iasm 9-11 nutrients and metabolism intro

• purpose of metabolism

  • degradation of large nutrients → simpler products → allow absorption into intestines
  • generation of energy in the form of ATP for synthesis of molecules and body functions
• energy is used in anabolic reaction
• energy is released in catabolic reaction
• What is the fate of toxic products generated from the degradation of nutrients?

  Detoxified and disposed of
• 3 macronutrients

  1. carbohydrates
  2. fats
  3. proteins
• 2 micronutrients

  1. vitamins
  2. minerals
• 3 things needed for survival

  1. oxygen
  2. water
  3. nutrients
• Human can survive without food between 60 and 90 days
• factor affecting nutritional status

  1. biological
  2. psychological
  3. social
  4. energy expenditure
  5. presence of disease
• carbohydrate

  • 4.1 kcal/g
  • main energy source
  • if the carb promotes satiety → helpful in weight control
  • if the carb stimulates craving → promote fat deposition in tissue = gain weight
• fibre is an indigestible carbohydrate. it does not serve as en energy source but it regulates gut motility and transit
• fat

  • 9.3 kcal/g
  • energy storage
  • linked to heart disease
• proteins

  • 4.1 kcal/g
  • provides cell structure
  • responsible for cell functions, communications, signalling
  • last resort energy substrate because muscle wasting is undesirable
• essential fatty acids

  1. linoleic acid
  2. alpha linoleic acid
• essential amino acids (PVT TIM HALL)

  1. phenylalanine
  2. valine
  3. tryptophan
  4. threonine
  5. isoleucine
  6. methionine
  7. histidine
  8. arginine (growing children only)
  9. leucine
  10. lysine
• proteins from animal sources contain all 10 essential amino acids
• proteins from plant sources only contain some essential amino acids except some eg. soy beans
• functions of vitamins and minerals in general

  1. act as coenzymes
  2. form functionally important prosthetic groups of enzymes
  3. involve in development and function of body (eg cell growth, proliferation and differentiation
• major purposes of nutrients

  1. provide energy needed for body to perform work
  2. provide building blocks for synthesis of other important molecules
  3. support function of metabolic pathways
• products of digestion are taken up by cells and oxidised to produce energy
• dietary fuel that exceeds body's immediate energy needs is stored
• when we are fasting, fuel is drawn from energy stores and is oxidised to provide energy
• atp stands for adenosine triphosphate
• TEE = total daily energy expenditure = basal metabolic rate + energy used up during physical activity + thermic effect of food = energy needed to meet body's need
• The thermic effect of food (TEF) is the amount of energy it takes for your body to digest, absorb, and metabolise the food you eat. Accounts around 10 % of TEE
• BMR = basal / resting metabolic rate = energy required to maintain normal physiological functions at rest

  • around 60 - 70 % of TEE
• factors affecting BMR

  1. body size
  2. age (child > adult)
  3. gender (male > female)
  4. lifestyle
  5. health (fever, hyperthyroidism, pregnancy and lactation elevates BMR)
• physical activity = energy required to support physical exertion. Amount is variable
• calories out > calories in = lose weight
• calories out < calories in = gain weight
• Major fuel store = fat in adipose tissue - there are 3 depots in body

  1. Visceral fat - within abdominal cavity - produces mediator molecules that promote atherosclerosis, cardiovascular diseases, type 2 diabetes
  2. Ectopic fat - cardiac and pharyngeal fat pads - obstruct heart nad pharnyx
  3. Subcutaneous fat - under skin - generally benign, energy source
• What causes obesity

  1. high intake of high calorie food
  2. decrease in physical activity
• Why does fat release more energy per gram?

  fat has more CH bonds to break to release energy
• Dietary reference intakes (DRIs) x4

  1. EAR = estimate average requirement = meet demand of 50% population
  2. RDA = recommended dietary allowance = 2 SD higher than EAR, meet demand 97.5% population
  3. UL = upper limit = intake limit that is unlikely to cause adverse health effects in population
  4. AI = adequate intake = adequate nutrient intake of group of healthy people (* only used when EAR or RDA is not available)
• Malnutrition Universal Screening Tool (MUST) → assesses nutrition status

  1. BMI sore
  2. weight loss score - unplanned weight loss in 3 - 6 months
  3. acute disease effect score
  4. use scores to find overall risk of malnutrition
  5. management guidelines for patients
• Nutritional status assessment ABCD

  1. Anthropometric measurement - eg BMI, WH, mid-arm cir, skin fold thickness)
  2. Biochemical data - biomarkers eg blood, urine
  3. Clinical - most direct examination
  4. Dietary data - dietary habits (biological, psychologic, sociologic, cultural factors)
• Patients receiving intravenous feeding need to have their micronutrient status checked regularly. Zinc (trace-metal / micronutrient) deficiency may develop during intravenous feeding.\
• Factors Affecting Nutritional Status

  1. social factors
  2. psychological factors
  3. biological factors - genes, age
  4. presence of disease
  5. energy expenditure
• individual response to nutrient is also determined by genetics
• Nutrigenomics is the study of the effects of nutrients on the expression of an individual's genetic makeup