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Table 3 Validity correlations between the webFFQ and FR estimates of nutrients and soy isoflavones, before and after energy adjustment (n = 55 adolescents)

From: Evaluation of the relative validity of a Web-based food frequency questionnaire used to assess Soy Isoflavones and nutrient intake in adolescents

Nutrient Without energy adjustment With energy adjustment
Crude r† Corrected r BCa 95 % CIa Crude r Sw2a Sb2a Corrected r BCa 95 % CI
Energy, kcal 0.32 0.37 (0.04, 0.62)      
Total isoflavones, mg 0.58 0.65 (0.44, 0.80) 0.59 1.272 0.753 0.67 (0.44, 0.81)
 Daidzein, mg 0.54 0.61 (0.36, 0.77) 0.55 0.733 0.413 0.63 (0.38, 0.79)
 Genistein, mg 0.56 0.63 (0.40, 0.80) 0.56 0.881 0.491 0.64 (0.42, 0.79)
 Glycitein, mg 0.46 0.53 (0.26, 0.73) 0.48 0.193 0.099 0.56 (0.27, 0.74)
Fat, g 0.33 0.39 (0.12, 0.66) 0.59 0.060 0.026 0.69 (0.44, 0.88)
 SFA, g 0.38 0.43 (0.12, 0.69) 0.66 0.124 0.076 0.74 (0.52, 0.88)
 MUFA, g 0.32 0.40 (0.14, 0.68) 0.55 0.096 0.027 0.69 (0.34, 0.92)
 PUFA, g 0.39 0.50 (0.18, 0.79) 0.43 0.176 0.032 0.59 (0.22, 0.81)
 Trans fats, g 0.28 0.37 (−0.02, 0.80) 0.54 0.693 0.195 0.68 (0.32, 0.89)
Carbohydrates, g 0.36 0.40 (0.11, 0.63) 0.56 0.023 0.010 0.66 (0.37, 0.84)
Protein, g 0.37 0.43 (0.18, 0.62) 0.39 0.053 0.027 0.45 (0.19, 0.64)
 Animal protein, g 0.65 0.70 (0.50, 0.85) 0.77 0.452 0.550 0.82 (0.67, 0.91)
 Veg protein, g 0.59 0.65 (0.50, 0.77) 0.72 0.080 0.069 0.79 (0.64, 0.89)
Dietary fiber, g 0.49 0.53 (0.35, 0.65) 0.65 0.103 0.092 0.71 (0.49, 0.85)
Beta carotene, mcg 0.30 0.37 (0.05, 0.62) 0.44 2.127 0.484 0.57 (0.24, 0.76)
Retinol, mcg 0.25 0.28 (−0.14, 0.64) 0.36 0.937 0.529 0.41 (0.08, 0.72)
Vitamin E, mg 0.15 0.18 (−0.45, 0.65) 0.34 0.226 0.086 0.41 (0.01, 0.77)
Vitamin C, mg 0.22 0.24 (−0.05, 0.52) 0.35 0.768 0.367 0.40 (0.08, 0.65)
Folate, mcg 0.36 0.40 (0.17, 0.59) 0.32 0.139 0.070 0.38 (0.11, 0.57)
Vitamin B12, mcg 0.26 0.30 (0.05, 0.55) 0.09 0.246 0.098 0.11 (−0.26, 0.40)
Calcium, mg 0.35 0.39 (0.12, 0.59) 0.32 0.168 0.072 0.38 (0.09, 0.63)
Iron, mg 0.40 0.47 (0.23, 0.66) 0.33 0.108 0.034 0.41 (0.18, 0.60)
Zinc, mg 0.27 0.31 (−0.01, 0.55) 0.24 0.098 0.052 0.28 (0.01, 0.49)
Caffeine, mg 0.39 0.49 (0.08, 0.80) 0.44 7.505 2.346 0.54 (0.10, 0.83)
  1. webFFQ web-based food frequency questionnaire, FR food records with digital photographs, SFA saturated fatty acid, MUFA monounsaturated fatty acid, PUFA polyunsaturated fatty acid
  2. ar = Pearson’s correlation coefficient where corrected r is the value after correcting for multiple measurements in the reference methods; Sw2 = within person variance in the multiple measures on the reference method; Sb2 = between-person variance in the multiple measures on the reference method; BCa (bias-corrected and accelerated) 95 % confidence interval (CI) provides nonparametric confidence limits for the r. If interval does not include 0, the correlation is statistically significant at alpha = 0.05
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