Vitamins

Question 1

Vitamin A

Answer 1

Adult male: 900mcg
Adult female: 700mcg
Pregnant female: 750-770mcg
Lactating female: 1200-1300mcg

*Doses less than 10,000IU/day are safe; 5,000IU/day are generally recommended.

More than 10,000IU/day may be teratogenic and more than 25,000IU/day IS teratogenic.

Question 2

Vitamin D

Answer 2

Active form is Calcitriol (by 1-alpha-hydroxylase in the kidneys)

Deficiency—rickets, osteomalacia and osteoporosis.

RDA is 400IU (<1 year old), 600IU (1-70 years old) and 800IU (>70 years old)

In pregnancy and lactation: 600IU.

Toxicity: Hypercalcemia, kidney stones and calcification of arteries and soft tissues.

Question 3

Vitamin E

Answer 3

Tocopherols and Tocotrienols.

Powerful antioxidant. Protective against age-related macular degeneration (AMD).

RDA:

<1 year old—4-5 mg
1-8 years old—6-7mg
>9 years old—11-15mg

Pregnancy—15 mg
Lactation—19mg

Question 4

Vitamin C (Ascorbic Acid)

Answer 4

Powerful antioxidant.

Co-factor in hydroxylation reactions:

• Synthesis of collagen, catecholamines, carnitine and bile acids.

*Deficiency—Scurvy.

RDAs

Adult male: 90mg
Adult female: 75mg
Pregnancy: 85mg
Lactation: 120mg

Toxicity may cause kidney stones—calcium oxalate stones.

Question 5

Vitamin B1

Answer 5

Thiamine.

Energy production—active derivative is Thiamine Pyrophosphate (TPP).

TPP acts as a coenzyme in carbohydrates and amino acids catabolism to provide energy for the body. (Krebs Cycle)

Deficiency—Beri Beri.

Diseases where Thiamine plays an important role:

• Alzheimer’s Disease
• Diabetes
• Heart Failure
• Wernicke-Korsakoff Syndrome

RDA
Adults: 1.1-1.2mg
Pregnancy and lactation: 1.4mg

Question 6

Vitamin B2

Answer 6

Riboflavin.

Main function is energy production. It is essential for two major co-enzymes—Flavin Mononucleotide (FMN) and Flavin Adenine Dinucleotide (FAD).

• Activation of B6 is FMN-dependent.
• Activation of B3 is FAD-dependent.
• Conversion of Retinol to Retinoic acid is FAD-dependent.

Deficiency: Ariboflavinosis—angular stomatitis, cheilosis and impaired body metabolism.

RDA
Adults: 1.1-1.3mg
Pregnancy: 1.4mg
Lactation: 1.6mg

Question 7

Vitamin B3

Answer 7

*Niacin. Produced from Tryptophan.

Energy production—Niacin is essential for two major co-enzymes:

• Nicotinamide Adenine Dinucleotide (NAD)
• Nicotinamide Adenine Dinucleotide Phosphate (NADP)

High doses are hepatotoxic.

Deficiency—Pellagra (dementia, dermatitis, diarrhea and death)

RDA
Adults: 14-16mg
Pregnancy: 18mg
Lactation: 17mg

Question 8

Vitamin B5

Answer 8

*Pantothenic Acid.

Biosynthesis of Coenzyme A (precursor). (Fatty acid synthesis and lipid metabolism)

Coenzyme A acts as an acyl group carrier to form Acetyl-CoA which is a precursor to ACh.

RDA
Adults: 5mg
Pregnancy: 6mg
Lactation: 7mg

Question 9

Vitamin B6

Answer 9

*Pyridoxine.

All vitamers are activated to Pyridoxal Phosphate (PLP) and Pyridoxamine Phosphate (PMP).

Source: Chickpeas.

• Protein Metabolism—ALL Transamination reactions, deamination reactions and trans-sulfuration and decarboxylation reactions.
• Trans-sulfuration: homocysteine detoxification.
• Heme synthesis, glycogenolysis and niacin synthesis.

*PLP is required for niacin synthesis from tryptophan.

RDA
Adults: 1.3mg
Pregnancy: 1.9mg
Lactation: 2mg

Question 10

Vitamin B7

Answer 10

Biotin—Vitamin H.

• Carboxylation reactions. It is a cofactor for 5 carboxylase enzymes:
  1. Acetyl-CoA Carboxylase Alpha (ACC1)
  2. Acetyl-CoA Carboxylase Beta (ACC2)
  3. Pyruvate Carboxylase (PC)
  4. Methyl crotonyl-CoA Carboxylase (MCC)
  5. Propionyl-CoA Carboxylase (PCC)

1st gen. AEDs may cause deficiency.

RDA
Adults: 30mcg
Pregnancy and Lactation: 35mcg

Question 11

Vitamin B9

Answer 11

*Folate. Tetrahydrofolate (THF) carry all biological functions.

• Single-carbon carrier—methylation reactions: (CH3, CH2, CHO). Methylation of proteins and DNA.
• Methyl-THF converts B12 into active Methyl-B12 (Methylcobalamin).
• Homocysteine detoxification.
• Methylenetetrahydrofolate Reductase (MTHFR) genetic polymorphism lead to elevated serum levels of homocysteine. Treatment: B12/Folate or 5-MTHF supplementation.

Deficiency: megaloblastic anemia, hyperhomocysteinemia and neural tube defects.

RDA
Adults: 400mcg
Pregnancy: 600mcg
Lactation: 500mcg

*Pregnant women with neural tube defects risk or epilepsy—use 5mg (5000mcg) per day of folic acid.

*Pregnant women can decrease risk of pre-eclampsia with 1mg (1000mcg) folic acid per day.

Question 12

Vitamin B12

Answer 12

Cobalamin

Hydroxycobalamin is inactive, but used in cyanide poisoning. Methylcobalamin is the active form, as well as 5-Deoxyadenosylcobalamin.

Not found in any plant source.

Single-carbon carrier—methylation reactions ONLY. (CH3)

Methionine synthesis. Homocysteine detoxification. Myelin Sheath synthesis. DNA & RNA synthesis.

Screening: Schilling Test

RDA
Adults: 2.4mcg
Pregnancy: 2.6mcg
Lactation: 2.8mcg