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Food Frequency Questionnaires: Not Irrelevant Yet

Department of Health Sciences Research, Mayo Clinic College of Medicine, Rochester, Minnesota

To the Editors: Kristal et al. (1) contend that the food frequency questionnaire (FFQ) be abandoned in epidemiologic studies of cancer for three reasons: (a) a growing lack of consistency within and across studies of diet and cancer risk; (b) poor correlations between the FFQ's measure of protein and total energy with urinary nitrogen excretion and doubly labeled water, respectively; and (c) one published account of a significant association of dietary fat with breast cancer risk when assessed by diet records collected from participants on seven consecutive days but not when assessed by an FFQ. One could reasonably counter the authors' arguments.

First, the difficulty in estimating dietary factors and cancer risk with consistency is due foremost to our poor understanding of the pathophysiology of this heterogeneous disease. The relevant window of exposure during which dietary factors exert their effects likely occurs decades before clinical onset: our inability to characterize this window, rather than our inability to measure diet accurately with an FFQ, is our Achilles heel. Indeed, characterizing this relevant window is the basis of several recent investigations that focus on early life (2) and in utero (3, 4) exposures. In contrast, effect estimates from studies of diet and coronary heart disease, a better elucidated pathophysiology, have been consistent when diet was assessed by a FFQ. A case in point is for the exposure, trans fat, which has now been assigned permanent residence status on food labels in the United States. Second, biomarkers, such as RBC and plasma folate concentrations, showed acceptable correlations when compared against total folate intake assessed by an FFQ: 0.55 (5) and 0.63 (6), respectively. These correlation coefficients are reasonable given that the peripheral circulation is an inadequate proxy for biologically relevant tissue levels, and that other metabolic factors, and not just dietary intake, influence the circulatory level of these nutrients. Last, consecutive days of dietary recording may result in decreased within-person variation in nutrient intake from highly correlated food intake on these days (7). The effect would be an exaggerated between-person variation in intake, which may explain the statistically significant association with breast cancer observed by the authors when diet was assessed with diet records (8).

The authors conclude "we should be very circumspect about the analyses of current studies that have used FFQs for dietary assessments". This places the authors' own recent publications (9, 10) that used FFQs in very good company.

	References

Top References

 

1. Kristal AR, Peters U, Potter JD. Is it time to abandon the food frequency questionnaire? Cancer Epidemiol Biomarkers Prev 2005;14:2826–8.[Free Full Text]
2. Elias SG, Peeters PH, Grobbee DE, van Noord PA. Breast cancer risk after caloric restriction during the 1944–1945 Dutch famine. J Natl Cancer Inst 2004;96:539–46.[Abstract/Free Full Text]
3. Bunin RG, Kushi LH, Gallagher PR, Rorke-Adams LB, McBride ML, Cnaan A. Maternal diet during pregnancy and its association with medulloblastoma in children: a children's oncology group study (United States). Cancer Causes Control 2005;16:877–91.[CrossRef][Medline]
4. Cerhan JR, Sellers TA, Janney CA, Pankratz VS, Brandt KR, Vachon CM. Prenatal and perinatal correlates of adult mammographic breast density. Cancer Epidemiol Biomarkers Prev 2005;14:1502–8.[Abstract/Free Full Text]
5. Giovannucci E, Stampfer MJ, Colditz GA, et al. Folate, methionine, and alcohol intake and risk of colorectal adenoma. J Natl Cancer Inst 1993;85:875–84.[Abstract/Free Full Text]
6. Selhub J, Jacques PF, Wilson PW, Rush D, Rosenberg IH. Vitamin status and intake as primary determinants of homocysteinemia in an elderly population. JAMA 1993;270:2693–8.[Abstract/Free Full Text]
7. Willett WC. Nutritional epidemiology. 2nd ed. New York (NY): Oxford University Press; 1998.
8. Bingham SA, Luben R, Welch A, Wareham N, Khaw KT, Day N. Are imprecise methods obscuring a relation between fat and breast cancer? Lancet 2003;362:212–4.[CrossRef][Medline]
9. Slattery ML, Sweeney C, Murtaugh M, et al. Associations between vitamin D, vitamin D receptor gene and the androgen receptor gene with colon and rectal cancer. Int J Cancer 2006;118:3140–6.[CrossRef][Medline]
10. Kristal AR, Chi C, Tangen CM, Goodman PJ, Etzioni R, Thompson IM. Associations of demographic and lifestyle characteristics with prostate-specific antigen (PSA) concentration and rate of PSA increase. Cancer 2006;106:320–8.[Medline]

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