B complex Flashcards by e steele

thiamine

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riboflavin

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niacin

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pantothenic acid

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pyridoxine

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B12

cobalamin

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Thiamine/B1 RDA

F - 1.1 mg/day
1.5 mg/day needed in pregnancy and lactation
M - 1.2 mg/day

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Thiamine/B1 active form

thiamine pyrophosphate (TPP)
= 95% of B1 in animals
[plants = non-phosphorylated form]
requires Mg and ATP for phosphorylation to active form

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Thiamine/B1 functions

coenzyme

energy transformation
synthesis of NADP
synthesis of RNA and DNA
nerve conduction (regulates sodium channels)

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Thiamine/B1 functions: energy transformation

enzymes:
- PDH
- alpha ketoglutarate dehydrogenase
(also require B2, B3, and lipoid acid)
- transketolase (NADPH and pentose synthesis)

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Thiamine/B1 deficiency

mild = fatigue, insomnia, HAs
beriberi
- dry: peripheral neuropathy, diminished reflexes, muscle spasm/pain/tenderness
- wet: CV manifestions - tachycardia, cardiomegaly, peripheral edema, CHF
- cerebral (W-K syndrome): ophthalmoplegia, ataxia, memory loss/confusion

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Thiamine/B1 food sources

whole grains
enriched flour
nuts/seeds = esp sunflower
legumes
peas

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Coenzymes made with riboflavin/B2

FAD - flavin adenine dinucleotide

FMN - flavin mononucleotide

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Riboflavin/B2 RDA

F - 1.1 mg/day

M - 1.3 mg/day

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Riboflavin/B2 absorption

bound to protein, must be released by HCl and peptidases
95% absorbed in proximal SI up to 25 mg
stored for 2-6 weeks

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Riboflavin/B2 functions

FMN and FAD = part of flavoproteins
- metabolism of carbs, lipids, proteins
- redox rxns: ETC, CYP450 metabolism, beta-oxidation
Dopamine synthesis (monoamine oxidase)
Uric acid metabolism (xanthine oxidase)
Glutathione regeneration (glutathione reductase)
Vitamin metabolism (B6, B3, folate)

Riboflavin/B2 excess

none known

Riboflavin/B2 deficiency

= rare, called ariboflavinosis
cheilosis
angular stomatitis
glossitis
seborrheic dermatitis

may lead to high homocysteine levels

Increased risk for riboflavin/B2 deficiency

DM
stress
OCP
alcoholism

Riboflavin/B2 food sources

dairy (highest)
eggs
mushrooms
meat
almonds
leafy greens
grains

Niacin/B3 RDA

F - 14 mg/day
M - 16 mg/day
can be synthesized endogenously from tryptophan (2-3%)
[aka nicotinic acid/niacinamide]

Niacin/B3 bioavailability

stable in foods (minimal loss from cooking/storing)
bound in complex carbs - corn/wheat
- only 10% available for absorption

Niacin/B3 functions

Redox rxns
- pyruvate decarboxylase
- oxidation of acetylCoA in TCA cycle
- beta-oxidation
- oxidation of alcohol
- biosynthesis of FAs and cholesterol
- proline synthesis
- glutathione and vit C regeneration
- folate synthesis
NADP used for anabolism/NAD used for catabolism

Niacin/B3 excess

= from supplementation
hepatotoxicity and incr liver enzymes
niacin flush d/t histamine release, PGE2 and PGD2
GI distress - N/V

Niacin/B3 deficiency

``` = pellagra dermatitis - symmetrical, thick, scaly diarrhea - N/V, glossitis, angular stomatitis dementia - HA, apathy, disorientation death ```

Niacin/B3 food sources

``` meat fish peas peanuts mushrooms eggs enriched grains ```

Pantothenic Acid/B5 adequate intake

5 mg/day | US consumption = 4-7 mg/day

Pantothenic acid/B5 absorption

85% = bound to CoA in food | absorbed as pantothenic acid in jejunum via sodium-dependent multivitamin transporter

Pantothenic acid/B5 absorption

``` component of CoA = necessary for synthesis of lipids, cholesterol, steroid hormones, ACh, melatonin - component of intermediaries in TCA cycle and beta-oxidation Acetylation rxns: - changes in protein structure - cell signaling - DNA replication - gene expression ```

Pantothenic acid/B5 deficiency

very rare | burning feet syndrome

Pantothenic acid/B5 food sources

``` meat egg yolk mushrooms potatoes avocado cruciferous vegetables yogurt whole grains ```

Pyridoxine/B6 absorption

active form = pyridoxal 5-phosphate (PLP) 75% absorbed destroyed by milling, refining, cooking

Pyridoxine/B6 RDA

F - 1.5 mg/day | M - 1.7 mg/day

Pyridoxine/B6 metabolism

liver = primary site; stores 5-10% muscle stores 75-80% half-life = 3-4 weeks

Pyridoxine/B6 functions

Protein metabolism - AA biosynthesis: trans/deamination - Neurotransmitter synthesis: Serotonin, DA, GABA - Hemoglobin synthesis - Glucose metabolism: gluconeogenesis and glycogenolysis - nucleic acid synthesis: homocysteine metabolism

Pyridoxine/B6 deficiency

hyperhomocysteinemia depression/depressed mood sideroblastic anemia, usu normocytic or macrocytic

Pyridoxine/B6 food sources

``` fish - salmon, tuna meat sunflower seeds spinach grains potatoes bananas nuts ```