake of folate, don’t need to bother recycling folate WE JUST USE NEW FOLATE, then we have healthy looking RBCs, we don’t know whether it is fresh folate all the time or if it is because we recycled it
What is the link between Alzheimer’s and folate intake?
- Characterized by brain atrophy associated with low plasma folate
- Highest levels of folate show lowest cognitive decline
High levels of folate decreases the risk of what?
Stroke and depression
How are vitamin B12 and folate interdependent?
- Vitamin B12 is activated by folate
- Folate is activated by vitamin B12
What is the chemical structure of vitamin B12?
Really complex molecule with a cobalt centre
What is the function of vitamin B12?
Helps maintain the sheaths that surround and protect nerve fibers
Name 2 causes of vitamin B12 deficiency.
- Lack of the vitamin in the diet (primary)
* Lack of the intrinsic factor/Lack of HCl (secondary)
What does a decreases in intrinsic factor cause?
Pernicious anemia (won’t go away), large, immature, red blood cells
Name sources of vitamin B12.
Animal sources: chicken, steak, cheese, tuna, etc.
How do are infants of vegetarian and vegan parents affected?
display nerve and cognitive problems caused by nervous system damage during fetus development
Explain regular vitamin B12 digestion and absorption.
- HCL + pepsin release B12 from proteins bound to it
- B12 binds to stomach secretion called intrinsic factor in the small intestine
- They travel to the end of the small intestine (jejunum) where receptors recognize the complex and absorb
Explain vitamin B12 digestion and absorption in an individual with a lack of production of intrinsic factor.
- HCL + pepsin release B12 from proteins
- B12 is unbound and is not recognized by intestinal surface receptor cells in the jejunum for absorption
- Secondary B12 deficiency occurs
What is megaloblastic vitamin B12 deficiency?
- Primary deficiency
- Large immature RBCs
- Vegans
- Not common, slow to develop
What is pernicious vitamin B12 deficiency?
- Secondary deficiency
- Neurological component
- Intrinsic factor deficiency
- Elderly at risk
Why don’t patients with pernicious anemia respond to B12 supplements? How would you treat?
You need to bypass the gut since intrinsic factor cannot bind to B12 for absorption (or there is a lack of HCl)
Given B12 injections or nasal sprays
What is associated to lower levels of vitamins B6, B12 and folate?
High homocysteine
What are high levels of homocysteine a risk factor for?
Independent risk factor for heart diseases (atherosclerosis, formation of blood clots)
How does vitamin deficiency cause high levels of homocysteine?
Causes a bottleneck of homocysteine removal, build up and the homocysteine damages arteries
Vitamin B12 and folate are implicated in the synthesis of methionine from homocysteine, if there is less of these nutrients, there will be more homocysteine and less methionine
Name sources of vitamin K. What is it produced by?
- Found naturally in green vegetables (phylloquinone)
* Produced by colonic bacteria (menaquinone)
Name 2 functions of vitamin K.
- Synthesis of blood clotting proteins
* Synthesis of bone proteins that bind minerals
Adequate intake of what vitamin may reduce the risk of hip fractures?
Vitamin K
What vitamin interferes with the function of blood thinners?
Vitamin K
Why do babies need to be given vitamin K?
- Born with a sterile gut
- Give syringe of vitamin K to babies until gut bacteria grows
How does a solid clot form?
- Precursors for Prothrombin need Vitamin K
- Prothrombin (inactive protein) requires calcium and thromboplastin from blood platelets to produce thrombin (active enzyme)
- Thrombin requires Fibrinogen (soluble protein) to form Fibrin (solid clot)
What is a special consideration for Vitamin K? Why?
- People who use Warfarin - Coumadin, anticoagulant
• Important to maintain vitamin K intake
• Sudden changes in vitamin K from foods can affect potency of medication
How does vitamin B12 and folate decrease the concentration of homocysteine?
Synthesizes homocysteine into methionine
How does vitamin B6 decrease the concentration of homocysteine?
Synthesizes homocysteine into cysteine
