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KUWAIT UNIVERSITY FACULTY OF MEDICINE CLINICAL MEDICINE AND PATHOLOGY (316) Dr. T. Chacko Mathew NUTRITIONAL AND ENVIRONMENTAL DISORDERS NUTRITIONAL DISORDERS Nutrition is the science of food and its relationship to health. Nutrients are chemical compounds in foods that are absorbed by the body. Nutrients are divided into essential and non-essential nutrients. Essential nutrients cannot be synthesized by the body and thus must be derived from the diet. The essential nutrients include vitamins, minerals, amino acids, fatty acids, and some carbohydrate. Nonessential nutrients are those that the body can synthesize from other compounds, although they may also be derived from the diet. Macronutrients Nutrients are generally divided into macronutrients and micronutrients. Macronutrients constitute the bulk of the diet and supply energy as well as essential nutrients needed for growth, maintenance, and activity. Carbohydrates, fats (including essential fatty acids), proteins, macrominerals, and water are macronutrients. During the process of digestion, carbohydrates are converted to glucose and other monosaccharides; fats, to fatty acids and glycerol; and proteins, to peptides and amino acids. These macronutrients are interchangeable as sources of energy; fats yield 9 kcal/g; proteins and carbohydrates yield 4 kcal/g. Biological Value of proteins The amino acid composition of proteins varies widely. The extent to which a protein matches the amino acid composition of animal tissues determines its biologic value (BV). A perfect match is egg protein, with a value of 100. Animal proteins in milk and meat have a high BV (~90), whereas proteins in cereal and vegetables have a lower BV (~40), and some derived proteins, such as gelatin, which lack tryptophan and valine, have a BV of 0. Essential amino acids and fatty acids Essential amino acids (EAAs) are the components of proteins that make them essential in the diet. Of the 20 amino acids in proteins, 9 are essential, ie, they cannot be synthesized in the body. Therefore, they must be obtained through diet. Eight EAAs are required by all humans. Infants require one more, histidine. Essential fatty acids (EFAs) must be provided by the diet. However, some EFAs can be made from others. EFAs are polyunsaturated fatty acids (PUFAs), but not all PUFAs are EFAs. Protein- calorie deficiency disorders Kwashiokor: Deficient protein intake despite normal or nearly normal calorie intake. It is characterized by edema of the abdomen, enlarged liver, decreased blood pressure, low pulse rate, lower than normal body temperature and sometimes mental retardation. Marasmus: It is due to protein-calorie under nutrition. Characterized by retarded growth, low weight, muscle wasting, dry skin and dull hair. The macrominerals Sodium, chloride, potassium, calcium, phosphorus, and magnesium are required in gram quantities per day by humans. Water is also considered a macronutrient because it is required in amounts of 1 mL/kcal of energy expended, or about 2500 mL/day. Micronutrients Vitamins, which are classified as water-or fat-soluble, and trace minerals are micronutrients. Water-soluble vitamins are vitamin C (ascorbic acid) and eight members of the vitamin B complex-thiamine (vitamin B1), riboflavin (vitamin B2), niacin, pyridoxine (vitamin B6), folic acid, cobalamin (vitamin B12), biotin, and pantothenic acid. Fat-soluble vitamins include retinol (vitamin A), cholecalciferol and ergocalciferol (vitamin D), alpha-tocopherol (vitamin E), and phylloquinone and menaquinone (vitamin K). Only vitamins A, E, and B12 are stored to any significant extent in the body. VITAMIN DEFICIENCY DISEASES Night blindness: the inability to see in dim light. Beriberi usually begins with mild symptoms, including muscle cramps, irritability, loss of appetite, and prickling or burning sensations in the skin Pellagra: Severe cases include three basic symptoms - diarrhea, skin problems, and dementia or learning difficulties. Advanced pellagra can cause death. Scurvy: Symptoms of include swollen gums, loose teeth, and small black-and-blue spots on the skin. Rickets: The deficiency results in the body not having enough calcium to maintain healthy bone structure and leads to softening of bones and serious bone deformities. 2 Vitamin E deficiency: It causes difficulty with walking, lack of reflexes, and paralysis of eye muscles. Vitamin E is protects cell structures from free radical damage. Vitamin K deficiency: Vitamin K helps promote clotting of blood. Folic acid deficiency: Folic acid is needed to prevent anemia. It also is needed by pregnant women to help prevent neural tube defects in the fetus. Vitamin A B1 (thiamine) B2 (riboflavin) Niacin B6 B12 C (ascorbic acid) D E K Deficiency disease Night blindness Beriberi Ariboflavinosis Pellagra Vitamin B6 deficiency Pernicious anemia Scurvy Rickets Vitamin E deficiency Vitamin K deficiency Food sources of vitamin Eggs, whole milk, cream, cheese, liver, green and yellow vegetables (carrots, squash, sweet potatoes, spinach, kale, and broccoli) Milk, fortified cereals, peanuts, liver, yeasts Liver and other organ meats, milk, green vegetables, fortified cereals, yeast Peanuts, lean meats, poultry, fish, bran, yeast, liver Whole-grain cereal, fish, legumes, liver and other organ meats, yeast Eggs, milk, liver Fresh fruits and vegetables (oranges and other citrus fruits, brussels sprouts, cabbage, etc.) Fortified milk, fish liver oil Vegetable seed oil, egg yolk, cereals, beef liver Leafy green vegetables, liver Essential trace elements Essential trace minerals include iron, iodine, fluorine, zinc, chromium, selenium, manganese, molybdenum, and copper. Except for iron and zinc, micromineral deficiencies are uncommon in industrialized countries. Other trace minerals implicated in animal nutrition (ie, aluminum, arsenic, boron, cobalt, nickel, silicon, and vanadium) have not been established as being required by humans. All trace minerals are toxic at high levels, and some (arsenic, nickel, and chromium) have been implicated as causes of cancer. In the body, lead, cadmium, barium, and strontium are toxic, but gold and silver are inert as components of teeth. Obesity The excessive accumulation of body fat. Traditionally, obesity has been defined as a body weight of > 30% above ideal or desirable weight on standard height-weight tables. Now, it is usually defined in terms of the body mass index (BMI)--weight (in kilograms) divided by the square of the height (in meters). 3 ENVIRONMENTAL DISORDERS Exposure to severe heat Direct exposure of the skin to severe heat produces burns. The severity of the burn depends on the degree and the length of exposure to heat. Two major factors that determine the outcome of burn injury are the depth of burn and the surface area of skin affected. Classification of burns Burns may be classified as major or minor, according to extent and depth. First degree burns: This type burns the epidermal layer of the skin. It is usually superficial. Second degree burns: In this type of burns, there are damage to the epidermis and the dermis of the skin (partial thickness burns). The immediate consequence of a seconddegree burn to more than 20% of the body is extravasation of fluid, including high protein exudate, from the burn site. Third degree burns: There is a destruction of all the epidermis and dermis. It goes to the root of the hair. It is called full thickness burns. Skin grafting is recommended. Fourth degree burns: In these burns, the tissue beneath the skin is destroyed. That includes the muscles, tendons, ligaments and bones. Skin grafting is usually required. Other injuries of fire They are airways injury by heat, carbon monoxide inhalation, and chemical inflammation of lung caused by inhalation of toxic smoke. There may be secondary bacterial infection of the burn. Hypothermia Hypothermia occurs most commonly at very cold environmental temperatures, but can occur even at cool temperatures (above 40°F) if a person becomes chilled from rain, sweat, or submersion in cold water. Frostbite: Frostbite is an injury to the body that is caused by freezing. Frostbite causes a loss of feeling and colour in affected areas. Usually, it affects the nose, ears, cheeks, chin, fingers, or toes. Frostbite can permanently damage the body, and severe cases can lead to amputation. 4 Exposure to ultraviolet (UV) radiation Ultraviolet (UV) radiation is defined as that portion of the electromagnetic spectrum between x rays and visible light, i.e., between 40 and 400 nm. Accidental UV overexposure can injure unaware victims due to the fact UV is invisible and does not produce an immediate reaction. After irradiation, vascular changes occur, which lead to secondary ischaemic damage to tissue. UV radiation is known to damage DNA in epidermal cells, and several malignant tumours of skin in Caucasians are believed to be caused by exposure to this type of radiation. Mechanical injury The most frequent types of mechanical trauma are skin and soft tissues injuries. Injuries to bone and tendon may be acute or chronic. Other environmental factors Toxic chemicals Toxic chemicals can gain access to the body by many routes including skin contact, inhalation, ingestion, and injection. Metals Metals cause disease as a result of environmental, occupational and therapeutic exposure. Many metals have adverse effects if present in high levels. Insecticides Insecticides and herbicides are frequently implicated in disease. For example, chlorinated hydrocarbons (DDT, dieldrin) are insecticides, chronic exposure leading to accumulation in the liver. Although toxicity to certain birds and carcinogenicity in rats is established, there is little evidence of toxicity in man. 5