Showing papers in "Food & Nutrition Research in 1998"

Assessment of the validity of reported energy intakes - review and recent developments

Abstract: Studies of dietary intake are based on the assumption that the methods used are valid and provide measures of habitual intake. It is only recently that data from whole-body calorimetry and doubly-labelled water studies of energy expenditure have yielded insights into the validity and interpretation of energy intake data. In this paper we review the evidence from these and other studies that have led to researchers' current level of understanding of how best to analyse and interpret reported energy intake data. We also discuss what we consider should be the focus of future research needed to refine experimental protocols and evaluate data.

Precoded food records compared with weighed food records for measuring dietary habits in a population of Swedish adults

Abstract: In a cross-over design, 82 women and men recorded their food intake by a precoded 7-day record book (PR) including both standard portions in household measures and photographs, and a weighed 7-day record (WR), respectively. Single 24-h urine samples, for determination of nitrogen excretion, were collected for 39 subjects during the WR period. Comparing the PR to the WR method, the mean intake of some foods, as cheese, was higher, and bread and vegetables lower. For energy and nutrients, the fat energy percent (E%) was higher, and protein E%, dietary fibre, iron, thiamin, folate, carotene and a-tocopherol were all lower. Protein intake registered by the PR method was 20% lower compared to 24-h urine samples, and 11 % lower for the WR method. The results indicate that some of the standard portion sizes, used by the PR method, contributed to the observed differences in food and nutrient intakes. The subjects found it easier and less time-consuming to record their food intake with the PR than with the WR method. The time spent on processing data was reduced by 50% when using the PR method. The results of the study will be used for improvements in the design of the PR for use in large-scale dietary surveys for monitoring dietary habits.

Evaluation of a food frequency questionnaire for assessing of calcium, protein and phosphorus intakes in children and adolescents

Abstract: The aim of the study was to assess validity and reproducibility of a self-administered quantitative food frequency questionnaire (FFQ) designed to assess calcium, protein and phosphorus intakes, and to be used in a semilongitudinal study on bone mineralisation in children and adolescents. Validation study: 23 children aged 13-14 years filled in the questionnaire and kept 3-day weighed food records. Reproducibility study: 293 children aged 5-19 years completed the questionnaire twice with a half year interval. Spearman rank correlations between nutrient intake values from the questionnaire and weighed food records were 0.56-0.62 (mean 0.60). There were no significant differences in intake estimated by FFQ and weighed record for either calcium (p=0.07) or protein (p=0.61), while phosphorus intake estimated by FFQ was 10% higher than phosphorus intake estimated by weighed record (p=0.04). On average regarding calcium, protein, and phosphorus intake, 43% of the subjects were classified in the same quartile in the questionnaire and the record, and 1% in the opposite quartile. Spearman rank correlation between nutrient intake from the two questionnaires was 0.72-0.73, with no significant difference between the measurements. It is concluded that this questionnaire is able to rank children according to their intakes of calcium, protein, and phosphorus and to give a reasonable estimate of the quantity of the nutrients in groups of children.

Cognitive aspects of dietary assessment

Abstract: Imprecise dietary reports are often cited as one reason for weak or non-existent relations between diet and disease in epidemiological studies. Studies in applied cognitive psychology have contributed to the improved utility of general survey questionnaires. However, only a few studies have examined cognitive processes in diet recall, and the designs of dietary assessment instruments that may enhance recall of habitual diet. This paper briefly summarises some research on cognition in diet recall, and gives some suggestions for future research.

Dietary assessment and validity: To measure what is meant to measure

Abstract: Nutritional assessment is the interpretation of information obtained from dietary, biochemical, anthropometric and clinical studies. In individuals, qualitative or quantitative food consumption data may be collected by food frequency questionnaires or interviews (retrospective methods), by use of food records (prospective methods); weighed food record, estimated food record or menu record, or by observations. Nutrient values derived from food composition data or direct chemical analysis represent the maximum available to the body and not the amount actually absorbed and utilized. The design of the study is crucial and the methods for carrying it out are aimed at minimizing bias to improve internal and external validity. This paper will focus on factors of importance to improve the internal validity of dietary assessment studies; selection of method; data collection, assessment of nutrient intakes from food consumption data and evaluation of data.

Dietary assessments: how to validate primary data before conclusions can be drawn

Abstract: Dietary assessment methods result almost without exception in an underestimation of energy intake. Energy turnover should consequently be evaluated on the basis of studies of energy expenditure and only with exceptions on determinations of energy intake. An objective and reliable reference to validate whether obtained data from dietary assessment may be realistic or represent an underevaluation can be based on a comparison between the observed or registered energy intake and the theoretical calculations of energy turnover based on calculated BMR with the addition of a relevant PAL factor, which is based on the lifestyle including physical activity. It is not scientifically relevant to draw any conclusions regarding the relationship between the dietary intake of various nutrients and health in a long-term perspective if energy needs are not met by dietary intake according to this assessment, nota hene if body weight is maintained.

Fatty acids in serum lipid fractions as indicators of fat intake in 5-year-old children in the STRIP project

Abstract: The objective of the present study was to investigate the association between dietary fat composition and the proportion of fatty acids in serum lipid fractions as biomarkers of previous dietary fat quality in 5-year-old children. Using 4-consecutive-day food records, the food consumption of half (n=50) of a group of randomly selected children who are participating in a prospective randomized coronary risk factor intervention project (STRIP; n=1062 at recruitment at 7 months of age) was estimated immediately prior to a blood sampling for analysis of fatty acids in serum lipid fractions, whereas in the other half of the group (n=52), food consumption was measured 5 to 15 days before the sampling. Nutrient intakes were analyzed using the Micro-Nutrica program. The fatty acid composition of serum triglycerides (TG), cholesterol esters (CE) and phospholipids (PL) was analyzed using gas chromatography. When intake was recorded immediately prior to measurement of serum fatty acids, SAFA intake was significantly correlated to TG-SAFA, but did not correlate with CE-SAFA or PLSAFA. PUFA intake was significantly correlated to serum TG-PUFA and CE-PUFA. When intake had been recorded 5 to 15 days prior to measurement of serum fatty acids, SAFA intake was significantly correlated to TG-SAFA. Significant correlation was also obtained between dietary and serum PUFA in serum TG fraction. The correlations between MUFA intake and serum MUFA concentrations were always poor irrespective of when intake had been recorded. In conclusion, serum TG-SAFAs reflect short-term SAFA intake and serum TG-PUFAS reflect short-term PUFA intake in 5-year-old children.

Food pollutants and child health with special reference to the situation in the Aral Sea region in Kazakhstan

Abstract: Despite all progress in child health during this century, a number of hazards, which also may cause severe consequences in adult life, still remain. Thus, it has become obvious that environmental pollutants, which are found in various food products and drinking water, constitute a severe threat to human health and particularly for young children. Among such compounds, different organochlorins, such as pesticides for the control of parasites (DDTs, HCHs), and products of industry and agriculture such as dioxins and dioxin-like compounds (PCBs) are much discussed, as well as organic mercury and heavy metals (lead and cadmium). Consequences of acute intoxications with PCB have been documented in Japan following the ingestion of rice oil contaminated by PCBs. In Sweden birth weight has been found to be reduced and perinatal mortality rate higher than expected in regions with high consumption of fat fish and in that children who have been exposed to PCBs in utero have retarded cognitive development. From the Aral Sea basin in Central Asia it has been reported that the population has been subjected to a long-term exposure to various organochlorins which in very large quantities have been distributed over the cotton fields. These compounds which are resistant in nature have entered the food chain leading to humans. As a consequence, organochlorins which have accumulated during fetal life continue to do so postnatally. The concentrations may be high in human milk. Children living in the Aral Sea region have poor health with high morbidity and mortality, high rate of chronic diseases and retarded development. They are subjected to many health hazards due to poverty and environmental pollution. By proper epidemiological studies, it may be possible to obtain accurate information about the health risks of people who are exposed to environmental pollution from organochlorins, and also to device means of improving the situation.

The rice-based diet in Bangladesh in the context of food and nutrition security

Abstract: The rice-based diet in Bangladesh in the context of food and nutrition security Bangladesh is experiencing a situation with both food and nutrition insecurity. Bangladesh has developed a national plan of action within the food and nutrition area following the international plans of action. Examples of different ongoing programmes and projects related to food and nutrition security are described, including a more detailed description of the authors's own research activities. Research components pertinent to the Bangladesh rice-based diet comprise dietary surveys in rural Bangladesh in villages with different production patterns, perception studies of the commonly consumed foods, studies of the nutritional quality of the most important foods (rice, fish and vegetables) and bioavailability studies of starch from rice and calcium from small indigenous fish. Results are presented along with needs for future research.

Dietary investigations - what are the effects of invalid selection procedures and measurement errors?

Abstract: In observational studies where average levels or percentiles in a population distribution of nutritional components are to be assessed it is essential that the participating subjects are representative of the population to which the results are to be generalised. The optimum way of achieving this is by random selection from the target population in which all members have equal probability (or at least a known probability) of being chosen and also that all selected subjects participate in the study. The effects of selection bias and non-response can be large and are in general difficult to estimate. In the presentation of results it should always be stated how selection bias and non-response could have influenced the results. In this paper a general selection procedure and certain problems with it is presented. A method for correction of nonresponse bias is also presented. The effect of measurement errors on correlation coefficients between nutritional components or between a nutritional component and other variables is discussed.