N UTRITION B ASICS Myths & Legends Dr Niikee Schoendorfer – n.schoendorfer@uq.edu.au
O BJECTIVES Appreciate the finer aspects of macronutrients and their physiological functions Recognise the determinants of nutrient needs Calculate water requirements and factors necessitating increased requirements Differentiate between the good, the bad and the ugly fats Understand glycaemic index versus glycaemic load Appreciate the roles of dietary fibre in both gastrointestinal and systemic health Understand issues related to micronutrition
W HAT IS N UTRITION ? Nutrition is – All the processes involved in taking in and utilization of food substances by which growth, repair and maintenance of activities in the body as a whole or in any of its parts, are accomplished. This includes ingestion, digestion, absorption and metabolism (utilisation) . Some nutrients are capable of being stored in various forms and can be drawn upon when the food intake is not sufficient. Thomas, C.L. (ed ) 1993. Taber’s Cyclopedic Medical Dictionary, 17th ed, Davis, Philadelphia p1337
C ONTRIBUTION OF N UTRIENT I MBALANCES TO D EVELOPMENT OF C HRONIC D ISEASES Habitual Nutrient Intakes UV Exposure Nourishment Smoking Genetics Functional Cell Environmental Inactivity Pollutants Stress Poor Hygiene Damaged Cell
D ETERMINANTS OF N UTRIENT N EEDS Absorption Efficiency Metabolic Demand Excretion Levels
O PTIMIZE C ELLULAR A CTIVITY AND T ISSUE /O RGAN F UNCTION Provide sufficient amounts to satisfy daily demands Adequacy of intake Balance and variety in food choices Maintain adequate reserves Habitual diet and dietary patterns Defensive approach
F UNCTIONS OF W ATER Recommended Daily Intake 2-3L/day (NHMRC 2009) Water (L) = body weight x 0.03 Role of water in body: • Participates in chemical and metabolic reactions Thermoregulation Maintain blood and cell volume (Pinna, Rolfes & Whitney 2009, p. 399)
Detailed information available – ‘Nutrition at a Glance’ ME Barasi, Blackwell Publishing 2007
P ROTEIN
P ROTEIN • Greek word ‘ protos ’ meaning prime importance • Second only to water in plant and animal tissues • Constantly broken down and reassembled according to body requirement • Daily diet must be sufficient to replace what has been used • Excess is either burned for energy or stored as fat
P ROTEIN F UNCTIONS • Growth and repair – DNA bases Structural constituent of most of the body • Contractile muscles – Fibrous other tissues – • Carry and store materials (transport proteins) Albumin – calcium, zinc and hormones – Retinol binding protein (RBP) – vitamin A – Hemoglobin – oxygen – – Transferrin – iron – Ceruloplasmin - copper
P ROTEIN F UNCTIONS Enzymes – digestive, catalytic • • Fibrinogen – blood clotting Blood group proteins – blood types • • Immune system proteins – immunoglobulins and antibodies Proteoglycans – everything in • between tissues
P ROTEIN F UNCTIONS Hormones – insulin, leptin, thyroxine • • Neurotransmitters production Cell membrane channels and pumps • Transport proteins – albumin and globulin • maintain fluid volume in the capillaries Acid-Alkaline balance •
D IETARY S OURCES Protein quality Digestibility Amino acid composition Complete • Contain all essential amino acids Animal sources only Incomplete • Lacking one or more essential amino acids Plant sources
D IETARY S OURCES Complementary Proteins • Combining a variety plant foods that together contain all the essential amino acids Not necessary per meal as body maintains an amino acid pool (Marsh 2012) Rolfes, Pinna & Whitney 2009
E XCESSIVE P ROTEIN I NTAKE Caution with pre-existing or high risk of kidney disorders • Ingestion of a high protein diet, kidney blood flow increases 20-30% in 1-2 hours. Need to monitor Mineral losses • May increase calcium excretion, esp. purified powders • Obesity and heart disease Animal proteins also high in saturated fat Cancer • High animal protein intake linked to colon cancer (Insel 2011)
P ROTEIN S UPPLEMENTS • Protein powders – Commonly used to increase skeletal muscle synthesis May only occur in response to exercise If excess is being consumed without exercise, may be burned for energy or stored as fat. If used for energy, increased nitrogen excretion can increase the burden on the kidneys and increases fluid intake requirements Purified protein powders lack other nutrient components found in foods which are needed to build muscle tissue (Whitney 2011)
P ROTEIN S UPPLEMENTS • Amino Acid supplements – Single amino acids do not occur naturally in nature High concentrations and unusual combinations may be harmful Excess single amino acids increase demand for a carrier at the expense of another amino acid possibility of deficiency High dose branch chain amino acids (popular with body builders) can raise plasma ammonia levels which is toxic to the brain . (Whitney 2011)
C ARBOHYDRATES
D IETARY S OURCES Grains – breads and cereals, including • corn Legumes – lentils, beans, peas • • Fruit and root vegetables Dairy foods – mainly milk and yoghurt • Processed foods – sweets and hidden •
T YPES AND F UNCTIONS Based on number of sugar molecules Simple sugars and starches Used to provide energy Unused → triglycerides → stored in fat cells Fibre Indigestible portion of plant foods Move foods through digestive system Absorb water, toxins and other substances Adds bulk to stools Increases beneficial microbiota in the intestines
W HOLE G RAINS Bran • “Outer shell” Fibre, B vitamins, trace minerals • Endosperm Provides energy Carbohydrate, protein • Germ Nourishment for the seed www.wheatfoods.org Antioxidants, vitamin E, B vitamins
R EFINING G RAINS (Slavin et al, 1999)
G LYCAEMIC I NDEX (GI) Lower GI foods = difficult to digest slower release • of sugars High GI foods = easy to digest release sugars more • rapidly high insulin levels • Processing of some grains can alter resistance to digestion Higher fiber and higher fat foods are also more • resistant due to their complexity
E FFECTS ON B LOOD S UGAR L EVELS (Jenkins et al, 2002)
G LYCAEMIC I NDEX (GI) (Rolfes, Pinna & Whitney 2009)
G LYCAEMIC L OAD (GL) What information does the glycaemic load provide us with? How does it differ from the GI of a food? http://www.mendosa.com/gilists.htm
G LYCAEMIC L OAD (GL) Calculating the GL Carbohydrate (g) x GI /100 = GL eg. ½ cup of watermelon = 6g x 0.72 = GL of 4.3 ½ cup of cornflakes = 47g x 0.71 = GL of 33 ½ cup of white rice = 36g x 0.72 = GL of 26
L OW G LYCAEMIC /L OAD F OODS A ID T O : Reduce post prandial blood glucose levels. Increase satiety Increase the variety of foods that are suitable for someone with diabetes. Reduce the frequency of overnight hypoglycaemic episodes. Reduce fasting blood glucose levels. Reduce the dose of oral hypoglycaemic medication. Reduce insulin requirements.
W ESTERN D IETS AND C ARBOHYDRATES Of major concern is the 40-50% of the Western Diet is carbohydrates, mainly from refined and processed nutrient poor sources. (Australian Bureau of Statistics)
W ESTERN D IETS AND C ARBOHYDRATES Consequences Depletion of nutrients required for carbohydrate metabolism Insufficient fibre consumption Most of carbohydrates in the Western diet are also of a high GL
E XCESSIVE R EFINED C ARBOHYDRATES Associated with Stroke (Oh K et al, 2005) High cholesterol (Fried,2003) Inflammation (Nakanishi, 2005) Diabetes mellitus (Liu, 2002) PCOS (Marsh and Brand-Miller, 2005) Gall bladder disease (Tsai et al, 2005)
D IETARY F IBRE Fruits, vegetables, wholegrains and legumes are a good source Adds bulk to foods, so the stomach turns off ghrelin (hunger hormone) sooner Delays gastric emptying and release of sugars from GIT which benefits satiety and blood sugar regulation (Brown et al 1999) Binds to bile acids, reducing both toxin and cholesterol resorption from the gut, the latter improving lipid profiles (Brownlee et al. 2005)
S OLUBLE F IBRE Found in fruits and vegetables Digested by intestinal bacteria producing anti-inflammatory SCFA’s Soluble fibers form gels Water holding capacity depends on pH of GI tract, size of fibre particles or degree of processing Coarsely ground bran with large particles increases hydration capacity than finely ground. (Ink and Hurt 1987)
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