Abstract
A diet questionnaire (DQ) designed to assess habitual diet and phyto-oestrogen intake was developed. This study aimed to examine the validity of the DQ in men, with and without having prostate cancer. The DQ was validated against alkylresorcinol metabolites measured in urine as objective biomarkers of whole grain wheat and rye (WG) intake, and a 4-d estimated food record (FR) was used for relative comparison. Participants (n 61) completed both methods and provided spot urine samples. We found a statistically significant correlation between the DQ and FR for reported whole grain intake and isoflavonoids, as well as for intake of macronutrients, except protein. The correlation coefficient between the two methods was on average r 0·30, lowest for lignans (r -0·11) and highest for alcohol (r 0·65). Reported energy intake was lower in the DQ compared with FR (8523 v. 9249 kJ (2037 v. 2211kcal), respectively; P=0·014). Bland-Altman plots showed an acceptable agreement; most cases were within the limits (95% CI) of agreement on reported energy intake, as well as intake of macronutrients, except protein (which was underestimated in the DQ compared with the FR). The correlation of alkylresorcinol with WG intake was statistically significant in the DQ (r 0·31, P=0·015), but not in the FR (r 0·18, P=0·12) and the weighted κ was 0·29 and 0·11, respectively. In conclusion, the results showed that the DQ have a reasonable validity for measuring WG intake and most nutrients, and, after some adjustments regarding protein intake assessment have been made, the DQ will be a promising tool.
Highlights
A diet questionnaire (DQ) designed to assess habitual diet and phyto-oestrogen intake was developed
Based on a previously developed and validated paper-based DQ that has been used in several studies, for example, the Swedish Obese Study and the Cancer of the Prostate in Sweden (CAPS) study[12,13], we further developed the questions regarding food intake
Reported energy intake was lower measured by the DQ compared with food record (FR) (8523 v. 9249 kJ/d (2037 v. 2211 kcal/d); P = 0·014, respectively)
Summary
A diet questionnaire (DQ) designed to assess habitual diet and phyto-oestrogen intake was developed. Since phyto-oestrogens are structurally similar to female sex hormones and bind to ER-β with high affinity, phyto-oestrogens and ER-β should be able to interact during the development of cancer[10,11] This association needs to be further investigated in order to draw any conclusions on the effect of phyto-oestrogen intake and the progress of prostate cancer. To meet the demand of convenient and updated tools for assessing dietary intake in large-scale studies, we developed a new web-based diet questionnaire (DQ) based on two previously validated paper-based questionnaires[12,13]. This study aimed to examine the validity of the questionnaire against a reference method (a 4-d diet record), in elderly men with and without prostate cancer. To ensure that the questions in the DQ were correctly understood, a ‘face-to-face’ validation was conducted with the first ten study participants
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