Differences in reported winter and summer dietary intakes in young adults in Spain.

Representative data of usual food consumption are necessary in order to establish accurate conclusions on the relationship between diet and disease. In most studies data are collected at one particular time of the year. The aim of this study was to determine the influence of season of the year on dietary intake estimates. Three hundred and three people aged 19-40 years from northwest Spain recorded their intake twice (in winter and summer) using the seven non-consecutive-day dietary record method. A total of 247 foods (arranged into 16 major food groups) and 27 nutrients were determined. Most fruits and vegetables, as well as some milk products showed significant seasonal differences. Daily total food consumption amount (g) was higher in winter than summer in males. Higher average intakes of energy (men) and a large number of nutrients (both sexes) were observed in winter. This seasonal influence on dietary intake estimates implies significant differences in fractions of Spanish recommendations covered (lower in summer) for energy (men) and most nutrients (both sexes). As expressed in amount/MJ (densities), most nutrients showed higher values in winter in women. Data in our study suggest that the substantial variations of nutrient intakes throughout the course of the year mainly depend on food (energy) amount variations (quantitative diet changes) in males, while changes in densities of nutrients (qualitative diet changes) are mainly responsible for dietary variations in females. Results in the present study suggest that considering the season of the year it will enhance the results of dietary surveys and ensure the accuracy of studies that link diet with disease.