Explain Metabolic changes during infection
With the rise in body temperature above normal (98.40F or 37°C) due to infection several metabolic changes occur in the body that increase nutritional needs. Sonle important changes are discussed below:
1) The Basal Metabolic Rate (BMR) increases in severe infection with fever. There is a 7% increase in BMR with every 1°F increase in body temperature or 13% increase in BMR with every 1°C rise in body temperature. The energy needs are estimated to be 20% above BMR for mild infections and 70% above BMR for severe infections. Injury factors can also be taken into consideration to workout the exact calorie expenditure.
2) Nutrient losses may be increased due to increased perspiration, vomiting and diarrhoea. Minerals like sodium, potassium, zinc, magnesium and phosphorus lost by the body.
3) Infection and fever sets in an environment of catabolism (breakdown) in the body. Infection can be related to a state of physiological stress. The body responds to this stress by altering the levels of several hormones to meet the increased requirements (Acute Phase Response).
4) Infection and fever is invariably accompanied by anorexia (lack of appetite) which limits the food intake causing decreased energy intake which is not sufficient to meet the increased energy requirements. Thus leading to weight loss which particularly marked in severe infections.
5) The absorption of nutrients also decreases if there are intestinal infections.
6) Excessive sweat and urination causes further loss of body fluids and electrolytes. This can be an outcome of severe infection with high fever. The sweating occurs in response to high fever while the volume of urine is increased for elimination of nitrogen wastes produced due to catabolic activities.
7) Glycogen and adipose tissue stores decrease significantly due to increased energy expenditure.