Metabolism & Nutrition

Metabolism and nutrition • • • • • Principles of nutrition Vitamins Thermoregulation Undernutrition Obesity 2 5 7 8 11 Nutrition 1 of 12 Principles of nutrition • Know the components of a Balanced Diet and define the term Nutrient Balance. Macronutrients – Fat, Protein and Carbohydrates Micronutrients – Minerals, Trace elements, Vitamins Others - Water & Fibre Nutrient balance – balancing so input = usage • Know what is meant by the term Energy Balance and state numerically the energy densities of the Macronutrients. 1kcal = 1 Cal = 4.184 kJ Energy balance – where input and usage are equal 1 lb of body fat = 3500 kcal Metabolised energy 1 mile walk = 100kcal CHO 4 kcal / g Protein Fat Alcohol 4 kcal / g 9 kcal / g 7 kcal / g Gross ingested (100%) • State the difference between Digestible and Metabolisable Energy. • Explain the importance of Dietary fibre Digestible (95%) Metabolisable energy Faecal losses (5%) Urinary losses (N2, urea, ketones, glucose) Can be soluble / insoluble Protects against colon cancer Increases cholesterol (bile salt) excretion Bulks up colon à increases transit speed Fermentation of soluble fibre = substrate for bacteria à short chain fatty acids produced = preferred fuel for colonic cells • Name the major minerals, their roles in metabolism and main food sources. Mineral Mg Ph K Zn Cu Se I Mn Mo F Cr • Found in Leafy green veg, beans, nuts Meat & dairy Milk, fruit, veg, fish and shellfish Cabbage, meat, cereals Nuts, shellfish, offal Brazil nuts, fish, cereal, eggs Fish, shellfish, sea salt Tea, milk, bread, cereals Legumes Drinking water Processed meats, pulses, spices Describe how a person’s Nutritional Status is assessed. Anthropometry – height, weight, girth, BMI Body composition – skin folds, MUAC, body water – BIA Biochemistry and haematology – plasma proteins, electrolytes, vitamins, lipids, FBC Function – muscle strength, physical signs (wound healing) Dietary assessment – diary, FFQs, 24 hr recall • Describe 2 ways of estimating body composition and define Body Mass Index Nutrition 2 of 12 Measuring body composition Densitometry Total body water BMI = weight / height 2 • Know the approximate Fat, Protein and Water percentages of healthy non-obese adults, and what Fat Content is indicative of obesity. Body composition Protein CHO Fat H2O Minerals Overweight fat Obese fat • Male Female 15-16 % 14-15 % 1-1.5 % 1-1.5 % 15-22 % 22-28 % 55-64 % 50-58 % 5% 5% 25-30% fat in males >30% fat in males 30-35% fat in females > 35% fat in females Define the terms Estimated Average Requirement and Reference Nutrient Intake and state which nutrients they apply to. Estimated average requirement (EAR) = average energy requirement for population Reference nutrient intake (RNI) = meets/exceeds the needs for 97% of a group (not for energy) Dietary reference values (prev. RDAs) Apply to healthy groups of people in UK only Amount required to prevent disease Recommendations are generally > requirements (except for energy) • State 3 ways of estimating Energy Intake. Harris-benedict equation estimates REE / BRM = BMR x Activity Factor Determine amount of food eaten Analyse food content • Describe the components of Resting, Food and Activity related Energy Expenditure Resting Food Activity • Thermogenesis Basal metabolism (Maintaining membrane potentials, Synthesis & degredation, Turnover & storage) Food digestion Posture & Exercise State what is meant by Indirect Calorimetry, and how it can be used to determine Energy Expenditure and substrate utilisation. Monitor O2 uptake and CO2 production Using chemical equations can calculate energy NB - RQ = CO2 / O2 (CHO = 1.0, Fat = 0.71) • Know the approximate Energy, Protein and Iron requirements of healthy adults and how Energy needs might be estimated. Recommended Dietary Composition Carbohydrate 50-60% of energy (2/3 starchy) Fat 30-35% of energy (max 10% saturated) Protein 10-15% of energy NB: Diet should be varied to ensure balance of vitamins and minerals Scholfield equation – predict resting energy requirements x activity factor Resting metabolism - used only for growth & digestion of food Nutrition 3 of 12 Physical activity – posture, exercise, all voluntary activity Physical Activity Level (PAL) = physical / resting Protein – used for growth and repair - 0-5 yrs is greatest energy requirement Adult RNI = 0.75g / kg / day WITH a balance of essential and non-essential amnio-acids Even if athlete / manual labour – do not need any more than 2x RNI Health Adults Male Sedentary Active Female Sedentary Active • Energy 10MJ 12MJ 8MJ 10MJ Protein 50g 50g 40g 40g Iron 10mg 10mg 15mg 15mg State the major nutrients required for growth and be able to compare an Infant’s and an Adult’s requirements of 5 nutrients. Child Teenager Adult Energy (MJ) 3 12 10 Protein (g) 5 55 50 Ca2+ (mg) 525 800 1000 Fe2+ (mg) 8 15 15 Vit D (µg) 10 2.5 NB: children can have upto 20% of their energy as fat (as required for neuronal development) • State the major nutrient requirements of pregnancy and lactation, and describe briefly why special attention is focussed on Folate and Vitamin A. Pregnancy requires extra nutrients to supply the growing fetus. Extra fat soluble (ADEK), water soluble and other nutrients Energy Protein Ca2+ Vit C Vit A Vit D • 2nd / 3rd trimester + 5-10% + 6g + 100% + 25% + 15% + 400% Lactation + 25% + 10-15g + 100% + 75% + 50% + 400% Other Infomation NB: no extra iron should be required Fatty N3 oils are important for fetal neuronal development Imp. to replenish stores after lactation Folic Acid – prevents NTDs Vit A Can be teratogenic in 1st trimester Briefly describe the Special Nutritional Requirements of the Elderly. Physical activity levels tend to decrease Low energy intake = low food intake with inadequate vitamins & minerals Need relatively more milk, eggs, meat, fruit and veg Ensure sufficient Vit D (supplement if required) • Give some common examples of the use of dietetics. HIV/AIDS – food safety, balance diet to boost immune system, try to limit diarrhoea, constipation, nausea, vomit, weight loss CF – impaired intake and absorption, Rx enzyme replacement Renal failure – proteinuria, increased K+ & Na+ plasma. Rx by NaCl and K+ restriction. Spread protein throughout the day Coeliac – gluten enteropathy à avoid gluten, correct dehydration and vitamin & mineral def Crohns – avoid trigger foods, supplement deficiencies, elemental diets counter malabsorption Head & neck – antiemetic, liquidise/PEG DM – regular meal pattern, increase fibre, decreased fat, increase complex carbs Hyperlipideamia – weight loss programme Nutrition 4 of 12 Vitamins • Define the term vitamins and explain the different classes. Vitamin = organic substances in food required in small amounts for normal metabolism, but cannot be synthesised in body in sufficient quantity Deprivation à clinical deficiency, restoration à recovery In 2 main groups – fat and water soluble • Name two factors increasing, and two decreasing, vitamin availability from food. Increases availability Provitamins (B carotene, tryptophan) Colonic bacteria (vit K, B12, folate) • Decreases availability Biliary dysfunction Binders (nicotinic acid) Antibiotics – kill colonic bacteria Losses in cooking, heat and light Name the Water Soluble vitamins, their major dietary sources, and outline their roles in metabolism and symptoms of deficiency. Many have more than one form (e.g. B1, B6, B12) Have many roles Have more than 1 deficiency symptoms Stores in the body vary (Vit C 3-6 months, Vit B12 1-2 years) Vit C (ascorbic acid) Antioxidant Co-factor in hydroxylation of collagen Important in intracellular matrix of capillaries, bones, teeth, connective tissue Found in citrus fruits, vegetables and potato Deficiency à scurvy – poor wound healing and bleeding gums Vit B1 (thiamine) Co-factor in the Krebs cycle Important in neural tissue Found in unrefined whole grains, cereals, organ meats, pork, nuts and legumes Also fortified in flour Deficiency à Beri-Beri – loss of weight, poor appetite, cardiac & NS problems Can occur in chronic alcohol abuse à wernicke-korsakoff syndrome Can only be stored by the body for 10 days Vit B2 (riboflavin) Co-enzyme Found in dairy products, poultry, meat, fish, cereals Fortified in cereals and milk Degraded by light Deficiency à ariboflavinosis – retarded growth, angular stomatitis, chellosis, glotitis Vit B6 Amino acid and glycogen metabolism Found in plants, meat, fish and potato Deficiency à seizures in infants, inflammation of tongue and peripheral neuropathy Can occur with malabsorption, renal dialysis and chronic alcoholism Vit B12 (Cobalamin) Enzymatic reactions Made in microorganisms Found in animal products (meat, milk, cheese) and yeast spreads – low in vegan diet Deficiency à megaloblastic anaemia, subacute neuropathy Can occur in elderly, malabsorption and post gastrectomy (needs IF). Stored in liver Niacin (nicotinic acid) Nutrition 5 of 12 Co-enzyme for numerous oxidoreductases (for glycolysis, fatty acid metabolism, tissue respiration & detox) Found in rice, wheat, oatmeal, cereals Niacin can be made in body from pro-vitamin tryptophan Deficiency à pellagra – dermatitis, dementia and diarrhoea Folic Acid Involved in methylation cycle Found in most foods Deficiency à pernicious anaemia (macrocytic), increased NTDs & increased risk of stroke & cardiovascular disease Can occur if poor intake, impaired absorption, pregnancy, drugs and chronic alcoholism Should be on supplements if pregnant Biotin Co-factor, fatty acid synthesis, gluconeogenesis, and branches chain amino-acid metabolism Found in liver, egg yolk, soy flour, cereals and yeast Deficiency à rare – seen only if bizarre diet / parenteral nutrition – fatigue, nausea, anorexia, muscle pain, allopecia, anaemia, dermatitis Pantothenic acid Involved in numerous reactions in lipid & carbohydrate metabolism Found in animal products, whole grains and legumes Deficiency – rare – paraesthesia, burning feet and postural hypotension • Name the 4 Fat Soluble vitamins, their dietary sources, role in metabolism and symptoms of deficiency. Deficiency can be caused by any fat malabsorption Fat free diets can also à deficiency Stored in liver & adipose tissue (1-2yr supply) Vit A (retinol) Can be produced from 50 different carotenines Required for vision, cell differentiation, embryogenesis, immune response, reproduction and growth Found in liver, dairy, oily fish and fish liver oils Pro vitamins found in carrots, dark leafy veg, tomato, orange, corn, papaya Deficiency à night blindness and xeropthalmia, increased mortality and infection Highest effects on children and lactating mothers Vit D (calciferols) Required for calcium absorption and homeostasis Found in eggs, liver, butter, and fortified marg. Can be synthesised with sunlight in skin Deficiency à rickets (bow legs, knock-knees in children) or osteomalacia in adults Common in house bound / poor sunlight exposure and vegans Vit E (tocopherols and tocotrienols) Radical trapping antioxidant in cell membranes Limits cell damage from oxidation of PUFAs Found in vegetable oils, nuts, seeds, fish and dark green leafy veg Deficiency à in CF / new born à haemolytic anaemia and damage to nerve & muscle membranes Vitamin K (phylloquinine, menoquinone, menadione) Co-factor for blood clotting and proteins in bone Found in green leafy veg, soya beans, rapeseed oil, liver Deficiency – haemorrhagic disease of the newborn (all given prophylactic dose) High intake will antagonise actions of warfarin Nutrition 6 of 12 Thermoregulation • Explain the factors affecting measurement of body temperature. In the cold In the heat Epinephrine increases Increased BMR à Liver increases blood glucose à Increasing core temperature à Throxine increases à Sweating maintains surface temperature à BMR increases Mean core temp – 35.5-37.5oC Mean skin temp – 33-34oC Diurnal variation - Minimum at 3am, maximum at 6pm (difference of 0.5-1.5oC) Menstrual variation – Rises by 0.2-0.5oc after ovulation Death – 2oC fall in 1st 2 hours, then 1.5oC / hour until equilibrium • Outline the mechanisms of body heat exchange with the environment, and acclimatization strategies. Major heat loss during exercise is via increased skin blood flow à evaporation heat loss Exercise in the heat à reduces heat loss by radiation Exercise performance Is improved by heat acclimatisation by improving sweating & circulatory responses Regular exercise and elevation of core temperature Full acclimatization is only achieved after 5-8 days of exercise in heat Resting in the heat has little effect – sunbathing à impaired sweat gland function) Types of acclimatisation Tolerance Increases from the BMR, change in vasomotor tone, altered sweating, breathing, shivering and tactile behaviour In heat – sweat faster and at lower temperatures with increased water intake In cold – no known changes Adaptation Changes in BMR, fat deposition, hair growth, sweat composition, sweating threshold & strategic behaviour In heat – sweat slower, more dilute and at higher temperatures In cold – shiver and increase BMR at lower temperatures • Explain how thermoregulation can be disrupted and how hypothermia and hyperthermia can arise. Some inflammatory mediators are pyrogenic Raise set point of hypothalamus Body ‘feels’ cold, shivering occurs & temperature rises to fever Thus febrility suggesting infection When set point returns to normal body is actually too hot à sweating and vasodilatation = fever breaks • Describe the mechanism of heat stroke, and the prevention of heat disorders. Sweat is hypotonic with blood Excessive sweating à hypertonic ECF à water moves from intra to extra-cellular Eventually à reduced blood volume and increased ECF concentration à disrupts cardiac return & membrane electrical activity à death! Reduced blood volume also à reduced à rapid core temp rise Prevention Forced drinking with hypotonic fluid & low glucose content Only need to consume salt tablets if conditions are severe for several days Nutrition 7 of 12 Undernutrition and nutritional support • Define the term Malnutrition and give examples of generalised and specific undernutrition. Malnutrition - is just inappropriate nutrition Primary malnutrition – diet Secondary malnutrition – disease PEM – semi-total starvation, form depends on protein-carbohydrate warming Dry PEM – marasmus – lack of calories, low breast milk nutrition Wet PEM – kwashiorkor – ok calories but no protein (bec oedema due to albumins) Combined PEM – marasmic kwashiorhor • List the incidence and complications of undernutrition. 25% of patients show signs of malnutrition Decreased muscle mass Lipolysis Decreased immune response Poor wound healing Decreased psychological function • List at least four parameters obtained from a patient's medical history that might indicate the presence of malnutrition. Surgery, GI disease, sepsis, trauma, dementia, malignancy, chronic inflammatory disease, psychosocial problems, any recent weight loss, any serious illness • Define cachexia and describe how it can develop. A chronic metabolic state – weight loss, anorexia and anaemia Causes – cancer, infectious diseaes (malaria, TB, HIV, CF) Some cases have increased BMR, with same intake, due to cytokines from tumour/infection • List the effects of protein-energy malnutrition, and explain the concept of refeeding syndrome. Increased susceptibility to infection Decreased barrier function of skin / mucous membranes Hypoplasia of lymphoid system Decreased immune function Wasting Adipose à loose skin Muscle à decreased exercise tolerance Atrophy of viscera & heart Potential for heart failure & circulatory collapse Reduced intestinal absorptive capacity à increased energy expenditure à impaired muscle function à impaired BP & temp control Refeeding syndrome In starvation – reduced insulin because decreased CHO intake Catabolism of fat & protein à decreased intracellular electrolytes On increased CHO intake à increased insulin à increased cellular uptake of electrolytes Clinical features Hypophosphataemia (<0.5mmol / l) Rhabsomylosis Leucocyte dysfunction Respiratory failure Nutrition 8 of 12 Cardiac failure Hypotension Arrhythmias Seizures à coma à sudden death At Risk Anorexia, cancer, alcoholism, surgical patients Treatment Restart feeding at 25-50% estimated requirements Monitor serum phosphate • List the indications for enteral and parenteral nutritional support; for each condition identify the appropriate route for administering support. Enteral nutrition is preferred wherever possible as it is the most natural way of the body obtaining nutrition Should check that the patient is safe to swallow (if not consider NG / PEG) NG tube may be preferred if increased volume (e.g. overnight feeds) required Risks – are those of aspiration, regurgitation, vomiting Benefits – more natural, patient has more choice of food and can be more independent Parenteral nutrition is preferred if enteral feeding is inappropriate / ineffective e.g. gut pathology preventing absorption e.g. trying to reduce pancreatic secretions to allow fistulae to heal Risks – infection from line, electrolyte & nutrient imbalance, patient becomes dependent on healthcare workers Benefits – avoids risks of enteral feeding • List the indications for insertion and removal of a nasogastric tube and describe alternative methods of gastric intubation Indications Used when oral feeding is considered unsafe / unsuitable Can be used for patients who refuse or are unable to eat e.g. impaired consciousness, dysphagia, allowing oesophagus to heal post surgery Contraindicated Facial trauma, skull base #s, oesophageal abnormalities, altered mental status or an impaired airway. Alternative would be PEG or TPN • Describe the complications that may be associated with the passage of a nasogastric tube; discuss their recognition and management. Minor complications Nose bleeds Sinusitis Sore throat Major complications Erosions in the nose Oesophageal perforation – rapid profound shock on feeding Pulmonary aspiration or feeding – ALWAYS check position before feeding Collapsed lung Intracranial placement of the tube (if # skull) Once the tube is inserted the tube should be aspirated through and the pH of the aspirate checked. Nutrition 9 of 12 The patient should be X-rayed to confirm tube position after insertion Aspiration and pH checking should be repeated every day • List the metabolic complications of total parenteral nutrition. There are 4 main types of complications of TPN Technical complications associated with vascular access (placing and maintenance of a central venous catheter) Metabolic complications related to nutrient excess or deficiency Hepato-biliary complications Catheter-related bloodstream infections. NB: TPN isHigh osmolarity – needs to be delivered into fast venous access – preferally into RA Metabolic complications Insufficient administration of nutrients Hypophosphatemia – during glucose overfeeding or intensely anabolic periods. Sx include paresthesia, muscular weakness and confusion that can lead to an areflexic paralysis, rhabdomiolysis, convulsions and coma. Vitamins and trace element deficiencies – based on condition affecting patient Essential fatty acids deficiency. à dermatitis, hair loss and impaired wound healing. Can occur after 1-2 months if no lipid in TPN. But most TPNs contain lipid emulsion Overfeeding. Excessive caloric intake – can be relative or absolute. Glucose intolerance – if load is too high à osmotic diuresis & hyperglycaemia Lipid intolerance – very rare with modern TPN mixes. Due to these possibilities the monitoring should include: U&Es Glucose Trigylceride levels Nitrogen Phosphate Nutrition 10 of 12 Obesity • Define the terms hunger, appetite, satiety, and outline the factors involved in food intake Hunger – the desire to eat Appetite – the desire for a specific food Satiation – having eaten enough – no hunger Satiety – preventing the start of the next meal Factors influencing food intake Internal Hormones – CCK, leptin, insulin, amylin Metabolites – glucose & amino acids GI Temperature Orexigenic peptides (increase hunger) Neuropeptide Y (NPY) Agouti related peptide (AGRP) Andogenous opioid peptide Endocanabinoid Melalin-concetrating hormone Hypocretins / orexins External Social factors Time of day Psychological Food palatability, variability and energy Anorexogenic signals (decrease hunger) a MSH Corticotrophin-releasing hormone Urocortin Neurotensin Glucagon-like peptide 1 Cocaine & amphetamines Hypothalamic ghrelin Android (apple) – affects heart, stomach, liver & lungs Gynoid (pear) – affects thighs and lower organs • Specify the definition, approximate prevalence and the risk factors for obesity. Obesity is when BMI > 30 Risk factors Medical causes Genetic – prader Willi, leptin deficiency, Susceptibility genes Hypothyroidism Cushing’s syndrome Drug induces (steroids) Hypothalamus damage PCOS Other causes Poor diet Low activity level Shift work Smoking Increasing age Race (increased risk in blacks) • Discuss the clinical and social complications of obesity Increased weight à increase psychological à decreased exercise Increased weight à comorbidities Osteoarthritis & back pain Increased BP DM Gall stones Hiatus hernia IHD à CVD & increased lipid profiles Heart failure Varicose veins Nutrition 11 of 12 SOB and sleep apnoea Increased cancer risk Stroke • Specify the management strategies for obesity. Dietary control Increased exercise - use with diet as obesity decreases exercise tolerance Behavioural modification (increased personal involvement) Drug therapy – orlistat (lipase inhibitor), Sibutramine (appeptite suppressant) Surgery – restrictive / malabsorbtive Prevention Nutrition 12 of 12