Micronutrients in Health and Disease
Twenty–eight essential vitamins and minerals play key roles in the metabolism of protein, carbohydrate, and fat, as well as in the structure of the human body (eg, vitamin K in bone matrix, calcium in bone tissue). Many micronutrients are also important antioxidants (eg, vitamins C and E) or act as cofactors for antioxidant enzymes (eg, selenium in glutathione peroxidase). Several trace minerals, though not considered essential, are being studied for their roles in human nutrition. Examples include silicon for bone health1 and vanadium for stimulation of glucose transport.2
Although vitamin deficiency diseases (eg, pellagra) are not widespread, suboptimal micronutrient intake is common. Recent studies show that 10% to 75% of Americans take in less than the recommended dietary allowance (RDA) for many micronutrients (eg, zinc, folate, iron, vitamin B6 and B12), and between 5% and 50% of Americans consume less than half the RDA for many micronutrients.3 While what constitutes sufficient intake is controversial for some nutrients, it is clear that a surprisingly large number of people are undernourished for certain micronutrients, even as they are overly nourished with respect to macronutrients.
Insufficient micronutrient intake has short–term and long–term implications for disease risk. As an example, immune function is adversely affected by poor intakes of nearly every essential vitamin and mineral.4 Thus, diets lacking essential micronutrients may theoretically, at least, affect health over the short term by impairing resistance to viral or bacterial infection. Among longer term problems, a lack of nutrients required for DNA methylation and gene stability may increase the risk for certain cancers.3
The following sections address issues of greatest concern to clinicians: deficiency states, diet–drug interactions, and at–risk populations. Three reference tables are included at the end of this chapter: Table 1, Conditions That May Be Improved by Nutritional Supplements; Table 2, Vitamin Functions, Deficiency Diseases, Toxicity Symptoms, and Dietary Reference Intakes; and Table 3, Mineral Functions, Deficiency Diseases, Toxicity Symptoms, and Dietary Reference Intakes.
Micronutrients in Health and Disease: Micronutrients in Clinical Practice >>