Some of the most important symptoms of vitamin A deficiency are:
(1) Changes in the eye.
The early symptoms start with itching, burning and inflammation of eyelids followed by various eye conditions.
Prolonged Vitamin A deficiency results in a condition known as nictalopia or blindness, in which one is unable to see well in dim light, particularly after exposure to a bright light. ‘Blindness’ is explained by the fact that Vitamin A is united to a protein in the retina of the eye to form a pigment called visual purple Rhodopsin. Rhodopsin is formed by the combination of Vitamin A-aldehyde (retinone) and protein (opsin). This is bleached in strong light. During the photochemical reaction some amount of Vitamin A is lost. If Vitamin A is sufficient then the eyes adapt quickly in subdued light and one can see almost at once.
Night blindness is more common in poor people. Males suffer more than females. Pregnant woman frequently suffers from night blindness partly due to underlying diseases and partly due to increased demand of Vitamin A during this period. Night blindness is sometimes due to physical defect in the eye or other cases. The Vitamin A deficiency condition is referred to as ‘Functional night blindness’.
It occurs when deficiency of Vitamin A is severe and prolonged. Xerophthalmia occurs due to changes in the epithelial tissues of the eye. The cornea becomes dry, wrinkled, lusterless, hazy and pigmented. The tear glands stop secreting tears which normally keeps the eye moist, washing away, bacteria and other foreign matter-resulting in dry, inflamed eyelids and loss of the glistening transparent appearance of the eye. The inflammation results in ulceration. The final stage is keratomalacia-softening and destruction of eyeball leading to blindness.
Xerophthalmia is at times associated with Bitot’s spots which are well demarcated foamy-white or grayish irregular areas found on the temporal side of the cornea. These spots do not interfere in vision. Keratomalacia usually affects children between 1-5 years due to absence of Vitamin A in their diet.
(2) Epithelial changes.
Deficiency of Vitamin A leads to atrophy (degeneration) and keratinization (hardening) of epithelium. These cells get flattened and collect one upon the other in a heap. There is increased susceptibility to severe infection of eye, nasal passages, sinuses, middle ear (incus), pharynx, mouth, respiratory tract, lungs and the urinogenital tract. The epithelium of the eye gets so severely damaged that the condition is incurable.
(3) Skin changes.
Deficiency of Vitamin A may lead to Xeroderma (dry and scaly skin with itching) and follicular hyperkeratosis (dry, rough, scaly skin). Thickening of the keratin layers of the skin on the palms and soles occurs. Follicle like goose pimples appear first on upper arm and thighs, then along the shoulders, back abdomen and buttocks. This condition is phrynoderma or Toad skin. The sweat glands of the skin become blocked with horny plugs of keratin so that their secretion diminishes.
(4) Changes in the respiratory tract
The linings of the respiratory organs like nose, throat, traches and bronchi become dry and rough. Thus the respiratory tract becomes prone to bacterial infection.
(5) Changes in the Alimentary tract
Due to Vitamin A deficiency the alimentary tract dries up resulting in diminished secretion of digestive juices, lack of absorption and increased susceptibility to intestinal infection and diarrhea.
(6) Changes in the reproductive tract
Keratinizing metaplasia occurs in the renal pelvis, baldder, uterus, oviduct and accessory sex glands. Vaginitis in females can be seen.
(7) Urolithiasis is a condition in which urinary calculi (stones) are present. The stones are composed of calcium phosphate. Keratinization of the urinogenital tract epithelium takes place due to Vitamin A deficiency which is later followed by bacterial invasion.
(8) Changes in the Skeletal System
Deficiency of Vitamin A leads to irregular development of the skeleton, including the skull and vertebral column. This leads to distortion and injury of the brain and the spinal cord. Growth of bone and teeth are markedly impaired.
(9) Lowered Resistance to Infection
Vitamin A is needed for the maintenance and functioning of the mucous membranes of the body. When there is a deficiency the membranes are thin, dry, porous and flaky. They are unable to perform their protective functions and bacteria have ready access. Thus a shortage of Vitamin A lowers barriers to certain infections.