Life depends on the appropriate supplies of necessary nutrients. In primitive human civilizations and underdeveloped areas of the world most of its forces man spends searching for food or its production. Health potential and the average length of life are significantly improved in the last 150 years, which coincides with the period of prominent economic, technological and scientific progress. Knowledge that has been accumulated during this period made the food available in larger quantities and more diversified than in some past periods in many areas. During recent decades, more adequate understanding of human nutritional needs is reached. Though better nutrition by no means has not been the only factor involved in the extension of life and better health prospects, it is reasonable to conclude that it significantly contributes to the improvement of health.
All people worldwide did not benefit to the same extent from the scientific and technological progress in the field of nutrition. In many areas food stocks remain quite unsatisfactory. The most severely affected people are those living in the most densely populated areas of the world, where only one type of food, such as rice, is the largest part of the diet. Therefore, malnutrition remains a major health problem in the world.
Malnutrition. Malnutrition includes all inadequacies and abnormalities in the diet, as well as defects in the absorption and utilization of food, leading to clinical manifestations of disease or determining its occurrence. On one side are the effects of inadequate nutrition in quality and quantity - the so-called malnutrition; on the other are the effects of excessive intake of food, which is manifested as obesity.
Reactions of the host (human) are determined by the absence or relative lack of a specific nutrient in some situations, such as semi starvation and calorie malnutrition. Lack, however, of specific nutrients from the diet leads to the occurrence of certain diseases due to inappropriate nutrition, such as nutritional macrocytic anemia, iron deficiency anemia (hypochromic microcytic anemia), beriberi, pellagra, scurvy, rickets, kwashiorkor and goiter.
In other cases, disorders can occur due to excessive consumption of food, i.e. obesity. Rarely, the disease may occur due to excessive intake of only one nutrient, as in hypervitaminosis A and D.
Using modern knowledge of nutrition provides practical approaches to prevention and improvement of both forms of poor nutrition.
Link between poor nutrition and the appearance of other types of diseases
Poor nutrition plays a role not only in the pathogenesis of diseases of poor nutrition; it is important in the natural history of a variety of other disorders that affect the human host. It is registered that some of the infectious diseases occur in epidemic form during periods of greatest food restriction. Thus, various diarrheal diseases can occur during periods of starvation, and it is also registered that the number of deaths due to tuberculosis was significantly higher during the periods of food restriction. Such an experience was in Denmark during World War I, when the country exported the bulk of locally produced meat and dairy products in their efforts to assist neighboring countries who were at war. Later, the export of these products was prevented by submarine blockade. This led to a significant increase of the local use of this food in Denmark, causing the tuberculosis mortality rates to decline few months later, compared to pre-war levels.
The nature of the diet may be important in the pathogenesis of a wide range of metabolic diseases. One example is portal cirrhosis (Laennec's cirrhosis) of the liver in people living on diet that lacks protein and water-soluble vitamins. Although this disease is frequent among people in Europe and United States who have tendency to consume large amounts of alcohol, it is found that it prevails also among Hindu people in southern parts of India, who, because of religious beliefs, refrain from taking alcoholic beverages, but whose diet is extremely low in protein and basic water-soluble nutrients. Similarly, the disease was registered among children of Jamaica and some countries in Africa and Asia, where there is chronic starvation. There is evidence indicating that cirrhosis in chronic alcoholics is significantly associated with anorexia and limited intake of protein, but also alcohol has direct hepatotoxic effects. Whether or not alcohol alone can produce fatty nutritional cirrhosis has been debated for decades. Current evidence is that it can. If so, the condition should be renamed "alcoholic cirrhosis".
Occurrence of some degenerative diseases can be conditioned by the type and quality of food consumed. Poor nutrition, resulting in obesity, has been accompanied by faster growth and more extensive atherosclerotic changes in major vessels. Deaths due to cardiovascular disease are more common in obese people than in those with normal weight.
Thirty to forty percent of all cancers are linked to diet. Primary dietary factors that increase the risk include obesity and alcohol consumption; with a diet low in fruits and vegetables and high in red meat being implicated but not confirmed.