D. Tech. (Food Service Management, Dept. of Hospitality, Faculty of Human Sciences)|cVaal University of Technology / Main Purpose of the study: To evaluate the impact of soy protein feeding intervention over a period of six months on the nutritional status of an elderly (≥60 years old) community of Sharpeville, in which poverty, household food security and malnutrition were prevalent. Methods: An experimental design that had no control group but a comparison between hypercholesterolaemic (HC) and normocholesterolaemic (NC) groups was used with 134 randomly selected elderly respondents. The first stage involved a baseline survey which determined the prevalence of risk factors for cardiovascular disease (CVD) and nutritional status among participants. Measurements included biochemical indices (serum lipids, vitamin B12, folate and homocysteine), anthropometry (weight, height and waist circumference) and dietary intake using 24h-recall and 7-day dietary diversity questionnaire. Socio-demographic information gathered from previous studies on the same subjects was used. The second stage was the preparation, formulation, and implementation of a nutrition education programme to assess its impact on nutrition knowledge after the nutrition education intervention. The nutrition education was conducted in two sections, namely an exploratory study and an experimental study. An exploratory study was conducted to assess the nutrition education needs of the elderly and was followed by the experimental study, which assessed nutrition knowledge before and after the intervention. The third stage was the implementation of the 10 grams soy protein daily feeding intervention for a period of six months and evaluation of its impact on risk factors for cardiovascular disease and on nutritional status. Sensory tests, compliance and the same measurements conducted at baseline were used at follow-up (feeding intervention). A comparison of the findings of the baseline study and follow-up study was conducted. Also to provide deeper insight into the effect of soy on the risk factors for CVD and nutritional status, respondents were further stratified into HC and NC groups based on their LDL-C levels at baseline study and results were also presented as such. The data analyses included descriptive statistics and t-tests on SPSS version 21.0. Results: From the baseline study, the dietary intake results revealed a poor dietary intake which contributed to inadequate estimated average requirements (EAR) and adequate intakes (AI) of nutrients. A mainly carbohydrate-based diet was consumed with minimal intake of dairy and legumes despite a medium dietary diversity score. The anthropometric indices at baseline indicated over-nutrition based on the reported waist circumference 97.32±10.32 (80.6%) above substantial risk of CDL, obesity (75.3%) and hypertension (56.7%), with the highest percentages for both waist circumference of substantial risk and overweight/obesity found among the women (80.9% and 79.9% respectively) and for hypertension among the men (79.1%). For the biochemical results at baseline, the prevalence of risk factors for CVD was observed as abnormal mean serum lipids such as LDL-cholesterol (3.6±1.1), HDL-cholesterol (0.73±0.4), total cholesterol:HDL-cholesterol ratio (7.9±2.9), triglyceride:HDL-cholesterol ratio (2.7±2.1) and homocysteine (17.1±9.2) in the total group. The women had high TC (5.2±1.1) indicating borderline risk of CVD as compared with men who had lower TC (4.5±0.8) and this was significantly different (p=0.049). The nutrition education programme was effective in increasing knowledge with an improvement of 14.5 percent from pre- (62.3%) to post-test (76.8%) for the total group which was statistically significant (p=0.000). The results for the soy protein feeding intervention, the dietary intake for the total group indicated a statistically significant decrease in energy intake (p=0.001), by about 20.4 percent form baseline to follow-up, while energy intake at baseline was already below the EAR. Also a statistically significant decrease was seen from baseline to follow-up for total dietary fat (p=0.004), cholesterol (p=0.008) and animal protein (p=0.000), with a statistically significant increase only on dietary folate (p=0.001) and iron (0.001). These dietary changes were also observed for the HC and NC groups after the intervention with only fat not decreasing significantly for the HC group. For the anthropometry indices, and hypertension no significant impact after the intervention for the total group and also for the HC and NC groups was observed. The biochemical results indicated a beneficial effect of the soy-based products on the following serum lipids: a significant improvement in LDL-C (p=0.000), HDL-C (p=0.000) and TC:HDL ratio (p=0.000) for the HC group while only TC:HDL ratio showed a significant improvement for the NC group after the intervention. However, high risk factors for CVD in this elderly group were still observed, with a significant decrease after the intervention of serum folate (p=0.000) below the recommended level and a significant increase in homocysteine (p=0.000) above the recommended level. Significant differences between the HC and NC groups were seen in TC, LDL-C, LDL:HDL-C ratio and TC:HDL-C ratio at the beginning of the intervention (baseline). However, at the end of the intervention (follow-up), significant differences were observed only in TC, LDL-C and homocysteine. Conclusion: Although the energy intake reduced significantly, only three of the micro-nutrients (pantothenate, Niacin and selenium) had a significant decrease between baseline and follow-up. Therefore the nutritional status of these elderly was not affected as it was also observed that there was no significant impact on anthropometric indices that took place. However this intervention had a significant impact on iron intake, which was one of the deficiencies identified amongst this elderly people from previous study. Also the nutrition education and a daily consumption of at least 10g of soy had a significant beneficial effect on LDL-C, HDL-C and TC:HDL ratio for the HC groups, thus reducing risk of CVD. Although soy had a beneficial effect on blood lipid profile no effect on hypertension was observed. The guideline of a 25g intake of soy should be encouraged as recommended by FDA as an effective cholesterol-lowering food item.

Une alimentation riche en protéines entraîne une importante diminution de la prise alimentaire, chez l’homme et l’animal, par rapport à une alimentation classique (riche en hydrates de carbones). Les précédents travaux du laboratoire chez le rat montrent que le mécanisme implique une induction de la production intestinale de glucose libéré dans la veine porte. Il s’ensuit un signal qui transite au cerveau via le nerf vague et se traduit par un effet anorexigène. Le régime protéique induit en fait une redistribution de la production endogène de glucose au profit du rein et de l’intestin chez le rat, et au profit de l’intestin et du foie chez la souris. L’effet anorexigène des protéines est présent également chez les souris, confirmant un rôle tout particulier de l’intestin, et du signal glucose portal, dans ce phénomène de satiété. Nos résultats montrent d’ailleurs que le signal glucose portal n’est pas impliqué dans l’augmentation de la production rénale de glucose induite par le régime protéique qui est observée uniquement chez le rat. Les mesures effectuées chez des rats nourris par différents régimes protéiques indiquent l’implication de mécanismes propres à la nature des protéines qui reste à déterminer. De plus nous avons mesuré une augmentation de la sensibilité à l’insuline de la production endogène de glucose chez le rat nourri par le régime protéique. Des études plus approfondies chez la souris devraient permettre de comprendre les mécanismes impliqués. Nos expériences suggèrent par ailleurs que le système mélanocortinergique ne serait pas impliqué dans l’effet anorexigène du régime à long terme mais pourrait constituer un élément important de contre-régulation face à l’hypophagie sévère temporaire provoquée par le changement de régime / Protein feeding is known to decrease hunger and subsequent food intake in animals and humans. Previous data point out the connection between the central nervous system and the intestinal glucose production in the central inhibitorycontrol of food intake by protein feeding. Our study demonstrates that protein feeding induces redistribution of endogenous glucose production to the kidney and intestine in rats and to the intestine and liver in the mouse. Anorexigenic effect of protein diet exists in both animal models, confirming a specific role of the intestine in this satiety phenomenon. Moreover, portal glucose sensing is not involved in the induction of renal glucose production by protein feeding that is only observed in rats. Measurement in rat fed with different protein diets suggest a role of the nature of the protein or structure, but proper mechanisms remain to be clarified. Moreover, protein feeding potentiates the endogenous glucose production suppression by insulin. Some additional studies have to be performed to find the mechanisms that are implicated. Our experiments suggest that the melanocortinergic system wouldn’t be involved in the longterm anorexigenic effect of protein feeding but could constitute an important counter-regulatory pathway against the temporary hypophagia induced by diet change