Ércio Oliveira, MD. Professor, Department of Pediatrics, Rio Grande do Sul State University School of Medicine (UFRGS). Pediatrics Specialist by the Brazilian Society of Pediatrics.

Ércio Filho, MD., MA in Pediatrics by the Rio Grande do Sul State University (UFRGS).


Malnutrition may be the result of either a poor diet or an excessive diet.

Both conditions are caused by an imbalance between the body’s needs and the intake of essential nutrients.


It’s a deficiency of essential nutrients and can result from insufficient intake due to a poor diet; a deficient uptake of ingested food by the intestine (malabsorption); abnormally high consumption of nutrients by the body; or excessive loss of nutrients by processes such as diarrhea, bleeding (hemorrhage), and renal insufficiency.


It’s an excess of essential nutrients and can result from eating too much (excessive intake), or excessive use of vitamins or other supplements.

Malnutrition develops in stages: first, changes occur in the concentration of nutrients in the blood and tissues; next, there are changes in enzyme levels, followed by malfunctioning of the body’s organs and tissues; and then symptoms of disease appear, with death being likely to occur.

The body needs more nutrients at certain periods of life, especially in childhood and adolescence, during pregnancy, and when the mother is breastfeeding. In senescence, nutritional needs are lower, but the ability of nutrient uptake is also often decreased. Thus, the risk of undernourishment is higher in these periods of life, and even more so amongst economically unprivileged people.

Nutritional assessment

In order to assess an individual’s nutritional state, the physician has to know their diet and medical problems that may exist, carry out a physical examination, and, at times, require lab tests – blood levels of nutrients and substances that depend upon these nutrient levels (such as hemoglobin, thyroid hormones and transferrin) can be measured.

To determine an individual’s dietary history, the doctor asks what foods were ingested in the previous 24 hours and what kind of food is habitually consumed. It’s quite common to require that the individual keep a diet log in which they record everything they eat for some days. During the physical exam, the doctor observes the individual’s general state and behavior, as well as body fat distribution, and evaluates the functioning of organs and systems.

Nutritional deficiencies may cause several diseases. For instance:

Gastrointestinal hemorrhage can cause iron deficiency anemia.
A person being treated on high doses of vitamin A for acne may develop headache and double vision as a result of vitamin A concentration.

Any of the body’s systems may be affected by a nutritional disorder. For instance:

The nervous system is affected by the deficiency of niacin (pellagra), deficiency of thiamin – vitamin B1 (beriberi), deficiency or excess of vitamin B6 (pyridoxine), and deficiency of vitamin B12.
The senses of taste and smell are affected by zinc deficiency.
The cardiovascular system is affected by beriberi, obesity, a very fatty diet that leads to hypercholesterolemia and coronary disease, or a diet with excess salt that leads to hypertension.
The gastrointestinal tract is affected by pellagra, deficiency of folic acid and alcoholism.
The mouth (lips, tongue, gingiva, and mucous membranes) is affected by the deficiency of complex B vitamins and scurvy (deficiency of vitamin C).
Iodine deficiency may result in enlargement of the thyroid gland.
An increased tendency towards bleedings and skin symptoms such as rashes, dryness and swelling due to fluid retention (edema) may occur in scurvy, deficiency of vitamin K, deficiency of vitamin A, and beriberi.
Bones and joints are affected by rachitis (deficiency of vitamin D), osteoporosis, and scurvy.

Risk factors

Children comprise a population group particularly susceptible to undernourishment, since they need a higher amount of calories and nutrients for their growth and development.

They, too, can develop deficiencies of iron, folic acid, vitamin C and copper, if receiving unsuitable diets.

The insufficient intake of proteins, calories and other nutrients may lead to protein-caloric malnutrition, a particularly severe form of undernourishment that delays growth and development.

As children reach adolescence, their nutritional requirements grow as a result of an increase in their growth rates.

Pregnant women or breastfeeding mothers have an increased need for all nutrients so as to prevent their undernourishment as well as their babies’.

An alcoholic mother’s baby may be physically and mentally impaired by alcoholic fetal syndrome, as alcohol abuse and the resulting undernourishment affect fetal development.

A child who is breastfed only by the breast may develop a deficiency of vitamin B12, if the mother is a vegetarian that doesn’t eat any animal-origin products.

Who’s at risk of undernutrition?

As crianças com pouco apetite.
Adolescentes que passam por surtos de crescimento rápido
Pessoas que têm doença crônica do trato gastrointestinal, fígado, ou rins
Pessoas em dietas rigorosas por muito tempo
Pessoas com dependência de álcool ou outra droga que não se alimentam adequadamente
As pessoas que tomam remédios que interferem com o apetite ou com a absorção ou exceção de nutrientes
Pessoas com anorexia nervosa
Pessoas que têm febre prolongada, hipertireoidismo, queimaduras, ou câncer


Children with low appetite.
Teenagers that undergo outbreaks of rapid growth.
The elderly.
People with chronic disease in the gastrointestinal tract, liver, or kidneys.
People on long-term strict diets.
People addicted to alcohol or other drugs that don’t feed themselves properly.
People taking medications that interfere with the appetite or with the absorption or excretion of nutrients.
People with anorexia nervosa
People with prolonged fever, hyperthyroidism, burns, or cancer.

The elderly may become undernourished because of loneliness, physical and mental disabilities, lack of motility, or chronic disease. In addition to these, their ability of nutrient uptake is reduced, contributing to problems like iron deficiency anemia, osteoporosis, and osteomalacia.

Aging is accompanied by a progressive loss of muscle mass, regardless of diseases or dietary deficiency. This loss accounts for the reduction that takes place in the metabolism, by a decrease in bodyweight and an elevation in body fat rate by approximately 20%-30% in men and 27%-40% in women. Owing to these changes and decreased physical activity, elder people need fewer calories and proteins than younger people.

People with some chronic disease causing malabsorption tend to have difficulty taking up liposoluble vitamins (A, D, E, and K), vitamin B12, calcium, and iron. Liver diseases impair the storage of vitamins A and B12 and interfere with the metabolism of proteins and glucose.

People with renal disease, including those on dialysis, are prone to deficiency of protein, iron and vitamin D.

Although most vegetarians don’t eat meat, they eat eggs and dairy products. Iron deficiency is the sole risk for this kind of diet.

Vegetarians tend to live longer and develop fewer chronic disabling conditions than people who eat meat. However, the better health shown by these people may also result from abstaining from alcohol and smoking and their tendency to work out regularly.

Vegetarians that don’t consume any animal product are at risk of developing vitamin B12 and iron deficiencies.

Many fashionable diet programs state they increase well-being on reducing weight; however, uptight diets are nutritionally risky: these diets can result in deficiency of vitamins, minerals, and proteins, as well as diseases affecting the heart, kidneys and metabolism; and can even lead to some deaths. People on very hypocaloric diets ( less than 400 calories a day) aren’t able to stay healthy for a long time.

In between extreme inanition and proper nutrition, there are several levels of unsuitable nutrition, such as protein-caloric malnutrition, one of the major causes of child death in developing countries.

Protein-caloric malnutrition

Protein-caloric malnutrition is caused by an unsuitable intake of calories, resulting in deficiency of proteins and micronutrients (necessary nutrients in small amounts, as vitamins and some minerals). Rapid growth, infection or chronic disease may increase the need for nutrients, particularly in children already undernourished.


There are three types of protein-caloric malnutrition : dry (the individual is thin and dehydrated), wet (the individual is swollen due to fluid retention), and an intermediate type.

The dry type called marasmus results from almost total starvation. The child suffering from marasmus eats little, often because the mother cannot breastfeed, and is extremely thin due to the loss of muscle and body fat. Almost invariably, these children develop some sort of infection.

The wet type is called kwashiorkor, an African word that means “first child-second child”. It stems from the observation that the first-born child develops kwashiorkor when a second child is born and replaces the previous as recipient of the mother’s milk. The first child, weaned, begins to be fed with an oat porridge that has low nutritional quality as compared with the mother’s milk; thus, the child doesn’t develop. The deficiency of protein in kwashiorkor is normally more significant than caloric deficiency, resulting in edema, skin disease and hair discoloration. As children develop kwashiorkor after they’re weaned, they’re generally older than those with marasmus.

The intermediate type of protein-caloric malnutrition is called marasmic- kwashiorkor. Children with this type retain some fluid and have more body fat than those with marasmus.

Kwashiorkor is less common than marasmus and normally takes place as marasmic- kwashiorkor. It tends to be restricted to some parts of the world (rural Africa, Caribbean, Pacific islands and southern Asia) where foodstuffs used for weaning babies off – as yam, cassava, rice, Spanish potato, and green bananas – are protein-deficient.

The deficiency of protein damages the body’s growth, immunity, scar tissue formation, and enzyme and hormone production. In both marasmus and kwashiorkor diarrhea is common.

Behavioral development may be extremely delayed in a severely undernourished child, and mental retardation may occur. Usually, a child with marasmus is more severely affected than an older one with kwashiorkor.


Up to 40% of children with protein-caloric malnutrition die. Death during the first days of treatment is usually caused by electrolytic imbalance, infection, hypothermia or cardiac arrest.

Recovery is faster in kwashiorkor than in marasmus.

The effects in the long run of childhood malnutrition are unknown. When children are correctly treated, the liver and immune system recover altogether. However, in some children, the intestinal absorption of nutrients remains impaired. The level of mental damage is related to the length of time the child remained undernourished, how severe the malnutrition was, and at what age it began.