Prevention of Micronutrient Deficiencies: Tools for Policymakers and Public Health Workers by Committee on Micronutrient Deficiencies

Author:Committee on Micronutrient Deficiencies
Language: eng
Format: epub
Tags: Food and Nutrition : Policy, Reviews and Evaluations
Publisher: NATIONAL ACADEMY PRESS
Published: 1998-02-27T00:00:00+00:00

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Prevention of Vitamin A Deficiency

Barbara A. Underwood, Ph.D.

National Eye Institute

Major Health Consequences

Xerophthalmia and Nutritional Blindness

Vitamin A deficiency (VAD) affects ocular tissue in two ways: by slowing the regeneration of the visual pigments following exposure to bright light and by disrupting epithelial integrity. The inability to see well in dim illumination (night blindness) is a symptom recorded in ancient Egyptian, Greek, and Assyrian medical literature and, more recently, in the writings of European physicians. Epithelial defects in ocular tissue leading to blindness were described in dogs by Magendie and in humans by Budd in the early 1800s. They observed progressive deterioration from conjunctival xerosis to corneal xerosis, ulceration, and liquefaction (keratomalacia) as a consequence of restricted diets, devoid of what we now recognize as sources of vitamin A (Wolf, 1996). Manifestations of these distinct debilitating effects were thus recognized before McCollum’s discovery of an essential nutrient, coined fat-soluble vitamin A, in the early 1900s (McCollum and Davies, 1913); description of tissue changes following deprivation of this nutrient (Wolbach and Howe, 1925); elucidation of its molecular role in vision (Wald, 1968); and the recent description of its role in the regulation of genetic expression (Kastner et al., 1994; Mangelsdorf et al., 1994).

The link in humans between clinically evident symptoms and signs and a faulty diet was suggested in about 1860 and subsequently confirmed in many societies (Guggenheim, 1981; Wolf, 1996). Cure was associated with certain foods—in early times with topical application or ingestion of animal and fish liver, and in later years with ingestion of plant foods containing green and yellow pigments (Wolf, 1996). McCollum and Davies (1913), followed shortly thereafter by Osborne and Mendel (1913), described the keratomalacia-preventing, growth-limiting, fat-soluble substances isolated from efficacious foods. These substances were later designated vitamin A and carotenoids.

Steenbock (1919) postulated, and later confirmed, that carotenoid from yellow maize could support growth and prevent ocular lesions by physiological conversion to biologically active vitamin A. Since Isler et al. (1947) discovered a cost-effective way to synthesize vitamin A, cure and prevention are also possible through commercially produced, synthetic vitamin A.

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