The Biology of Malnutrition

1. The Biology of Malnutrition

2. The cycle of malnutrition • How and where to break the cycle is the issue • The focus of intervention is now on the Lifecycle or life course

4. Types of Malnutrition • Overnutrition • Secondary malnutrition • Micronutrient malnutrition • Protein Calorie malnutrition

5. Overnutrition • Too many calories leading to obesity, diabetes, hypertension and cardiovascular disease • “Transition diets” now a consideration of WHO due to increase worldwide in chronic disease due to dietary change

6. Overnutrition • On a global basis 79 % of all deaths attributable to chronic disease are already occurring in developing countries • Public health implications are “staggering” • Overnutrition following fetal malnutrition has also been linked to chronic disease risk in adulthood

7. Secondary Malnutrition • Condition that prevents proper digestion or absorption • Often accompanies and exacerbates other types of malnutrition

8. Secondary Malnutrition- causative conditions • Loss of appetite • Alteration of normal metabolism • during infection/fever • HIV/AIDS • Prevention of nutrient absorption • Diarrheal infection causing changes in GI epithelium

9. Secondary Malnutrition- causative conditions • Diversion of nutrients to parasitic agents themselves • Hookworms, tapeworms, schistosome worm • Malaria

10. Children with Intestinal Parasites(courtesy of WHO)

11. Prevention of nutrient diversion • Sanitary waste disposal and clean water important in reducing secondary malnutrition • Prevention of transmission of parasites and diarrheal diseases • Hookworm acquired by walking barefoot over contaminated soil • Other roundworm infections use oral-fecal route

12. Prevention of nutrient diversion • Soap an important factor in nutritional status • Education of women extremely important in this regard

13. Micronutrient Malnutrition • Dietary Deficiencies of • Vitamin A • Iodine • Iron • Others: Zinc, vitamins D, C, and Bs

14. Protein Calorie Malnutrition • More food needed for normal growth, health and activity • Rarely have protein deficiency without caloric deficiency due to the nature of the food supplies • exception seen with cassava and plantain as staples

15. Role of calories • Involuntary use: breathing, blood circulation, digestion, maintaining muscle tone and body temperature • Physical activity • Mental activity • Fighting disease • Growth

16. Role of protein • For building cells that make up muscles, membranes, cartilage and hair • Carrying oxygen • Nutrient transport • Antibodies • Enzymes needed for most chemical reactions in the body

17. What happens to people when they have inadequate amounts of food and nutrients? • Metabolic changes • Physiologic changes • Psychological changes

18. Metabolic Response to Starvation • Hunger subsides after 2-3 days • Defecation ceases after 3-4 days • Urine output drops after 1 week in the majority of people to 100-700 ml/day • Blood glucose levels drop to 35 to 65 mg/dl without clinical signs of hypoglycemia • Nausea occurs in about 1/3 from ketone production from body fat breakdown

19. Metabolic Response to Starvation • Serum electrolytes do not change • Renal conservation occurs promptly • Rarely see low potassium in prolonged fast

20. Metabolic Response to Starvation • Negative nitrogen balance - 1st 5 to 7 days • 12 to 15 grams of nitrogen per day is excreted in the urine (based on 1800 kcal daily needs) • Skeletal muscle is catabolized to produce glucose (gluconeogenesis), using about 75 grams per day of protein • This is equal to ¾ lb of wet tissue per day • About 160 gm per day of body fat is also used

21. Metabolic Response to Starvation • Negative nitrogen balance • Gradually slows so that at about 1 month • 2-4 grams of nitrogen is loss per day • Skeletal muscle catabolism decrease significantly • Only for cells that have to have glucose • Central nervous system • Red blood cells • White blood cells

22. Metabolic Response to Starvation • Gradual shift in metabolic fuels • First glucose is produced from protein breakdown to provide energy • Then fat breakdown and metabolism provides ketones for all tissues except CNS, RBC and WBC • Brain will eventually use ketones but red blood cells have no mitochondria, so must use glucose • Serum fatty acid levels increase • Serum albumin is normal until late in starvation

23. Production of Ketones

24. Metabolism

25. Metabolic Response to Starvation • Hormonal changes • Plasma insulin decreases • Plasma cortisol and growth hormone stay the same and glucagon increases • These changes are responsible for the mobilization and oxidation of fat stores • Changes in sympathetic nervous system and metabolism of thyroid hormone lowers basal metabolic rate

26. Metabolic Response to Starvation • Weight loss • First week 0.7 to 1.3 kg per day, much of which is slat and water loss • After the first week 0.3 to0.5 kg/day • Basal Metabolic Rate and Total Energy Expenditure decrease in prolonged starvation • See decreased activity, increased sleep • Decrease in body temperature

28. Classic study by Keyes described physical and psychological changes during a period of semi-starvation. • Traditionally used to describe what happens during dieting • Perhaps should think about traditional stereotypes of the poor in relationship to the findings of this study

29. Keyes Study • Impetus: realization WWII would be over soon and food relief was going to be necessary – needed data • Subjects: • 32 men • Conscientious objectors • Ages 25.5 +/-3.5 years • Time period: • 11/19/44 to 1/20/45

30. Keyes Study -Diet • 12 weeks of baseline diet ad lib • Normal diet of 51% carbohydrate, 13% protein, 32% fat • 24 week semi-starvation diet • 12 weeks of rehabilitation (normal diet)

31. Keyes Study • 24 week semi-starvation diet • Consisted of food designed to represent the types of foods available in European famine areas – whole wheat bread, potatoes, cereals, considerable amounts of turnips and cabbage, token amounts of meat and dairy products • About 1600 kcal per day, 71% carbohydrate, 12% protein and 17% fat • Served in 2 meals per day at 8:30AM and 5 PM

32. Keyes Study - Activity • Assigned specific tasks such as general maintenance, laboratory assistance, shop duties and desk work about 15 hours per week • Educational programs, about 25 hours per week • Walked 35 km out-of-doors per week and were on a treadmill for ½ hour

33. Keyes Study – Body changes • Body weight decreased about 25% • From mean of 69.4kg (BMI 21.4) to 52.6 kg (BMI 16.3) • Weight loss decreased progressively and nearly reached a plateau at the end of the semi-starvation period • Subjects adjusted their energy expenditure to reach a balance after 24 weeks at 45% of the ad lib diet

34. Keyes Study - Adaptations • Adaptation accompanied by a loss of active tissue • Relatively high loss of lean body mass • Body fat loss made up about 1/3 of the weight change

35. Keyes Study - Adaptations • Reduced activity costs were the main part of the energy savings • Decrease BMR due to less lean body mass • Less thermic effect of food due to lower intake • Reduced body weight resulting in less caloric cost of physical activity

36. Keyes Study - Adaptations • “Real” adaptation • Reduction in tissue metabolism • Decreased BMR • Reduction in physical activity

37. Keyes Study – Physical signs • After about 3 months, participants complained of • Fatigue • Muscle soreness • Irritability • Hunger pains

38. Keyes Study – Physical signs • After 3 months, participants • Exhibited a lack of • Ambition • Self-discipline • Poor concentration • Were often moody and depressed • Became less able to laugh heartily, sneeze and tolerate heat • Heart rate and muscle tone decreased

39. Keyes Study - recovery • When permitted to eat normally again, the desire for more food and a feeling of fatigue continued, even after 12 weeks of rehabilitation. • Full recovery required 33 weeks.

40. Study Questions • What are the implications of this research to population groups with cyclical food availability? • What might happen to the capacity to work with undernutrition?