Starvation is the result of a severe or total lack of nutrients needed for the maintenance of life.
Adequate nutrition has two components, necessary nutrients and energy in the form of calories. It is possible to ingest enough energy without a well-balanced selection of individual nutrients and produce diseases that are noticeably different from those resulting from an overall insufficiency of nutrients and energy. Although all foods are a source of energy for the human body, it is possible to consume a seemingly adequate amount of food without getting the required minimum of energy (calories). For example, marasmus is the result of a diet that is deficient mainly in energy. Children who get enough calories, but not enough protein have kwashiorkor. This is typical in cultures with a limited variety of foods that eat mostly a single staple carbohydrate like maize or rice. These conditions overlap and are associated with multiple vitamin and mineral deficits, most of which have specific names and set of problems associated with them.
- Marasmus produces a very skinny child with stunted growth.
- Children with kwashiorkor have body fat, an enlarged liver, and edema—swelling from excess water in the tissues. They also have growth retardation.
- Niacin deficiency produces pellagra characterized by diarrhea, skin rashes, brain dysfunction, tongue, mouth and vaginal irritation, and trouble swallowing.
- Thiamine (Vitamin B1) deficiency causes beriberi, which can appear as heart failure and edema, a brain and nerve disease, or both.
- Riboflavin deficiency causes a sore mouth and throat, a skin rash, and anemia.
- Lack of vitamin C (ascorbic acid)—scurvy—causes hair damage, bleeding under the skin, in muscles and joints, gum disease, poor wound healing, and in severe cases convulsions, fever, loss of blood pressure, and death.
- Vitamin B12 is needed to keep the nervous system working properly. It and pyridoxine (vitamin B6) are both necessary for blood formation.
- Vitamin A deficiency causes at first loss of night vision and eventually blindness from destruction of the cornea, a disease called keratomalacia.
- Vitamin K is necessary for blood clotting.
- Vitamin D regulates calcium balance. Without it, children get rickets and adults get osteomalacia.
Causes and symptoms
Starvation may result from a number of factors. They include:
- anorexia nervosa, which is an eating disorder characterized by extreme calorie restriction
- intentional fasting
- inability to obtain food (famine; child abuse ; aftermath of war or other disaster; being lost in wilderness or desert areas)
- severe gastrointestinal disease
Since the body will combat malnutrition by breaking down its own fat and eventually its own tissue, a whole host of symptoms can appear. The body's structure, as well as its functions, are affected. Starved adults may lose as much as 50% of their normal body weight.
Characteristic symptoms of starvation include:
- shrinkage of such vital organs as the heart, lungs, ovaries, or testes, and gradual loss of their functions
- chronic diarrhea
- reduction in muscle mass and consequent weakness
- lowered body temperature combined with extreme sensitivity to cold
- decreased ability to digest food because of lack of digestive acid production
- irritability and difficulty with mental concentration
- immune deficiency
- swelling from fluid under the skin
- decreased sex drive
Complete starvation in adults leads to death within eight to 12 weeks. In the final stages of starvation, adult humans experience a variety of neurological and psychiatric symptoms, including hallucinations and convulsions, as well as severe muscle pain and disturbances in heart rhythm.
In children, chronic malnutrition is marked by growth retardation. Anemia is the first sign to appear in an adult. Swelling of the legs is next, due to a drop in the protein content of the blood. Loss of resistance to infection follows next, along with poor wound healing. There is also progressive weakness and difficulty swallowing, which may lead to inhaling food. At the same time, the signs of specific nutrient deficiencies may appear.
If the degree of malnutrition is severe, the intestines may not tolerate a fully balanced diet. They may, in fact, not be able to absorb adequate nutrition at all. Carefully prepared elemental diets or intravenous feeding must begin the treatment. A formula consisting of 42% dried skim milk, 32% edible oil, and 25% sucrose plus electrolyte, mineral, and vitamin supplements is recommended for the first phase of refeeding. The treatment back to health is long and first begins with liquids. Gradually, solid foods are introduced and a daily diet providing 5,000 calories or more is instituted.
People can recover from severe degrees of starvation to a normal stature and function. Children, however, may suffer from permanent mental retardation or growth defects if their deprivation was long and extreme.
Anemia— Not enough red blood cells in the blood.
Anorexia nervosa— Eating disorder marked by malnutrition and weight loss commonly occurring in young women.
Cornea— The clear part of the front of the eye that admits light.
Kwashiorkor— Severe malnutritution in children caused by mainly by a protein-poor diet, characterized by growth retardation.
Marasmus— Severe malnutritution in children caused by a diet lacking mainly in calories. Can also be caused by disease and parasitic infection.
Beers, Mark H., MD, and Robert Berkow, MD., editors. "Starvation." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Btaiche, I. F., and N. Khalidi. "Metabolic Complications of Parenteral Nutrition in Adults, Part 1." American Journal of Health-System Pharmacy 61 (September 15, 2004): 1938-1949.
Nagao, M., Y. Maeno, H. Koyama, et al. "Estimation of Caloric Deficit in a Fatal Case of Starvation Resulting from Child Neglect." Journal of Forensic Science 49 (September 2004): 1073-1076.
In normal circumstances, with an adequate and balanced diet, all tissues take up the required amounts of nutrients from the passing blood, in the form of simple sugars (mainly glucose), fatty acids, and amino acids. Tissues differ in the ratio of different fuels used: the brain and spinal cord, and also the red blood cells, can normally utilize only glucose. Excesses from the diet are converted to storage forms, mainly as lipid in fatty tissue and as glycogen in the liver.
Adults can survive for many weeks without food, provided they have water. For just how long depends partly on the extent of their body stores of nutrients, mainly fat. But unfortunately it is not only the fat which is broken down to simpler substances to be used for metabolic energy production and for essential repair and maintenance of the body's tissues. As soon as carbohydrate stores have run out, proteins are mobilized from muscles for the manufacture of sugars by the liver, causing progressive physical weakness.
The physiological priorities in the face of zero food intake no doubt evolved in early millenia when hunting and gathering was an unpredictable and variable source of food. The first priority is to provide the brain with glucose, which is its staple diet, and this requires a certain level of glucose in the circulating blood. The carbohydrate store in the form of liver glycogen is used first to provide this glucose but is used up in the first day or two. Then glucose has to be made from lactic acid and from amino acids derived from muscle protein, released into the blood and taken up in the liver.
But how do the various parts of the body involved ‘know’ that there is a state of starvation and ‘act’ accordingly? A fall in blood glucose directly affects the endocrine part of the pancreas to change the balance of its hormonal secretions, suppressing insulin and enhancing glucagon synthesis and release. A fall in blood glucose is sensed also in the hypothalamus in the brain, which is the co-ordinating centre for homeostatic processes — those which tend to maintain the body's status quo. This orchestrates a complex hormonal response and also switches on autonomic nervous mechanisms, which stimulate the release or synthesis of glucose in the liver; adrenaline secretion is increased from the adrenal medulla; and the anterior pituitary gland is brought into action, releasing growth hormone, and ACTH which in turn stimulates the release of cortisol from the adrenal cortex.
Glucagon promotes all the processes which tend to raise blood glucose — first its release from liver glycogen, then its synthesis from amino acids. Adrenaline, growth hormone and cortisol all promote mobilization of lipid from adipose tissue (fat stores) and the use of the resulting circulating fatty acids as metabolic fuel in preference to glucose — everywhere except the brain and the red blood cells, which do not have the necessary chemical apparatus to use them. In the liver, the predominant metabolic use of fatty acids produces the ‘ketone bodies’, acetoacetate and b-hydroxybutyrate, which circulate in the blood and can be used by other tissues for energy production. If starvation is prolonged even the brain is able to utilize these when glucose is seriously depleted. Some of the acetoacetate is converted to acetone — another ‘ketone body’ — mainly in the lungs, and this becomes noticeable on the breath. The blood becomes progressively more acidic.
In the end, of course, there can be no hope of maintaining life in the absence of food intake. Some of the defence mechanisms become counter-productive. Thus the necessary production of extra acid as a by-product of altered metabolism puts an additional load on the kidneys to deal with H+ excretion; the acidity also stimulates breathing, helpfully counteracting acidity by the excretion of more carbon dioxide, but imposing extra breathing work on a weakening body. Muscles waste away; oedema and accumulation of fluid in body cavities follows depletion of plasma proteins. Ultimately there is multi-organ failure from lack of fuel and loss of vital enzyme activity. Shortages of minerals and vitamins will also take their toll if starvation is not total, and hence attenuated enough for these deficiencies to take effect, but in terms of aid to starving communities, the urgent requirements are for the basic nutrients.
See also acid base homeostasis; blood sugar; fasting; hormones; hunger.