Browsing by Subject "Provitamin A"

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Can genetic engineering for the poor pay off? : an ex-ante evaluation of Golden Rice in India
(2006) Qaim, Matin; Sachdev, H. P. S.; Stein, Alexander J.
Genetic engineering (GE) in agriculture is a controversial topic in science and society at large. While some oppose genetically modified crops as proxy of an agricultural system they consider unsustainable and inequitable, the question remains whether GE can benefit the poor within the existing system and what needs to be done to deliver these benefits? Golden Rice has been genetically engineered to produce provitamin A. The technology is still in the testing phase, but, once released, it is expected to address one consequence of poverty ? vitamin A deficiency (VAD) ? and its health implications. Current interventions to combat VAD rely mainly on pharmaceutical supplementation, which is costly in the long run and only partially successful. We develop a methodology for ex-ante evaluation, taking into account the whole sequence of effects between the cultivation of the crop and its ultimate health impacts. In doing so we build on a comprehensive, nationally representative data set of household food consumption in India. Using a refined disability-adjusted life year (DALY) framework and detailed health data, this study shows for India that under optimistic assumptions this country?s annual burden of VAD of 2.3 million DALYs lost can be reduced by 59.4% hence 1.4 million healthy life years could be saved each year if Golden Rice would be consumed widely. In a low impact scenario, where Golden Rice is consumed less frequently and produces less provitamin A, the burden of VAD could be reduced by 8.8%. However, in both scenarios the cost per DALY saved through Golden Rice (US$ 3.06-19.40) is lower than the cost of current supplementation efforts, and it outperforms international cost-effectiveness thresholds. Golden Rice should therefore be considered seriously as a complementary intervention to fight VAD in rice-eating populations in the medium term.
Einfluss von Karotten- und Tomatensaft-Konsum auf Coloncarcinogenese-relevante Faecesmarker beim Menschen
(2006) Schnäbele, Kerstin; Briviba, Karlis
Colorectal cancer is one of the most common tumor diseases in the world. Most of the colorectal tumors are sporadic and develop somatically in epithelial cells. Nutritional factors can markedly affect tumor development. A high intake of fruits and vegetables is often associated with a reduced risk of colorectal cancer. Protective effects of fruits and vegetables are attributed to ingredients, such as fibers, vitamins, and secondary plant products (e.g. carotenoids), which have potential anticarcinogenic properties. The aim of this study was to investigate, by means of a human intervention trial with carrot and tomato juice consumption, whether a diet rich in carotenoids, especially high in beta-carotene and lycopene, can modify processes relevant to colon carcinogenesis in the gastrointestinal lumen. Therefore, several faecal markers had to be established and used in this study. In the randomized crossover trial, 22 healthy male subjects on a low-carotenoid diet consumed 330ml of carrot or tomato juice daily for a period of two weeks. The two juice intervention periods were preceded by two-week depletion phases. At the end of each study period the stool of twelve volunteers was collected over a 48-hour period. This stool was used to produce some preparations such as non-filtered and sterile-filtered faecal water, as well as faecal lipid extracts, in order to use them in cell culture systems. Spectral photometric and flow cytometric methods were used to determine the effects of the above-mentioned preparations on colon adenocarcinoma cells (HT-29), as well as to determine the activities of the bacterial enzymes beta- glucosidase and beta-glucuronidase in faecal water. HPLC methods were used to measure the concentrations of several bile acids in faecal water, as well as to determine the concentrations of carote-noids and malondialdehyde (MDA) in faecal samples. The concentrations of the major short chain fatty acids (SCFA) were measured via gas chromatography. Consumption of carrot juice led to a marked increase of beta-carotene and alpha-carotene in faeces and in non-filtered faecal water, as did lycopene after consumption of tomato juice. In the succeeding depletion phases, the contents of those carotenoids in faeces and faecal water returned to their initial values. Changes in faecal MDA concentrations by carrot and tomato juice interventions could not be observed. Faecal water showed high, dose-dependent cytotoxic effects on HT-29 cells. Those effects were, however, not markedly changed by carrot and tomato juice consumption. Neither bile acid concentrations nor the bile acid profile in faecal water changed after carrot and tomato juice consumption. Bacterial activities of beta-glucosidase and beta-glucuronidase also did not change. While tomato juice consumption did not significantly affect the pH value of faecal water, this value was, however, decreased by carrot juice consumption. Although faecal water concentrations of acetate and butyrate contributed to the decrease in faecal water pH values, SCFA were probably not responsible for the observed pH changes after carrot juice consumption. SCFA concentrations in faecal water and SCFA proportions did not change significantly. Neither bile and SCFA concentrations, nor the activities of tested bacterial enzymes, had any influence on the cytotoxic effects of sterile-filtered faecal water. These cytotoxic effects, however, decreased with increasing proportions of the primary bile acids cholic and chenodesoxycholic acid, independent of the study phases. As determined by multiple regression analysis, the most probable leading factors for the growth inhibitory effects of faecal water are the faecal MDA content and bacterial beta-glucosidase activity. Further studies should investigate whether the parameters mentioned directly influence cytotoxic and antiproliferative effects of faecal water or if those parameters are indirect markers for the activity of individual microflora. Carrot and tomato juice consumption strongly increased the cytotoxic effects of faecal lipid extracts in HT-29 cells, likely caused by the induction of apoptosis. Which mechanisms account for these effects and the consequences of these effects in the in vivo situation should be investigated in further studies. This work shows that two-week interventions with carotenoid-rich juices lead only to minor changes in luminal processes relevant to colon carcinogenesis in young healthy volunteers on an energy- and macronutrient-balanced diet. Lacking effects on 1) the toxic and antiproliferative properties of faecal water, 2) lipid peroxidation in faeces, 3) the bile and SCFA concentrations in faecal water, and 4) bacterial enzyme activities indicate that related physiological effects can not be influenced by a diet rich in carotenoids under the just described conditions. Other anticarcinogenic mechanisms seem to be of greater importance.
Public attitudes towards genetically modified provitamin A Cassava in Brazil
(2010) Gonzalez Rojas, María Carolina; Qaim, Matin
Cassava is a basic staple food crop with worldwide distribution, mainly in developing countries. A fundamental source of energy for the poor, cassava grows well on marginal soils and resists pests and drought. In Latin America, Brazil is the largest cassava producer and consumer. The crop is especially important in the northeastern (NE) part of the country, where poverty and malnutrition rates are higher than in the rest of the country. However, despite the crop?s dietary importance, relatively little is known about consumer preferences, which holds true not only for Brazil but also for other developing countries. Understanding consumer preferences is crucial for technology and market development, especially in the context of provitamin A biofortification, as this entails a yellow-colored cassava root. The first article, titled ?Consumer Preferences for Cassava Characteristics in Pernambuco, Brazil?, addresses this research gap. Consumer preference for different cassava attributes are analyzed using household survey data and econometric techniques. A hedonic price model is specifically developed to estimate the values that consumers place on specific product attributes. Results show the most important characteristics for local consumers are ease of peeling, time of cooking, and texture; however, root color and size as well as market location are other relevant attributes in determining price. The second article, titled ?Consumer Acceptance of Second-Generation GM Foods: The Case of Biofortified Cassava in the Northeast of Brazil?, examines whether consumers would appreciate provitamin A biofortification and accept GM cassava. For this purpose, stated preference data, collected as part of the household survey, are used. Findings suggest that attitudes towards GM biofortified cassava are generally quite positive among local consumers. Three-quarters of all respondents in the survey said they would support the introduction of this new technology. Using contingent valuation techniques, consumers were shown to be willing to pay an average price premium of 64% for GM biofortified cassava. This is high but not unrealistic, given that vitamin A deficiency and related health problems are widespread in NE Brazil. In addition, a contingent ranking choice experiment was used to better understand the trade-offs between different cassava characteristics and estimate the partial willingness to pay (WTP) for each relevant attribute. For the provitamin A attribute alone, the average consumer is willing to pay a large premium of 160%. However, a discount is required for the color change of cassava from white to yellow (-29%), and an additional discount results from the fact that the cassava is genetically modified (-61%). These are important findings for biofortification research programs that have to make choices between conventional and GM breeding techniques. It is noted that a significantly positive WTP does not imply that GM provitamin A cassava will indeed be sold at a premium. The technology is being developed by the public sector with the aim to reduce malnutrition among the poor, so a low price should be sought to enable easy access. Hence, the WTP survey is a tool to better understand consumer attitudes rather than an approach to develop a pricing strategy for a new commercial product. The third article, titled ?Stakeholder Positions toward GM Food: The Case of Vitamin A Biofortified Cassava in Brazil?, gathers experiences from around the world and shows that stakeholder positions can crucially influence the efficiency of GM regulatory approaches and the success of new technologies. This research builds on a survey of a large range of local stakeholders. Overall, stakeholder perceptions about GM foods are relatively positive in Brazil. Statistical analysis shows that three groups of stakeholders can be distinguished: those in favor of GM crops, those against, and those that have a more or less neutral position. Representatives of local and multinational industries and those of several governmental entities belong mostly to the first group; international and national NGOs form the second group, while scientists are mostly found in the third group. Information sources and institutional/personal relationships influence individual stakeholder positions, as do socio-demographic characteristics, such as the level of education and age. An important result is also the high level of trust that stakeholders in Brazil have, in general, in the country?s research and academic sectors. Therefore, taking into account the relevance of information and the role played by the research sector, an effective system of distributing GM crop information via government agencies and/or public media is necessary to complement the knowledge of consumers so that they can make their own informed decisions.