Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 1)

Harrisons Internal Medicine Chapter 71. Vitamin and Trace Mineral Deficiency and ExcessVitamin and Trace Mineral Deficiency and Excess: IntroductionVitamins and trace minerals are required constituents of the human diet since they are either inadequately synthesized or not synthesized in the human body. Only small amounts of these substances are needed for carrying out essential biochemical reactions (e.g., acting as coenzymes or prosthetic groups). Overt vitamin or trace mineral deficiencies are rare in Western countries due to a plentiful, varied, and inexpensive food supply; however, multiple nutrient deficiencies may appear together in persons who are chronically ill or alcoholic....
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Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 1) Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 1) Harrisons Internal Medicine > Chapter 71. Vitamin and Trace MineralDeficiency and Excess Vitamin and Trace Mineral Deficiency and Excess: Introduction Vitamins and trace minerals are required constituents of the human dietsince they are either inadequately synthesized or not synthesized in the humanbody. Only small amounts of these substances are needed for carrying outessential biochemical reactions (e.g., acting as coenzymes or prosthetic groups).Overt vitamin or trace mineral deficiencies are rare in Western countries due to aplentiful, varied, and inexpensive food supply; however, multiple nutrientdeficiencies may appear together in persons who are chronically ill or alcoholic.Moreover, subclinical vitamin and trace mineral deficiencies, as diagnosed bylaboratory testing, are quite common in the normal population—especially in thegeriatric age group. Famine, emergency-affected and displaced populations, and refugees are atincreased risk for protein-energy malnutrition and classic micronutrientdeficiencies (vitamin A, iron, iodine), as well as for thiamine (beriberi), riboflavin,vitamin C (scurvy), and niacin (pellagra) overt deficiencies. Body stores of vitamins and minerals vary tremendously. For example,vitamin B12 and vitamin A stores are large, and an adult may not become deficientfor 1 or more years after being on a depleted diet. However, folate and thiaminemay become depleted within weeks when eating a deficient diet. Therapeuticmodalities can deplete essential nutrients from the body; for example,hemodialysis removes water-soluble vitamins, which must be replaced bysupplementation. There are several roles for vitamins and trace minerals in diseases: (1)deficiencies of vitamins and minerals may be caused by disease states such asmalabsorption; (2) both deficiency and excess of vitamins and minerals can causedisease in and of themselves (e.g., vitamin A intoxication and liver disease); and(3) vitamins and minerals in high doses may be used as drugs (e.g., niacin forhypercholesterolemia). The hematologic-related vitamins and minerals (Chaps. 98,100) are considered only briefly in this chapter, as are the bone-related vitaminsand minerals (vitamin D, calcium, phosphorus; Chap. 346), since they are coveredelsewhere (Tables 71-1, 71-2, and Fig. 71-1). Table 71-1 Principal Clinical Findings of Vitamin Malnutrition Nutrient Clinical Finding Dietary Contributing Level per Day Factors to Deficiency Associated with Overt Deficiency in Adults Thiamine Beriberi: Nutrient Clinical Finding Dietary Contributing Level per Day Factors to Deficiency Associated with Overt Deficiency in Adults seborrhea, cheilosis Niacin Pellagra: Nutrient Clinical Finding Dietary Contributing Level per Day Factors to Deficiency Associated with Overt Deficiency in Adults anemia Folate Megaloblastic Nutrient Clinical Finding Dietary Contributing Level per Day Factors to Deficiency Associated with Overt Deficiency in Adults methylmalonic acidVitamin C Scurvy: Nutrient Clinical Finding Dietary Contributing Level per Day Factors to Deficiency Associated ...