The aim of the work within Population Nutrition Research (PNR) is to identify diet-disease relationships through the assessment of dietary intakes and health outcomes of populations.
Led by Dr Ziad Abdeen, this is achieved through the creation and maintenance of comprehensive and contemporary food composition databases, the development of innovative dietary assessment and statistical tools, and provision of guidance to collaborators on the appropriate use of dietary methodologies.
PNR specializes in dietary assessment using dietary records or recalls and the analysis of dietary data, in terms of food and nutrient intakes and dietary patterns and behaviors. PNR collaborates with other research groups to provide dietary assessment and analysis expertise for studies of all types and sizes from intervention studies to national surveys.
The work of the PNR group is summarized in the figure below, which illustrates the interface of the methodological aspects of the work and its public health significance.
1- Food Composition Databases
When conducting dietary assessment, there is a need for an up to date food composition database to translate the record of foods consumed into intake of nutrients. The basis for the nutrient content of foods in Palestine is primarily based on the USDA food composition database, modified appropriately with reference to local food composition tables, and supplemented with recipes of locally eaten mixed dishes. The Composition of Foods has an extensive list of foods, but it cannot keep up-to-date with all the products now available in the supermarket. In PNR our food composition experts are continually updating our database to incorporate many additional foods via recipe calculations and the use of manufacturers’ ingredient information. Current collaborative studies in PNR on infants and young children, require specific additions to the database to include foods eaten by these groups.
Data are available for macro and micronutrients and food constituents are added as required by new research hypotheses on the aetiology and prevention of cardiovascular, bone and other degenerative diseases. We are also disaggregating many mixed dishes to be able to calculate consumption of meat and fruit and vegetables accurately, which is important for finding out if dietary recommendations are being met.
2-Dietary assessment methodologies
PNR is continually advancing dietary assessment methods in order to obtain the most accurate information as possible from study participants. Our most common dietary assessment methodology is the estimated (unweighed) diet diary, where subject participants record food and drinks consumed over a period of several days. In recent years, we have made efforts to capture the social and cultural factors influencing food quality and quantity, and by developing food diaries where information about the socio-ecological environment of the foods consumed are recorded.
Many individuals, particularly children, find it hard to describe the food they have eaten, either in terms of content or portion size. New technologies are emerging in the field to enable photographs to be taken of the foods consumed, and in some cases, handheld devices to record information either verbally or in text. PNR has undertaken a pilot study to investigate the feasibility and usefulness of giving children digital cameras alongside their diaries to take photographs of the food items consumed. This pilot study has shown that digital photography can enhance the accuracy of the diet record by providing more detail on types and amounts of foods eaten than the diary alone.
3-Dietary analysis statistics and modelling
Traditional nutritional epidemiology relates intakes of single nutrients and foods in food groups to health outcomes. In recent years there has been a move to explore the overall diet in terms of diet the patterns of foods consumed together. Dietary pattern analysis has emerged with a number of approaches such as principal component analysis (PCA), cluster analysis, and reduced rank regression (RRR). There is also increasing interest in the way food is eaten, in terms of eating frequency, timing of eating and meal skipping, for example, in relation to health. PNR has been investigating these various approaches and establishing methods for compiling the dietary data to explore them. In longitudinal studies, tracking of dietary intakes and behaviours may also be important and a thorough investigation of tracking methods, their advantages and limitations has been undertaken. Work has also been done on developing an algorithm for available iron, taking into account food constituents that improve or limit iron absorption.
4-National Nutrition And Health Examination Survey
The National Nutrition and Health Examination Survey (NNAHES) is designed to assess the dietary habits and nutritional status of adults and children in Palestine. The survey is unique in that it provides data on dietary intake, nutritional and health status in a representative sample of the population.
The survey is carried out by a consortium comprising the following two organisations:
- Joint surveys team, Department of Public Health at Ministry of Health
The NNAHES gathers quantitative and qualitative information on the dietary habits and nutritional status of a representative sample of the Palestinian population, comprising between 4000 and 4500 individuals every ten years. Adults and children aged 5 years and above are being recruited from the West Bank and Gaza.
The survey combines computer assisted personal interviews (CAPI) and self-completion questionnaires with an examination component. All survey components are carried out in the respondent’s home.
The NNAHES interview collects data on:
- Oral health
- Dietary habits, food and nutrient intake and population trends in food consumption
- Demographic and socio-economic characteristics
- Physical activity
- General health and lifestyle
The food intake data is collected using an estimated (unweighed) food diary.
The examination component consists of anthropometric and blood pressure measurements and urine and blood collections for various laboratory tests. Clinical relevant results are reported back to the respondents themselves and/or their doctors as requested on consent to participation.
A new feature of the NNAHES is to provide feedback to respondents about their diet within 3 to 4 months of participation in the survey.
The following nutrients were selected for feedback:
- Iron mg
- Folate ug
- Non Starch Polysaccharide (NSP) g
- Fat intake as % total energy
- Saturated fat as % total energy
- Vitamin C mg
- Calcium mg
- Energy intake kcal
PNR’s role within the NNAHES
PNR is responsible for 5 different elements in the NNAHES rolling programme:
- Dietary assessment
- Blood and urine specimen logistics and analysis
- Data management and statistical analysis
A dedicated team of about 19 staff split between the 4 different areas of work support the NNAHES at HNR.
Uses of the data
- The NNAHES data are used to assess the adequacy of food and nutrient intake and nutritional status in different population groups.
- The NNAHES also provides the evidence base for dietary advice, health promotions and /or interventions in response to health targets, and for shaping new
- Ministry of Health policy in nutrition and public health.
Key Survey Objectives can be summarized as follows:
- provide information on oral health status in relation to diet and nutritional status
- provide height, weight and other measurements of body size and examine their relationship to social, dietary, biochemical and health data
- provide information on trends in food consumption, nutrient intake and nutritional status in different age groups
- describe the characteristics of individuals with intakes of specific nutrients that are above or below the national average
- provide quantitative data on the food and nutrient intake, sources of nutrients, and nutritional status of the Palestinian population
- monitor the extent to which the diets of population sub-groups vary from expert recommendations/dietary guidelines
- measure blood and urine indices (dietary biomarkers) that provide an assessment of nutritional status, and to relate these to dietary, physiological and social data
- assess physical activity levels
- provide data which will enable the calculation of likely dietary exposure to natural toxicants, contaminants, additives and other food chemicals for risk assessment.
PNR conducts additional investigations to explore the NNAHES dataset in more detail to address issues of strategic importance for our research or on behalf of our collaborators. This may include the analysis of the diet or nutritional status of specific subgroups, examining the relationship between specific nutrients or foods on health outcomes and modelling the impact of reformulation or wider dietary change on the nation’s health.
The survey data are also a resource for further analyses and the biological specimen residues can provide a valuable starting point for further research studies, linked to the survey.