Vitamin and Mineral Replacement

The sale of vitamins in the United States is a multibillion-dollar business. About 73% of the population uses a variety of nutritional supplements. Older women and people with higher education are typical users of nutritional supplements. Numerous vitamins and herbal medications are available for specialized needs such as cholesterol, memory, menopause, and prostate support. Before purchasing these agents, the patient should discuss with their health care provider the use and health benefits of multiple vitamins and herbal medications. Vitamin supplements are not necessary if the individual is healthy and consumes a well-balanced daily diet on a regular basis.

The Food and Nutrition Board of the Institute of Medicine (IOM) has established the Dietary Reference Intakes (DRIs).

The DRI nutrient recommendations include these components:

Vitamin deficiencies can cause cellular and organ dysfunction that may result in slow recovery from illness. Vitamin supplements are necessary for the vitamin deficiencies described in Table 13.1, but vitamins are frequently taken prophylactically rather than therapeutically.

With the goal of facilitating better nutrition, the U.S. Department of Agriculture (USDA) has developed Choose My Plate, part of a communications initiative based on its 2010 Dietary Guidelines for Americans. Available at www.ChooseMyPlate.gov, Choose My Plate is an interactive tool that helps Americans to eat more healthfully (Fig. 13.1). This website offers a variety of features, including both consumer and professional information.

The Food and Nutrition Board at the IOM publishes the U.S. RDA for daily dose requirements of each vitamin. The U.S. Food and Drug Administration (FDA) requires that all vitamin products be labeled according to the vitamin content and the proportion of the RDA provided by the vitamin product. Individuals should be encouraged to check the RDA listed on the vitamin label to determine whether the product provides the RDA dose requirements. The RDA may need to be modified for patients who are ill.

Megadoses of vitamins are available and are advertised for specific health conditions, but high doses of some vitamins can be toxic. Patients should be advised to contact their health care provider before taking these products. Megadoses of fat-soluble vitamins (A, D, E, and K) may cause toxic effects, whereas megadoses of water-soluble vitamins are eliminated via the urine and thus are generally not toxic. Adverse reactions—kidney stones and nerve damage, respectively—have been reported from vitamin C and vitamin B6. However, it is also claimed that B vitamins may positively influence metabolism in older adults.

Foods rich in vitamins A, D, E, and K are shown in Table 13.2.

The upper limit (UL) for vitamin A is 3000 mcg/daily = 10,000 IU). Vitamin A toxicity affects multiple organs, especially the liver. Mineral oil, cholestyramine, alcohol, and antihyperlipidemic drugs decrease the absorption of vitamin A. Vitamin A is excreted through the kidneys and feces.

Vitamin A taken orally is readily absorbed from the GI tract and peaks in 3 to 5 hours. Its duration of action is unknown. Because vitamin A is stored in the liver, the vitamin may be available to the body for days, weeks, or months.

Calcitriol, the active form of vitamin D, functions as a hormone, and along with parathyroid hormone (PTH) and calcitonin, it regulates calcium and phosphorus metabolism. Calcitriol and PTH stimulate bone reabsorption of calcium and phosphorus. Excretion of vitamin D is primarily in bile; only a small amount is excreted in the urine. If serum calcium levels are low, more vitamin D is activated; when serum calcium levels are normal, activation of vitamin D is decreased. The normal adult RDA of vitamin D is 1000 mg daily (600 IU/day).

Excess vitamin D ingestion (>4000 IU/day) results in hypervitaminosis D and may cause hypercalcemia (an elevated serum calcium level). Anorexia, nausea, and vomiting are early symptoms of vitamin D toxicity.

Although early evidence had suggested the potential for vitamin E to reduce cardiovascular disease (CVD), more recent outcome studies have not shown benefits with vitamin E. Currently, the American Heart Association guidelines do not recommend vitamin E therapy for women as a preventative measure for CVD. Vitamin E has been of interest for its antioxidant properties, and it has been used off label for various conditions, including Alzheimer disease.

The RDA of vitamin E in adults is 30 IU daily and should not exceed the upper limit (UL) of 1000 mg/day in oral intake. The dosage is determined by nutritional intake or degree of deficiency by the health care provider. Side effects of large doses of vitamin E may include fatigue, weakness, nausea, GI upset, headache, bleeding, and breast tenderness. Vitamin E may prolong the prothrombin time (PT), and patients taking warfarin should have their PT monitored closely. Iron and vitamin E should not be taken together because iron can interfere with the body’s absorption and use of vitamin E.

Vitamin K is needed for synthesis of prothrombin and clotting factors VII, IX, and X. For oral anticoagulant overdose, vitamin K1 (phytonadione) is the only vitamin K form available for therapeutic use and is most effective in preventing hemorrhage. Vitamin K is used for two purposes: as an antidote for oral anticoagulant overdose and to prevent and treat the hypoprothrombinemia of vitamin K deficiency. Spontaneous hemorrhage may occur with vitamin K deficiency due to lack of bile salts and malabsorption syndromes that interfere with vitamin K uptake (e.g., celiac disease). Newborns are vitamin K deficient, thus a single dose of phytonadione is recommended immediately after delivery. This practice is common in the United States but is controversial in other countries because it can elevate the bilirubin level and can cause hyperbilirubinemia with a risk of kernicterus. Oral and parenteral forms of phytonadione are available; intravenous (IV) administration is dangerous and may cause death.

Thiamine deficiency can lead to the polyneuritis and cardiac pathology seen in beriberi or to Wernicke encephalopathy that progresses to Korsakoff syndrome, conditions most commonly associated with alcohol abuse. Wernicke-Korsakoff syndrome is a significant central nervous system (CNS) disorder characterized by confusion, nystagmus, diplopia, ataxia, and loss of recent memory. If not treated, it can cause irreversible brain damage. IV administration of thiamine is recommended for treatment of Wernicke-Korsakoff syndrome. Thiamine must be given before giving any glucose to avoid aggravation of symptoms.

Riboflavin may be given to manage dermatologic problems such as scaly dermatitis, cracked corners of the mouth, and inflammation of the skin and tongue. To treat migraine headache, riboflavin is given in larger doses than for dermatologic concerns.

Niacin is given to alleviate pellagra and hyperlipidemia, for which large doses are required. Chapter 41 offers a discussion of niacin use to reduce cholesterol levels. However, large doses may cause GI irritation and vasodilation, resulting in a flushing sensation.

Pyridoxine is administered to correct vitamin B6 deficiency. It may also help alleviate the symptoms of neuritis caused by isoniazid (INH) therapy for tuberculosis. Vitamin B6 is essential as a building block of nucleic acids, in RBC formation, and in synthesis of hemoglobin. Pyridoxine is used to treat vitamin B6 deficiency caused by lack of adequate diet, inborn errors of metabolism, or drug-induced deficiencies secondary to INH, penicillamine, or cyclosporine (or hydralazine) therapy. It is also used to treat neonates with seizures refractive to traditional therapy. Vitamin B6 deficiencies may occur in alcoholics along with deficiencies of other B-complex vitamins. Patients with diabetes or alcoholism may benefit from daily supplementation. Pyridoxine is readily absorbed in the jejunum and is stored in the liver, muscle, and brain. It is metabolized in the liver and excreted in the urine.