VITAMINS

Definition Vitamins are naturally occurring organic essential micronutrients present in very small quantity in diet ( from few microgram to mg) and needed for normal metabolism, development, function and optimal health.

Specific role played by vitamins now is confirmed that Required for the execution of Metabolic functions If deficient, certain specific metabolic disorders are seen. Participate as coenzyme in various enzyme catalyzed reaction. Vitamins do not provide energy.

DIETARY SOURCES Mainly derived from food meat, fish, milk, vegetables, fruits As Can not be synthesized in appropriate quantities, must be present in human diet.

Other Sources Few are synthesized by normal intestinal flora ( Vitamin K and B 9) Few others are synthesized by some body tissues like skin ---------- Vit-D

Functions (Contd.) Maintenance of optimal Health Prevention of chronic diseases may require certain vitamins in amounts greater than RDA. Normally 15 iu/day of vit E is required for health 100 iu of vit E is required for significant reduction in risk of CAD It is also believed that vitamins play a role in prevention of Cancer.

Classification 14 different vitamins so far have been isolated and purified into crystalline form. These are classified in to two groups Classification is based on solubility characteristics.

Requirements Varies with metabolic activity Age, Size, Sex of an individual Requirement increase during Exercise Fever Disease Pregnancy Lactation

Requirements (Contd.) Requirement of B, are particularly increased in CHO rich diet. For every 1000 Calories obtained form carbohydrate rich diet 1mg of B1 is needed

Storage Water Soluble: Not stored in our bodies. Must therefore be present in diet to an appreciable extent for normal health and growth. Fat Soluble: Are stored, if taken in excess. Stores are sufficient to meet the demand of our body for almost 6 months, if no vitamins are taken through diet.

Wastage During therapy and intestinal infection, drugs like sulfonamides and antibiotics kill the normal intestinal flora which synthesizes vit.of B complex group. Demand increases, and Supplementation is advised

Wastage Water soluble vitamins are lost when cooked in water and Specially when water is thrown away. Vegetable should not be washed after cutting. Milling and polishing of rice destroys B2. Hydrogenation of oils, inactivates Vit A & D,and before marketing fortification with A & D be done.

Wastage Water soluble vitamins are lost when cooked in water and Specially when water is thrown away. Vegetable should not be washed after cutting. Milling and polishing of rice destroys B2. Hydrogenation of oils, inactivates Vit A & D, and before marketing fortification with A & D be done.

Vitamin D

Vitamin D is a group of fat-soluble Secosteroids. In humans, vitamin D is unique It functions as a hormone and As the body can synthesize it (as vitamin D3) when sun exposure is adequate.

IS VIT D A VITAMIN ? Although "vitamin D" is commonly called a vitamin , some say it should not be classified as a vitamin because it can be synthesized by the human body.

VIT . D AS VITAMIN Vitamin D fits within the definition of vitamin as it is "an organic compound required as a vital nutrient in small amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet". Additionally, like other compounds called vitamins, in the developed world vitamin D is added to milk,ghee and oil, to avoid disease due to deficiency.

DISCOVERY As with other compounds called vitamins, it was discovered in an effort to find the dietary substance that was lacking in a disease, namely, ricket, the childhood form of osteomalacia.

Vitamin D occurs in two forms: “Vitamin D2” (ergocalciferol), chief Vit D precursor in plants is, ergostreol. 2 “Vitamin D3” (cholecalciferol), the main form occurring in animal cells and developing in skin on exposure to ultraviolet light from 7- dehydro cholesterol.

Animal sources of Vit D Eggs Liver Butter Fish

Absorption Vit D is stable through storage, processing and cooking and is absorbed effectively from GIT Any abnormality in fat absorption may cause mal- absorption of Vit D

Absorption and metabolism Before it can function, Vit D3 must be activated by hydroxylation which takes place both in liver & kidney. The initial conversion in the liver results in 25-hydroxy cholecalciferol (calcidiol), the major circulating form of Vit D3.

Absorption and metabolism 2nd hydroxylation takes place in the proximal tubule of the kidney, giving rise to 1,25-dihydroxycholecalciferol or calcitriol. This form is then transported to bones, kidneys and intestines.

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