nutrition & infection

Nutrition & InfectionMalimu .E ZKIU

Session outline Historical background Relationship between infection and nutrition Effects of nutrition on resistance to infection Effects of infection on nutritional status Mechanisms of infection-nutrition

Historical background 1950s textbooks of nutrition – little/no mention of a relation to infection Same was true for articles on infectious diseases Studies in experimental animals and clinical observations were pointing out

the role of infection in precipitating nutritional disorders

Historical background Clinicians and nutritionists did not recognize the importane of the

relationship Late 1950s – field and metabolic studies demonstrated the synergism in

humans Effects were then extensively investigated

Historical background Explosion in knowledge of cell-mediated immune mechanisms led to an

understanding of how malnutrition lowers body resistance Interaction – leading cause of morbidity and mortality in children – Africa,

Asia, Latin America Malnutrition – infection complex remains the most prevalent PH problem

globally

Malnutrition – infection interactions Relationship is reciprocal and synergistic

Infection leads to a deterioration in nutritional status and at the same time

Malnutrition increases susceptibility to infections

Malnutrition – infection interaction – reciprocal and synergistic

Nutritional Status

Health status

Nutritional and Health status are closely related

Disease contributes to malnutrition

While malnutrition makes an individual more susceptible to disease

This vicious cycle is known as the malnutrition-infection cycle

Inadequate dietary Intake Weight loss, growth faltering, and reduced immunity, which lower the body’s ability to resist infection

Loss of appetite, malabsorption of nutrients, altered metabolism and increased nutrient needs

Longer, more severe and more frequent disease episodes

This causes This results

Leads to

Leads to

Effects of Malnutrition on resistance to infection

• Malnutrition may reduce body’s resistance to infection by reducing• Antibody formation especially PEM• Production of nonspecific protective substances e.g. Interferons, lysosomes,

hydrolytic enzymes • Phagocytic activity of macrophages • Non specific resistance to bacterial toxins• Inflammatory response• Wound healing and collagen formation

Effects Example of effects of micronutrient deficiency VAD reduces leukemia numbers, lymphoid tissue weights, T-cell function,

etc Iron deficiency – reduces cytotoxic activity of phagocytes and proliferation

of T helper cells

Effects Vitamin B deficiency reduces lymphocyte numbers, lymphoid tissue weight,

antibody response and depresses phagocyte function and T cell proliferation Zinc deficiency reduces T cell development and function

Effects of infection on nutritional status Profound effects on the intake, metabolism and excretion of most nutrients Cause protein catabolism Increase resting energy metabolism Reduces serum vitamin A concentration, precipitating xeropththalmia

Effects • Metabolic responses to infections – have deep effects on utilization of food

and endogenous nutrient stores – leading to malnutrition• Increased energy expenditure, 10-15% per 1oC rise in BT• CHO stores for energy are rapidly depleted• Increased fecal losses and/or poor absorption of nutrients• Increased permeability of intestinal mucosa• Macroscopic blood loss – certain parasites e.g. Schistosoma haematobium

IDA

Examples of disease affecting nutritional status

• Malaria – frequent effects - anaemia, growth failure

• Measles – weight loss is obvious– Poor food intake - anorexia, dehydration, fever, buccal lesions– Virus may damage GI mucosa – causing malabsorption and protein loss– Severe metabolic disturbances in the acute phase

• Hookworm – IDA, proteins• A. Lumbricoides – wight loss• T. Trichura - abdominal pain and diarrhoea, weight loss, anaemia• S. Stercoralis – anorexia, malabsorption, loss of endogenous nutrients• Schistosoma – anaemia, poor growth and reduced proteins• G. lamblia – diarrhoea, malabsorption

Effects of HIV/AIDS on nutritional status• Depressed appetite, poor nutrient take and limited food availability• Fever, nausea, vomiting and diarrhoea • Depression• Increased energy requirements – 20-30% in symptomatic HIV and AIDS• Side effects from drugs – opportunistic infections• Chronic infections, malabsorption, metabolic disturbances, muscle and

tissue catabolism

General mechanisms – infection-malnutrition

1. Shifts in the types and quantities of foods consumed (custom or loss of appetite)

2. Adverse effects of treatment on nutrition – Purgatives to children with diarrhoea or worms– Prolonged antibiotics may interfere – synthesis of vitamin K and B vitamins

3. Impaired absorption – diarrhoea-proteins, Vitamin A, Vitamin B12 and Folate

4. Energy, protein and micronutrient needs are elevated in order to fight off infection

5. Parasitic organisms – malaria or schistosomiasis or intestinal worms divert nutrients for their own use

6. Increased urinary loss– Nitrogen, vitamin A, ascorbic acid, Fe, Zn as a result of stress response– Urinary schistosomiasis – loss of Fe and protein

7. Increased fecal loss– Leaking gut phenomenon in hookworm infestation leads to loss of nitrogen and Fe

8. Sweat loss – Loss of amino acids, nitrogen, minerals

END