The Malmö Food Study: the relative validity of a modified diet history method and an extensive food frequency questionnaire for measuring food intake.
OBJECTIVE
To assess the relative validity of two diet assessment methods, an extensive quantitative food frequency questionnaire (method A) and a novel shorter quantitative food frequency questionnaire with a 14 day food record (method B).


METHODS
A randomized prospective cohort study.


METHODS
General community.


METHODS
206 residents of the town of Malmö, aged between 50-69 years, 101 men and 105 women who completed the methods during one year.


METHODS
Both diet methods were designed to cover the whole diet and portion sizes were estimated using a booklet with 120 photographs; method A comprised 250 items and method B combined a two-week food record measuring lunch and dinner meals and a shorter 130 item quantitative food frequency questionnaire for average consumption of foods, snacks and beverages during the past year. An 18 day dietary record comprising six 3-day weighed records evenly distributed over one year served as a reference method.


RESULTS
Pearson's correlation coefficients varied from 0.25 for fat intake to 0.84 for milk products for method A and from 0.32 for fish to 0.88 for meat for method B. Correlations for most food groups ranged between 0.50-0.80, and were higher for method B. Only small changes were noted after adjustment for energy intake. On average for most food groups categorization of subjects into quartiles, 55% of subjects belonging to the lowest quartile, and 57-59% of those belonging to the highest quartile for method A and B were correctly classified.


CONCLUSIONS
A combined food record with a quantitative food frequency questionnaire is a better tool for food assessment than an extensive food frequency questionnaire.
Elmståhl
S
S
Department of Community Medicine, Lund University, Malmö, Sweden.
Riboli
E
E
Lindgärde
F
F
Gullberg
B
B
Saracci
R
R
D000368:Aged; D018592:Cross-Over Studies; D004032:Diet; D015930:Diet Records; D004034:Diet Surveys; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D013548:Sweden