Study design for dietary intake of aflatoxins of the adult Malaysian population

Transcription

1 Mycotoxins Vol. ( ), Study design for dietary intake of aflatoxins of the adult Malaysian population Cheow Keat CHIN, Aminah ABDULLAH Food Safety and Quality Division, Ministry of Health Malaysia (Level, Block E, Putrajaya, Malaysia) & Graduate Student at School of Chemical Science & Food Technology, Faculty of Science and Technology, University Kebangsaan Malaysia School of Chemical Science & Food Technology, Faculty of Science and Technology, University Kebangsaan Malaysia ( UKM Bangi, Selangor, Malaysia) Abstract The dietary intake of aflatoxin was targeted at the adult Malaysian population aged to years using the Total Diet Studies (TDS) approach as recommended by the World Health Organization (WHO). Data from the Malaysian Food Consumption Survey in was reviewed and foods were selected based on bibliographical knowledge and on expertise of analysts specialized in the routine analysis of raw and processed products for aflatoxin. Taking into consideration variabilities in contaminants as a result of production and processing, the selected food was split into two food categories namely national food, which encompass processed foods and are likely to contain homogenous levels of contamination with respect to their production and/or processing methods; and regional foods, which are foods that are unprocessed and untransformed and therefore might contain heterogenous levels of contamination resulting from production and/or preparation method specific to the region. Based on these criteria, the initial food list consisting of foods were further split into foods categorized as national food and foods categorized as regional food. Food samples from the food list were collected to represent the food consumption pattern and encompass all geographical areas in Malaysia, which included regions (North, Central, South, East, Sabah and Sarawak) with each region having sampling points. Sampling was performed at retail markets to ensure that the sampled products represent the foods available to the public. Collected samples were then prepared as consumed based on individual food composite approach. Analysis of individually composited samples were then carried out using methods that have demonstrated its acceptability including adequacy of its limit of detection, limit of quantification, accuracy and precision. Based on the results of the analysis and information from the food consumption, the dietary exposure and risk from getting liver cancer of the Malaysian adult population will then be estimated. (Received: May, ) Introduction Estimating the actual dietary intake of contaminants is important to assess the public health risks arising from the presence of contaminants in foods consumed by the population. Three basic approaches have been proposed by World Health Organization ) (WHO) in carrying out dietary intake studies; namely the total diet studies, selective studies of individual foods and duplicate portion studies. The total diet studies (TDS) provide a more accurate estimate of dietary intakes of contaminants for a country as compared with other

2 Mycotoxins method; though it is a more complex and costly approach ). The primary purpose of total diet studies is to measure the average amount of each chemical ingested by different age/sex groups living in a country. The dietary exposures of the chemicals can be compared with national or international safety guidelines to assess whether or not a specific chemical poses an unacceptable risk to health. Thus, total diet studies provide a direct measure of the safety of the diet. The World Health Organization (WHO), the lead United Nations agency for public health, recommends total diet studies as the most cost-effective method for assuring that people are not exposed to unsafe levels of chemicals through food ). The importance of this approach is further reemphasised in the Beijing Declaration on Food Safety ), which was adopted by consensus by the High-level International Food Safety Forum on Enhancing Food Safety in a Global Community held in Beijing, People s Republic of China on - November. The Declaration urged all countries to: Establish food and total diet monitoring programmes with linkages to human and food-animal disease surveillance systems to obtain rapid and reliable information on prevalence and emergence of foodborne diseases and hazards in the food supply. Therefore the objective of this paper is to highlight the study design of the total diet study approach in attempting to:- i. Determine exposure of the adult Malaysian population to aflatoxins through the diet ii. Identify foods that contribute significantly to the intake of aflatoxins iii. Estimate liver cancer risk for non-hepatitis B and hepatitis B population from the consumption of aflatoxins in a typical adult Malaysian Diet iv. Identify specific vulnerable group (sex/ethnic group) of the adult Malaysian population most at risk from their diet to aflatoxins exposure v. Recommend risk management options vi. Compare dietary exposure with those estimated in other countries, where comparative data are available Scope of Study Population group of interest in this study is the Malaysian adult population aged between - years, with the focus on aflatoxins contamination in a typical adult Malaysian diet based on food consumption pattern from the Food Consumption Statistics of Malaysia. Elements of the Study Design The study design is summarized in Figure and essentially consists of the following: - Develop a food list reflecting a typical Malaysian diet based on the existing Food Consumption Statistic of Malaysia The list of foods consumed by the general adult Malaysian population was based on the results of individual Malaysian Food Consumption Survey, for which data were collected over a months period

3 Vol. ( ), Figure Summary of Study Design

4 Mycotoxins using food frequency survey questionnaire with a list of foods involving a total of, adults (- years old) ). The good national representativeness of the sample was ensured through a random stratified sampling (population size and zones). Food portion sizes and food description were standardized using a food photo album of local foods and local household measurement, which was then converted to a standardized serving size. A trained interviewer asked each respondent on the frequency of consumption of each food item (intake either per day, per week, per month of per year) and the number of servings each time the food was consumed based on his or her habitual intake during the last one year. The standardized serving size measured as cooked or ready for consumption is then converted to average consumption per year using the following formula: - Amount of food (g) per day = frequency on intake conversion factor serving size total number of servings weight of food in one serving. The conversion factor used to estimate food intake was based on frequency of intake ). Based on the food items, a food list was prepared based on the following criteria:- Aflatoxins are only present in certain types of food products. This has been widely documented, and it was therefore deem unnecessary to analyse aflatoxins in all the foods in the food consumption list. Selection of the type of food in the food list to be analysed for aflatoxins was based on bibliographical sources and experiences in routine analysis of raw and processed products ). Taking into consideration variabilities in contaminants as a result of production and processing, the selected food list was split into two food categories as described in the New Zealand Total Diet Study ) : - national food (N), since these were processed foods (made in one or two places and distributed widely) and likely to contain homogenous levels of contamination with respect to their production and/or processing methods. regional food (R), since these were processed and distributed only at the region or these were unprocessed and untransformed and therefore might contain heterogenous levels of contamination resulting from production and/or preparation method specific to the region. Based on the above criteria, a food list consisting of foods was derived, out of which foods were categorized as national and foods categorized as regional food (Table ). Sampling/purchase of samples Based on the food list, food samples were collected to represent the food supply and encompass all geographical areas in Malaysia, which include regions (North, Central, South, East, Sabah and Sarawak) with each region having sampling points (Figure ). Purchase of samples was only carried out once over a period of months as there is no seasonal variation in Malaysia. Sampling was performed at retail markets (wet markets, sundry shops, supermarkets and hypermarkets) to ensure that the sampled products represent the foods available to the public. To ensure consistency in the samples collection procedure, the types of food item to be sampled, the number of sub-samples, weight and location of sampling is clearly defined in a standard food purchasing protocol. Due

5 Vol. ( ), Table. Food List with categorization as National (N) and Regional (R) Foods Food Code Food Item N/R Cereal & Cereal Products (Group C) C Rice N C Porridge N C Glutinuous Rice N C Wheat Noodle R C Rice Noodle R C Loh Shi Fun R C Pasta N C Sago N C Bread R C Bread (bun type) R C Roti Canai R C Capati R C Tosai R C Breakfast cereal N C Instant cereals N C Pizza R C Corn R C Local traditional Cake R C Cake R C Biscuit N C Snack N Meat & Meat Products (Group M) M Chicken R Fish & Fish Products (Group F) F Fresh Water Fish R Egg & Egg Products (Group E) E Chicken Eggs R Food Code Food Item N/R Nut & Nut Products (Group N) N Pulses & Nuts R N Soybean curd R N Tempeh (Fermented Soy) R N Peanut Buttter N N Peanuts/Groundnuts R Dairy Products (Group DP) DP Fresh/UHT Milk N DP Powdered Milk N DP Evaporated Milk N DP Sweetened Condensed Milk N DP Yoghurt N DP Cheese N DP Cream Cheese N DP Ice Cream N DP Butter N Fruits & Fruit Products (Group FR) FR Dried Fruits N Drinks (Group D) D Tea N D Coffee N D Chocolate drink N D Soybean drink N D Botanical/herbal drink N Seasoning (Group S) S Thick soy sauce N S Thin soy sauce N S Chili/Tomato sauce N Total of food items, with categorized as national (N) food and categorized as regional (R) food to unavailability of information on the main brands of foods and their market share, purchases were carried out randomly at the different types of retail outlets available at the sampling site. From the foods, the foods categorized as regional foods (R), samples were collected in all regions (north, central, south, east, Sabah and Sarawak) involving all the sampling points. For each sampling point, sub-samples were collected. While the foods categorized as national food (N), samples of different brands were collected at only one sampling point from the Central region (Table ). Preparation of foods as consumed and compositing of samples Preparation of food as consumed was based on individual food composite approach rather than a food group composite approach. The individual food composite approach provided greater flexibility in the undertaking of exposure estimates, which can then be considered on either regional, age/sex or even ethnic basis, given the associated Malaysian consumption data was also obtained on this basis. This approach will also help to minimize the dilution effect inherent in the food group composite approach, whereby contaminants

6 Mycotoxins Figure Sampling Location for Dietary Intake Aflatoxins Table. Food Samples and Composites National Food Regional Food Total Number of foods Number of region Number of sampling points per region ( regions ) Number Sub-Samples/Brands No. of composites for analysis Total samples purchased/sampled,, in food consumed in small amount are mixed in proportion with other bigger proportion foods in the group and subsequently is diluted by the bigger portions in the mixture. As recommended by the GEMS/Food Total Diet Studies, distilled water was always used for sample preparation whenever needed ). For each of the regional food ( food items) listed in the food list, sub-samples were purchased from each region ( sub-samples sampling points per region), prepared as consumed, if necessary and subsequently combined into one composite samples for the region. While for national food ( food items), samples of different brands will be collected from one sampling point, prepared as consumed, if necessary and composited as individual brand (Table ). A food preparation guide is prepared to ensure consistency in the food preparation, precaution to be taken to avoid undue contamination of food from environment and utensils and adequacy of composite for analysis. The food preparation essentially can be divided into: use as it is (processed foods or raw foods that are eaten as it

7 Vol. ( ), is), prepare as on label and cooking using techniques such as boiling, blanching or pan-frying without the use of oil. The schematic for the sampling and preparation of samples is reflected in the Figure and. Validation of Test Method & Analysis of Individual Food Composite Method of analysis was validated to ensure acceptability of the test method including adequacy of its limit of detection, limit of quantification, accuracy and precision. Deterrmination of Aflatoxins B, B, G and G was by using immunoaffinity clean-up column and HPLC with post-column photochemical derivatization method. While determination of aflatoxin M was by immunoaffinity clean-up column and HPLC. Figure Schematic for Sampling and Preparation of Food Samples Categorized as National Food

8 Mycotoxins Figure Schematic for Sampling and Preparation of Food samples Categorized as Regional Foods

9 Vol. ( ), Determination of dietary intake and risk characterization The mean concentration of aflatoxins levels are used in the intake calculation, as this approach is internationally recognized as providing a satisfactory estimate of long-term exposure and is considered suitable for comparison with reference health values ). During the collation of aflatoxin contamination data on various food items, there are generally some or a proportion of analytical results reported as non-detectable or non-quantifiable and the value assigned to these samples will affect the estimated exposures. The way for dealing with such non-detectable or non-quantifiable samples in this study will be based on current approach recommended by WHO GEMS/Food ), which is widely accepted and used by international scientific committees. Dietary intake estimate will be obtained by multiplying mean food consumption data for the Malaysian adult population by the mean aflatoxin concentration in the food prepared as consumed. This estimated dietary intake will then be used to estimate Malaysian adult population risk to liver cancer based on Joint Food and Agriculture Organization/World Health Organization (FAO/WHO) Expert Committee on Food Additives (JECFA) estimate of potencies values of. cancers/year per, population per ng aflatoxin/kg body weight/day for hepatitis B surface antigen positive individuals and. cancers/year per, population per ng aflatoxin/kg body weight/day for hepatitis B surface antigen negative individuals ). A Margin of Exposure (MOE) can also be estimated, which is the ratio between a between a dose leading to tumors in experimental animals and the human intake for aflatoxin based on Benchmark Dose Level (BMDL ) of ng/kg body weight/day ),). (Note: BMDL is an estimate of the lowest dose, which is certain to cause a cancer incidence in rodents). CONCLUSION Total Diet Study (TDS) is increasingly being adopted by many countries as one of the tool in estimating the dietary exposure of their population to various contaminants and it also provide the basis for countries to defend their consumer protection regulations on the basis of scientific results obtained using this method. As such, Malaysia is no exception in committed to undertaking TDS. It is hoped that this study will be able to estimate the likelihood and severity of the adverse health effects caused by aflatoxins, i.e. incidence of liver cancer, in the adult Malaysian population. This is because aflatoxins are among the most potent mutagenic and carcinogenic substances known as extensive experimental evidence showed that aflatoxins were capable of inducing liver cancer in most test species studied and most epidemiological studies showed a correlation between exposure to aflatoxin B and increased incidence of liver cancer. REFERENCES WHO (). Guidelines for the study of dietary intake of chemical contaminants. WHO Offset Publication No.. Geneva, Switzerland. WHO (). Total Diet Studies A Recipe for Safer Food. Brochure prepared by GEMS/Food, Food Safety Department WHO. Available at en.pdf. WHO.. Beijing Declaration on Food Safety. Available at management/meetings/beijing_decl.pdf

10 Mycotoxins Ministry of Health Malaysia (). Food Consumption Statistics of Malaysia for Adult Population Aged to. Family Health Development Division and Food Safety & Quality Division, Ministry of Health Malaysia. Leblanc, J.C., Tard, A., Volatier, J.L. & Verger, P. () Estimated dietary exposure to principal food mycotoxins from the first French Total Diet Study. Food Additives and Contaminants; ( ):. Vannort, R.W., Cressey, P.J. & Silvers, K. ( ). / New Zealand Total Diet Study Part : Elements. Wellington, Ministry of Health. WHO (). GEMS/Food Total Diet Studies - Report of the rd International Workshop on Total Diet Studies. Paris, France - may FAO/WHO (). Food Consumption and Exposure Assessment of chemicals: Report of a FAO/WHO Consultation February, Geneva, Switzerland GEMS/Food-EUROS ( ). Reliable Evaluation of Low-Level Contamination of Food. Second Workshop. GEM/Food-EUROS; - May; Kulmbach, Federal Republic of Germany. Joint FAO/WHO Expert Committee on Food Additives. (). Forty-ninth Meeting of the Joint FAO/ WHO Expert Committee on Food Additives. Safety Evaluation of Certain Food Additives and Contaminants in Food: Aflatoxins. WHO Food Additives Series, (Geneva: WHO), pp.. European Food Safety Authority ( ). A Harmonised Approach for Risk Assessment of Substances Which are both Genotoxic and Carcinogenic. EFSA Journal (),. Benford, D., Leblanc, J.C. and Setzer, R.W. ( ). Application of the margin of exposure (MoE) approach to substances in food that are genotoxic and carcinogenic Example: Aflatoxin B (AFB ). Food and Chemical Toxicology S.