Nutrition and Oral Medicine (Nutrition and Health)

Chapter 6 / Medications, Nutrition, Diet, and Oral Health 93release of energy from carbohydrate, protein, or fat metabolism. Pyridoxine (vitamin B 6 )is a coenzyme for reactions of protein metabolism, glycogen release from the liver andmuscles, and the synthesis of the neurotransmitter -aminobutyric acid (GABA). Pantothenicacid and biotin are particularly important in fatty-acid synthesis and glucogenisis.Vitamin A is an essential hormone for maintaining the structural and functional integrityof the epithelial membranes. Vitamin K is necessary for the synthesis of blood-clottingfactors II, VII, IX, and X by acting as a cofactor of the carboxylase that forms -carboxyglutamate in the precursor proteins of those clotting factors. Vitamin D is asteroid hormone that in its biologically active form, 1,25-dihydroxy vitamin D 3 [1,25-(OH) 2 D 3 ,or calcitriol], functions primarily to regulate calcium and phosphorous homeostasis.Most vitamins cannot be synthesized in the body and must be absorbed from foodsources, either in an active form or as precursors that are then transformed into activeentities. Vitamin K, biotin, and small amounts of vitamin B 12 are produced by intestinaltract flora; folate needs to be activated by intestinal enzymes. Vitamin D is synthesizedfrom a precursor in the skin by sunlight and is found in enriched milk and cereal products.Based on their solubility characteristics, vitamins are classified as fat or water soluble.The fat-soluble vitamins include A, D, E, and K, which circulate with lipoproteins in theblood before reaching their target tissues. Excess amounts of these vitamins can be storedin fat tissue and utilized when needed, compensating for short-term intake deficits. Sincefat-soluble vitamins are readily absorbed and stored, doses in excess of the dietary referenceintake (DRI) should be avoided because of the risk of toxicities, particularly withvitamin A. An exception may be vitamin E, which, when taken in large doses, haspharmacologic properties as an antioxidant. The B vitamins (B 1 , B 2 , B 6 , B 12 , niacin,panthothenic acid, biotin, and folic acid) and vitamin C are water soluble and are absorbeddirectly into the bloodstream. Frequent consumption of these vitamins is necessary tomaintain necessary tissue levels because there is limited storage, and excesses are quicklyeliminated by the kidneys. Trace elements and minerals, such as calcium and magnesium,are needed in large quantities by the body as essential building blocks, while iron, zinc,copper, iodine, and a number of other trace elements have limited but essential functions(14) and are needed in much smaller amounts.Whether drug-induced nutritional deficits translate into frank nutrient deficienciesdepends on several factors, including the overall nutrition status of the individual. Inadequatediet and subsequent low store of nutrients can increase the chance of nutritionaldrug depletion, causing clinical symptoms of nutrient deficits. For example, nursinghomepatients on anticonvulsants who get little exposure to sunlight and marginal dietaryintake of vitamin D have a higher incidence of developing osteomalacia and osteoporosis(15). The length of time that a drug is taken also has significant impact on depletion ofnutrients. The incidence of vitamin D deficiency in patients on anticonvulsants increasesthe longer the drug is taken (15). Multiple drug regimens also may increase the risk ofnutritional deficiency if the drugs affect the same absorption or metabolic pathway.Individuals with tuberculosis and concurrent malnutrition taking isoniazid and paraaminosalicylic acid can develop B 6 , B 12 , and folic acid deficiency and subsequentlydevelop pellagra (niacin deficiency) because B 6 is needed to convert tryptophan to niacin.Increased body fat, decreased muscle mass, or dehydration can also effect the distributionof lipophilic (such as benzodiazapines, digitoxin, and synthetic steroids [16]) or hydrophilic(as warfarin, procainamide, atenolol, quinidine, propanolol, theophylline, digoxin,