NUTR 1010 Lecture Notes - Heme, Myelin, Cysteine

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10 Apr 2012
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Nutrients Involved in Blood Health
Week 10
March 19, 2012
Folate (latin for “foliage”)
- Water-soluble B vitamin
- RDA for men and women >19 y is 400 μg/d
Folic acid is the active form of folate
- Naturally-occurring food folate converted to folic acid in the body
- We also consume folic acid
o In supplements
o In Fortified foods (e.g. grain products)
- We absorb almost 100% of folic acid, but only ~50% folate
Functions of folic acid (active form of folate)
- Plays a role in DNA synthesis
o Important in new cell and tissue formation
o Critical during first few weeks of pregnancy
- With vitamin B6 and B12, maintains normal homocysteine levels
o Homocysteine: amino acid with increases blood coagulation and LDL
oxidation
o ~10% of risk of developing cardio vascular disease due too
hyperhomocysteinemia
What happens if we consume too much folate or folic acid?
- No problems w/ consuming too much folate (naturally-occurring form)
- Too much folic acid can mask vitamin B12 deficiency [more on this next
class]
o Because of this, Upper Level for folic acid= 1000 μg/day
What happens if we consume too little folate?
- Cannot produce folic acid
- Results:
o Impaired DNA synthesis and cell division, leading to macrocytic
anemic and possibly neutral tube defects
o Increases homocystein levels
Macrocytic anemia
- Signs and symptoms
o Tired, pale
o Headache, irritable
o Dizzy week
o Loss of appetite weight loss
- Good news: reversible
o Folic acid supplements
At risk for macrocytic anemia
- Infants
o Premature
o Those fed goats milk (very low in folate)
- Elderly
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- People who abuse alcohol
- Cigarette smokers
- People on certain anticancer drugs (e.g. methotrexate)
- Pregnant women
And while we’re talking about pregnancy…
- Folate RDA increases 600 μg to support
o High rates of cell development for uterus, placenta and fetus
o Expansion of mom’s red blood cells
- Deficiency of folate can lead to
o Marcocytic anemia (in mom)
o Neutral tube defects (in infant of genetically-predisposed women)
Neural tube defects (NTD)
- Neural tube develops into brain and spinal cord
o It closes at ~28 post conception
o Poor folate status may cause improper closure
- Improper closure leads to NTD:
o If defect in spinal cord: spinabifida (some form are minor, can be
surgically repaired; 85-90% of children survive into adulthood)
o If defects in brian; anencephaly (partial absence of brain tissue; fatal)
Has mandatory folic acid fortification made a difference in the incidence of
NTDs in Canada?
- Yes!!!
- Prior to mandatory folic acid fortifcation incidence of NTDs in Canada = 1.58
per 1000 births
- From 1993 to 2002, incidence of NTDs decreases to 0.86 per 1000 (46%
reduction)
Vitamin B12
- Water-soluble B vitamin
- B12 is bound to animal proteins, so found in dairy, meats, fish, eggs, &
poultry
- RDA for men and women >19 y is 2.4 μg/d
B12 absorption
- B12 separated from protein in stomach due to action of gastric acid
- “Free” B12 then binds to intrinsic factor
o A protein made in the stomach
o Required for B12 absorption in small intestine
- What if you don’t produce gastric acid or intrinsic factor?
o You won’t absorb B12
Functions of vitamin B12
- Helps demethylate folate
- Like folate, helps prevent marcocytic anemia, control homocysteine levels
- Also maintains myelin sheath around nerve fibres
o Essentials for healthy functioning of nervous systems (brian, spinal
cord, nerves)
o Had nothing to do with folate
March 21st
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What happens if we consume too little B12?
- Macrocytic anemia
o Deficiency of B12 means folate cannot be demethylated
o Deficiency of either vitamin can lead to macrocytic anemia
- Pernicious anemia
o Can be caused by a decrease in production of gastric acid and/or
intrinsic factor (B12 not absorbed)
o Remember B12 helps maintain myelin sheath, so deficiency affects
nervous system
Pernicious anemia
- Early pernicious anemia
o Mild impairment of intelligence, orientation and short-term memory
o Good news: reversible
- Advanced pernicious anemia
o Paralysis begins at extremities, works inward and up the spine
o Not-so-good-news: irreversible
At risk for B12 deficiency
- Vegans/fruitarians
o Low intake (no animal products)
o Decrease in production of intrinsic factor
- Infants weaned from breast milk to vegan diets
o Low B12 stores coupled with low intake
- Elderly
o Many have a decrease in gastric acid secretion and a decrease in
production of intrinsic factor
Deficiency of folate and/or B12 causes macrocytic anemia
- Folic acid (supplements, fortified foods) can treat macrocytic anemia,
regardless of whether anemia caused by folate OR b12 deficiency
Reminder (Slide 25)
What happens if we consume too much folate or folic acid?
- No problems with consuming too much folate (naturally-occurring form)
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