Objective: Practical use of the glycaemic index (GI), as recommended by the FAO=WHO, requires an evaluation of the recommended method. Our purpose was to determine the magnitude and sources of variation of the GI values obtained by experienced investigators in different international centres. Design: GI values of four centrally provided foods (instant potato, rice, spaghetti and barley) and locally obtained white bread were determined in 8 -12 subjects in each of seven centres using the method recommended by FAO=WHO. Data analysis was performed centrally. Setting: University departments of nutrition. Subjects: Healthy subjects (28 male, 40 female) were studied. Results: The GI values of the five foods did not vary significantly in different centres nor was there a significant centre  food interaction. Within-subject variation from two centres using venous blood was twice that from five centres using capillary blood. The s.d. of centre mean GI values was reduced from 10.6 (range 6.8 -12.8) to 9.0 (range 4.8 -12.6) by excluding venous blood data. GI values were not significantly related to differences in method of glucose measurement or subject characteristics (age, sex, BMI, ethnicity or absolute glycaemic response). GI values for locally obtained bread were no more variable than those for centrally provided foods. Conclusions:The GI values of foods are more precisely determined using capillary than venous blood sampling, with mean between-laboratory s.d. of approximately 9.0. Finding ways to reduce within-subject variation of glycaemic responses may be the most effective strategy to improve the precision of measurement of GI values.

OBJECTIVE: To develop and test a book of photographs of commonly eaten foods to be used as a visual aid in the description of portion sizes in a large cross-sectional study on the health profile of Africans in transition (THUSA - Transition, Health and Urbanization in South Africa). SETTING: Clinics in the North West Province of South Africa. PARTICIPANTS: One hundred and sixty-nine adult African volunteers DESIGN: Data on commonly eaten foods, preparation methods, recipes and portion sizes were collected in a pilot study. Colour photographs, taken of foods prepared by the researchers and measured into three or four portion sizes, were enlarged and put together in a book. The food portion photograph book (FPPB) was tested by presenting subjects with a portion of real food and asking them to estimate the portion size by matching it with one of the portion photographs. MAIN RESULTS: Of 2959 portions tested, 68% were accurately estimated (estimated weight within 10% of actual weight). Clearly defined solid foods were better estimated than foods that had an amorphous appearance. Accuracy of estimation was not affected by gender, age or education. CONCLUSION: The FPPB was accepted as a useful and convenient visual aid to estimate portion sizes in the cross-sectional dietary intake study.

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Diabetes mellitus and CVD are some of the leading causes of mortality and morbidity. Accumulating data indicate that a diet characterised by low-glycaemic index (GI) foods may improve the management of diabetes or lipid profiles. The objective of the present meta-analysis was to critically analyse the scientific evidence that low-GI diets have beneficial effects on carbohydrate and lipid metabolism compared with high-GI diets. We searched for randomised controlled trials with a crossover or parallel design published in English between 1981 and 2003, investigating the effect of low-GI v. high-GI diets on markers for carbohydrate and lipid metabolism. Unstandardised differences in mean values were examined using the random effects model. The main outcomes were fructosamine, glycated Hb (HbA 1c ), HDL-cholesterol, LDL-cholesterol, total cholesterol and triacylglycerol. Literature searches identified sixteen studies that met the strict inclusion criteria. Low-GI diets significantly reduced fructosamine by 2 0·1 (95 % CI 2 0·20, 0·00) mmol/l (P¼ 0·05), HbA 1c by 0·27 (95 % CI 2 0·5, 2 0·03) % (P¼0·03), total cholesterol by 2 0·33 (95 % CI 2 0·47, 2 0·18) mmol/l (P, 0·0001) and tended to reduce LDL-cholesterol in type 2 diabetic subjects by 2 0·15 (95 % CI 2 0·31, 2 0·00) mmol/l (P¼0·06) compared with high-GI diets. No changes were observed in HDL-cholesterol and triacylglycerol concentrations. No substantial heterogeneity was detected, suggesting that the effects of low-GI diets in these studies were uniform. Results of the present meta-analysis support the use of the GI as a scientifically based tool to enable selection of carbohydrate-containing foods to reduce total cholesterol and to improve overall metabolic control of diabetes.

Objective: To describe how urbanisation influences the nutrition and health transition in South Africa by using data from the THUSA (Transition and Health during Urbanisation of South Africans) study. Design: The THUSA study was a cross-sectional, comparative, population-based survey. Setting: The North West Province of South Africa. Subjects: In total, 1854 apparently healthy volunteers, men and women aged 15 years and older, from 37 randomly selected sites. Pregnant and lactating women, those with diagnosed chronic diseases and taking medication, with acute infections or inebriated were excluded but screened for hypertension and diabetes mellitus. Subjects were stratified into five groups representing different levels of urbanisation in rural and urban areas: namely, deep rural, farms, squatter camps, townships and towns/cities. Outcome measures and methods: Socio-economic and education profiles, dietary patterns, nutrient intakes, anthropometric and biochemical nutrition status, physical and mental health indicators, and risk factors for non-communicable diseases (NCDs) were measured using questionnaires developed or adapted and validated for this population, as well as appropriate, standardised methods for the biochemical analyses of biological samples. Results: Subjects from the rural groups had lower household incomes, less formal education, were shorter and had lower body mass indices than those in the urban groups. Urban subjects consumed less maize porridge but more fruits, vegetables, animal-derived foods and fats and oils than rural subjects. Comparing women from rural group 1 with the urban group 5, the following shifts in nutrient intakes were observed: % energy from carbohydrates, 67.4 to 57.3; from fats, 23.6 to 31.8; from protein, 11.4 to 13.4 (with an increase in animal protein from 22.2 to 42.6 g day 21 ); dietary fibre, 15.8 to 17.7 g day 21 ; calcium, 348 to 512 mg day 21 ; iron from 8.4 to 10.4 mg day 21 ; vitamin A from 573 to 1246 mg retinol equivalents day 21; and ascorbic acid from 30 to 83 mg day 21. Serum total cholesterol, low-density lipoprotein cholesterol and plasma fibrinogen increased significantly across groups; systolic blood pressure . 140 mmHg was observed in 10.4 -34.8% of subjects in different groups and diabetes mellitus in 0.8-6.0% of subjects. Women in groups 1 to 5 had overweight plus obesity rates of 48, 53, 47, 61 and 61%, showing an increase with urbanisation. Subjects from group 2 (farm dwellers) showed the highest scores of psychopathology and the lowest scores of psychological well-being. The same subjects consistently showed the lowest nutrition status. Conclusions: Urbanisation of Africans in the North West Province is accompanied by an improvement in micronutrient intakes and status, but also by increases in overweight, obesity and several risk factors for NCDs. It is recommended that intervention programmes to promote nutritional health should aim to improve micronutrient status further without leading to obesity. The role of psychological strengths i...