Vitamin B9
Presented by Ali Asghar
Mphill Human Nutrition
Khyber Medical University Peshawar
Content
• Form
• Structure
• Properties
• Sources
• Digestion and absorption
• Transport and metabolism
• Functions
• Requirement
• Deficiency
• Toxicity
Vitamin B9 is also known as folic acid
or folate
Folate occurs naturally in food, and
folic acid is the synthetic form of
Vitamin B9
Introductio
n
It was discovered by LUCY WILLS IN
1933
The word folic acid is derived from latin
word folium means leaf and it is also
isolated from leafy vegetable spinach
Structure of vitamin B9
• vitamin B9 consists of three main components:
• pteridine ring,
• P-aminobenzoic acid (PABA)
• glutamic acid residue.
• The pteridine ring and PABA are synthesized de novo in bacteria and
plants, while the glutamic acid residue is added during the absorption
process in the human intestine.
STRUCTURE OF VITAMIN B9
Food sources
• Vitamin B9 is found in a variety of foods
• including leafy green vegetables
• citrus fruits
• Legumes
• nuts and seeds
• fortified cereals and grains.
DIGESTION AND ABSORBTION
• Vitamin B9 is present in polyglutamate form in foods which is
converted into monoglutamate in the small intestine by hydrolases or
congugases found in pancreatic juice and bile and transported to the
liver.
• Where it is converted to its active form, 5- methyltetrahydrofolate (5-
MTHF).
• 5-MTHF is then transported to other tissues, where it is used in
various metabolic pathways, including homocysteine metabolism and
DNA synthesis and repair.
Different
form of
folate
Absorbtion and transportation
• absorbed as folic acid, 5-methyl-FH4 and 5-formyl-FH4.
• The overall efficiency of folate absorption appears to be ∼50% (10-90%).
• Malabsorption of the vitamin occurs in diseases affecting the intestinal
mucosa.
• Folate absorption is dependent on the pH of the proximal jejunum, with an
optimum at pH 6,0-6,3.
• Folic acid is actively transported across the jejunum, and perhaps the
duodenum, by a Na+-coupled, carrier-mediated process that is stimulated by
glucose and shows a pH maximum at about pH 6.
• The transporter is a transmembrane protein with much greater affinities for
folic acid than for reduced folates.
Absorption and transportation
• A high-affinity, folate-binding protein, also called the folate receptor (FR),
has been identified in the intestine and other tissues.
• • The intestine contains three isoforms, each of which is associated with
the brush border.
• • Two isoforms (α- and ß-) are glycosylphosphatidylinositol (GPI)-anchored
to the membrane.
• • β-type is a soluble protein
• GPI-anchored receptor FRα has been shown to cycle between intracellular
and extracellular compartments while remaining bound to the membrane,
thus effecting the high-affinity uptake of folate and nonmolar
concentrations.
Functions
• Synthesis of DNA
• Normal maturation of RBC AND WBC
• Synthesis of purines and pyrimidines
• Cell growth and division
• Proper development of nervous system
• Reduce risk of CVD and stroke
Requirements
Deficiency
• Inadequate intake
• Overcooking of food resulting in loss of
folic acid
• Impaired absorption due to small intestine
disease
• Increased demand during pregnancy
• Dialysis
Spina
bifida
• Not having enough folic
acid during pregnancy is
one of the most
important factors that
can increase chances of
having a child with spina
bifida
Homocyst
eine
• Deficiency of folic acid is
associated with increased
plasma level of
homocysteine
• Folic acid is required for
conversion of
homocysteine to
methionine
Megalobla
stic
Anemia
• Folate and vitamin B12
deficiency can cause
megaloblastic anemia
• form of macrocytic
anemia, a blood disorder
that happens when your
bone marrow produces
stem cells that make
abnormally large red
blood cells due to
diminished purine
synthesis
Depression
• People with low blood levels of
folate might be more likely to
have depression. In addition,
they might not respond as well
to antidepressant treatment as
people with normal folate
levels.
Deficiency
Tongue
Poor growth Gingivitis
inflammation
Loss of Shortness of
Diarrhea
appetite breath
Irritability
Toxicity of folic acid in moderate
doses reportedly is virtually
nonexistent
Folate intake of 15mg daily are
Toxicity problematic include
insomnia,malaise, irratability, and
gastrointestinal distress
A tolerable upper intake level for
adults of 1000ug (1mg) for synthetic
folic acid in supplements and
fortified foods has been suggested.
References
• The Vitamins. Fundamental
Aspects in Nutrition and Health.
Elsevier Inc. 2008. 16
• www.hsph.harvard.edu/nutritio
nsource/folic-acid
• https://www.medicalnewstoday.
com/articles/287677
• Scan the code for more
information on folic acid
