Folic acid

1. FOLIC ACID

2. Water-soluble B-vitamin, discovered in 1930 by Lucy
Wills.
identified folate in prevention of anemia during pregnancy
Vitamin also known as Folate or Folic Acid
Natural vs synthetic
Must be ingested in diet (cannot be synthesized by body)

4. Folate
 Metabolically active form found in body
Folic acid
 Used commercially in supplements and fortified foods
In 1998 FDA mandated
 Folic acid be added to all items labelled “enriched” cereal grain products (bread,
pasta, wheat fours etc)
 To reduce prevalence of neural tube defects-(NTDs)
 140 mcg FA per 100 grams of flour
Some cereals are fortified with 100% DV
(400 mcg) folic acid per serving
https://www.youtube.com/watch?v=ouMi5z1vwbE

5. Neural tube defects:
 Fetal growth and development is
characterized by widespread cell division
 Adequate folate is critical because of its
role in DNA synthesis
 Neural tube defects (NTD) results in either
 anencephaly
 spina bifida
 defects occur between the 21st and 27th
days after conception, a time when many
women do not realize they are pregnant
 Risk of NTD in US prior to fortification of
foods with folic acid was estimated to be 1
per 1000 pregnancies
Anencephaly
(no-in head or brain)
Spina bifida

6.  Results of randomized trials have demonstrated
 60% to 100% reductions in NTD cases when women consumed folic acid supplements in
addition to a varied diet
 during the periconceptional period (about 1 month before and 1 month after
conception)
 U.S. Public Health Service - recommends that all women capable of
becoming pregnant consume 400 mcg of folic acid daily to prevent NTD
 Recommendation was made to all women of childbearing age, because
adequate folic acid must be available very early in pregnancy

7. Folate is the natural (complex) form found
in foods such as:
 dark-green leafy vegetables, broccoli, asparagus,
lentils, beans, peanuts, strawberries, kiwi, orange
juice, liver
Folate in foods can be lost through processing and
cooking, reducing amount of available folate

8. Folic acid is synthetic (simple) form of folate
1. Used in nutritional supplements and food
fortification
2. Only form that can be transported across
membranes
3. Most oxidized and stable form of folate
4. It is biologically inactive until cells convert it to
active form
• tetrahydrofolate
5. Once activated it serves same functions as Folate

9. Folic Acid (Pteroyl-monoglutamic acid)

10. Pteridine- precursor in the synthesis of folic acid in many
microorganisms
Pteridine compound + Aminobenzoic acid (enzyme- dihydro-
pteroate synthetase)-----→into folic acid in presence of
glutamate
Glutamate

11. FOLYL CONJUGASE
BODY FOLATE 5-
10mg (1/2 in liver)
FA transportation-FBP,
Albumin, free)
Folic acid is metabolically inactive until it is converted into tetrahydrofolate

12. Average daily intake of folate from foods is about 200 mcg
Efficacy of folate absorption is estimated at 50%
Of the 200 mcg consumed, only about 100 mcg actually used by the
body
Alcohol-reduces activity of Folyl conjugase
 Impairs absorption, transport, release and metabolism of folates
 Reduces absorption by 80%

13. Folic acid is metabolically inactive until it is
converted into tetrahydrofolate
Primary metabolic function of tetrahydrofolate is -
a carrier molecule for the transfer of one carbon
groups
1. provides one-carbon groups (such as methyl groups)
for the biosynthesis of other molecules
2. source of these one- carbon groups is from the
metabolism of some amino acids
DHR-(Dihydro folate
reductase)

14.  One-carbon metabolism
 Mediating transfer of 1 carbon units
 Folate coenzymes act as acceptors and donors of one-carbon
units in a variety of reactions critical to metabolism of nucleic
acids and amino acids

15. MTHFR
Methyl donor for DNA methylation
produces purines and pyrimidines required for DNA synthesis

16. Folate and Nucleic Acid Metabolism
Interaction of B6, B2, B9, B12

18. Nucleic acid metabolism:
 Folate coenzymes play a vital role in Nucleic acid metabolism
 Involves 2 pathways
Nucleic acids
–involves purine (A,G) and pyrimidine (T,C) synthesis
which makes folic acid essential for cell division and
DNA synthesis
–2nd pathway includes synthesis of methyl donor (1
Carbon unit) S-adenosylmethionine (SAM)
– used in methylation reactions
– including methylation of DNA (which plays a key role in gene expression)

19. Amino acid metabolism
 synthesis of methionine from homocysteine requires a folate
coenzyme as well as a vitamin B12 dependent enzyme
 folate deficiency can result in decreased synthesis of methionine
and a build up of homocysteine.
Increased levels of homocysteine
may be a risk factor for heart disease
& Alzheimer’s disease

20. Homocysteine Metabolism
Interaction of B2, B9, B12, B6

21. Healthy individuals utilize two different pathways to metabolize
homocysteine
 One pathway (methionine synthase) results in synthesis of
methionine from homocysteine, and is dependent on a folate
coenzyme and a vitamin B12 dependent enzyme
Other pathway converts homocysteine to another amino acid,
cysteine, and requires two vitamin B6 dependent enzymes
 Amount of homocysteine in the blood is regulated by three vitamins: folic
acid, vitamin B12, and vitamin B6

22. Cysteine and taurine and tri-peptide glutathione (glutamine,
cysteine and glycine)
Sulfur compounds very important -under conditions of absolute
deficiency of sulfur, there is no living material
 Every cell in body contains sulfur compounds
SAM is the Precursor for Sulfur-Containing Amino
Acids
Polyamine synthesis
(cell growth)

23.  Folate status is influenced by presence of genetic variations in folate
metabolism, particularly those found in the 5,10-methylenetetrahydrofolate
reductase (MTHFR) gene.
 Genetic variation in folate requirements
 A common polymorphism or variation in the sequence of the gene for
the enzyme, 5, 10-methylenetetrahydrofolate reductase (MTHFR), known
as the MTHFR c.677C>T polymorphism, results in a thermolabile enzyme.
 substitution of a cytosine (C) by a thymine (T) at nucleotide 677 in the exon 4 of MTHFR gene
leads to an alanine-to-valine transition in the catalytic domain of enzyme.
 Depending on population, 20% to 53% of individuals may have inherited one T
copy (677C/T genotype), and 3% to 32% of individuals may have inherited two
T copies (677T/T genotype) for the MTHFR gene.
 MTHFR catalyzes reduction of 5,10-methylenetetrahydrofolate (5,10-
methylene THF) into 5-methyl tetrahydrofolate (5-MeTHF).
 folate coenzyme required to form methionine from homocysteine

24.  Bioavailability
 Dietary folates exist
predominantly in the
polyglutamyl form (containing
several glutamate residues),
whereas folic acid—the
synthetic vitamin form—is a
monoglutamate, containing just
one glutamate moiety.
 natural folates are reduced
molecules, whereas folic acid is
fully oxidized.
 These chemical differences
have major implications for
the bioavailability of
the vitamin such that folic acid is
considerably more bioavailable
than naturally occurring food
folates at equivalent intake
levels.

25. Bioavailability of folates from various foods considered
to be dependent on a number of factors including:
1. Intestinal de-conjugation of polyglutamyl folates
2. Food matrix
3. Instability of certain labile folates during digestion (or
before ingestion)
4. Presence of certain dietary constituents that may enhance
folate stability during digestion (e.g. folate-binding protein
ascorbate)
Factors Contributing to Incomplete Bioavailability
of Natural Food Folates

26. 1. Chemical structure of FA renders it very stable to oxidation and resistant to
destruction
2. Natural folates are labile and prone to oxidative cleavage
3. Reduced forms, particularly unsubstituted dihydro- and tetrahydro- forms, are
unstable chemically
 are easily split between the C-9 and N-10 bond to yield a substituted pteridine
and p-aminobenzoylglutamate, which have no biologic activity
 Substituting a carbon group at N-5 or N-10 decreases tendency of molecule
to split; however, substituted forms are also susceptible to oxidative
chemical rearrangements and, consequently, loss of activity
4. Extensive losses of folate can occur during cooking and preparation of foods
 May considerably reduce amount of folate ingested
 Folate losses in the range of 50–80% have been reported in green vegetables
after boiling and in processed legumes

27.  Unstable to oxygen under aerobic conditions of processing & storage
 Heat, light, metal ions
 Major loss-Leaching in cooking water
 Vitamin C
 Enhances utilization of 5 Methyl FH4 by preventing oxidation to 5 Methyl FH2 (which does not
enter metabolic process)
FH4 Oxidized
FH2 (dihydrofolic
acid, partially
oxidized)
Folic acid (fully
oxidized, but
physiologically
active)
Further oxidation
(physiologically
inactive
products)

28.  Food matrix as a whole and its components can also
influence folate bioavailability by:
 entrapment in the matrix - hinders diffusion to the
absorptive surface during digestion
 Incomplete release from plant cellular structure may be a
factor affecting folate bioavailability in certain plants

29. Folate plays animportant role in pathogenesis of several disorders
in humans
1. Anemia - megaloblastic
2. cardiovascular disease
3. neural tube defects (NTDs) and other congenital defects
4. neuropsychiatric disorders
5. cancer
6. osteoporosis

30.  DNA is constantly damaged by a host of endogenous and exogenous
factors
 sophisticated repair mechanisms available in cells to eliminate such
damage
 Folate deficiency
 imbalance and uracil mis-incorporation into DNA
 Results in abnormal DNA replication
 imposes greater dependence on the repair system
 Folate essential for regenerating methionine
 Methyl donor for DNA methylation
 produces purines and pyrimidines required for DNA synthesis
 Inadequate availability of folate may contribute to aberrations in DNA
methylation
 May lead to abnormalities in DNA synthesis or repair

32. DNA methylation plays an integral role in
oncogenesis
Decreased level of genomic methylation
universal cause in tumorigenesis
Folate depletion has been shown to induce
hypomethylation of p53 tumor suppressor gene
Altered DNA Methylation

33. DEFICIENCY
Causes
 Folate deficiency occurs in a number of situations
 low dietary intake and diminished absorption, as in alcoholism, can
result in a decreased supply of folate.
 Certain conditions like pregnancy or cancer result in increased rates of
cell division and metabolism, leading to an increase in the body's
demand for folate
 Several medications may also contribute to deficiency
 Elderly people - due to conditions such as ill-fitting dentures, physical
disabilities
 Patients with renal and liver failure, anorexia
 Restriction of foods rich in protein, potassium, and phosphate

34. • Megaloblastic Anemia
 Decreased DNA synthesis
 Failure of bone marrow cells to divide
 Normal protein synthesis
 Results in large immature RBC’s
 contrast with microcytic hypochromic anemia
 Megaloblastic anemia is a condition in which bone marrow produces unusually
large, structurally abnormal, immature red blood cells (megaloblasts).
 When DNA synthesis is impaired, cell cycle cannot progress--- leads to continuing cell growth
without division, which presents as macrocytosis

35. Symptoms
 Individuals in early stages of folate deficiency may not show obvious symptoms, but
blood levels of homocysteine may increase
 Rapidly dividing cells are most vulnerable to effects of folate deficiency
 When folate supply to rapidly dividing cells of bone marrow is inadequate, blood cell
division becomes abnormal resulting in fewer but larger red blood cells
 type of anemia is called megaloblastic or macrocytic anemia, referring to large immature red blood cells
 Because normal red blood cells have a lifetime in circulation of approximately 4
months, it can take months for folate deficient individuals to develop characteristic
megaloblastic anemia.
 Progression of such an anemia leads to a decreased oxygen carrying capacity of
blood and may ultimately result in symptoms of fatigue, weakness, and shortness
of breath

36. • Homocysteine
–Coronary Heart Disease risk factor
genetic homocystinuria - premature CHD
high [homocys] related to high CHD risk
low [folate, B-12, B-6] related to high CHD risk
low intake of B-vit related to high CHD risk

37. Homocysteine undergoes autooxidation and
oxidation
Resulting in reactive oxygen species
hydrogen peroxide and superoxide anion radical
generate oxidative stress
linked to damage of endothelial lining of arterial
vessels

38. Examples of molecular cascades induced by
homocysteine that can lead to cell dysfunction and/or
death in cardiovascular disease, and neurodegenerative
diseases
Homocysteine in Neurodegenerative Disorders

39. Congenital malformations due to failure
of closure of the neural tube which
eventually forms central nervous system
anencephaly-failure of closure at end
of neural tube
spina bifida- caudal neuropore end
 2nd most prevalent congenital
malformation associated with mortality
in immediate prenatal period

40. Anencephaly Encephalocele

41. Spina Bifida
What are Neural Tube Defects?

42. Researchers are studying other potential benefits of
multivitamins containing folic acid
 Heart Defects
 Cleft Lip/Cleft Palate
 Limb Defects
 Urinary Defects

43. Dietary Folate Equivalents (DFE)
 FNB of Institute of Medicine set new dietary recommendations for folate
 Dietary Folate Equivalent (DFE) (introduced a new unit)
 Use of DFE reflects higher bioavailability of synthetic folic acid found in
supplements and fortified foods compared to naturally occurring food
folates
 1 microgram (mcg) of food folate provides 1 mcg of DFE
1 mcg of folic acid taken with meals or as fortified food provides 1.7 mcg
of DFE
1 mcg of folic acid (supplement) taken on an empty stomach provides 2
mcg of DFE
 Eg. a serving of food containing 60 mcg of folate would provide 60 mcg of DFE, while a serving
of pasta fortified with 60 mcg of folic acid would provide 1.7 x 60 = 102 mcg DFE due to the
higher bioavailability of folic acid
 A folic acid supplement of 400 mcg taken on an empty stomach would provide 800 mcg of DFE

44. Recommended Dietary Allowance for Folate in Dietary Folate
Equivalents (DFE)
Life Stage Age Males (mcg/day)
Females
(mcg/day)
Infants 0-6 months 65 (AI) 65 (AI)
Infants 7-12 months 80 (AI) 80 (AI)
Children 1-3 years 150 150
Children 4-8 years 200 200
Children 9-13 years 300 300
Adolescents 14-18 years 400 400
Adults 19-years and older 400 400
Pregnancy all ages - 600
Breastfeeding all ages - 500

45. Food Serving Folate (mcg)
Fortified breakfast cereal 1 cup 200-400
Orange juice (from
concentrate)
6 ounces 82
Spinach (cooked) 1/2 cup 131
Asparagus (cooked) 1/2 cup (~ 6 spears) 131
Lentils (cooked) 1/2 cup 179
Garbanzo beans (cooked) 1/2 cup 141
Lima beans (cooked) 1/2 cup 78
Bread 1 slice 20 (Folic acid)*
Pasta (cooked) 1 cup 60 (Folic acid)*
Rice (cooked) 1 cup 60 (Folic acid)*
*In order to help prevent neural tube defects the FDA required 1.4
milligrams (mg) of folic acid per kilogram (kg) of grain to be added to
refined grain products, which are already enriched with niacin, thiamin,
riboflavin, and iron, as of January 1, 1998

46. Factors that increase the metabolic rate
1. Infancy (a period of rapid growth)
2. Pregnancy (rapid fetal growth)
3. Lactation (uptake of folate into breast milk)
4. Malignancy (increased cell turnover)
5. Chronic hemolytic anemia (increased hematopoiesis) all can
result in an increased folate requirement