In the developing areas of the world, some of the greatest health problems are directly related to inadequate nutrition. These include early childhood malnutrition due to calorie-protein deficiencies as well as iodine deficiency goiter, blindness due to lack of vitamin A, and a host of infectious diseases made worse by poor nutrition.

Iron-deficiency anemia and dental caries, widespread disorders related to malnutrition, have neither geographic nor socioeconomic boundaries. Even in highly developed societies there may be large segments of the population in which hunger and undernutrition impair physical and mental performance.

Nutrition is the science of food, the materials or nutrients in food, what they do and how they interact all in relation to health. Nutrition comes from food, good food that one enjoys (for eating has always been one of the pleasures of life), from food in variety so as to supply the more than 50 known nutrients that are necessary for proper nutrition, thereby providing the best of health that one's genetic or hereditary background permits.

Nutrition is important in modern health and medicine in improving and maintaining good health and in improving poor health.

The acute and severe vitamin deficiencies as manifested by the classical nutritional diseases scurvy, pellagra, beriberi, and xerophthalmia are prevalent in many other parts of the world.


Protein-calorie malnutrition in young children constitutes the most important and widespread nutritional problem in the world today. The two main clinical syndromes are kwashiorkor and nutritional marasmus. In kwashiorkor the principal deficiency is of protein, whereas in marasmus there is an overall deficit in food intake resulting in insufficient calories and protein. From the clinical point of view, there are many intermediate cases that are difficult to fit into either category; they show some of the symptoms and signs of both conditions.

Kwashiorkor and nutritional marasmus can be regarded as the two extremes of protein-calorie malnutrition of young children. However, very many cases of protein-calorie malnutrition are intermediate, and this has given rise to such names as "marasmic kwashiorkor" to describe cases in which kwashiorkor is superimposed on marasmus. Separate descriptions are given kwashiorkor and nutritional marasmus, but the clinicians must expect many cases to be intermediate between the two extremes.

Kwashiorkor occurs mainly in children 1 to 3 years of age. It is common in many developing countries of Asia, Africa, and Latin America, but has been reported also in Europe and the United States, where it is associated with poverty.

The disease occurs in children whose diet is grossly deficient in protein. Often the food that the child is receiving is of a type that contains mostly carbohydrate and little protein. In many parts of the world, kwashiorkor is a disease of the weaning period when the child is taken from the breast and given a diet that is primarily starch. An adequate intake of breast milk will provide a satisfactory diet for the first four to six months of an infant's life. After that, chiefly because of reduced quantities, breast milk provides merely a useful protein-rich dietary supplement to whatever other food the child is receiving.

Important factors often implicated in the complex etiology of kwashiorkor are:

a)     The rapid growth and relatively high protein requirements of the rapidly growing young child;

b)    A protein-poor, staple food for the child, e.g. manioc, bananas, sugar

c) Poor infant-feeding practices;

d) A lack of protein-rich foods, both animals (e.g., meat, milk, fish, eggs) and vegetable (e.g. beans, peanuts);

e) Poor distribution of available food in the family (e.g., the adults and older children often get the major share of protein-rich foods such as meat);

f) Seasonal food shortages

g) Poverty and its attendant ills

h) Cultural dietary practices, including food taboos, may preclude the child's consumption of certain available and nutritionally desirable foods

i) Infections such as diarrhea, measles, whooping cough

j) Ignorance or lack of knowledge on the part of parents or guardians concerning what foods are needed in the child's diet

k) Psychological factors that may affect the appetite of the child

Nutritional Marasmus is common in nearly all developing countries and, in contrast to kwashiorkor, is more common among children younger than 1 year, although it is not restricted to this age group. The disease is a form of starvation and therefore the underlying causes are numerous but all involve serious lack of food. In many countries nutritional marasmus is occasionally seen in grossly neglected children but may also occur secondary to such diseases as cystic fibrosis, celiac disease, or overwhelming infections.

A common cause of nutritional marasmus among peoples of developing countries is early cessation of breast-feeding. This may be due to death of the mother, failure of lactation, separation of the infant from the mother, or most commonly the mother's desire to feed her infant from the bottle rather than the breast. In this latter event she may be influenced by advertisements and the impact of alien cultures into believing that bottle-feeding is superior or more sophisticated. Early cessation of breast-feeding does not of course necessarily lead to marasmus. However, a large proportion of people in developing countries do not have sufficient income to purchase enough milk formula to feed a baby properly. As a result, the tendency is to over dilute the mixture with water, which then fails to provide adequate calories. Similarly, few in these countries have a safe water supply or items in their homes with which to simplify the sterile preparation of bottles of formula for an infant. Combined with a lack of knowledge concerning hygiene, those problems commonly lead to the development of gastrointestinal infection, which starts the vicious circle leading to marasmus.

Clinical feature


Nutritional marasmus

Growth failure






Mental changes






Hair changes




(flaky paint)

Fairly common



Very common


Subcutaneous fat

Reduced but present






Xerophthalmia, which is the clinical manifestation of vitamin A deficiency, is a common cause of blindness in some parts of the world, particularly in Asia. It is caused by a diet deficient in vitamin A and its precursor, carotene. The disease occurs most commonly in young children and is often associated with protein-calorie malnutrition.An early sign of vitamin A deficiency is night blindness (the inability to see well in dim light), which may be difficult to detect objectively, especially in young children. Although vitamin A deficiency may also cause follicular hyperkeratosis of the skin, the characteristic lesions of the disease are seen in the eye. Xerophthalmia usually begins with a drying of the conjunctiva, which then loses its shining luster. Thickening, wrinkling, or pigmentation of the conjunctiva may accompany this condition of conjunctival xerosis. Another common lesion that may or may not be present is Bitot spots - usually small, foamy, oval or triangular plaques situated on the bulbar conjunctiva. The spots are nearly always bilateral, temporally situated, and are sometimes associated with conjunctival xerosis.


Beriberi is caused by a deficiency of the B vitamin thiamin, also known as B1, when the ratio of its intake to the number of calories obtained from carbohydrate is low. The disease occurs predominantly among rice-eating peoples of the world because of their use of refined or polished rice.

From a clinical viewpoint, there are various ways to classify beriberi. Here it will be grouped into three forms: (1) wet beriberi, (2) dry beriberi, and (3) infantile beriberi. These three clinical forms of the disease have many different features and yet appear to be caused by the same dietary deficiency and occur in the same endemic areas.

PELLAGRA The disease is associated with a corn (maize) diet and is primarily due to a dietary deficiency of niacin, one of the B-complex vitamins. Although there is more niacin in corn than in some other staple foods, the vitamin is evidently not completely utilized, most likely because it is in a bound form unavailable to the body. The human body can convert the amino acid tryptophan into niacin, so a high-protein diet rich in tryptophan will help prevent pellagra.

To the medical student, the Four Ds - dermatitis, diarrhea, dementia, and death, portray pellagra.

SCURVY is a rare disease today. It results from a deficiency of vitamin C and usually occurs only after considerable time in persons on a diet containing very little fresh fruit or vegetables. Daily intakes of vitamin C considerably less than the recommended allowances, even for periods of several months, usually do not result in scurvy. Vitamin C is necessary for the formation and healthy upkeep of intercellular material. In scurvy, the walls of the capillaries lack solidity and become fragile, resulting in hemorrhage from various sites.

The following symptoms and signs characterize scurvy:

a Tenderness of the extremities, muscle weakness, and suppressed appetite may be evident.

b Gums become swollen and bleed easily; teeth may become loose.

c Hemorrhages of a petechial type often occur in the skin.

d Hemorrhages in other areas may manifest themselves as nose bleeds, hematuria, melena, splinter hemorrhages below the nails, and painful subperiosteal hemorrhages.

e Delayed healing of wounds and heightened risk of infection may occur.

f Anemia and shortness of breath may be noted.


In both rickets and osteomalacia, there is a lack of calcium retention in the skeleton. The conditions are, however, due mainly to a deficiency of vitamin D and not of dietary calcium. Vitamin D is obtained both from the diet and from exposure of the skin to sunlight. The average unsupplemented diet contains only relatively small amounts of vitamin D, but nowadays-young children add the vitamin to many-processed foods.especially those commonly consumed. Vitamin D deficiency is therefore uncommon in children and is very rare in adults in many countries.

Osteomalacia is the adult counterpart of rickets and has the same general causes. It occurs much more frequently in women than in men. It is most common in women on a poor diet who have been depleted of calcium by many years of pregnancies and lactation, who get very little vitamin D in their diet, and who are protected from the sun by their clothing and confinement indoors.Pain occurs in the bones of the pelvis, lower back, and legs. Tenderness may be elicited by pressure on the affected bones. Deformities occur later, especially in the pelvis and spine. The patient may walk with his feet widely spaced and mayappear to waddle. Spontaneous fractures often are a complication of severe osteomalacia. In some cases, tetany develops and may be seen as involuntary twitchings of the muscles of the face and as carpopedal spasms.


Iron deficiency is one of the most common nutritional deficiencies in the many country. It occurs most frequently in

        infants beyond six months of age,

        in adolescent girls, and

        in women of childbearing age.

Iron absorption is influenced by many factors. In general, only about 10 % of dietary iron is believed to be absorbed. The adult male loses only about 0,5 to 1,0 mg of iron daily; his daily requirement for iron is therefore about 10,0 mg/day. On an average monthly basis, the adult premenopausal woman loses about twice that amount. Similarly, iron is lost during childbirth and in lactation; pregnant women and growing children need additional dietary iron.

ENDEMIC GOITER is the name used for any swelling of the thyroid gland. When it occurs sporadically it may be due to any of various causes not related to diet. However, where goiter is common or endemic in a district or in a community, the cause is usually nutritional, due to a lack of the mineral nutrient iodide.

In endemic goiter areas, many people have some enlargement of the thyroid gland and a smaller number have large and obvious swellings of the neck.

By far the commonest cause of endemic goiter is a deficiency of iodide in the diet of those affected. The amount of iodide present in soil varies from place to place, and the soil content affects the quantity both in food grown and in the water supply of the area. Seafoods such as fish, shellfish, and seaweed are rich sources of iodide. Endemic goiter areas are usually far from the sea.

Cretinism in children occurs most commonly in endemic goiter areas and is usually due to severe iodide deficiency of the mother. The infant might appear normal at birth but is slow to develop, small in size, mentally dull, and has thick skin and characteristic facial features such as a depressed nose and, often, a protruding, enlarged tongue. Deaf mutism and mental retardation are common among the children of mothers with enlarged thyroid glands.

Thermal interaction between the human body and the environment

In order to give a basic background of the perception of thermal comfort and the parameters that influence it, a brief description of  the  the thermal interaction between the human body and the environment is given.

The Heat Generated (M-W) is the total metabolic heat production within the body (M = metabolic rate required for the persons activity + metabolic level required for shivering) minus the energy production expended as external work done by the muscles (W). The net heat production (S) can either be stored increasing the body temperature or dissipate to the environment through the skin surface and respiratory tract.The heat dissipation from the body to the immediate surroundings occurs by several modes of heat exchange:

   Sensible heat flow from the skin. The sensible heat exchange from the skin surface must pass through clothing to the surrounding environment (the unit that expresses the clothing insulation is clo; 1clo = 0.155m2KW-1). These paths are treated in series and can be described in terms of heat transfer from the skin surface, through the clothing insulation to the outer clothing surface and to the environment. This heat flow is equal to the sum of convection and radiation heat transfer at the outer clothing surface. The heat losses are typically expressed in terms of environmental factors, skin temperature and skin wettedness.

   Evaporative heat loss from the skin. The evaporative skin loss from the skin depends on the amount of moisture on the skin and the difference between the water vapour pressure at the skin and the ambient environment. It is a combination of latent heat flow from the evaporation of sweat and from the evaporation of moisture diffused through the skin.

   Respiratory losses. According to ASHRAE Fundamentals, (2001), During respiration the body loses both sensible and latent heat by convection and evaporation of heat and water vapour from the respiratory tract to the inhaled air. A significant amount of heat can be associated with respiration because the air is inspired at ambient conditions and expired nearly saturated at a temperature only slightly cooler than tcr (temperature of core compartment). Respiratory heat loss is often expresses in terms of sensible and latent heat losses.

Because of that interestingly will learn how the heat is lost by skin. Appear, that skin loses a heat by three ways:

by radiation,

taking and

on evaporation of sweat moisture.

For data of Rubner, we can say, that man attached to light work in room conditions

loses by radiation about 40%,

taking - about 30% and

by evaporation - about 20% of heat.

These ciphers are directed for orientation, and really they consider vacillate dependency on conditions.

Over the years, researchers of human comfort have established the variables that affect a human's thermal sensations and they have established the ranges of these variables within which the average person is comfortable.

Six primary comfort variables

These "comfort" variables include air temperature, relative humidity, air motion, and mean radiant temperature. The mean radiant temperature is the average temperature of all of the surfaces that surround the person in question. These four variables are called the "environmental variables" because they represent the environment surrounding the body.

A second set of variables, called the "personal" variables, are controlled by the individual. The two are the clothing insulation value, termed the "clo" value, and the metabolism rate, with units of "met" as described above.

Microclimate is meteorological conditions in work zone, which characterized by complexes of factors that act on organism of peoples it is temperature, humidity and rate movement of air, and also radiation temperature and warm radiation. Temperature of air is favorable factors which influence on heat exchange. Radioactive temperature it is the temperature that surround people of superficiality or intensive sun or another radiation.

Microclimate is a thermal status of the limited space. It results from combined action of air temperature, radiation heat, air humidity and air movement velocity. Microclimate defines heat state of an organism. Microclimate is influenced by latitude, topography, human activities and vegetation as well as other factors. Sometimes they mean microclimate as variations of the climate within a given area, usually influenced by hills, hollows, structures or proximity to bodies of water. The warmth and humidity of the air in close proximity to a plant or heat/moisture source may differ significantly from the general climate of the premise.

Air treatment/air cooling differs from ventilation because it reduces the temperature of the air by removing heat (and sometimes humidity) from the air. Air conditioning is a method of air cooling, but it is expensive to install and operate. An alternative to air conditioning is the use of chillers to circulate cool water through heat exchangers over which air from the ventilation system is then passed; chillers are more efficient in cooler climates or in dry climates where evaporative cooling can be used.

Local air cooling can be effective in reducing air temperature in specific areas. Two methods have been used successfully in industrial settings. One type, cool rooms, can be used to enclose a specific workplace or to offer a recovery area near hot jobs. The second type is a portable blower with built-in air chiller. The main advantage of a blower, aside from portability, is minimal set-up time.

Another way to reduce heat stress is to increase the air flow or convection using fans, etc. in the work area (as long as the air temperature is less than the worker's skin temperature). Changes in air speed can help workers stay cooler by increasing both the convective heat exchange (the exchange between the skin surface and the surrounding air) and the rate of evaporation. Because this method does not actually cool the air, any increases in air speed must impact the worker directly to be effective.

If the dry bulb temperature is higher than 35C (95F), the hot air passing over the skin can actually make the worker hotter. When the temperature is more than 35C and the air is dry, evaporative cooling may be improved by air movement, although this improvement will be offset by the convective heat.

When the temperature exceeds 35C and the relative humidity is 100%, air movement will make the worker hotter. Increases in air speed have no effect on the body temperature of workers wearing vapor-barrier clothing. Heat conduction methods include insulating the hot surface that generates the heat and changing the surface itself. Simple engineering controls, such as shields, can be used to reduce radiant heat, i.e. heat coming from hot surfaces within the worker's line of sight. Surfaces that exceed 35C (95F) are sources of infrared radiation that can add to the worker's heat load. Flat black surfaces absorb heat more than smooth, polished ones.

Having cooler surfaces surrounding the worker assists in cooling because the worker's body radiates heat toward them. With some sources of radiation, such as heating pipes, it is possible to use both insulation and surface modifications to achieve a substantial reduction in radiant heat.

Instead of reducing radiation from the source, shielding can be used to interrupt the path between the source and the worker. Polished surfaces make the best barriers, although special glass or metal mesh surfaces can be used if visibility is a problem.

Shields should be located so that they do not interfere with air flow, unless they are also being used to reduce convective heating. The reflective surface of the shield should be kept clean to maintain its effectiveness.

Whole-House Balanced Ventilation Systems

Balanced ventilation systems, if properly designed and installed, neither pressurize nor depressurize a house. Rather, they introduce and exhaust approximately equal quantities of fresh outside air and polluted inside air, respectively. A balanced ventilation system usually has two fans and two duct systems. It facilitates good distribution of fresh air by placing supply and exhaust vents in appropriate places. Fresh air supply and exhaust vents can be installed in every room. But a typical balanced ventilation system is designed to supply fresh air to bedrooms and living rooms where people spend the most time. It also exhausts air from rooms where moisture and pollutants are most often generated (kitchen, bathrooms, and perhaps the laundry room). Some designs may use a single-point exhaust. Because they directly supply outside air, balanced systems allow the use of filters to remove dust and pollen from outside air before introducing it into the house.Balanced ventilation systems are appropriate for all climates. However, because they require two duct and fan systems, balanced ventilation systems are usually more expensive to install and operate than supply or exhaust systems.