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Introduction to Nutrition

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  1. Introduction to Nutrition This slide presentation is the non- illustrated version and is suitable for those with GCSE Science/Biology and above Dr Alan Stewart MB BS MRCP

  2. Introduction to Nutrition: what you will learn • Nutrition - one of the Functions of Life • What are the Essential Nutrients • Undernutrition and Overnutrition • How Common are Nutritional Problems? • Deficiencies - How They Develop and Why • Who informs you about nutrition? • Further Information on Life Functions Written by Dr Alan Stewart

  3. Do you remember Mrs NERG?The 7 Functions of Life that characterise living organisms • Movement • Respiration • Sensitivity • Nutrition • Excretion • Reproduction • Growth

  4. Movement Respiration Sensitivity Nutrition Excretion Reproduction Growth Defence Adequate nutrition plays a central role in all of these characteristic functions Lack of one or more of the essential nutrients leads to a loss of one or more of these life functions If deficiency is uncorrected then it can lead ultimately to death of the organism Nutritional deficiencies are often diagnosed due to characteristic disturbance in these life functions What is the Missing Life Function?Welcome Mrs NERGD!

  5. Life Functions: What organs are involved? • Movement Bone, muscle and nerves • Respiration Food + oxygen = energy • Sensitivity Special senses, nerves and the brain • Nutrition Gut, liver and many other organs • Excretion Liver and kidneys and also skin, gut and lungs • Reproduction Eggs, sperm and baby • Growth All tissues • Defence Immune system (white cells + antibodies), skin Each life function and organ have different nutrient requirements

  6. Essential Nutrients There are two types of nutrients essential to life: • MacronutrientsNutrients required in large amounts - proteins, fats, carbohydrates.They are needed for energy productionProtein is needed for growth and maintenance functionsWater and fibre are also needed in significant amounts • MicronutrientsNutrients required in small amounts - vitamins, minerals and essential fatty acids.They are needed for numerous functions

  7. Essential Nutrients - Macronutrients Macronutrient Energy Provision in average adult diet • Carbohydrates 50%sugars and complex carbohydrates • Fats 35%saturated and unsaturated fats • Protein 15%provide essential and non-essential amino acids • Alcohol (non-essential) 0%-5%

  8. Food Energy SourcesNational Diet and Nutrition Surveys 1992-2001

  9. Food Energy Sources: % of Total IntakeNational Diet and Nutrition Survey: British Adults 19-64 yrs

  10. Essential Nutrients - Micronutrients • Minerals: Bulk Ca, Mg, Na, K, Cl, P Trace Fe, Zn, Cu, Mn, I, Se,? others • Vitamins: fat-soluble A,D,E, and K water-soluble B group and C • Essential Fatty Acids: n-3 series Linoleic acid and derivatives n-6 series Linolenic acid and derivatives

  11. The Six Criteria for Nutrient Essentiality The nutrient…. • is essential for one or more of the (8) functions of life • is not synthesized or synthesized adequately in the body • has a function that is either biochemical or structural • if deficient, a recognizable loss of function or structure results • if deficient the loss of function or structure is proportional to degree and duration of depletion • if deficient the loss of function is, in the short term, reversible by the specific nutrient

  12. Essential Nutrients and Life Functions Life Functions Key Essential Nutrients • Movement Calcium and vitamin D – bones, Protein and potassium - muscles • Respiration Vitamin B – metabolism, iron – oxygen transport, Iodine – thyroid hormone and metabolic rate • Sensitivity B vitamins - central and peripheral nerves Iron and iodine - intellectual development • Nutrition Zinc and iron - appetite • Excretion Water, sodium and potassium - urine excretion • Reproduction Iron and B vitamins – fertility and pregnancy outcome • Growth Energy, protein, iron, zinc, vitamin A – infant growth • Defence Protein, vitamin A and zinc - immune function

  13. Nutrition and Health • Nutrition plays a central role in all life functions • Animals often spend a large amount of time and energy obtaining food and feeding, but we humans do not • Nowadays we can choose between nutritious/non-nutritious foods • Food choice makes a big difference to our health and the risk of: deficiency – undernutritionexcess – overnutrition • Our food choices are determined by: - habits usually established in childhood- personal likes and dislikes- cost of food- convenience of shopping and preparing- education about what is nutritious and healthy

  14. What are the Common Nutritional Problems? These can be classified relating to the supply of macro and micronutrients: • Undernutritioniron, calcium, vitamin D, folate, vitamin B12 and protein-energy • Overnutritionenergy – obesity, sodium salt, saturated fats, sugar, vitamin A The prevalence of these problems in the British and UK populations have been assessed in a series of national surveys called The National Diet and Nutrition Surveys and others conducted by the Food Standards Agency and related organisations

  15. The National Diet and Nutrition Surveys • Four surveys ages 1.5 to >85 yrs • Random samples of the British population • Conducted between 1992 and 2002 • Collected information on: - 4-7 day weighed dietary macro- and micronutrient intakes- laboratory measures of many essential nutrients- alcohol intake, supplement use- Blood Pressure, cholesterol and other tests - Height, Weight and Body Mass Intake • No clinical assessment • See

  16. Problems of Undernutrition

  17. Prevalence of Undernutrition in the UKData Taken from National Diet and Nutrition Surveys

  18. Supplemental Milk and GrowthIncrease in Height in Inches per Boy in One Year Mann H C Corry (1926) Sp. Rep Ser Med Res Coun. London No. 105. • 219 Institutionalised boys many of whom were considered to be below the standard for height and weight despite the diet being adequate • 41 Boys were given 1 pint of whole pasteurised milk per day • Additional sugar, margarine and butter were isocaloric

  19. Common Problems of Overnutrition

  20. Prevalence of Overnutrition in the UKData Taken from National Diet and Nutrition Surveys

  21. Undernutrition vs. Overnutrition • Problems of both under and over nutrition are commonplace across the UK • They are usually mild in degree but if they are long-standing they can produce significant adverse health effects • Many of them will be adequately addressed by:- simple targets for eating a healthy diet- limiting intake of alcohol- adequate exercise • The extremes of life – very young and old, are most at risk of undernutrition • Socio-economic deprivation is still a significant risk factor for both undernutrition and overnutrition • Education is often a vital part in resolving both types of problems

  22. Development of a Nutritional Deficiency • Adequacy • State of Negative Balance • Decline in Tissue Stores • Alteration in FunctionSymptoms Physical SignsOrgan Failure • DeathAfter M. Brin JAMA 1964;187:762-766

  23. State of Negative Nutrient Balance: Causes 1. Inadequate Intake Loss of appetite Poor quality diet 2. Reduced Absorption Diet: tea inhibits iron absorption Diseases causing malabsorption 3. Increased Losses Heavy periods – iron Sweating – sodium loss Diarrhoea – sodium, potassium 4. Increased Need Growth and pregnancy 5. Altered Metabolism Disease: liver and kidney Drugs, alcohol, genetic variation

  24. Time Scale for the Development of a Deficiency State • DaysWater; 2-7days - dehydration, renal and circulatory failure • WeeksProtein/Energy 8 weeks - death from respiratory failure if BMI<12.0 kg/m2Vitamin B1; 2-8 weeks - fatigue, neurological deficit and cardiac failure • MonthsPotassium; 2 months - fatigue, muscle weakness and necrosisZinc; 4 months - loss of appetite, loss of night vision and infectionsVitamin C; 4 months - fatigue, haemorrhage and sudden deathVitamin B 2-6 months - fatigue, skin changes, inanition and infection • YearsVitamin A; 2 years - loss of night vision, infectionsVitamin B12; 4 years - fatigue, pernicious anaemia, SACD • DecadesCalcium; 3-4 decades - osteoporosis and fracturesChromium; decades - glucose intolerance, type II diabetes and CHD

  25. Who informs you about nutrition? • GlobalThe World Health OrganisationThe Food and Agriculture Organisation • EuropeanEuropean Food Safety Agency • National Department of the Environment and Rural AffairsFood Standards Agency • CommunitySchool/Work place • FamilyParents/Grandparents/Partner • HealthcareDoctor/Dietitian/Nutritionist/Research Scientists • OtherBooks/Magazines/Newspapers/TV/Internet/Friends/Packaging • You!Education and Experience

  26. Introduction to NutritionSources of Information • Standard Reference TextsABC of Nutrition. A Stewart Trusswell BMJ Publications 2000 - Excellent introductory book that covers the basics £20.00 Modern Nutrition in Health and Disease. Ed. Shils et al. Lippincott Williams and Wilkins. 1999 - This American book in its ninth edition is the only serious reference work £120.00 Dietary Reference Values TSO London 1991 - This old small reference volume is still a good source of information £20.00 • National Diet and Nutrition Surveys 1990-2004All four surveys of the British population (infants, children, adults and the elderly) are available in print from TSO London £ 40.00 to £160.00 The latest on adults is available from www.defra/ • Web Much needed guidance on nutrition screening and assessment US government website has information about most but not all Website of the Linus Pauling Institute has non-commercial information

  27. Introduction to Nutrition: End Thank you for your attention The full illustrated version of this presentation is presented in person by Dr Stewart to school, college and university students. Please contact Dr Alan Stewart MB BS MRCP Tel 01273-487003 For additional lectures see related presentations on: Nutritional AssessmentNational Diet and Nutrition SurveysHow Safe are Nutritional Supplements? at

  28. Life Functions: Further Information • Eight further slides on the effects of undernutrition on life functions • One further slide on the effects of overnutrition and life functions

  29. Mrs NERGD – Movement and Undernutrition • Movement requires:muscles, bones and nerves to muscles • Muscles, bones and motor nerves need:protein – 0.8g of dietary protein per kg body weight per dayvitamin B - energy release in musclescalcium, sodium and potassium - muscle contractionmagnesium – muscle relaxation calcium and vitamin D – bone formationvitamin B – motor nerve function • Deficiency = loss of muscle bulk and weakness osteoporosis loss of motor nerve function resulting in reduced mobility, falls and fractures

  30. Mrs NERGD – Respiration and Undernutrition • Respiration:food + oxygen = energy + waste • Energy sources are macronutrients:fats, carbohydrates and protein (plus alcohol) • Respiratory processes need micronutrients:vitamin B – for energy releasing enzymes liver and musclesmagnesium – for the same enzymesiodine – controls rate of metabolism through thyroid hormonesiron and vitamin B – haemoglobin for oxygen transport in the blood • Deficiency = fatigue and loss of many functions

  31. Mrs NERGD – Excretion and Undernutrition • Excretion eliminates the waste products of respiration, drugs, toxins and some nutrients • Waste is excreted by:kidneys – water-soluble compounds: urea, drugs, sodium & other mineralsliver – fat-soluble drugs, hormones and some mineralsand also the lungs, intestines and skin • Excretion processes need:water – adequate blood volume and urine outputvitamins B, C and potassium – many enzyme processes in kidneys and liverzinc – in cells for CO2 excretion (enzyme carbonic anhydrase) excretion process require lots of energy • Deficiency = reduced renal function altered liver functionaccumulation of waste products especially drugs

  32. Mrs NERGD – Nutrition and Undernutrition • The metabolism of nutrients are interlinked • Being adequately nourished makes it easier to obtain food and maintain a healthy metabolism:vitamin D - absorption of calciumzinc - metabolism of vitamin Acopper - absorption of iron • Deficiency = changes in:Appetite: iron - loss or alteration in appetite (pica), zinc - loss of taste vitamin B1 - nausea and delayed stomach emptyingGrowth: protein/energy – reduced child growth and adult size and reduced lifelong demand for all nutrients Metabolism: one nutrient deficiency can cause anotherMobility: reduced ability to obtain food and feed themselves

  33. Mrs NERGD – Sensitivity and Undernutrition • Awareness of the external environment requires an intact nervous system and specialized organs • The sensory functions require different nutrients:vitamin A – retinal function and health of the cornea iodine - hearing and mental development in infantszinc – taste and visionvitamin B1 - touch sensitivityvitamin B12 – vibration sense and position sense iron, essential fats and vitamin B – higher mental function • Deficiency = loss of sensory or neurological functionThe loss is often characteristic of the specific nutrient

  34. Mrs NERGD - Reproduction and Undernutrition • Reproduction is a vital biological goal and mammals have only a few (high quality) offspring • Successful reproduction needs many nutrientsprotein-energy, body weight (>40 kg) - age of menarcheprotein-energy - regularity of periodsfolic acid and vitamin B12 - miscarriagefolic acid and vitamin B12 – birth defectsprotein-energy and iron – low birth weight many nutrients in maternal diet - breast milk quality and infant nutritionzinc and folic acid - male sperm quality • Deficiency = infertility, reduced fertility poor pregnancy outcomeThe full consequences of nutritional deficiency on reproduction and growth may take several generations to undo

  35. Mrs NERGD – Growth and Undernutrition • Growth is one of the four main uses of nutrients (reproduction, maintenance and storage) • Many nutrients are essential for good growth:protein-energy essential at all ages for good growthcalcium and vitamin D – for skeletal growth from birth to early 20svitamin A – influences production of growth hormone in infants iodine – deficiency results in reduced height and poor mental developmentzinc – deficiency causes poor longitudinal growth and delayed puberty • Deficiency = smaller birthweight reduced growth increased health risks in adult lifeCatch-up growth is possible if deficiencies are corrected quickly

  36. Mrs NERGD – Defence and Undernutrition • Defence is a life characteristic for most organisms • Defence mechanisms involve different organs:protein-energy, vitamin A, vitamin B, zinc, copper – immunity (antibody production and white cells)vitamin C, zinc, essential fatty acids – skin quality and wound healingiron, vitamin B – healthy gut wallvitamin A - reduces the ability of bacteria to adhere to the respiratory tractmany nutrients - physical defence (muscles, skeleton, nerves)many nutrients – needed for internal protection against cancer developing • Deficiency = decline in defence mechanisms death from infection, injury or cancer

  37. Life Functions and Overnutrition • Movement Obesity reduces mobility Vitamin A excess increase the risk of osteoporosis • Respiration Obesity increases energy need by 9 kcl for each kg of weight/day • Sensitivity Water excess can lead to sodium deficiency, mental confusion or a stroke • Nutrition Dietary sugar causes dental caries and loss of teeth • Excretion Salt and soft drinks increase calcium losses in urine Obesity + high fructose intake cause liver disease • Reproduction Vitamin A excess can cause birth defects • Growth Obesity increases the risk of small-for-date babies • Defence High doses of vitamins may increase cancer risk High dose zinc supplements may reduce immunity