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- Volume 18, Issue 3, 2005
South African Journal of Clinical Nutrition - Volume 18, Issue 3, 2005
Volumes & issues
Volume 18, Issue 3, 2005
Source: South African Journal of Clinical Nutrition 18, pp 206 –210 (2005)More Less
African governments should adopt clear and coherent food safety policies as part of a comprehensive national strategy, based on the sharing of responsibilities for food safety between public authorities, industry and consumers and taking into account the entire food chain from farm to table.
Author Christine S. VenterSource: South African Journal of Clinical Nutrition 18, pp 211 –212 (2005)More Less
The glycaemic index (GI) of a carbohydrate-containing food reflects its blood glucose raising potential, while the glycaemic load (GL) is defined as the mathematical product of the GI of a food and its carbohydrate content. Evidence from prospective studies shows that low-GI diets are associated with reduced risk of diabetes, cardiovascular disease, cancer and the metabolic syndrome.
Source: South African Journal of Clinical Nutrition 18, pp 214 –221 (2005)More Less
Background. Controversy exists regarding practical use of the glycaemic index (GI), often with reference to the responsibility of health professionals to advise consumers only when scientific evidence supports their recommendations. There are indications that low-GI diets may improve health, but the strength of the evidence is not known.
Objectives. The objective of this systematic review was to determine the strength of scientific evidence encouraging dieticians to incorporate the GI concept when planning diets.
Design. A meta-analysis was performed as part of the systematic review. We searched for randomised controlled trials with a cross-over or parallel design published in English between 1981 and 2003, investigating the effect of low-GI versus high-GI diets on markers of carbohydrate and lipid metabolism. The main outcomes were fructosamine, glycosylated haemoglobin (HbA1c), high-density lipoprotein cholesterol (HDLC), low-density lipoprotein cholesterol (LDLC), total cholesterol (TC) and triacylglycerols (TGs).
Results. Literature searches identified 13 studies that met strict inclusion criteria. Low-GI diets significantly reduced fructosamine by -0.1 mmol/l (confidence interval (CI): -0.20, 0.00, p = 0.05), HbA1c by 0.27% (CI: -0.5, -0.03; p = 0.03), LDLC in type 2 diabetics by -0.24 mmol/l (CI: -0.45, -0.04; p = 0.02) and TC by -0.33 mmol/l (CI: -0.47, -0.18; p < 0.0001) compared with high-GI diets. No effects were observed for HDLC and TGs.
Conclusion. This systematic review presents convincing evidence to recommend the use of the GI as a scientifically based tool when choosing carbohydrate-containing foods to reduce TC and LDLC concentrations and to improve overall metabolic control of diabetes.
Author Hattie H. WrightSource: South African Journal of Clinical Nutrition 18, pp 222 –228 (2005)More Less
Carbohydrate (CHO) is the main fuel for exercising muscles, therefore the amount, timing and type of CHO food ingested is an important part of an athlete's daily dietary intake. The amount and timing of CHO ingestion has been investigated extensively. It has been suggested that the glycaemic index (GI) of CHO foods influences CHO availability during exercise and the rate of glycogen synthesis post-exercise. Although low-GI (LGI) CHO foods are mostly recommended for the pre-exercise meal, ingesting high-GI (HGI) CHO foods pre-exercise mostly does not result in hypoglycaemia in healthy individuals during exercise. HGI and LGI CHO foods yield similar results in terms of exercise performance and perceived rate of exertion. HGI and moderate GI (MGI) CHO foods are recommended during exercise. However, fructose in high concentrations is not recommended owing to increased risk of gastrointestinal distress. LGI CHO foods are not recommended during a short recovery period (< 6 hours) because of their slow rate of absorption and indigestible CHO, which seems to be a poor substrate for glycogen synthesis.
Source: South African Journal of Clinical Nutrition 18, pp 232 –236 (2005)More Less
South Africa is in the process of legislating food labelling for the glycaemic index (GI). This paves the way for inclusion of specific health messages regarding the GI on product labels. However except for the Food and Agriculture Organization (FAO) guidelines there is currently no internationally approved, detailed and standardised method for determination of the GI.
Source: South African Journal of Clinical Nutrition 18, pp 238 –242 (2005)More Less
Introduction and objective. The glycaemic index (GI) can be determined using capillary blood or venous plasma sampling. The aim of this study was to compare the GIs of three South African oat products determined using both capillary blood and venous plasma.
Methods. Twenty healthy, non-smoking male students (mean age 21.0 years, standard deviation (SD) 1.28 years, mean body mass index (BMI) 24.55, SD 2.62) volunteered to participate. Each subject received a standard pretest meal the evening before test days. The reference food used was glucose, and the test meals were three oat porridges, namely Jungle oats (66 g dry weight), Bokomo oats (72.8 g) and Oatso Easy (101 g) in the form they are normally consumed, namely with milk (150 ml) and sugar (20 g), or water only in the case of Oatso Easy, an instant porridge. Each meal contained 50 g glycaemic carbohydrate as determined by the Englyst method. Capillary blood glucose and venous blood samples were taken simultaneously at 0, 15, 30, 45, 60, 90 and 120 minutes and areas under the curve (AUC) and GI were calculated.
Results. The mean fasting glucose value obtained from venous plasma before all tests (N = 80) was significantly lower (4.5 mmol/l, SD 0.7, p < 0.002) than the mean capillary blood glucose concentration (4.8 mmol/l, SD 0.04). The mean incremental AUCs obtained from venous plasma after all test meals and the reference (oral glucose) differed significantly (p < 0.01) from the AUCs obtained from capillary blood. The SDs for GIs calculated from venous plasma samples were at least 3 times larger than the SDs for GIs calculated from capillary samples. No significant differences were found between the GIs of the three oat products.
Conclusion. The present data are consistent with previous results showing that glycaemic responses measured in venous plasma are lower and more variable than those in simultaneously obtained capillary blood. The most precise and accurate determination of GI may be achieved using capillary rather than venous blood sampling, supporting the recommendation of the working group on the standardisation of GI testing in South Africa.
Source: South African Journal of Clinical Nutrition 18, pp 244 –249 (2005)More Less
Background. Both wheat pasta and dry beans have low glycaemic indices (GIs). However, it has been shown that several factors, including method of processing, may influence the GI of a food. Extrusion of dry beans is a relatively new dry cooking process and provides a convenient alternative to the ingestion of dry beans.
Objective. To determine the GI of pasta and muffins made from extruded dry-bean flour.
Methods. Ten healthy male and 10 healthy female students participated in this study. The subjects resided in the Metabolic Unit of North-West University during the period of testing. Subjects randomly consumed test meals of glucose (reference), bean muffins, whole-wheat muffins and pasta (men only) on different days. The Englyst method was used to determine the 50 g glycaemic carbohydrate portion. Fasting capillary blood samples were taken, the test foods were administered, and further capillary samples were taken at 15, 30, 45, 60, 90 and 120 minutes after the subjects had started to ingest the test meals. The area under the glycaemic response curve for each test and subject was calculated where the GI is based on the area under the blood glucose response curve above the baseline value only.
Results. The GI of the muffin baked with extruded dry-bean flour (mean 53, 95% confidence interval (CI) 42 - 64) was not significantly different from that of the whole-wheat muffin (mean 55, 95% CI 42 - 69). The mean GI of the extruded dry-bean pasta was 83 (95% CI 58 - 108). Both the extruded dry-bean muffins and the whole-wheat muffins fell in the top border of the low-GI category, while the GI of the extruded dry-bean pasta fell within the high-GI category.
Conclusion. Several factors may have contributed to the high GI of the dry-bean pasta. The composition of the pasta and the extrusion process (which seems to alter particle size, antinutrient activity and resistant starch content), are most likely to have influenced the GI of the extruded dry-bean products.
Complexities of consumer understanding of the glycaemic index concept and practical guidelines for incorporation in dietsAuthor M. SlabberSource: South African Journal of Clinical Nutrition 18, pp 252 –257 (2005)More Less
The glycaemic index (GI) concept has been widely debated during the past two decades. Controversies still reign among health professionals regarding the practical application of the concept despite numerous reports on the health benefits associated with low-GI diets. Those opposed to the practical implementation of the GI concept argue that the use of technical terminology and numerical figures, limited food choices and potential misconceptions about unrestricted amounts of low-GI foods that may result in concomitant high fat intake, may confuse the consumer and will distract from other important dietary advice. Conversely, proponents of the GI concept state that consumers find the GI to be simple, logical and helpful and acknowledge that by expanding the range of foods they may include in their diets the GI concept is a major step forward for people with diabetes mellitus. Complexities of consumer understanding of the GI concept are discussed and suggestions are made to incorporate high- and low-GI foods in the context of current dietary guidelines and client education. If health professionals apply the GI concept in a practical way and explain the concept in a clear, uncomplicated manner, current dietary advice will be supported (and not opposed), resulting in short- and long-term health benefits for consumers.
Source: South African Journal of Clinical Nutrition 18, pp 260 –264 (2005)More Less
A group of 36 dietitians and nutritionists evaluated the practical application of the glycaemic index (GI) of foods during a master class at the 2002 South African Nutrition Congress (Potchefstroom, 5 - 9 November 2002). The group reached consensus that the GI is a useful concept and a scientifically based tool to choose carbohydrate-containing foods. The group agreed that the GI of a food reflects the immediate effect of the food on blood glucose homeostasis. There was agreement that the habitual consumption of low-GI carbohydrate foods probably reduces risk of cardiovascular disease through effects on lipid risk factors and that it probably improves prevention and control of diabetes mellitus through effects on insulin resistance. The group further agreed that the evidence that the GI of foods may play a role in planning of diets with higher satiety value, preventing and controlling obesity and behavioural disorders, and improving physical performance, needs to be strengthened with more research. There was consensus that there is sufficient potential and experience with low-GI diets to support labelling of South African food products for GI, creating a mechanism to inform and educate the public towards responsible use of the concept. However, the group also agreed that there are problem areas and potential pitfalls in measuring and reporting the GI of foods, and therefore recommends standardisation of methodology. There was consensus that more research on the GI of typical South African foods, knowledge and attitudes of consumers, as well as the development of suitable teaching aids are needed.
Nutrient intake and consumption of indigenous foods among college students in Limpopo Province, South African Journal of Clinical Nutrition, 18(1) 2005, pp: 32-38 : erratumSource: South African Journal of Clinical Nutrition 18 (2005)More Less
Author Karin FritzSource: South African Journal of Clinical Nutrition 18 (2005)More Less
To the Editor: I refer to an article published in a recent issue of SAJCN. It was interesting to read, but a huge disappointment that information was incorrectly presented. In their article the researchers stated that mageu (a drink made from fermented cooked maize meal porridge and other ingredients) was 'the most popular alcoholic drink'.
Source: South African Journal of Clinical Nutrition 18 (2005)More Less
The 18th International Congress of Nutrition was held for the first time in Africa, on 19 - 23 September 2005 in Durban. The lists of delegates and speakers read like the Who's Who of global nutrition: 2 519 registrations (of whom 2 103 attended) were received from 113 different countries. The programme consisted of 22 plenary lectures, 10 workshops, 2 debates, 7 special lectures, 48 symposia and a similar number of poster categories.
Source: South African Journal of Clinical Nutrition 18 (2005)More Less
It gives me great pleasure to congratulate the organisers of the IUNS 'Nutrition Safari for Innovative Solutions' Congress recently held in Durban. They did us and South Africa proud! The extensive congress programme ran smoothly and professionally thanks to the well-organised and dedicated team. ADSA and NSSA shared a stand where the profession was promoted and the 'If it's about Nutrition, ask your Dietitian!' pamphlet was distributed. Get your copy now!