What are Vitamins?
A vitamin is an organic compound distinct from fats, carbohydrates and proteins.
Pseudo vitamins are those compounds with no solid evidence for purported activity. Examples of pseudo vitamins are –
Laetrile: a cyanogenic glycoside. These have unsubstantiated claims of anti-tumorigenicity e.g. Vitamin B17 helps against cancer; Vitamin P having bioflavonoid activity.
Gerovital: an anti-aging elixir with unsubstantiated evidence.
Orotic acid: a normal metabolic intermediate of pyrimidine biosynthesis with hypocholesterolemic activity.
Pangamic acid: ill-defined substances originally derived from apricot kernels, with unsubstantiated claims for a variety of health benefits.
Classification of Vitamins
|Fat soluble vitamins||Compounds with biological activity|
|Vitamin A||retinol, retinal, retinoic acid precursor: beta-carotene, etc.|
|Vitamin D||cholecalciferol (Vitamin D3), ergocalciferol (Vitamin D2)|
|Vitamin E||alpha-tocopherol, gama-tocopherol, tocotrienols, etc.|
|Vitamin K||phylloquinones (K1), menaquinones (K2), menadione (K3)|
|Water soluble vitamins||Compounds with biological activity|
|Vitamin C||Ascorbic acid, dehydroascorbic acid|
|Vitamin B1 (Thiamine)|
|Vitamin B2 (Riboflavin)|
|Niacin||Nicotinic acid, nicotinamide|
|Vitamin B6||Pyridoxine, pyridoxal, pyridoxamine|
|Folate||Folic acid (pteroylmonoglutamic acid)|
|Vitamin B12||Cyanocobalamin or cobalamin|
General Properties of Vitamins
Fat soluble vitamins are soluble in fat and fat solvents. If intake is in excess of daily need, it is stored in the body. Small amounts of these vitamins are excreted in bile. Symptoms of deficiency develop slowly. These are not absolutely necessary in the diet everyday as these are stored. These have precursors or provitamins. These contain only carbon, hydrogen and oxygen. These are absorbed into lymphatic system. These are needed only by complex organisms. Some are toxic at relatively low levels (6-10 X RDA)
Water soluble vitamins are soluble in water. There is minimal storage of these vitamins during dietary excesses. These are lost through urine. Symptoms of deficiency may develop rapidly. These must be supplied in the diet every day. These generally do not have precursors. Contain carbon, hydrogen, oxygen and nitrogen and in some cases other elements such as sulphur, cobalamine. Water soluble vitamins are absorbed into blood through portal vein. These are needed by simple and complex organisms. Toxic only at megadose levels i.e. 10 times greater than RDA.
When are vitamin supplements prescribed?
1. During increased nutrient requirements such as in pregnancy, lactation, chronic alcoholism
2. When food intake is inadequate, for example, weight loss crash diets, illness etc.
4. Malabsorption syndromes during chronic diarrhea, surgical removal of small intestine, chronic pancreatitis.
5. Drug nutrient interactions which deprive the body from nutrient absorption e.g. anticonvulsants or bile acid sequesterants.
6. Therapeutic excess vitamin doses. i.e. Niacin may be prescribed at doses greater than 1000 mg/d for lowering cholesterol.
Know more about vitamin overdose – deficiency effects, anti nutritional factors and much more…