00 05/03/2003 10:52 Page iPrinciples ofHuman Nutrition
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00 05/03/2003 10:52 Page iiiPrinciples ofHuman NutritionSecond editionMartin EastwoodEdinburgh, UK
00 05/03/2003 10:52 Page iv 2003 by Blackwell Science Ltd,a Blackwell Publishing CompanyEditorial Offices:9600 Garsington Road, Oxford, OX4 2DQ, UKTel: 01865 776868Blackwell Publishing, Inc., 350 Main Street, Malden,MA 02148-5018, USATel: 1 781 388 8250Iowa State Press, a Blackwell Publishing Company,2121 State Avenue, Ames, Iowa 50014-8300, USATel: 1 515 292 0140Blackwell Publishing Asia Pty Ltd,550 Swanston Street, Carlton South,Victoria 3053, AustraliaTel: 61 (0)3 9347 0300Blackwell Wissenschafts Verlag, Kurfürstendamm 57,10707 Berlin, GermanyTel: 49 (0)30 32 79 060The right of the Author to be identified as the Authorof this Work has been asserted in accordance with theCopyright, Designs and Patents Act 1988.All rights reserved. No part of this publication may bereproduced, stored in a retrieval system, ortransmitted, in any form or by any means, electronic,mechanical, photocopying, recording or otherwise,except as permitted by the UK Copyright, Designsand Patents Act 1988, without the prior permission ofthe publisher.First edition published 1997 by Chapman & HallThis edition first published 2003 byBlackwell Science LtdLibrary of CongressCataloging-in-Publication Datais available0-632-05811-0A catalogue record for this title is available from theBritish LibrarySet in Times and produced by Gray Publishing,Tunbridge Wells, KentPrinted and bound in Great Britain byAshford Colour Press, Gosport, HantsFor further information onBlackwell Publishing, visit our website:www.blackwellpublishing.com
00 05/03/2003 10:52 Page vContentsAcknowledgementsviiChapter 1Introduction and overview1Part IFactors influencing the food that a community eats7Chapter 2Chapter 3History of foodSocial, population and environmental influences on nutritionPart IICalculating how much food a community eatsChapter 4Chapter 5Chapter 6The food chainNutritional requirementsNutritional epidemiologyPart IIIFactors influencing how an individual metabolises nutrientsChapter 7GeneticsPart IVCalculating the nutritional status of an individualChapter 8Chapter 9Chapter 10Evaluation of dietary intakeMeasurements of energyBody compositionPart VNutrients and non-nutrientsChapter 11Chapter 12Chapter 13Chapter 14Chapter 15Chapter 16Principles, amino acids and proteinsLipidsCarbohydratesDietary fibreAlcohol as a 79195213224239
00 05/03/2003 10:52 Page viviChapter 17Chapter 18Chapter 19Chapter 20Chapter 21ContentsPlant secondary metabolites and herbsWater, electrolytes, minerals and trace elementsNon-nutritive components of foodAgricultural chemicals in the food chainDrugs and nutritionPart VIEating, digestion and metabolismChapter 22Chapter 23Chapter 24Chapter 25Chapter 26Chapter 27Chapter 28Chapter 29Chapter 30Chapter 31Chapter 32Chapter 33Chapter 34Chapter 35Chapter 36Chapter 37Chapter 38Chapter 39Chapter 40Chapter 41Smell and tasteIntake and satietyThe gastrointestinal tract and food availabilityCarbohydrate digestion and absorptionProtein absorptionLipid absorptionFoetal and placental nutritionThermodynamics and metabolismMitochondriaCytochrome P450Free radicalsCarbohydrate metabolismLipid metabolismEicosanoidsCholesterol and lipoproteinsAmino acid metabolismAmino acid neurotransmittersOrgan metabolic fuel t VIISpecial nutritional requirements and conditionsChapter 42Chapter 43Chapter 44Chapter 45Chapter 46Chapter 47Pregnancy, lactation and weaningChildhood and youth; middle age and old ageSportNutrition in outer spaceDietary deficiencyNutrition in the aetiology of disease601603617632641643655Index673
00 05/03/2003 10:52 Page viiAcknowledgementsWhile the responsibility for this book is entirelymine, there are many people who have given helpand encouragement: Neil Eastwood, Gill Poole,Janet Lambert, Ann de Looy, Bizan Pourkomailian, Rosalind Skinner and Jon Warner.I am grateful to Nigel Balmforth at Blackwell forhis kindness, understanding and support during thepreparation of this new edition. Also his very supportive staff. Robert Gray and his staff have beenso helpful during the production of this book.
00 05/03/2003 10:52 Page viiiThis book is dedicated to Jenny for allthe reasons she knows and withoutwhom it would not have been possible.
01 05/03/2003 10:53 Page 11Introduction and overviewThis book looks at nutrition as an exciting disciplinethat draws on all branches of biology. Nutrition isboth an art and a science: it observes, measures andtries to explain the constantly changing process ofthe optimal mix of chemicals necessary for the functioning of an individual at all stages of life.This book is written at a number of levels toencompass: traditional nutrition (Chapters 2–6, 8–17, 39–45) evolving nutrition (Chapters 20, 22–26, 31–37,46) complex concepts, which although not currently central will influence the future of nutrition:an awareness of these will be necessary for thenext generation of nutritionists (Chapter 7, andparts of Chapters 11, 18, 19, 21, 27–30, 38).Take what is appropriate for your requirementsat different stages of your development in nutrition.The selection, processing and manner of eatingfood will be strongly influenced by what is availableand by the history, social stability and economy ofthe community. What and how a person eats is significantly affected by their family background andtraditions, although travel is increasingly changingfood choices. War, pestilence and famine canrestrict food availability, and food may also be contaminated by pollutants from the environment.Being able to eat optimal amounts is dependenton agriculture and the political, educational andsocial organisation in which the person lives. Thechemical substances should be available in optimalamounts and in an attractive form for metabolism.Nutrition identifies, measures and recommendsoptimal dietary intakes of the nutrient chemicals inhealth and disease.All living creatures require a range of dietarychemicals for metabolism, growth and activity.These chemicals are obtained from a range ofsources. The digestion, absorption and metabolismof ingested nutrients are determined in each individual by many factors, including inherited constitution, gender, age, activity, growth, fecundity andlactation. A person needs an adequate energyintake as well as essential nutrients to provide forthe needs and control of a genetically determinedconstitution (genome), which dictates protein andenzyme structure and hence metabolism. Thisbrings nutrition to a central role in the story. Thesynthesis, maintenance, functioning and control ofthe protein complex and hence overall metabolismrely on ingested nutrients.This book is written in the belief that the basisof nutrition lies in molecular biology, geneticmake-up, biochemistry and physiology. Even themysteries of the cooking art are dependent onphysicochemical transformations of raw food intoavailable edible food.The book is divided into seven parts.Parts I and II deal with food in the community.The first part deals with the historical influencesthat decide what food a community eats and howit is cooked. This is followed by a description ofthose environmental factors that can adverselyaffect food availability. Part II looks at the calculation of how much food a community requires andactually eats. The remaining parts deal with theindividual.Part III looks at how a person metabolisesnutrients in an individual manner dictated bygenetic make-up, then Part IV describes themeasurement of the individual nutritional status.
01 05/03/2003 10:53 Page 22Part V describes the core nutrients, essential, nonessential and non-nutrients, and Part VI their selection for eating, ingestion and subsequent digestion,absorption and metabolism. Part VII looks at specialnutritional requirements in the normal conditionand for some specific diseases.At the end of each part there are key points forunderstanding and learning, and thinking points.Important references are listed at end of eachchapter.Some companion material relating to thisbook will be available on Blackwell Publishing’sweb pages: please look at details of the book,which can be found on the publisher’s website:www.blackwellpublishing.com.LITERATUREThe enjoyable and productive analysis of the literature is important, and there are many great booksand journals. The following may be of help andinterest to the reader: Biological dictionaryOxford Dictionary of Biochemistry and MolecularBiology (1997). Oxford University Press, Oxford. Nutrition reference booksSadler, M.J., Strain, J.J. and Caballero, B. (eds)(1999) Encyclopedia of Human Nutrition. Academic Press, San Diego, CA. Biochemistry and biology reference booksNelson, D.L. and Cox, M.M. (eds). (2000)Lehninger’s Principles of Biochemistry, 3rd edn.Worth, New York. Lodish, H., Berk, A., Zipursky, S.L. et al. (eds)(2000) Molecular Cell Biology, 4th edn. WH Freeman, New York.Jones, L. and Atkins, P. (2000) Chemistry, Molecules, Matter and Change. WH Freeman, NewYork. JournalsAmerican Journal of Clinical Nutrition, BritishJournal of Medicine, British Medical Journal,Nutrition Journal, Nutrition Review, New EnglandJournal of Medicine, Science, Annual Review ofNutrition, British Journal of Nutrition, EuropeanJournal of Clinical Nutrition, Lancet, Nature andProceedings of the Nutrition Society.Introduction and overview The InternetThe manner in which written information ishanded on is changing rapidly with the availability of the World Wide Web. The printedtextbook can be seen as a primer, an introduction at varying levels of sophistication. From thissound knowledge base educated forays can bemade into the Internet for retrieval of information. This book is intended to provide a goodbasic knowledge for such rewarding searches. Itis recommended that this book is supplementedby using Medline and other searches, e.g.Google or Metacrawler. These are a starter packand it is suggested that readers develop theirown list of favourite websites which can beupgraded. The website associated with thisbook will be kept up to date with new referencesand links. Navigating around the Internet isfacilitated by the use of helpful search engines.Even so, the top 11 search engines only reach42% of the Web. The search engines can bebased on the directory model placing sites intocategories and subcategories. This requireshuman input and has the potential for error.‘Robots’, ‘spiders’ and ‘crawlers’ navigatethrough the following links pages and return tothe database with the result.Specialist sites dealing with a subject aremore specific, e.g. PubMed and Medline.PubMed was developed by the National Libraryof Medicine and developed in conjunction withpublishers of biomedical literature as a searchtool for accessing literature citations and linkingto full-text journals at websites of participatingpublishers.Medline is the National Library of Medicine’spremier bibliographic database covering thefields of medicine, nursing, dentistry, veterinarymedicine, the health-care system and the preclinical sciences. Medline contains bibliographic citations and author abstracts from more than4000 biomedical journals published in the USAand 70 other countries. The file contains over 11million citations dating back to the mid-1960s.However, it is important to appreciate that thecitations miss the massive literature precedingthe 1960s and these have to be traced by traditional library methods. Coverage is world-wide,but most records are from English-languagesources or have English abstracts.
01 05/03/2003 10:53 Page 3Introduction and overviewWEBSITES OF INTERESTwww.arbor.com Clinical informationwww.health.gov.au/index.htm Australian GovernmentHealth and Ageingwww.bda.uk.com British Dietetic Associationwww.eufic.org European Food Information Councilwww.europa.eu.int European Communitiywww.afssa.fr Agence Française de Sécurité Sanitairedes Aliments (France’s food safety agency)www.defra.gov.uk UK Department for Environmentand Rural Affairs (DEFRA)www.foodstandards.gov.uk UK Food StandardsAgency3www.nutrition.org.uk British Nutrition Foundation:general food and nutrition informationwww.nutrition.org American Society for NutritionalScienceswww.nutsoc.org.uk British Nutrition Societywww.usda.gov USA Department of Agriculturewww.healthfinder.gov US Department of Health andHuman Services, US dietary advicewww.who.int World Health Organisationwww.soilassociation.org UK Soil Associationwww.medbioworld.com Medical and biosciencesjournal link system, 25 000 linkswww.FreeBooks4Doctors.com Free medical texts onlinewww.canada.gc.ca/depts/major Canadian governmentsiteOVERVIEW5. nutritional deficiency and excess1. nutrientsoverview4. metabolism of nutrients2. essential nutrients3. food utilisationFig. 1.1 Chapter outline.NUTRIENTSA definition of a nutrient is any chemical substancethat can be used by an organism to sustain its metabolic activities. These metabolic activities inhumans and other animals include the provision ofenergy, growth, renewal of tissues, reproductionand lactation.The status of some chemicals as nutrients isassured: amino acids, carbohydrates, essentialfatty acids, vitamins and trace elements. Otherchemicals, such as dietary fibre and secondary plantmetabolites, are part of the food but may not soreadily be classified as nutrients.ESSENTIAL NUTRIENTSSome nutrients are essential in that these moleculescannot be synthesised within the body and can onlybe provided by the diet. Such essential nutrientsprovide for metabolic processes: vitamins, e.g.ascorbic acid, and trace elements, e.g. selenium;and for structure, e.g. proteins, essential aminoacids, vitamins and trace elements.The science of nutrition is devoted to definingrequirements for essential nutrients, amino acids,essential fatty acids, vitamins and trace elements.Recommendations for daily requirements of nutrients made by expert committees are dependent on
01 05/03/2003 10:53 Page 44Introduction and overviewdiverse factors such as growth, pregnancy and illness and are only carefully determined approximations. Implicit in the requirement for essentialdietary constituents is that the human race is notindependent of the environment. Thus, people arepart of a food chain as recipients or producers offood.FOOD UTILISATIONAn important aspect of nutrition is the availability of dietary sources of nutrients. Causes ofdietary deficiencies range from a lack of all nutrients (famine), to absence or omission of individualfood items from the diet for social, economic,cultural, religious or personal reasons. Nutrientsmay not be absorbed from the intestine in someillnesses. A deficiency or excess of overall calorieintake or of individual nutrients may result in nutritional disorders.Ingested food is broken down to chemicals of amolecular size that is readily absorbed and utilisedby the body. The process of absorption is dictatedby the nutrient needs of the body and bioavailabilityvalue.Bioavailability is a measure of the relative amountof the ingested nutrient that is absorbed from theintestinal content and reaches the systemiccirculation. It is described as the rate and extent towhich the nutrient is absorbed and becomesavailable to the body’s metabolic processes.In general, energy-providing nutrients are readily absorbed and have a high bioavailability value,whereas there are more controls on the absorptionof micronutrients and their bioavailability value islower and more variable. Some nutrients, e.g. divalent cations, calcium and magnesium, are onlyabsorbed in an amount necessary for the needs ofthe body, as an excess can be toxic.Waste products of metabolism are excreted inbreath (carbon dioxide), urine [in general, watersoluble compounds of molecular weight less than300 Daltons (Da: a unit of measure of atomic andmolecular mass)] and bile (in general, fat-soluble,molecular weight more than 300 Da). The accu-mulation of metabolic waste products has disadvantageous effects on growth, metabolism and wellbeing.Nutrients contribute to bodily needs in severalways: provision of energy creation of structure provision of essential small molecular substances that the body cannot synthesise.Some nutrients are sources of carbon and nitrogen, which pass into the metabolic pool to meet thebody’s general needs, e.g. carbohydrates, fats andamino acids. Carbohydrates and lipids are necessary fuels for metabolic activity, to a variable extentfor structure and in some instances in the synthesis of hormones. The whole range of amino acidsis relevant for adequate structural growth. Aminoacids may also be utilised at times of nutritionaldeprivation as a source of energy.METABOLISM OF NUTRIENTSThe metabolism of nutrients by enzymes is dictated by the individual’s gene structure and the induction of enzymes and, in turn, by species and gender.These distinctions are complex, subtle and only partially understood (Figure 1.2).The nutrient needs and subsequent metabolismby the individual will be influenced by growth in theyoung and in pregnancy, and modified by disease,drugs, alcohol and tobacco. As the person agesthere are important changes in the effectiveness ofthe absorption and utilisation of the nutrients consumed.It has been suggested that diet may affect behaviour. In some ancient cultures certain foods werethought to have magical qualities capable of givingspecial powers of strength, courage, health, happiness and well-being. It is possible that some foodconstituents may affect the synthesis of brain neurotransmitters and thus modify brain functions. Itis therefore important to integrate dietary effectson brain chemicals into our wider understandingof human behaviour.Until there is an understanding of such nutritional and metabolic mechanisms, confused advice
01 05/03/2003 10:53 Page 5Introduction and overviewFig. 1.2 Metabolism represents a relationship betweenfood intake and the enzymes characteristic of an individual, which are dependent on genetic constitution. Alsoimportant are oxygen and water intake and the ability toexcrete carbon dioxide, water and metabolic breakdownproducts.may be disseminated. Pathology that is provokedby the metabolic response in even a small proportion of the population may erroneously be appliedto the population as a whole.NUTRITIONAL DEFICIENCY ANDEXCESSIt is not possible to live for more than 2–3 minwithout oxygen. However, human life can continue without water for between 2 and 7 days, depending on the ambient temperature and the amount5of exercise being taken. Survival without any foodat all, but with water, may be for 60–120 days,depending on the body stores. Females and thosewith considerable subcutaneous fat generally survive for longer than slightly built males.There are individual responses to nutritionaldeficiency and excess, although in general weightincrease is associated with overall excessive eatingand weight loss is associated with inadequatedietary intake. A failure to provide amino acids, fats,vitamins and trace elements leads to specific lesionswhich may progress to morbidity and death.There is no nutritional explanation for the apparent synthesis of essential vitamins by some individuals. When scurvy was a problem in the RoyalNavy the fleet would come into land every 2 monthsto take on board provisions specifically to reducethe prevalence of scurvy. However, on the long seavoyages some individuals died quite quickly ofscurvy, whereas others appeared to be unaffected.Similarly, the different types of beri-beri suggestindividual metabolic responses to thiamin deficiency.In general, the body copes better with an excessthan with a deficiency of nutrients, with the exception of alcohol. Consequently, there is an inclination to eat somewhat more than is required. Thebody copes less well with an excess of dietary fattyor fat-soluble compounds than an excess of watersoluble dietary components. Fatty nutrients, e.g.lipids, are stored and, if the storage load becomesexcessive, then the body is disadvantaged. Watersoluble dietary excesses may be excreted, metabolically modified or unchanged in the urine.Excess dietary protein and lipid intakes may bemetabolically modified to structural or storage tissues, or possibly be excreted in bile and urine. Thevariable pathways whereby these processes occurwill be determined by the range of variants of thesame enzyme (isoenzymes) that forms the metabolic enzyme structure of the individual.THINKING POINTWhat are the criteria for classifying a dietary chemical as a nutrient?
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01 05/03/2003 10:53 Page 7Part IFactors influencing the food that acommunity eats History of food Social, population and environmental influences on nutrition
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01 05/03/2003 10:53 Page 92History of food1. history of diet around the worldhistory of food2. history of European dietHISTORY OF DIET AROUND THEWORLDCookery books are the recordings of how food wasprepared and reflect the cooking practices of theera in which they were written. Babylonian claytablets and Ancient Egyptian scrolls containrecipes. Cookery books in English are to be foundfrom the fourteenth century from the cooks serving Richard II. Now cookery books are major sellers, being of universal interest.Fig. 2.1Chapter outline.be made from a raw flour. Subsequently, the Egyptians found out how to produce beer and used thisknowledge in bread making to create sponginess inthe dough when baked, and so leavened bread wasproduced.Egyptian bread is said to have had a sour taste,suggesting they used lees of beer or a sour doughfor their leaven. Sour dough is a piece of fermented dough saved from a previous baking and is usedto start the fermenting process of the new dough.In thirteenth century BC Egypt, it was usual forpeople to eat two meals a day, a light morning mealand a more substantial evening meal consisting ofseveral dishes.Ancient EgyptAncient GreeceGrain, bread and porridge have been the basis ofthe human diet since the beginning of nutritionalhistory. In Egypt, bread was made as flat cakes fromtoasted grains of barley, wheat or millet. The mealmixed with water in a paste was either dried in thesun or baked on the flat stones of the hearth. Primitive grains required toasting before the hard outerhusks could be removed. However, the Egyptiansfound a strain of wheat that could be threshed without being toasted, and consequently dough couldThe Greeks made unleavened bread from coarsewheat, which they favoured over barley meal, baking their bread in hot ashes and later in breadovens. Increasingly, they used flour which had beenfinely sieved to remove most of the chaff. A widerange of breads was available to both the AncientGreeks and the Romans. For leaven, like the Egyptians, both the Greeks and the Romans used sourdough.
01 05/03/2003 10:53 Page 1010The Roman EmpireThe earliest Romans were a rural people who atea thick porridge of barley or beans and green vegetables with flat barley bread, hard-baked inashes. Cheeses were made from goat’s milk, meatwas a rarity and fish was hardly used. Food wasflavoured with garlic, parsnip, olives and olive oil.When Rome became all-powerful, the poor still atethick grain soups of millet and coarse bread, together with a little turnip or a few beans. Raw olives,goat’s cheese and figs were delicacies, and occasionally cooked pork or meatballs were available;these were produced in cook shops which werefound throughout the cities. For long periods inRome bread was given without payment.The wealthy few had food from all over the knownworld: spices from India, south-east Asia andChina, wheat from Egypt, ham from Gaul and winefrom Greece. Ginger came from China throughcentral Asia; cloves from Indonesia by sea to Ceylon and then on by sea and land to Alexandria.Pepper was a very important element in Romancooking and was brought overland from Indiathrough Egypt. A meal might consist of hors d’oeuvres: a salad of mallow leaves, lettuce, leeks, mintand fish dishes, garnished with sliced eggs, rue andtuna. The main course included a kid, meatballsand beans, together with chicken and a ham. Themeal finished with a dessert of ripe apples and vintage wines. The salads were dressed with wine, oiland vinegar and liquamen, a sauce made from fermented salted anchovies. Hams were boiled withdried figs and bay leaves, and baked with honey ina pastry coating. Chickens were roasted or boiledin a variety of spiced sauces. Roman manors hadtheir own oyster tank to ensure a fresh supply. TheRoman physician Galen taught his followers thatit was harmful to eat fruit with a meal.By the second century BC cooking had becomean art in Rome. The Romans ate three meals a day.Breakfast, between 8 and 10 am, consisted of breadand cheese and a glass of water. Lunch, eaten atnoon with little ceremony, was usually bread withcold meat and vegetables, and fruit with a littlewine. Dinner was eaten at about 8 pm in winter and9 pm in summer. Most food was eaten with the fingers, which were rinsed occasionally, although thediners were provided with knives, toothpicks,spoons and napkins.Factors influencing the food that a community eatsThe requirement for grain necessitated theimportation of wheat on a large scale from Egypt,Sicily and north Africa. Special docks and lighthouses were built for these grain ships. Rotary millspowered by animals were used and sophisticatedovens with systems of draughts and chimneys controlled the heat. The flour was milled into variousgrades, ranging from the finest white to coarse flourconsidered suitable only for slaves.The Roman army stretched from the Scottishborder through to Egypt and as far east as the edgeof the Black Sea. The soldiers were issued withdaily rations of grain or bread, meat, wine and oil,and the cost was deducted from their pay. Cheese,vegetables and salt were included in their basicrations. When the legions were on the march theycarried a scythe to cut crops, a metal cooking pot,a mess tin and 3 days’ emergency food of hard tack,dried cooked grain which could be eaten withoutfurther cooking, salted pork and sour wine. Meatwas boiled or grilled and the soldiers were issuedwith spits as standard equipment. A quern to grindflour and a portable oven were carried for every tenmen. During peacetime a soldier was expected togrind his own grain and bake his own bread. Soldiers supplemented their diet by hunting. Inwartime troops foraged from the enemy countryside. Soldiers made their own cheeses from themilk of animals kept at the forts.Roman army officers lived on fresh meat andimported edible snails, olives, vintage wine, pepper,fish sauce, hams and oysters. The Roman army washuge: 300 000 men in the first century AD. Thisrequired substantial organisation in supplying thegarrison and moving food around the Empire. Thecost of such provision of food eventually becamean intolerable burden on the Roman taxationsystem.Mosaic dietary lawsThe Jewish diet is established under Mosaic law,which defines clean and unclean food. Blood wasseen as the life-force and was forbidden, so all foodanimals had their blood drained as in kosher ritual slaughter. Fish that swim with their fins and hadscales were accepted as clean; shellfish that haveneither fins or scales but swim in water wereunclean. Cows, sheep and goats, which chew the
01 05/03/2003 10:53 Page 11History of foodcud and have cloven hooves, were clean; the pig,which cannot live on grass, was difficult to herd andhad little stamina for the nomadic way of life, wasunclean. The modification to that diet depended onthe dispersal of the Jewish race either to the northof Europe or along the southern shores of theMediterranean Sea. Eastern European Jews adopted central European cooking, e.g. ‘gefilte fish’,poached fish cakes made with the flesh scrapedfrom the skin and bones, and mixed with onions,seasoning and breadcrumbs bound with egg. TheJews of the Mediterranean lands used fish, fruit,nuts and vegetables.IndiaIndian philosophers stressed the importance offood for the uplifting of the soul and the health ofthe body. They suggested that spices such as clovesand cinnamon were warming; coriander andcumin cooling. They also believed in pure andimpure foods: rice and honey were consideredpurer than other foods.The Indus valley was the centre of civilisationaround 2000 BC, when it was invaded by Aryaninvaders from Iran and Afghanistan. The economyof these Aryan warrior nomads was based on cattle. They lived primarily on meat and milk products. Barley was the staple grain, ground into flourand cakes and eaten with butter. Crushed toastedbarley was mixed into a gruel with curds, clarifiedbutter and milk. Food was eaten by hand. Thickgruels were licked off the fingers and thin onesdrunk from bowls or cups made of clay. The inhabitants of the Indus valley were driven south intoIndia. Aryans gradually adopted the use of rice,wheat and beans, and learned the use of spices,including tumeric, long peppers (pepper from vinessimilar to black pepper), sour oranges andsesame, but continued to use clarified butter forcooking. Rice was cooked with mung beans into athick gruel or khicri. Raw ginger was eaten aftermeals to aid digestion. The juice of the soma plantwas mixed with rice or curds.The early Aryans were tribal and their societywas divided into castes. The Brahmins were thehighest caste, with strict rules of purity, particularlyconcerning food. Food could be polluted by beingtouched by lower caste people, as this was believed11to affect its purity. To protect themselves from pollution, strict laws governing the toilet and behaviour of cooks were developed. Brahmins could onlyeat food prepared by
Nutrition, British Journal of Nutrition, European Journal of Clinical Nutrition, Lancet, Nature and Proceedings of the Nutrition Society. The Internet The manner in which written information is handed on is changing rapidly with the avail-ability of the World Wide Web. The printed textbook can be seen as a primer, an introduc-File Size: 8MB