Vitamins for vitality
Vitamins are a group of potent organic compounds that are not carbohydrates, fats or proteins in nature. They are present in foods and are needed by the body in small quantities for its normal functioning. They are classified along with minerals as micronutrients and with the exception of vitamins D and K which can be synthesised in the body, the others have to be obtained from food. Based on their solubility, vitamins are classified into two groups as fat-soluble vitamins and water-soluble vitamins.
The fat-soluble vitamins are called so because they are absorbed into the body along with dietary fat and are transported to various parts of the body in the lipoproteins. There are four vitamins belonging to this category – vitamins A, D, E and K. The excess fat-soluble vitamins are stored in the liver and become available to the body when dietary intakes are reduced. Excessive storage of the fat-soluble vitamins leads to hypervitaminosis which has harmful effects on one’s health. Fat-soluble vitamins are not lost during normal cooking procedures but are affected by frying. They are also destroyed when fats turn rancid and their absorption gets affected in the presence of mineral oil.
Water-soluble vitamins are a large family consisting of vitamin C and eight B-complex vitamins – B1, B2, B3, B6, B10, B12, folic acid and biotin which are easily absorbed into the body. Excess water-soluble vitamins are not stored in the body but are excreted in the urine, hence they have to be obtained from one’s daily diet. The water-soluble vitamins are unstable and are greatly affected by factors such as heat, light and air. They get leached out into the water used for cooking, by exposure to sunlight and air and by prolonged cooking. Discarding the water after cooking rice or boiling vegetables or making paneer results in the loss of these vitamins.
There are some compounds present in food or in the body which get converted into vitamins. Such compounds are known as pro-vitamins. Beta-carotene the yellow orange pigment found in dark green leafy vegetables and yellow orange vegetables and fruits is one such pro-vitamin compound as within the body beta-carotene gets converted into vitamin A. Another pro-vitamin compound is 7-dehydrocholesterol, a cholesterol derivative that is present in the skin. 7-dehydrocholesterol in the presence of sunlight undergoes a series of transformations into the active form of vitamin D- 1, 25 dihydroxy vitamin D-3 or calcitriol.
Each vitamin performs specific functions and a deficiency has various consequences on health. For example if there is a vitamin D deficiency then the absorption of calcium will decreased thereby affecting bone health. If you do not get enough vitamin C then iron absorption is affected leading to anaemia.
The amount and type of vitamins present in foods varies greatly and only a balanced diet can ensure adequate intake of vitamins.
(Writer is a consultant nutritionist with 18 years of experience, practising at Panaji and can be contacted on email@example.com)