Diseases resulting from nutrient deficiencies or excesses

Malnutrition
Definition: Impaired health due to dietary deficiency, excess, or imbalance. It can be divided into:
 * Undernutrition = lack of nutrients due to insufficient intake or disease leading to decreased uptake
 * Overnutrition = excess of nutrients because of too much eating, eating too many of the "wrong foods", taking too many food supplements, or simply not exercising enough

Undernutrution
Hunger and malnutrition are one of most devastating problems in the world's poor nations. Approximately 49% of the 10.7 million annual deaths in children under five in developing nations are associated with malnutrition. In addition, nearly 30% of all humans are currently suffering from one or more forms of malnutrition. The consequences of this (death, disability, stunted mental and physical growth) result in retarded national socio-economic development, further adding to the problems of poverty.

Iron deficiency:
 * is the world's most widespread disorder. It affects both industrialized as well as developing nations.
 * In industrialized nations it manifests as anemia, being one of the main causes of it.
 * In developing countries, the the deficiency is accompanied by other micronutrient deficiencies ( folic acid, vitamins A and B12), parasitic infestations such as malaria and hookworm, as well as chronic infections such as for example HIV. In addition, a monotonous diet consisting mostly of cereals in the poorest countries is low in iron and contains high levels of absorption inhibitors. This leads to iron stores which are characteristically low, and particularly affects young children and pregnant women.
 * In infants and young children: impaired psychomotor development, coordination and scholastic achievement, and decresed physical activity.
 * In adults: reduced work capacity and decreased resistance to fatigue.
 * In pregnant women: anemia that is associated with increased risk of maternal mortality and morbidity, fetal mortality and morbidity, and intrauterine growth retardation.
 * Prevention: iron supplements mainly to pregnant women and young children, as well as trying to increase access to food.

Iodine deficiency:
 * Iodine deficiency is the largest cause for preventable brain damage in fetus and infant, and of retarded psychomotor development in children.
 * Mainly affects preschool children and pregnant women in low-income countries.
 * Result in goitre, stillbirth, miscarriages, mental retardation, impaired educability, deaf-mutism, and cretinism.
 * The more subtle mental changes that lead to poor school performance, reduced intellectual ability, and impaired work capacity are of greater significance.
 * Prevention: Iodisation of salt. Salt was chosen because it was widely consumed and for the cheap cost of salt iodising. An alternative is to administer iodine directly, either as iodide or iodised oil. Focus is mainly on women and children.

Vitamin A deficiency:
 * Preschool children and pregnant women in poor countries are the ones most susceptible to vitamin A deficiency
 * In children, the major effect of vitamin A deficiency is preventable visual impairment and blindness. Vitamin A deficiency also causes decreased resistance to infection, and hence increases the risk of severe illnesses and death from common childhood infections like measles and diarrhoeal diseases.
 * In pregnant women the risk of maternal mortality as well as poor pregnancy and lactation outcomes are increased. The deficiency also contributes to increased cases of night blindness.
 * Prevention: Vitamin A supplementation (on national vaccination days) and food fortification programmes.

Zinc deficiency:
 * Major problem worldwide, in which estimates are that 20.5% of the world population has zinc deficiency.
 * The most vulnerable are infants, young children and lactating women in the poor population of the world.
 * Severe zinc deficiency in men may manifest as hypogonadism and dwarfism, as observed among men in Iran.
 * The deficiency also affects the immune system, being associated with increased frequency of infection.
 * Supplementation with zinc has showed to improve immune responses to diarrhoeal diseases, respiratory infections and malaria, reducing morbidity and mortality of these diseases. It has also shown to increase growth in malnourished infants and growth retarded children.

Folate deficiency:
 * Causes megaloblastic anemia
 * Often accompanies already existing iron deficiency anemia
 * Especially dangerous for the developing fetus as it may result in neural tube defects such as anencephaly and spina bifida.
 * Associated with elevated homocysteine levels, making it a risk factor for coronary heart disease and stroke
 * Also associated with cancer, particularly of the colon.

Calcium deficiency:
 * Associated with osteoporosis, osteoarthritis, cardiovascular diseases, hypertensive disorders of pregnancy, diabetes, dyslipidemias, obesity and cancer of colon.
 * It is unclear what role dietary calcium plays in these diseases.
 * It is widely accepted that calcium supplementation should be given to the older populations of the world (especially postmenopausal women), even though in some countries there has been no clear evidence of increased incidence of osteoporosis and low calcium intake.

Selenium deficiency:
 * 2 main diseases associated with selenium deficieny:
 * 1) Keshan disease: a selenium responsive endemic cardiomyopathy that results in heart failure. It affects mainly children and women of childbearing age. In studies done in areas of China, there was found low selenium levels in human blood, hair and tissue due to the low selenium cereal diet.
 * 2) Kashin-Beck disease: is an endemic osteoarthropathy which primarily affects children in certain regions of China and former Soviet Union. The characteristic of the disease is enlarged and deformed joints.

Others:
 * Beriberi = thiamine deficiency.
 * 1) Dry beriberi: causes wasting and partial paralysis resulting from damaged peripheral nerves. It is characterized by: Difficulty walking, tingling or loss of feeling (sensation) in hands and feet, loss of muscle function or paralysis of the lower legs, mental confusion, pain, nystagmus and vomiting.
 * 2) Wet beriberi: affects the heart; it causes a combination of heart failure and weakening of the capillary walls, which causes the peripheral tissues to become edematous. It is also characterized by: arteriovenous shunt due to vasodilation, increased heart rate and dyspnea on exertion. It is often fatal.
 * Pellagra = niacin and tryptophan deficiency (precursor to niacin). The characteristic 3 D's: diarrhea, dermatitis, dementia (and death)
 * Scurvy = vitamin C deficiency. Characterized by lethargy, myalgia and followed by poor wound healing, gum disease with loosening of teeth and mental changes.

Overnutrition and Obesity
Obesity is an imbalance between energy intake and energy expenditure. Excess energy is stored in the body as fat. Obesity is an growing epidemic worldwide, affect developing as well as developed nations. Problems are exacerbated when obesity coexists with undernutrition, which is often the case in many developing countries.
 * The easiest way to classify weight is according to body mass index (BMI = weight in kg/(height in m)2)
 * 1) Underweight: BMI <18.5
 * 2) Optimum weight:  BMI 18.5-25
 * 3) Grade I obesity: BMI >25-30
 * 4) Grade II obesity: BMI >30-40
 * 5) Grade III obesity: BMI >40
 * Also the distribution of fat on the body determines how much at risk a person is:
 * 1) Gynecoid fat distribution = excess fat on hips.
 * 2) Android fat distribution = excess abdominal fat. People with this type of fat distribution are more at risk for getting the diseases listed below.
 * Obesity is one of the key risk factors for amongst others the following diseases:
 * 1) cardiovascular diseases
 * 2) hypertension
 * 3) non-insulin dependent diabetes mellitus
 * 4) various forms of cancer
 * 5) gastrointestinal and liver diseases
 * 6) gallbladder diseases
 * 7) varicose veins
 * Management of obesity:
 * 1) Dietary therapy = decrease total energy and fat
 * 2) Increase physical activity
 * 3) Behavioral therapy includes self monitoring by keeping a food journal, strictly assessing how the food is eaten and in which emotional setting. Stimulus control has a goal of separating the events that trigger eating from the actual process of eating. And lastly, there must be a system of rewards, where appropriate behavior is awarded.
 * 4) Pharmacological therapy is currently used as adjunctive treatment, and usually consists of centrally acting appetite suppressants or drugs that decrease the fat uptake from the intestine.
 * 5) Surgical treatment is reserved only for the morbidly obese with an BMI over 45. It consists of variations of gastric restrictions to decrease the amount of food ingested.