Hormones and Vitamins
The word hormone has been derived from a Greek word (hormon) meaning 'to arouse to activity'. By the classic definition, a hormone is a substance that is synthesized in minute quantities in one tissue and transported by circulatory system to another organ. The tissue or organ where they are reduced are called effectors and those where they exert their influence are called targets. Based on their site of action hormones are of two types: local and general. The local hormones have specific local effects, for example, cholecystokinin. On the other hand, the general hormones are secreted by various endocrine glands and are transported through the blood to cause physiological action at points away from their place of origin, e.g. growth hormones, thyroxine, adrenocorticotropin, etc.
The hormones are required in extremely small quantities and perform a variety of regulatory functions ranging from growth, vegetative and sexual development, cellular oxidation to thermal regulation and the metabolism of carbohydrates, proteins and fats. Hormone action at the cellular level begins by its association with specific receptor.
The plant hormones are known as 'phytohormones'. These are organic compounds produced naturally in higher plants and controlling growth or other physiological function either at the site of their origin or far remote from their place of production. Auxins, gibberellins, cytokinins, abscisic acid(ABA), and ethylene are the five major types of hormones found in plants.
These are organic molecules in food that are required in minute quantities for normal metabolism but cannot be synthesized in adequate amounts by humans and animals. A dietary or physiologic deficiency of anyone of them leads to a specific set of disease symptoms that can be corrected by administration of that vitamin alone. The vitamins are synthesized by plants and bacteria. These are classified on the basis of solubility as:
- Water soluble vitamins which include the B-complex group of vitamins, and vitamin C (ascorbic acid). B-complex vitamins are found in whole grain cereals, legumes, leafy green vegetables, meat and dairy products. Citrus fruits are a good source of vitamin C.
- Fat soluble vitamins are soluble in fats, e.g. vitamin A, D, E and K. These are present in food fats, e.g. fatty meats, liver, dairy fats, yolks, vegetable seed oils, etc. The vitamins function as coenzyme or cofactor and are required in very small quantities for normal metabolism of animals including us.