Dietary deficiencies are disorders that occur because of a lack of essential nutrients * in the diet or because the body cannot absorb and process those nutrients when they are eaten. Most dietary deficiencies are caused by a lack of protein, vitamins, or minerals.
Whenever individuals do not get enough of an essential nutrient, they are at risk for a dietary deficiency disease. Most dietary deficiency diseases result from a lack of protein, vitamins, or minerals. Protein deficiency diseases occur when a person does not eat enough protein; these diseases are prevalent in developing countries, where people are too poor to buy protein-rich foods or where such foods are hard to find. Generally speaking, vitamin and mineral deficiencies result from diets lacking in certain essential nutrients. In some cases, genetic * disorders, metabolic * disorders, or illnesses that prevent the body from digesting or absorbing particular nutrients cause the deficiencies.
Proteins are an essential component of all organs and chemical activities. Proteins make up muscles, connective tissue, skin, and other tissues, as well as hormones and various components of blood. Some proteins called enzymes help digest food and convert sugar into energy, which the body needs to function properly.
When protein is missing from the diet, the body cannot function properly. The term protein-energy malnutrition describes the range of conditions related to calorie (energy) and protein deficiency disorders. It develops in people whose consumption of protein and calories is not enough to fill their nutritional needs. Kwashiorkor (kwash-e-OR-kor) and marasmus (ma-RAZ-mus) are two diseases that can result from protein and energy (calorie) deficiencies. These diseases primarily affect children, with as many as half of the children in starvation-prone countries not surviving to five years of age. While adults rarely suffer from protein deficiency diseases, some have underlying conditions that prevent the intestines from absorbing amino acids.
Kwashiorkor is caused by a lack of protein in the diet. The term originates from an African word that describes the situation of an infant being weaned from breast milk to make room for the next baby. When weaning occurs and protein-rich food (such as milk, meat, or legumes) is not available, the baby can experience tiredness, muscular wasting, and edema * . The hair and skin lose color, the skin becomes dry and peeling, and the child may experience diarrhea and anemia. Children with kwashiorkor often have fluid retention and distended abdomens.
Marasmus is caused by total calorie depletion. It causes stunted growth and the wasting away of body tissue and muscle. Children with marasmus lose body fat and muscle strength. They often have a skeletal appearance and are small for their age. With a weakened immune system, they also suffer from frequent infections.
Although animals, including humans, can construct all the proteins they need from the building blocks called amino acids, they cannot make most vitamins. Vitamins are chemicals, and almost all of them must be obtained from foods. Thirteen vitamins are essential for healthy growth, development, cell function, and metabolism: vitamins A, C, D, E, K and eight B vitamins (together they are called the B-complex vitamins). All vitamins must be taken into the body from outside food sources, except for vitamins D and K, which can be made under specific circumstances by the body.
Vitamin A is necessary for eye health, to protect the retina * and to promote the normal growth and health of skin and membrane cells. Vitamin A can be obtained directly from foods such as milk, eggs, and liver, as well as from carotene, a chemical that is found in green and yellow fruits and vegetables such as apricots, cantaloupe, oranges, peaches, collards, broccoli, turnip greens, kale, carrots, sweet potatoes, and squash. Carotene is converted to vitamin A in the body.
A deficiency of vitamin A can cause night blindness, a condition in which the eyes fail to adjust to the dark as a result of problems with the retina. The deficiency also may cause glare blindness, or problems seeing when the eye is exposed to too much light or to a sudden change in the amount of light when entering a darkened room.
Vitamin A deficiency can also cause the disease xerophthalmia (zeeroff-THAL-mee-uh). The symptoms of this disease are eye dryness and thickening of the surface of parts of the eye. If left untreated, xerophthalmia may lead to blindness.
Vitamin B1 (also called thiamine) is an important part of the body's nervous system. It also helps the body turn carbohydrates into energy. Food sources for this vitamin are meats, wheat germ, whole grain and enriched bread, legumes, nuts, peanuts, and peanut butter. Beriberi (BEAR-ee-BEAR-ee) is a disease that results from the lack of thiamine in the diet. It affects the heart, digestive system, and nervous system. The early stages of beriberi are characterized by fatigue, loss of appetite, and a numb or tingling feeling in the legs.
There are two main types of beriberi (wet or dry):
In severe cases, beriberi is linked to Wernicke-Korsakoff syndrome. The syndrome is two separate conditions that occur at the same time. Wernicke's encephalopathy causes bleeding and damage to lower sections of the brain, including the thalamus and hypothalamus. The damage affects vision, coordination, and balance. Korsakoff psychosis is brain damage that affects the areas of the brain that control memory. Alcohol abuse is the most common cause of Wernicke-Korsakoff syndrome, as alcohol use interferes with the body's ability to break down and absorb thiamine.
Vitamin B3 (niacin) is a mineral that helps the body convert food into energy. Most proteins contain niacin. Good sources of niacin include liver, lean meat, whole-wheat products, fish, eggs, roasted peanuts, poultry white meat, avocados, dates, figs, prunes, whgerm, and brewer's yeast.
A severe deficiency of niacin can lead to a disease called pellagra (peLAG-ra). Pellagra affects the skin, nervous system, and digestion, and can cause the “four Ds”: diarrhea * , dermatitis * , dementia *
B vitamins play an important role in producing energy in the body and maintaining healthy cells. Deficiencies in any of the B vitamins can cause health problems. Vitamin B12 plays a role in regulating the nervous system and helps the growth and formation of red blood cells. A lack of B12 can cause anemia and confusion in the elderly. Vitamin B6 helps the body turn food into energy and fight infections. A B6 deficiency can lead to anemia, skin problems, depression, confusion, and increased risk of infection.
Vitamin C plays an important role in the body's formation of collagen, a component of connective tissue. It also is important for the functioning of the body's immune system, iron absorption, cholesterol metabolism, and other body processes. A deficiency in vitamin C can lead to a disease called scurvy. Symptoms of scurvy begin with loss of appetite, poor weight gain, diarrhea, rapid breathing, fever, irritability, discomfort in the legs, swelling, bleeding, and feelings of paralysis. As the disease progresses, a person may experience bleeding of the gums, loose teeth, and tiny hemorrhages of the skin and mucous membranes. Wounds heal slowly, and bleeding in or around vital organs can be fatal.
Scurvy is one of the oldest deficiency diseases recorded and the first one to be cured by adding a vitamin to the diet. It was a common malady of sailors during the 16th and 17th centuries, the age of exploration of the New World. In modern times, people whose diets lack vitamin C–rich foods, such as citrus fruits, are still at risk of developing scurvy. Those most at risk are infants, the elderly, and people on fad diets.
Without enough vitamin D, a person can develop a disease called rickets, which causes softening and weakening of bones. Rickets affects children primarily, as their bones are still growing. Rickets can cause the legs to become bowed by the weight of the body, and it can cause the wrists and ankles to become thickened. All the bones are affected by not having sufficient calcium and phosphorous for their growth and development. Childhood rickets was once a common disease of infants and children, but it is rarely seen today because milk and infant formulas have vitamin D added to them.
Osteomalacia (os-tee-o-ma-LAY-sha) is an adult version of rickets, a softening of the bones caused by a deficiency of vitamin D, calcium, and phosphorous. In this disease, the bones become soft, deformed, and painful. This disease is seen more often in the Middle East and Asia than in Western countries.
Vitamin E helps prevent reproductive problems and promotes good skin health. Vitamin K promotes normal blood clotting by aiding in the manufacture of fibrinogen (fy-BRIN-o-jen) and other proteins needed for blood clotting. Vitamin E deficiencies are not very common, and vitamin K deficiencies are rare except in newborns. To prevent newborn bleeding, newborns receive a shot of vitamin K.
A deficiency in folate (also known as folic acid or folacin) in pregnant women can result in some central nervous system birth defects in their babies. To help prevent these birth defects, pregnant women should supplement their diet with folate very early during their pregnancies. Excellent food sources for folate include deep-green and leafy vegetables, carrots, liver, egg yolk, cantaloupe, apricot, pumpkin, avocado, beans, and whole-wheat and dark-rye flours.
Minerals are formed as a result of geological processes, are normally crystalline, and usually appear in the form of simple salts. The human body contains about 25 minerals. Those minerals that appear in large amounts are called macrominerals; those that are in small or trace amounts are called microminerals. Minerals known to be essential to a healthy body include calcium, phosphorous, cobalt, copper, fluorine, iodine, iron, and sodium. The effect of a mineral deficiency depends on which mineral is missing from the diet.
Iodine is necessary for the proper functioning of the thyroid, a gland that controls the body's metabolic rate and produces essential hormones *
A lack of iodine can also lead to hypothyroidism (underactive thyroid), and to slower physical and mental development in infants. Many people consume iodine through iodized salt, which is produced and distributed in developed parts of the world. Another excellent source of iodine is kelp, a type of sea vegetable.
Iron is necessary for the formation of certain proteins and enzymes. Hemoglobin (HE-mo-glo-bin), which is a protein that carries oxygen in blood, depends on iron. Iron deficiency can lead to anemia, which is characterized by low levels of either healthy red blood cells or hemoglobin. This can cause fatigue and other complications. Good food sources of iron are liver, lean meats, legumes, dried fruits, and green leafy vegetables.
Zinc and copper are trace elements found in a variety of foods. Dairy products, red meat, sunflower seeds, cooked dried beans, walnuts, sardines, and whole grains are good sources of zinc. Copper is found in many foods, including fish, poultry, meats, whole grains, nuts, and seeds. Calcium and phosphorus are other minerals that are important for bone development.
Deficiencies of these minerals are rare; when they do occur, however, they can lead to several health problems. A zinc deficiency can bring about prostate * and skin disorders, whereas a copper deficiency can lead to metabolic disorders. Deficiencies of calcium and phosphorus lead to softening of the bones or to hypercalcemia (hy-per-kal-SEE-mee-uh), a condition in which too much calcium leads to a surplus formation of bone.
Dietary deficiencies are generally more common in the lesser-developed areas of the world. According to the World Health Organization (WHO), iron deficiency is the most common and widespread dietary deficiency worldwide. It affects an estimated 2 billion people, which is more than 30 percent of the world's population. Iron deficiency affects large numbers of children and women in developing countries, along with many in industrialized countries.
Dietary deficiencies are not contagious.
People may not know they have dietary deficiencies until they begin to exhibit symptoms such as pallor, fatigue, weight loss, constipation, hair loss, difficulty concentrating, difficulty breathing, irregular menstrual cycles, or unusual food cravings. Doctors can evaluate patients for dietary deficiencies by discussing regular diet and performing blood work (usually used to diagnose iron-deficient anemia).
If dietary deficiencies are suspected, a doctor will discuss diet and eating habits with a patient. They will ask about the symptoms the person is experiencing. They may also order blood tests, including a complete blood count (CBC), which can identify anemia and many other dietary deficiencies.
In most cases, treatment for dietary deficiency diseases depends on the type and severity of the deficiency. Doctors may recommend changes to a person's eating habits to include more foods rich in the missing nutrients. They may also recommend that the person take dietary supplements. The recovery (none, partial, or full) depends on the particular disease, at what age the disease developed, and whether the effects are reversible after they have occurred.
Most dietary deficiency diseases can be prevented by people eating a well-balanced diet consisting of many types of foods. Ongoing medical care can help prevent dietary deficiency diseases caused by genetic problems and by metabolic problems that prevent the body from absorbing or using nutrients properly. In countries where food and money are scarce, however, dietary deficiency diseases remain common.
See also Anemia, Bleeding, and Clotting • Birth Defects: Overview • Kwashiorkor • Malnutrition • Metabolic Disease • Rickets • Scurvy
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* nutrients are the components of food (protein, carbohydrate, fat, vitamins, and minerals) needed for growth and maintenance of the body.
* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.
* metabolic (meh-tuh-BALL-ik) pertains to the process in the body (metabolism) that converts food into energy and waste products.
* edema (e-DEE-ma) means swelling in the body's tissues caused by excess fluids.
* retina (REH-tuh-na) is the tissue that forms the inner surface of the back of the eyeballs. It receives the light that enters the eye and transmits it through the optic nerves to the brain to produce visual images.
* coma (KO-ma) is an unconscious state, such as a very deep sleep. A person in a coma cannot be awakened and cannot move, see, speak, or hear.
* diarrhea (di-ah-RE-uh) is frequent, watery stools (bowel movements).
* dermatitis is a skin condition characterized by a red, itchy rash. It may occur when the skin comes in contact with something to which it is sensitive.
* dementia (dih-MEN-shuh) is a loss of mental abilities, including memory, understanding, and judgment.
* formula is a prepared, nutritious drink or a dry drink mix designed specifically for infants.
* prostate (PRAH-state) is a male reproductive gland located near where the bladder joins the urethra. The prostate produces the fluid part of semen.
* hormones are chemical substances produced by various glands and sent into the bloodstream to carry messages that have certain effects on other parts of the body.
* vaccination (vak-sih-NAY-shun) is a preparation of killed or weakened germs, or a part of a germ or product it produces, that is given (usually by an injection) to prevent or lessen the severity of the disease caused by that germ. Also called immunization.
* exotoxin (ek-so-TOK-sin) is a substance produced by bacteria that has harmful effects on the infected person.
* shock is a serious condition in which blood pressure is very low and not enough blood flows to the body's organs and tissues. Untreated, shock may result in death.