the glycaemic index: a physiological classification of dietary carbohydrates

The Glycaemic Index: A PhysiologicalClassification of Dietary Carbohydrates

Wolever TMS. Cabi Publishing, Oxfordshire, UK, 2006,272 pages, 60 pounds, ISBN 1-84593-0517So, you think you know everything you need to know aboutthe glycaemic index (GI), glycaemic load (GL) and glycaemicresponse? You may be surprised . . .

The seminal paper ‘Glycemic index of foods: a physiologi-cal basis for carbohydrate exchange’ was published in theAmerican Journal of Clinical Nutrition in March 1981. Alongwith Dr David Jenkins, Tom Wolever was one of theco-inventors of the glycaemic index concept. As the title ofthe paper suggests, the GI was originally invented to ‘correct’carbohydrate exchanges so that they more closely reflectedthe physiological response of people with diabetes to carbo-hydrates in foods, and was envisaged to be only of use to thatparticular group of people. Over 25 years later, several thou-sand studies from around the world have examined theaccuracy, reliability, validity, epidemiological associationswith chronic disease, and clinical utility of the GI concept.Throughout this time period, Professor Wolever has beenone of the main driving forces behind this research.

It was only in 1997 that the glycaemic load (GL), which isthe product of the GI multiplied by the amount of availablecarbohydrate (GL = GI (%) ¥ available carbohydrate), wasconceptualised by the nutritional epidemiologists at HarvardUniversity in the USA.

In the past 10 years, both the GI and the GL have capturedthe imagination of researchers, clinicians and lay people alike,triggering a dramatic upsurge in scientific research into car-bohydrate metabolism, and much popular debate.

Perhaps to mark the end of the first 25 years of GIresearch, Professor Wolever has written this comprehensivereview and analysis of most, if not all, the research into theGI and the GL.

The journey starts with a brief history of the scientificinvestigation of the effect of carbohydrates on health goingback 150 years. The author then very carefully defines GI,explaining clearly why it is not the same as glycaemicresponse. While at first glance this may not sound all thatground breaking, it is this very issue that is one of the majorunderlying causes of much of the current confusion aboutthe measurement, and clinical utility of both the GI and GL.Following this, we are given an in-depth description of howto determine the GI of a food accurately and reliably, withcareful consideration of the factors which do and do notaffect the final result.

Many people may also have heard of the insulin index,and thought that, due to the hormone’s central role in fuelmetabolism, it is probably more important than either the GIand GL? Professor Wolever meticulously analyses the currenttechniques used to assess insulin metabolism, and comparesand contrasts it to glucose metabolism and the GI. The resultwill surprise many . . .

Next, we visit the much vexed issue of the use of the GI inmixed meals. As well as critically reviewing the published

data on the topic, Professor Wolever demonstrates his math-ematical prowess by re-analysing the published data fromaround the world, so that we are comparing like with like.These data provide compelling evidence that the GI of mixedmeals can be predicted with an acceptable degree of accuracyto enable its clinical use.

From here the book traces the role of the GI in thepromotion of good health through improvements in physicaland mental performance, as well as the prevention and man-agement of overweight and obesity.

Finally, he explores the complex relationship that isemerging between GI and chronic disease risk. The evidencelinking the development of type 2 diabetes, cardiovasculardisease and certain cancers is critically examined, and sug-gestions for further areas of research are put fourth.

Targeted squarely at health professionals, this book istruly the definitive summary of research into the GI, GL andglycaemic carbohydrate. In fact, if anything, some will find itjust a little too detailed and may find the complex math-ematical proofs a little overwhelming. However, it is anabsolute must for anyone conducting serious research in tothe area of glycaemic carbohydrate, and a great resource foranyone interested in this much debated and often misunder-stood concept.

Alan Barclay, APDPhD Candidate, University of Sydney

Sydney, New South Wales, Australia

The Oxford Handbook of Nutritionand Dietetics

Webster-Gandy J, Madden A, Holdsworth M. Oxford Uni-versity Press, Oxford, UK, 2006, 730 pages, 24.95pounds, ISBN 0-19-856725-1This publication is one of a series 40 or so Oxford Hand-books which cover a wide range of health-care specialitiesfrom urology to applied dental science, and includes publichealth practice. The authors indicate they have notintended to publish yet another pocket book for use byclinical dietitians. They have instead aimed to presentcompact, concise and accessible information on key aspectsof nutrition science, therapeutics and community publichealth nutrition that will be useful to a range of healthprofessionals practicing in a variety of settings. The editorsare all registered dietitians with substantial research andpractice track records. There are 19 additional contributorswith a good mix of academics and practitioners, at least 12of whom are dietitians. The editors and contributorsare certainly well credentialled to produce this publication.

There is a comprehensive list of abbreviations and medicalshorthand. Ten appendices provide a range of useful andmostly expected information, a good deal of which is, asexpected, UK specific. Some particularly useful and genericinclusions in the anthropometric appendix are the Cole bodymass index (BMI) cut-offs for overweight and obesity in 2- to

Book reviews

© 2007 The AuthorsJournal compilation © 2007 Dietitians Association of Australia

217