Water soluble vitamins
د. هديل فاضل فرهود
INTRODUCTION — Vitamins are a number of chemically unrelated families of organic substances that cannot be synthesized by humans but need to be ingested in the diet in small quantities to prevent disorders of metabolism. They are divided into water-soluble and fat-soluble vitamins .vitamin A,E,D &K are fat –soluble vitamin and may be store in the body, the remainder being water- soluble vitamine and the body has limited or no store.
Water – soluble vitamins:
VITAMIN B1 (THIAMINE) — Thiamine, Formerly known as vitamin B1, thiamine is soluble in water and partly soluble in alcohol.
Metabolism — Thiamine is absorbed in the small intestine via both passive diffusion and active transport. The maximal absorption of thiamine is in the jejunum and ileum . Thiamine passes through the mucosal cells to enter the blood stream, Bound to albumin, it is carried by the portal circulation to the liver. Thiamine enters the red blood cells by passive diffusion while its entry into other cells is via an active energy requiring process . The highest concentrations are found in the skeletal muscles, the liver, the heart, the kidneys, and the brain. Thiamine s biologic half-life is approximately 10 to 20 days; due to limited tissue storage, continuous supplementation is required . Thiamine and all of its metabolites are excreted in the urine.
Function :
It form part of the coenzyme thiamine pyrophosphate (TPP) which is involved in major decarboxilation steps . it serve as a catalyst in the conversion of pyruvate to acetyl CoA,
Thiamine is also involved in many other cellular metabolic activities Thiamine has a role in the initiation of nerve impulse propagation that is independent of its coenzyme functions . also it needed for the metabolism of fat , CHO, and alcohol .
Deficiency —
Thiamine deficiency has been associated with three disorders: Beriberi (infantile and adult) Wernicke-Korsakoff syndrome & Leigh s syndrome
Infantile beriberi — Beriberi in infants becomes clinically apparent between the ages of two and three months. The clinical features are variable and may include a fulminant cardiac syndrome with cardiomegaly, tachycardia, a loud piercing cry, cyanosis, dyspnea, and vomiting . A form of aseptic meningitis has also been described in which the affected infants exhibit vomiting, nystagmus, purposeless movements, and seizure, despite a "normal" cerebrospinal fluid
Adult beriberi — Adult beriberi is described as dry or wet. Dry beriberi is the development of a symmetrical peripheral neuropathy characterized by both sensory and motor impairments, mostly of the distal extremities. Wet beriberi includes a neuropathy, as well as signs of cardiac involvement with cardiomegaly, cardiomyopathy, congestive heart failure, peripheral edema, and tachycardia
Beriberi has been reported as a complication of weight loss surgery, presenting as a polyneuropathy with a burning sensation in the extremities, weakness, and falls .or patients with heart failure especially those treated with loop diuretics
Thiamine deficiency can occur as a complication of total parenteral nutrition if adequate thiamine supplements are not provided.
Wernicke-Korsakoff syndrome — Wernicke s disease is a triad of nystagmus, ophthalmoplegia, and ataxia, along with confusion. Korsakoff s psychosis is impaired short-term memory. This combination is almost exclusively described in chronic alcoholics with thiamine deficiency.. There may be a genetic predisposition for the development of Wernicke-Korsakoff s syndrome since not all thiamine deficient patients are affected.
Leigh s syndrome — Leigh s subacute necrotizing encephalomyopathy is a condition also seen in thiamine deficiency. with a subacute neurologic course, leading to symmetrical foci of spongy necrosis and demyelinating changes in the thalami, brainstem, and even peripheral nerves. It is manifested with ataxia, dysarthria, movement disorders, muscle atrophy, and weakness.
Toxicity — No real syndrome of excess thiamine exists since the kidneys can rapidly clear almost all excess thiamine
Daily Values — thiamin requirements are related to energy metabolism 2mg/d for men & 1.54 mg/d for woman .
Good food sources of thiamin : cereal products (including breakfast cereals and bread ) , yeast , pulses ,nuts , pork & other meats, vegetables& milk .
Riboflavin ( vitamin B2 ) : FUNCTION :
* promotion of normal growth .
* assisting synthesis of steroid , red blood cell and glycogen *maintenance of mucous membranes , skin , eyes and nervous system
*aiding Fe absorption
Deficiency :
Lesions of the mucosal surfaces of mouth , angular stomatitis
Glossitis , surface lesions of genitalia , seborrhoeic skin lesion & vascularization of the cornea
nutrient deficiency
Good food sources of Riboflavin :
Eggs , milk and milk product , liver and kidney , Yeast extract , fortified breakfast cereals
Average daily intake in men is 2.11mg\d & in female 1.60 mg\d
Vitamin B6 : Function :
*Transamination of amino acids to produce Ketoacids and synthesis of non –essential amino acids
*decarboxylation to yield biologically active amines , e.g, neurotransmitters
* prophyrin synthesis , including haemoglobin.
Vitamin B6 is also involved in the conversion of glycogen to glucose in muscle, and in hormone metabolism.
Deficiency :
Sever deficiency of vitamin B6 is rare . patient suffering malabsorption , receiving dialysis or alcoholic are at risk to deficiency . clinical signs include :
Lesion of the lips and corners of the mouth and inflammation of the tongue , Neuropathy , anaemia (due to poor haem synthesis)
Due to the importance of vitaminB6 in amino acid metabolism requirement are linked to protein intake . the average daily intake in men 33mg\d and in female 31mg\d .
Good food sources of vitamin B6 :
Meat , whlegrain cereals , fortified cereals , bananas , nuts ,pulses .
Cobalamin B12 : the function of vitamin B12 include * recycling of folate coenzymes *Normal myelination of nerves
Synthesis of methionine from homocystein
Deficiency : pernicious anaemia ( megaloblastic) & \ or neurologic problem .
The most common cause of deficiency is malabsorption due to atrophy of the gastric mucosa
Good food sources of vitamin B12: vitamin B12 does not found in plant food . meat and meat product , eggs ,milk and dairy products , fish ,yeast products , breakfast cereals ( fortified)
VITAMIN C (ASCORBIC ACID) — Vitamin C (ascorbic acid) has a prominent role in history for clinical manifestations of scurvy. Ascorbic acid is absorbed in the distal small intestine through an energy dependent process. Usual dietary doses of up to 100 mg/day are almost completely absorbed.
Actions — Ascorbic acid has a number of biologic actions. As a general rule, it provides electrons needed to reduce molecular oxygen. These anti-oxidant capabilities also stabilize a number of other compounds, including vitamin E and folic acid.
* Fatty acid transport — The transport of long-chain fatty acids across the mitochondrial membrane is a carnitine dependent process. Carnitine synthesis requires ascorbic acid as an enzymatic cofactor
*Collagen synthesis — Formation of collagen requires Ascorbic acid . Failure in collagen synthesis results in impaired wound healing, defective tooth formation, and deficient osteoblast and fibroblast function
* Neurotransmitters
* Prostaglandin metabolism — Ascorbic acid has a role in prostaglandin so It may be capable of attenuating the inflammatory response or even sepsis syndrome
Deficiency — ascorbic acid is an essential nutrient derived from the diet. Scurvy is a clinical syndrome seen with ascorbic acid deficiency largely due to impaired collagen synthesis with disordered connective tissue. Symptoms (occurring as early as three months after deficient intake) include ecchymoses, bleeding gums, petechiae, coiled hairs, hyperkeratosis, , arthralgias, and impaired wound healing. Generalized systemic symptoms are weakness, malaise, joint swelling, arthralgias, edema, depression, neuropathy, and vasomotor instability . ascorbic acid deficiency occurs mostly in severely malnourished individuals, drug and alcohol abusers, or those living in poverty.
Daily Value — The DV for ascorbic acid is 60 mg per day for most adults; pregnant or lactating women and the elderly have requirements up to 125 mg/day.
Good food sources of vitamin C : Kiwi fruit , citrus fruit , sweet potato , broccoli, mango.
Folate (folic acid ) : folic acid is the synthetic form of vitamin . function :it is essential for the synthesis of DNA & RNA , folate supplement in early pregnancy has been show to reduce neural tube defect . deficiency result in megaloplastic anemia with abnormal neutrophil nuclei and giant platelates , there may also be infertility . Good food sources of folate :
– Brussels sprouts , spinach, fortified bread and breakfast cereals, cabbage , cauliflower , kidneys ,beans , peas ,most nuts , brown rice , milk . average daily intake = 2oo Mg\day for adults . to prevent NTD in pregnancy = 400Mg\day until 12 week of pregnancy . to prevent recurrence of NTD =5000Mg
Vitamin B3 NIACIN (nicotinamide , nicotinic acid )
Function : are involve in numerous oxidoreductase reaction including glycolysis, fatty acid metabolism, tissue respiration and detoxification.
Deficiency of niacin is known as pellagra , and classically characterize by 3D: dermatitis , diarrhea , dementia.
Food sources :beef,chicken,eggs,milk and wheat flour, seeds.
15 to 20 mg per day for adult males, and 13 to 15 mg per day for adult females