No abstract

The reproducibility of food intake data from elderly men in the Zutphen Study (Zutphen, The Netherlands) was investigated in repeated dietary surveys carried out three (n = 115) and 12 (n = 145) months after the initial survey (April 1985). The differences in the reproducibility estimations for the two different time periods were generally small. The ratios of the interindividual and intraindividual variance were large for carbohydrates (2.6 and 2.7 for three months and 12 months, respectively) and small for vitamin A (1.1 and 0.4 for three months and 12 months, respectively). The larger this ratio, the higher the probability of detecting an existing relation. Information about inter- and intraindividual variation was used to calculate the attenuation factor. For most nutrients, the attenuation factor was about 0.8. This implies that a simple correlation between a nutrient and a risk factor will be only slightly lowered because of measurement error and the temporal variability of the dietary measurement when the cross-check dietary history method is applied once (e.g., a "real" correlation of 0.40 would be expected to be lowered to 0.32).

Within the Zutphen Study dietary surveys using the cross-check dietary history method were carried out in 1960, 1965, 1970, and 1985. Of the 872 men aged 40-59 y examined in 1960, 315 participated in all four surveys. In 1985 a small random sample of 51 men aged 40-59 y was also investigated. Between 1960 and 1985 the consumption of bread, potatoes, and edible fats decreased and the consumption of fruits, pastries, nuts, and alcoholic beverages increased in both the aging cohort and in the two independent samples of middle-aged men examined 25 y apart. These changes were accompanied by a substantial decrease in the intake of monounsaturated fat, polysaccharides, and potassium and a substantial increase in animal protein and alcohol. Small changes were observed in the intake of saturated fatty acids, polyunsaturated fatty acids, dietary cholesterol, and dietary fiber. Since 1960 some changes in a nutritionally desirable direction were observed but the diet of the Zutphen men in 1985 departs substantially from the guidelines for a healthy diet formulated by The Netherlands Nutrition Council in 1986.

In the Leiden Pre-School Children Study the 24-hour recall method was used to determine the energy and nutrient intake of children from four to 28 months. A validation study was carried out in order to get insight into the validity of the collected dietary data. In the first part of the study the validity of the Dutch food table, supplemented with data on commercial babyfoods, was tested. The calculated average energy and nutrient intake of 111 six-month-old non-breastfed infants was compared with the results of chemical analysis of an equivalent composite corresponding with the average food intake of these children. With the exception of calcium and phosphorus the difference between the calculated and analysed values was less than 5%. Secondly the 24-hour recall was validated against the duplicate portion technique among 41 six-month-old non-breastfed infants. With the exception of sodium and iron, energy and nutrient intake data calculated from the 24-hour recall were significantly higher than those obtained after chemical analysis of the duplicate portions. However, on a relative level the results of the 24-hour recall and the duplicate portion technique corresponded very well. These results suggest that for infants a systematic difference exists between both methods.

To study the impact of dietary intervention on the plasma total and high density lipoprotein cholesterol (HDL cholesterol) levels in hypercholesterolemic men, the authors selected 80 male participants in a monitoring risk factor project carried out in Amsterdam, The Netherlands. These men had plasma total cholesterol levels of between 6.5 and 10.0 mmol/liter (between 251 and 387 mg/dl) and were randomly assigned to either the intervention (n = 39) or the control (n = 41) group. At the start of the intervention period, after 5 weeks, and after 26 weeks, both the intervention and the control groups were examined. This examination consisted of a measurement of height, weight, plasma total and HDL cholesterol, and a dietary interview. The intervention program consisted of a personalized dietary advice to the respondent, based on the report of the Netherlands Nutrition Council. The study took place between September 1987 and November 1988. Because of this intervention program, the plasma total and HDL cholesterol levels decreased. The difference in change in plasma total cholesterol between the intervention and control groups was 0.47 mmol/liter (18 mg/dl) after 5 weeks and 0.30 mmol/liter (12 mg/dl) after 26 weeks. For HDL cholesterol, a significant difference in change after 5 weeks disappeared after 26 weeks. The public health implications of the decrease in plasma total cholesterol are discussed.