Objective: To study the influence of the days of the week on calculated food and nutrient intake.
Study design: Daily variation in food and nutrient intake was studied by using 4-, 5- and 7-d estimated food records, all including Friday, Saturday and Sunday.
Subjects and setting: Two groups of untreated hypertensive patients (60 men and 31 women, aged 31-55 y, and 132 men and 94 women, aged 35-54 y) and a random population sample of 131 men and 139 women, aged 35-64 y, all from the City of Turku and three neighbouring municipalities in south western Finland.
Results: The intakes of meat and meat products, carbohydrate, alcohol and energy varied significantly across the week in all study groups with increased intakes of meat and meat products on Saturday and Sunday, of carbohydrate and alcohol on Friday and Saturday, and of energy on Friday, Saturday and Sunday. Food and nutrient intakes did not vary consistently with weekdays (Monday to Thursday) with the exception of alcohol intake being lowest on Monday. Macronutrient, alcohol and energy intake data calculated from the 5-d (Monday, Tuesday, Friday, Saturday and Sunday) and from 5 to 7 d converted food records were nearly equal to and correlated highly (r=0.96-0.98) with the data calculated from the 'true' 7 d records.
Conclusion: The daily variation in food and nutrient intakes should be taken into consideration when food diaries are recorded. 5-d food records including two weekdays (from Monday to Thursday) and Friday, Saturday and Sunday is recommended.
Sponsorship: Social Insurance Institution of Finland.