OIA1003_VITAMINS_I

Micronutrients

Macromineral & trace minerals + vitamins -> micronutrients

Provitamins: precursor consumers in inactive form -> active vitamins

Bioavailability: rate & extent of a nutrient absorbed & used

Vitamins

Organic substance in minute amount

Essential in normal metabolism & cannot be synthesised in human body

Water Soluble Vitamins - Vit B & Vit C

Readily excreted

Coenzyme in pathways for energy generation

Source: milk, meat, egg & seed product

Deficiencies?

Cheilits, glossitis, dermatitis, diarrhea, neurological symptoms

B complex

Energy-Releasing

Thiamine, B1

Active form: Thiamine pyrophoshate (TPP)

Functions

Energy metabolism - coenzyme for oxidative decarboxylation of a-keto acids

Other metabolism - transketolase (PPP)

Transmission of nerve impulse - ACh Synthesis, ion translocation & direct role of Thiamine triphosphate

Deficiencies?

Mild : loss appetite, constipation, nausea, fatigue & etc.

Moderately severe : Wernicke-Korsakoff syndrome - mental confusion, ataxia, common in chronic alcoholics

Severe : beri-beri & opthalmoplegia

Dry beri-beri: muscular atrophy & weakness

Wet beri-beri: coupled w/ edema

Associate with heat failure - high CO

Riboflavin, B2

Active form: FAD & FMN

Function

Redox reactions

Energy production

Cellular respiration

FMN (flavin mononucleotide, Riboflavin phosphate)

FAD (flavin adenine dinucleotide)

Deficiency?

Not associate with major disease, frequent along w/ other deficiencies

Scaly dermatitis, angular cheilitis, glossitis

Niacin, B3

Active form: nicotinamide adenine dinucleotide (NAD) & NADP

Function

Redox reaction - glucose & alcohol metabolism

Hyperlipidemia treatment - Niacin (1.5g/d) inhibits lipolysis in adipose tissues (reduce VLDL & LDL level)

MOA - average 3.3% of tryptophan convert to Niacin

Deficiency?

Moderate: weakness, skin problem, glossitis (redness)

Pronounced:

Pellagra - Dermatitis (rash in sunlight), diarrhea, dementia (degenerate nervous tissue) -> lethal if untreated

Pantothenic Acid, B5

Function - component of CoA, acyl-carrier protein

Deficiency?

Unlikely & rare, no toxicity

Biotin, B7

Function: Coenzyme (Carboxylation reaction - CO2 carrier)

Assist in glycogen & fat synthesis + amino acid metabolism

Source: 🥜 , 🍫 , 🥚 liver, 🍅 & synthesised by intestinal bacteria

Deficiency - dermatitis, glossitis, nausea

Rare, only when consumed >20 raw eggs (contain avidin protein that inhibits Biotin absorption)

Water soluble vitamins - Haemotopoietic

Folic acid, B9

Involve in DNA synthesis & new cell formation

Coenzyme THF (tetrahydrofolate) & DHF (dihydrofolate) need Vit B12 to function

Sources: fortified grains, leafy green vegetables, legume & seed

*Common among pregnant women & alcoholics

Why?

Inadequate intake, increase demand, impaired absorption & metabolism

How?

Retarded growth

Megaloblastic anemia (macrocytic RBC) due to diminished synthesis of purine & thmidine mono phosphate -> unable make DNA

Folic acid & neural tube defect (spina bifida & anencephaly)

Metabolism?

Folate supplement = 0.4mg/day

Cobalamin, B12

Sources: animal flesh & derived proteins (milk cheese eggs)

Function

Combined conversion of: homocysteine -> methionine & methylTHF -> THF

Coenzyme (methylcobalamin): methionine synthase

Isomerization of methylmalonyl-CoA -> succinyl-CoA

Coenzyme of methylmalonyl CoA mutase (significant for gluconeogenesis)

methylmalonyl CoA -> succinyl CoA (odd C fatty acid metabolism)

Metabolism?

Deficiency?

Symptoms - pernicious anemia (megaloblastic anemia & neurological disorder due to progressive demyelination of nerve - accumulate abnormal fatty acids

Hyperpigmentation of skin

Why?

Reduce intrinsic factor, reduce HCl, severe malabsorption, long-term vegans

Others (Pyridoxine, B6)

Active forms: Pyridoxal phosphate

Function

Coenzyme: amino acid metabolism (aminotransferase) - energy production & stabilise glycogen phosphorylase

Haeme synthesis: incorporate aminoacyl into haeme

Neurotransmitters: synthesis serotonin, NE, GABA & sphingolipids (myelin)

Conversion homocysteine -> cysteine

Deficiency - symptoms

Sideroblastic microcytic anemia (although Fe normal)

Neurological symptoms (mild: irritation, nervous, depressed; severe: peripheral neuropathy)

Decreased glucose tolerance

Dietary deficiency of Pyridoxine - rare, for women take oral contraceptives (long-termed)

Other reasons?

Drug interaction: isoniazid (anti TB) - form hydraozne w/ pyridoxal

Alcoholics: ethanol metabolism of Acetaldehyde - stimulate hydrolysis of Coenzyme phosphate

Non B-complex (Vitamin C)

Ascorbic acid aka Vitamin C

Function

Collagen synthesis - Coenzyme hydroxylation of proline & lysine -> protocollagen (maintain bone matrix)

Iron absorption (Fe3+ -> Fe2+)

Synthesis of epinephrine from tyrosine - dopamine b-hydroxylase step

Bile acid formation - 7a-hydroxylase step

Antioxidant agent - prevent vitamin A, E & some B from oxidation by free radicals & reduce risk of cancer + heart + aging

Degradation of tyrosine - Oxidation of p-hydroxyphenylpyruvate -> homogenisate

Deficiency?

Moderate: easy bruising, form petechiae

Severe form (scurvy) - soft swollen gum w/ loose teeth, muscle weakness, anemia, decreased wound healing

Overdose of Vitamin C (1-4gm/day) - not effective in prevent common cold, may moderate symptom or shorten duration only

Toxicity? Diarrhea & risk form oxalate kidney stone