nutrition & infection
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Transcript of 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