Chapter 10
Water Soluble
Vitamins
(continued)
Folate
In foods, folate naturally occurs
as polyglutamate. (Folate occurs
as monoglutamate in fortified
foods and supplements.)
Ring structure + Glutamate
Folate
In the intestine, digestion breaks
glutamates off... and adds a
methyl group. Folate is absorbed
and delivered to cells.
Spinach
Cell
Intestine
Activation of Folate (1)
DNA
Fig. 10-9, p. 339
1
In foods, folate naturally occurs
as polyglutamate. (Folate occurs
as monoglutamate in fortified
foods and supplements.)
Spinach
Activation of Folate (2)
In the cells, folate is trapped
in its inactive form.
To activate folate, vitamin B12
removes and keeps the methyl
group, which activates vitamin
B12.
Both the folate coenzyme and the vitamin B12
coenzyme are now active and available for DNA
synthesis.
Cell
DNA
Fig. 10-9, p. 339
Folate Functions
1. Helps to transfer carbon atoms
from one compound to another
2. Involved in coenzyme systems
for new cell synthesis - helps
synthesize DNA
3. Needed in increased amounts
in pregnancy - help prevent
neural tube defects
Spina Bifida
2
Spina Bifida (2)
Spina Bifida (3)
Spina Bifida (4)
3
Change in Incidence of
Spina Bifida
Folate RDA
RDA
Adults: 400 µg/day
Upper level for adults: 1000 µg/day
Folate
Food
Sources
4
Folate Needs in
Pregnancy
Folate needs double during pregnancy
A pre-natal supplement with appropriate
folate levels recommended during
pregnancy
All women of child-bearing years should
take a folate supplement
Folate and Heart Disease
Research indicates a possible
role for folate in preventing
heart disease by reducing level
of homocysteine in blood
5
Folate Deficiency
Deficiency symptoms:
Anemia (large-cell type)
Smooth, red tongue
Mental confusion, weakness,
fatigue, irritability, headache
Folate Toxicity
Toxicity symptoms:
Masks vitamin B12-deficiency
symptoms
Vitamin B12
6
Vitamin B12 Absorption
Requires a protein carrier in
stomach (called intrinsic
factor) for absorption
Person lacking the intrinsic
factor cannot absorb dietary B12
Vitamin B12 Functions
1. Part of coenzyme systems
for new cell synthesis
2. Helps protect the nervous
system
3. Required to convert folate
to active form
Vitamin B12 RDA
RDA:
Adults: 2.4 ug/day
7
Vitamin B12 Sources
Significant food sources:
Animal products (meat, fish, poultry,
shellfish, milk, cheese, eggs)
Fortified cereals
Fortified soy products
Easily destroyed by microwave cooking
Vitamin B12 Deficiency
Deficiency disease:
pernicious anemia
Deficiency symptoms:
Anemia (large-cell type)
Fatigue, degeneration of
peripheral nerves progressing
to paralysis
Normal blood cells. The size, shape,
and color of these red blood cells
show that they are normal.
Blood cells in pernicious anemia
(megaloblastic). These megaloblastic
blood cells are slightly larger than
normal red blood cells, and their
shapes are irregular.
Fig. 10-12, p. 344
8
Causes of Vitamin B12
Deficiency
Physiological deficiencies of Vitamin
B12 can be due to either:
Lack of intrinsic factor
or
Lack of stomach HCl
Dietary deficiencies can result from
failure to ingest Vitamin B12, such
as vegan dietary patterns
Vitamin B12 Toxicity
None reported
To learn more about Vitamin B12
deficiency, please visit the following
website.
http://www.webmd.com/a-to-zguides/Vitamin-B12-DeficiencyAnemia-Topic-Overview
9