Vitamin deficiency syndromes develop gradually. Symptoms are commonly non-specific, and the physical examination is rarely helpful in early diagnosis. Most characteristic physical findings are seen late in the course of the syndrome. Other characteristics physical findings, such as glossitis and cheilosis, are seen with deficiencies of many B vitamins. Such abnormalities suggest the presence of a nutritional deficiency but do not indicate which nutrient is deficient.

Although any cause of protein-calorie undernutrition can result in concurrent vitamin deficiency, most deficiencies are associated with malabsorption, alcoholism, medications, hemodialysis, total parentral nutrition, food faddism or inborn errors of metabolism.

Let’s throw some light on the types of vitamins:

• THIAMIN (B₁)

the primary role of Thiamin is as a precursor of Thiamin pyrophosphate, a coenzymne required for several important biochemnical reactions necessary for carbohydrate oxidation. Thiamin is also thought to have an independent role in nerve conduction  in peripheral nerves. There is no known toxicity of Thiamin.

• RIBOFLAVIN (B₂)

Riboflavin as the co-enzymnes falvin mononucleotide and flavin adenine dinucleotide – participates in a variety of important oxidation – reduction reactions and is an essential component of a number of other  enzymnes. there is no known toxity of ribloflavin.

• NIACIN

Niacin is a generic term of nicotinic acid and other derivatives with similar nutritional activity. Unlike most other vitamins, niacin can be synthesized from the amino acid tryptophan. Niacin is an essential component of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are involved in many oxidation -reduction reactions.  The major food sources of niacin are protein foods containing tryptophan and numerous cereals, vegetables and dairy products.

• VITAMIN B₆ (PYRIDOXINE)

Vitamin B₆ (pyridoxine) is actually a group of closely related substances involved in intermediary metabolism. These include pyridoxine itself, pyridoxal, pyridoxamine and their 5-phosphate esrers. As a major enzyme involved in the metabolism of amino acids, pyridoxal 5-phosphate is the most important. Pyridoxal phosphate is also required for the synthesis of heme.

Vitamin B₆ deficiency most coomonly occurs as a result of interactions with medications- especially (isoniazid, cycloserine, penicillamine and oral contraceptives) or of alcoholism.

• VITAMIN B₁₂ & FOLATE

Vitamin B₁₂ belongs to a family of cobalamins and serves as a cofactor for two important reactions in humans. As methylcobalamin, it is a cofactor for methionine synthetase in the conversion of homocysteine or methionine, and as adenosylcobalmin for the conversion of methylmalonyl-coenzymeA (CoA) to succinyl -CoA.

All vitamin B₁₂ comes from the diet and is present in all foods of animal origin. The daily absorption of Vitamin B₁₂ is 5mcg.

Since Vitamin B₁₂ is present in all foods of animal origin, dietary B₁₂ deficiency is extremely rare and is seen only in vegans who avoid all dairy products as well as  meat and fish.

• Vitamin C (ASCORBIC ACID)

Vitamin C is a potent antioxidant involved in many oxidation- reduction reactions and is also required for the synthesis of collagen. It increases the absorption of nonheme iron and is involved in tyrosine metabolism, wound healing and drug metabolism.

The major food sources of Vitamin C are fresh fruits and vegetables.

• VITAMIN A

Vitamin A(Retinol) is a high molecular weight alcohol either ingested preformed or synthesized from plant carotenoids, particularly b-carotene.

Vitamin A is essential for normal retinal function and plays an important but still not understood role in cell growth and differentiation, particularly of epithelial cells. Vitamin A is also necessary for wound healing. The principal food sources of Vitamin A are highly pigmented vegetables.

Because of its role in cell differentiation, Vitamin A has been postulated to have a role in cancer prevention.  The provitamin b-carotene may play an even more important role in prevention of cancer and heart disease by virtue of its antioxidant activity.

• VITAMIN D:

Adequate dietary intakes of Vitamin D and calcium are required throughout life to maintain peak bone mass and reduce the risk of subsequent osteoporosis and osteomalacia. The major source of Vitamin D is fortified milk, but sunlight on the skin is a prime resource as well.

• VITAMIN E

Vitamin E activity is derived from at least eight naturally occurring tocopherols, the most potent of which is a-tocopherol. Although the actual function and  mechanism of action of vitamin E in humans are unclear, it is commonly thought to function as an antioxidant, protecting cell membranes and other cellular structures from attack by free radicals.

The major food source of Vitamin E is vegetable seed oil.

Vitamin E, like b-carotene and Vitamin C, may also play a role in protection against cancer, coronary heart disease, Alzheimer’s disease, and cataracts through its antioxidant function.

• VITAMIN K:

Vitamin K plays a role in coagulation by acting as a cofactor for the posttranslational g- carboxylaxation of zymogens II, VII, IX and X. Vitamin K is supplied in the diet primarily in leafy vegetables and endogenously from synthesis by intestinal bacteria.

Body stores of Vitamin K are small, and deficiency may develop in as little as a week. Factors that contribute to Vitamin K deficiency include poor diet, malabsorption, and broad-spectrum antibiotics suppressing colonic flora.

References

“Current Medical Diagnosis & Treatment”, 45th edition