Protein Deficiency Diseases

You all studied earlier that protein constitutes the major portion of our body mass after water. There are a number of diseases related to protein metabolism and its deficiency in diet. For better understanding its better to deal deficiency diseases in correlation to functional importance of protein. The subject has been dealt here under different headings.

Protein Turnover

Tissue proteins are continuously being broken down into amino acids and are then rebuild into tissue proteins. This process is called protein turnover and varies in different tissues. High protein turnover is observed in the intestine (epithelium), liver, pancreas and kidney whereas; muscle, brain and skin have low. Structural tissues such as collagen and bone have very low turnover. Dietary deficiency of protein may lead to structural and functional alteration of these important body parts.

Protein Balance

Body proteins exist in two compartments: Tissue proteins and plasma proteins. Balance between the two compartments is maintained by dietary protein intake. There is a give and take relationship between the two compartments at times. During growth, the protein synthesis is higher so that the new tissues could be formed whereas during ageing, tissue breakdown exceeds that of synthesis and the body gradually deteriorates.

Criteria to assess a person's state of protein balance are the measurement of total nitrogen. Total body nitrogen includes, protein nitrogen and non-protein nitrogen represented by compounds such as urea, ammonia, uric acid etc. It is an indication of all nitrogen gains and losses in the body protein. A net negative nitrogen balance is not a healthy sign and reflects increased loss of body protein and low input of food protein. It is observed during long illness, starvation or hyper metabolism (higher body activity).

Protein Requirements

The primary purpose of protein in the diet is to supply amino acids in sufficient quantity for growth and tissue maintenance. There is an enhanced protein requirement during growth. Also important is the nature of protein in the diet and its amino acid composition. Sufficient non-protein foods in the diet are also essential so that proteins are not used up for energy production. This is called protein-sparing effect. The digestibility and absorbability of the protein is affected by cooking methods and other factors. The recommended amount of protein per day (RDA) amounts to about 60-65 gramsfday for a healthy man and 50 grams 1 day for a woman, which increases during pregnancy and lactation. The nutritive value of a food protein is often expressed in terms of its chemical score, a value reflecting its amino acid composition. The chemical score of aprotein is calculated by comparing its amino acid composition with that of egg protein, taken as a standard, having a value of 100. Other criteria that are also considered during the calculation of chemical score of a protein are:

• Biological value (BV) based on nitrogen balance.
• Net protein utilization (NPU) based on biological value and degree of digestibility
• Protein efficiency ratio (PER) based on weight gain of a growing test animal divided by its protein intake.

As we discussed in the protein function that it plays a vital role in the regulation of body process. Deficiency may lead to hormonal imbalance, poor immune status, anemia, wasting condition as well as impairment of several body processes because of lack of necessary enzymes.

Protein Calorie Malnutrition (PCM) 

Growing children require a higher amount of protein and energy (Kcal) per kilogram of body weight than adults. Breast milk usually provides these needs during infancy (first six months). After that, weaning foods adequate in calories, protein, vitamins and minerals need to be added to the breast milk diet for growth.

Protein calorie malnutrition (PCM), a nutritional deficiency, is prevalent among infants and small children particularly in underdeveloped poor countries. PCM is characterized by poor growth and is manifested in two forms: Marasmus, a chronic state with severe wasting of the body tissues and Kwashiorkor, in which edema occurs.

Marasmus is seen in young children (three months to three years) and kwashiorkor occurs in the age group of one to five years. Marasmus is due to low calorie low protein diet whereas kwashiorkor develops due to protein deficiency even though there are sufficient kilocalories in the diet.