Vitamins
“Vita” is the Latin word for “life.” The word “vitamin” signifies the importance of vitamins to humans. Vitamins consist of carbon, oxygen, hydrogen, and sometimes nitrogen or other elements. When first discovered, vitamins were given alphabetical names such as vitamin A, vitamin B, and so on. Research has shown that vitamins belong to groups. Because they are organic substances, vitamins can be converted to other forms and are susceptible to oxidation and destruction. They may also be precursors to other chemicals. As a result of the increasing awareness of individual vitamins, vitamins are more accurately referred to by a group name or a specific name such as “ascorbic acid” for vitamin C. Table 30-7 and Table 30-8 contain both common and specific names of most known vitamins.
Small amounts of vitamins are necessary to help regulate body processes, including synthesizing body compounds, such as bone and blood, and extracting energy from carbohydrates, fat, and protein. Most vitamins work in the form of a coenzyme that promotes the action of enzymes. Without vitamins, thousands of chemical reactions cannot occur. The body, with a few exceptions, cannot produce vitamins; therefore, vitamins are an essential component of a healthy diet. Box 30-4 provides some general principles related to vitamins.
BOX 30-4.
General Principles Related to Vitamins
• Some vitamins are lost by exposure to air or during food storage. Fresh foods retain most vitamins when properly stored. Frozen foods are second, although their vitamin C content may be higher than that of improperly handled fresh food. Canned foods are third. (Canned foods should be processed carefully and not stored too long.)
• Some vitamins are fat soluble and are stored in the body in this form. The diet must include sufficient fat to carry an adequate supply of these vitamins (15-20 g).
• Some vitamins are water soluble. Cook foods in a small amount of water and use the cooking water; if possible, in gravies, sauces, and soups.
• High temperatures destroy vitamins. Do not overcook food, and serve it at once.
• Avoid discarding the high-nutrient portion of some foods. The highest concentration of some vitamins may be found in the outer leaves of lettuce and vegetable peels.
• A clinical condition called hypervitaminosis can occur as a result of an excess of a particular vitamin or vitamins. Hypervitaminosis occurs almost exclusively from supplement use, not from dietary intake.
These principles are important for the NCLEX.
TABLE 30-7. Summary of Fat-Soluble Vitamins
| VITAMIN AND SOURCES | FUNCTIONS | DEFICIENCY/TOXICITY SIGNS AND SYMPTOMS |
| Vitamin A
Retinol • Liver • Dairy products • Egg yolk • Rready-to-eat cereals Beta-Carotene • Green leafy vegetables • Broccoli • Carrots • Peaches • Pumpkin • Red peppers • Sweet potatoes • Winter squash • Mango • Watermelon • Apricots • Cantaloupe |
• Enables the eye to adapt to dim light
• Normal growth and development of bones and teeth • Formation and maintenance of mucosal epithelium to maintain healthy functioning of skin and membranes, hair, gums, and various glands • Important role in immune function |
Deficiency
• Night blindness • Slow recovery of vision after flashes of bright light at night • Bone growth ceases • Bone shape changes • Enamel-forming cells in the teeth malfunction • Teeth crack and tend to decay • Skin becomes dry, scaly, rough, and cracked • Keratinization or hyperkeratosis develops • Mucous membrane cells flatten and harden • Xerosis (eyes become dry) • Irreversible drying and hardening of the cornea can result in blindness • Decreased saliva secretion s difficulty chewing, swallowing s anorexia • Decreased mucous secretion of the stomach and intestines s impaired digestion and absorption s diarrhea, increased excretion of nutrients • Susceptibility to respiratory, urinary tract, and vaginal infections increases. Toxicity • Headaches • Vomiting • Double vision • Hair loss • Bone abnormalities • Liver damage • Can cause birth defects during pregnancy |
| Vitamin D
• Sunlight on the skin • Liver • Some fish • Egg yolks • Fortified milk • Some ready-to-eat cereals • Margarine |
• Maintains serum calcium concentrations
by: • Stimulating gastrointestinal (GI) absorption • Stimulating the release of calcium from the bones • Stimulating calcium reabsorption from the kidneys |
Deficiency
• Rickets (in infants and children) • Retarded bone growth • Bone malformations (bowed legs) • Enlargement of ends of long bones (knock-knees) • Deformities of the ribs (bowed, with beads or knobs) • Delayed closing of the fontanel s rapid enlargement of the head • Decreased serum calcium and/or phosphorus • Malformed teeth; decayed teeth • Protrusion of the abdomen related to relaxation of the abdominal muscles • Increased secretion of parathyroid hormone • Osteomalacia (in adults) • Softening of the bones s deformities, pain, and easy fracture • Decreased serum calcium and/or phosphorus, increased alkaline phosphatase • Involuntary muscle twitching and spasms Toxicity • Kidney stones • Irreversible kidney damage • Muscle and bone weakness • Excessive bleeding • Loss of appetite • Headache • Excessive thirst • Calcification of soft tissues (blood vessels, kidneys, heart, lungs) • Death |
| Vitamin E
• Vegetable oils • Margarine • Salad dressing • Foods made with vegetable oil • Nuts & seeds • Wheat germ • Dark green vegetables • Whole grains • Enriched cereals |
• Acts as an antioxidant to protect vitamin A and polyunsaturated fatty acid (PUFA) from being destroyed
• Protects cell membranes |
Deficiency
• Increased red blood cell (RBC) hemolysis • In infants: anemia, edema, and skin lesions Toxicity • Relatively nontoxic • High doses enhance action of anticoagulant medications |
| Vitamin K
• Bacterial synthesis • Green leafy vegetables • Liver • Eggs • Cabbage-related vegetables |
• Synthesis of blood clotting proteins
• Synthesis of a bone protein that regulates blood calcium |
Deficiency
• Hemorrhaging Toxicity • No symptoms have been observed from excessive vitamin K |
TABLE 30-8. Summary of Water-Soluble Vitamins
| VITAMIN AND SOURCES | FUNCTIONS | DEFICIENCY/TOXICITY SIGNS AND SYMPTOMS |
| Thiamin (Vitamin Bj) | • Coenzyme in energy metabolism | Deficiency |
| • Whole grain | • Promotes normal appetite | • Beriberi |
| • Enriched breads and cereals | • Promotes nervous system functioning | • Mental confusion |
| • Liver | • Decrease in short-term memory | |
| • Nuts | • Fatigue | |
| • Wheat germ | • Apathy | |
| • Pork | • Peripheral paralysis | |
| • Dried peas and beans | • Muscle weakness and wasting | |
| • Painful calf muscles | ||
| • Anorexia, weight loss | ||
| • Edema | ||
| • Enlarged heart | ||
| • Sudden death from heart failure | ||
| Toxicity
• No toxicity symptoms reported |
||
| Riboflavin (Vitamin B2) | • Coenzyme in energy metabolism | Deficiency |
| • Milk and other dairy products | • Aids in the conversion of tryptophan into niacin | • Dermatitis |
| • Whole grain | • Cheilosis | |
| • Enriched breads and cereals | • Glossitis | |
| • Eggs | • Photophobia | |
| • Meat | • Reddening of the cornea | |
| • Green leafy vegetables | Toxicity | |
| • No toxicity symptoms reported | ||
| Niacin (Vitamin B3) | • Coenzyme in energy metabolism | Deficiency |
| • All protein foods | • Promotes normal nervous system functioning | • Pellagra (4 Ds) |
| • Whole grain | • Dermatitis and glossitis | |
| • Enriched breads and cereals | • Diarrhea | |
| • Dementia, irritability, mental confusion s psychosis
• Death, if untreated Toxicity (from supplements/drugs) • Flushing • Liver damage • Gastric ulcers • Low blood pressure • Diarrhea • Nausea • Vomiting |
||
| Vitamin B6 | • Coenzyme in amino acid and fatty acid metabolism | Deficiency |
| • Meats | • Helps convert tryptophan to niacin | • Dermatitis |
| • Fish | • Helps produce | • Cheilosis |
| • Poultry | • Insulin | • Glossitis |
| • Fruits | • Hemoglobin | • Abnormal brain wave pattern |
| • Green leafy vegetables | • Myelin sheaths | • Convulsions |
| • Whole grains | • Antibodies | • Anemia |
| • Nuts | Toxicity | |
| • Dried peas and beans | • Depression
• Fatigue • Irritability • Headaches • Sensory neuropathy characteristic |
|
| Folate | • Coenzyme in DNA synthesis, therefore vital for | Deficiency |
| • Leafy vegetables | new cell synthesis and the transmission of | • Glossitis |
| • Dried peas and beans | inherited characteristics | • Diarrhea |
| • Seeds | • Macrocytic anemia | |
| • Liver | • Depression | |
| • Orange juice | • Mental confusion | |
| • Some fruits | • Fainting | |
| • Breads | • Fatigue | |
| • Cereals and other grains fortified with folic acid | Toxicity
• Too much can mask B12 deficiency |
TABLE 30-8. Summary of Water-Soluble Vitamins Continued
| VITAMIN AND SOURCES | FUNCTIONS | DEFICIENCY/TOXICITY SIGNS AND SYMPTOMS |
| Vitamin Bj2 | • Coenzyme in the synthesis of new cells | Deficiency |
| • Meat | • Activates folate | • GI changes |
| • Fish | • Maintains nerve cells | • Glossitis |
| • Poultry | • Helps metabolize some fatty acids and amino acids | • Anorexia |
| • Shellfish | • Indigestion | |
| • Milk & dairy products | • Recurring diarrhea or constipation | |
| • Eggs | • Weight loss | |
| • Some enriched foods | • Anemia
• Pallor • Dyspnea • Weakness • Fatigue • Palpitations • Neurologic changes • Paresthesia of the hands and feet • Decreased sense of position • Poor muscle coordination • Poor memory • Irritability • Depression • Paranoia • Delirium • Hallucinations Toxicity • No toxicity symptoms reported |
|
| Pantothenic Acid | • Part of coenzyme A used in energy metabolism | Deficiency (Rare) |
| Widespread in foods | • General failure of all body systems | |
| • Meat | Toxicity | |
| • Poultry
• Fish • Whole grain cereals • Dried peas and beans |
• No toxicity symptoms reported, although large doses may cause diarrhea | |
| Biotin | Coenzyme in: | Deficiency (Rare) |
| Widespread in foods | • Energy metabolism | • Anorexia |
| • Eggs | • Fatty acid synthesis | • Fatigue |
| • Liver | • Amino acid metabolism | • Depression |
| • Milk | • Glycogen formation | • Dry skin |
| • Dark green vegetables | • Heart abnormalities | |
| • Synthesized by GI flora | Toxicity
• No toxicity symptoms reported |
|
| Vitamin C | • Collagen synthesis | Deficiency |
| • Citrus fruits and juices | • Antioxidant | • Bleeding gums |
| • Red and green peppers | • Promotes iron absorption | • Pinpoint hemorrhages under the skin |
| • Broccoli | • Involved in the metabolism of certain amino | • Scurvy, characterized by |
| • Cauliflower | acids | • Hemorrhaging |
| • Brussels sprouts | • Thyroxin synthesis | • Muscle degeneration |
| • Cantaloupe | • Immune system functioning | • Skin changes |
| • Kiwi fruit | • Delayed wound healing | |
| • Mustard greens | • Reopening of wounds | |
| • Strawberries | • Softening of the bones s malformations, | |
| • Tomatoes | pain, easy fractures
• Soft, loose teeth • Anemia • Increased susceptibility to infection • Hysteria and depression Toxicity • Diarrhea • Abdominal cramps • Nausea • Headache • Insomnia • Fatigue • Hot flashes • Aggravation of gout symptoms |
Foods are the natural sources of vitamins and should supply daily vitamin needs. Foods differ greatly in the amount and number of vitamins they contain. Table 30-7 and Table 30-8 identify the major vitamins, their sources, their functions, and deficiency disorders that occur when the body does not get enough of a particular nutrient.
Vitamins are available in commercial, over-the-counter forms. Some vitamins are available by prescription because physicians may want to prescribe high dosages for certain marked deficiencies. Vitamins vary in their solubility, which influences how they are absorbed, transported through the blood, stored, and excreted. Vitamins with the United States Pharmacopoeia (USP) seal on the label are guaranteed to meet set purity and solubility standards.
Key Concept A, D, E, and K are fat-soluble vitamins; C and B complex are water-soluble vitamins.
Many healthy individuals choose to take commercial vitamins as a safeguard against less-than-optimal food choices. Those who take supplements should select a balanced multivitamin that does not exceed the UL for any nutrient. It is important to note that nutrients in foods, namely phytochemicals, are still being discovered today. Therefore, people should strive to meet their vitamin and mineral needs through diet. See In Practice: Educating the Client 30-1 for more information about vitamin supplements.
