5 Principles of Nutrition MCT 2024 PDF

Royal College of Surgeons in Ireland Medical University of Bahrain GIHEP Principles of Nutrition Salim Fredericks  Principles of nutrition Learning objectives Describe the composition and caloric content of the healthy diet Explain the principles of energy balance in the body Explain...

Royal College of Surgeons in Ireland Medical University of Bahrain GIHEP Principles of Nutrition Salim Fredericks  Principles of nutrition Learning objectives Describe the composition and caloric content of the healthy diet Explain the principles of energy balance in the body Explain Basal Metabolic Rate (BMR) and diet-induced thermogenesis (DIT) Explain the concept of Daily Energy Expenditure (DEE) Explain the basics of Dietary Reference Intakes (DRI) Describe the basic concepts of Total Parenteral Nutrition (TPN) Describe essential dietary factors Describe the consequences of nutritional deficiencies in the body Nutrition A multi-step process that provides energy and nutrients for the body, including 1. consumption of food/drink 2. degradation of food/drink into nutrients 3. absorption and utilization of nutrients Nutrients provide energy and components for the body’s molecules and cells We exist in a steady state The atoms and molecules of the body are continually changing even though the structures (tissue and organs) and external appearance are relatively constant Skin – replaced entirely by new cells in 7 years Adipose fat pads 1 year RBC – 120 days The lining of the small intestine is replaced every 4-5 days Continual steady state To maintain this state, the depletion from the general growth and maintenance must be replaced. This replacement is essentially what nutrition is all about Over- & Under- Nutrition Food intake ˃ energy expenditure → obesity. Food intake ˂ energy expenditure → emaciation and wasting, marasmus, and kwashiorkor Both obesity and severe under nutrition are associated with increased mortality. Energy The energy content of food may be fully quantified Calories: 1 Calorie = the amount of energy it takes to raise one the temperature of 1 gram of water by 1 °C 1 Dietary ‘Calorie’ is 1000 of these; = 1kCal Some prefer the more “SI” unit of kilojoule Energy Energy content of food – calculated from heat released by total combustion in calorimeter Estimated adult energy requirement: – Sedentary: 30 kcal/kg – Moderately active 35 kcal/kg – Very active 40 kcal/kg – Average 2000 kcal/day Energy balance: intake/ storage/expenditure Energy Energy expenditure from individual to individual varies considerably. It is influenced primarily by four principles 1. Surface area – Thin people have larger surface area and therefore a larger energy requirement compared to obese people 2. Age – Changes in proportion of lean muscle mass through the stages of life 3. Gender – Females have lower BMR as they have lower percentage of lean muscle mass 4. Levels of physical activity Inter-individual variation With all of these differences between ‘normal’ individuals in energy requirements is it possible to have generalised recommendations and guidelines? Energy requirements increase with activity. So how do we account for levels of physical activity? The most useful way of expressing the energy cost of physical activities is as a multiple of BMR Sedentary activities use only about 1.1–1.2 x BMR By contrast, vigorous exertion, such as climbing stairs, cross-country walking uphill, etc., may use 6–8 x BMR  “Standardised” terminology and measures How much? e.g. very young infants were data is Specific life-stage or not available gender group  Energy consumption, expenditure and balance To achieve energy balance, the amount of energy entering the body in the form of food should be the same as the amount of energy used by the body.  Energy consumption, expenditure and balance Energy Expenditure: 1. Basal metabolic rate – BMR The energy the body uses for its chemical reactions (life) and heat generation Clinically, BMR can be estimated by measuring the rate of O2 consumption at rest with 12 hr. fast 2. Physical activity 3. Diet Induced Thermogenesis - DIT (Thermic effect of food ) – energy needed for digestion, absorption, conversion, storage Influenced by composition of food Basic Caloric requirements In kcal/day Basic requirement to maintain BMR: Male : 1800 Female 1300 Recommended Dietary Allowances: Male 2800 Female 2100* * +300 in pregnancy; +500 in lactation What we eat and why How is your food intake influenced? Personal Preference Habit Ethnic Heritage & Tradition Social gatherings Convenience & availability Positive associations Body weight and image Emotion & comfort Medical reasons Health befits Proportions for Healthy Eating About half of the, energy intake should be in the form of carbohydrates a third, at most, in the form of fat, and the rest as protein Koolman, Color Atlas of Biochemistry, Healthy Eating Pyramid Healthy eating plate http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/pyramid Essential nutrients Essential Nutrients Water Carbohydrate Lipids Proteins Vitamins Minerals Deficiencies, excess, and imbalance of nutrients lead to diseases of malnutrition Macronutrients Energy providing molecules consumed in relatively large amounts i.e. carbohydrates, lipids, proteins Acceptable macronutrient distribution range (AMDR) - to reduce risk of disease but still provide adequate nutrition Lippencott’s 27.7 How much energy is produced? 10 8 6 Kcal/g 4 2 0 Carbs Protein Fats Alcohol Lipids Elevated plasma cholesterol associated with coronary heart disease (CHD) – LDL bad – HDL associated with decreased risk Lippencott’s 27.9 Reducing plasma cholesterol with drug treatment (statins) effective in decreasing risk Lipids Saturated fat – strongly correlated with high cholesterol, LDL and CHD. Sources : dairy, meat, some veg oils e.g. palm “most experts strongly advise limiting intake” Monounsaturated fat Sources: vegetable oil, fish When substituted for saturated fat: lower chol., LDL, increase HDL Mediterranean diet: olive oil, fish, seasonal fresh food – low sat. fat  associated with low cholesterol and LDL. Lower CHD Polyunsaturated fats ω-6 Sources: nuts, avocadoes, sesame oil Principally linoleic (18:2; Δ9, Δ12) Lowered LDL – but also lowered HDL ω-3 Sources: fatty fish, flaxseed oil, walnuts Principally linolenic (18:3; Δ9, Δ12, Δ15) Little effect on LDL, HDL But: supress cardiac arrhythmias, reduce serum triacylglycerols etc Both essential FA Linoleic  Required for synthesis of eicosonoids (prostaglandins, leukotrienes, thromboxanes) Linolenic  precursor for other ω-3 fatty acids – other versions of eicosanoids Humans lack the ability to insert double bonds between Δ9 and ω Lipids contd. Trans fatty acids Chemically - unsaturated, but behave like saturated.  Elevated LDL Only small amounts found naturally, but formed during industrial hydrogenation of vegetable oils Dietary cholesterol Only found in animal products Less important than amount/type FA consumed Fat soluble vitamins A, D, K, and E Dietary carbohydrate Mono-, di-, polysaccharides; Fibre – indigestible carbohydrates – Bulk; delays gastric emptying  feeling of fullness – Increases bowel motility – Soluble fibre lowers LDL – Recommended intake 25 g/day f ; 38 g/day m; (USA diet avg. 11 g/day) Lippencott’s 27.17 Blood glucose Glycemic index – low tends to generate satiety over longer time period, may help limit caloric intake (low better for blood glucose management in diabetes) Carbohydrate requirements Carbohydrates not ‘essential’ – carbon skeletons of AAs can be converted to glucose Recommended 130 g/day – based on needs of carbohydrate dependent tissues Simple sugars Same energy content as complex carbs and protein  not inherently fattening Linked to dental caries Recommended that simple sugars < 25% of total energy intake (may displace nutrient-rich foods) ‘protein sparing effect’ If intake less than 130 g/day, dietary protein which could otherwise be used for repair and maintenance, is used for gluconeogenesis Proteins Essential amino acids: “cannot be synthesised out of materials normally available to the cell at a speed commensurate with normal growth” Protein Quality of dietary protein Protein digestibility corrected amino acid score Animal sources – high quality – contain essential AAs in required proportions Plant sources Lower quality However, can be mixed to create high quality diet Egg wheat (-K, +M) + kidney beans (+K, -M)  balanced diet Other essential dietary factors Vitamins – Group of chemically unrelated organic compounds that cannot be synthesised by humans and are necessary for normal metabolism – co-factors for enzymes/precursors (e.g. for hormones) – Recognizable deficiency states due to metabolic dysfunction Minerals & trace elements – Inorganic elements that have a physiological function – Cofactors/membrane potentials/bone/ – Most common deficiencies : Iron, iodine ; zinc selenium Water Under - nutrition There Are Two Extreme Forms of Under nutrition Marasmus – can occur in both adults and children, and occurs in vulnerable groups of all populations. Kwashiorkor – affects only children, and has been reported only in developing countries. The distinguishing feature of kwashiorkor is that there is fluid retention, leading to edema, and fatty infiltration of the liver. Protein Protein-calorie malnutrition Kwashirkor Protein deprivation relatively greater than total calorie deprivation Often occurs on weaning Stunted growth, skin lesions, depigmented hair, oedema Marasmus Calorie deprivation relatively greater than protein deprivation Arrested growth, wasting, anaemia Nutritional support Spectrum of nutritional support: simple advice to long-term total parenteral nutrition Severe Major Obesity Constipa- Lactose Coeliac Pernicious anorexia abdominal tion intolerance disease anaemia and surgery malignancy and sepsis Reduce High Dietary Gluten- Vit-B12 Enteral TPN calories fiber restric- free injection nutrition tion Total Parenteral Nutrition Indications for parenteral nutrition – Patients who are unable to eat or absorb food adequately from the GIT Inflammatory bowel disease e.g. Crohn’s disease Short bowel syndrome, mesenteric artery infarction Total Parenteral Nutrition Route of administration – Via peripheral veins Used for short period of 1 – 2 weeks If nutrients are infused directly into peripheral veins (peripheral parenteral nutrition), nutrition concentrations must be limited to avoid inflammation of the veins – Via a central venous catheter Infusion into central veins can supply nutrient- dense solutions and is used for long-term i.v. feeding Total Parenteral Nutrition As name suggests this provides complete artificial nutrition What would be the components of TPN? Components of TPN: – Water – Source of calories (mix of Glucose and Lipids) – Salts – Amino acids – Vitamins Total Parenteral Nutrition What are the complications associated with TPN? Complications: – Infection (sepsis at the catheter site) – blood clots – fatty liver and liver failure – Cholecystitis – metabolic abnormalities including hyperglycemia,… Some terms and definitions: BMR Basal Metabolic Rate Amount of energy consumed by a person : at rest, awake, 12 hrs post prandially DIT Diet Induced Thermogenesis Additional energy expenditure post- prandially; caused by digestion and metabolic inter-conversions etc DEE Daily Energy Expenditure Total energy expenditure; must equal energy intake to maintain weight DRI Dietary Reference Intake Reference value for nutrient intake TPN Total Parenteral Nutrition Practice of intravenous feeding, bypasses the gut