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Table 3 Diet-related environmental impact according to the food frequency questionnaire (FFQ) and two replicates of the 24-h recall (24hR, with intra-class correlation coefficient) and group level bias, with correlation between the methods (crude, adjusted, de-attenuated) and attenuation coefficient (crude, adjusted)a for observed and energy-adjusted values standardised to a 2000 kcal diet

From: FFQ versus repeated 24-h recalls for estimating diet-related environmental impact

  FFQ 2 replicates of 24hR Correlation coefficient (24hR with FFQ) Attenuation coefficient λ1
Dietary variables Mean (SD) Mean (SD) ICC %bias Crude (95%CI) Adjustedb(95%CI) De-attenuated (95%CI) Crude (SE) Adjustedb (SE)
Observed values
 Energy, kcal/d 2139 (532) 2012 (583) 0.31 6.3 0.47 (0.43; 0.52) 0.38 (0.33; 0.43) 0.68 (0.59; 0.77) 0.52 (0.03) 0.42 (0.03)
 Protein, g/d 77.6 (18.5) 78.2 (23.5) 0.27 −0.8 0.46 (0.41; 0.50) 0.39 (0.34; 0.44) 0.75 (0.65; 0.84) 0.58 (0.03) 0.51 (0.04)
 GHGE, kgCO2e/d 3.50 (0.87) 3.64 (1.46) 0.21 −3.8 0.35 (0.30; 0.40) 0.30 (0.25; 0.35) 0.66 (0.54; 0.77) 0.59 (0.05) 0.53 (0.05)
 FE, MJ/d 30.19 (6.71) 31.10 (9.20) 0.28 −2.9 0.45 (0.40; 0.49) 0.40 (0.35;0.44) 0.75 (0.66; 0.84) 0.62 (0.04) 0.57 (0.04)
 LU, m2*year/d 4.01 (1.08) 4.15 (1.82) 0.17 −3.4 0.37 (0.32; 0.42) 0.31 (0.26; 0.36) 0.75 (0.62; 0.87) 0.63 (0.05) 0.56 (0.05)
 pReCiPe 0.41 (0.10) 0.43 (0.16) 0.19 −4.7 0.39 (0.34; 0.43) 0.33 (0.28; 0.38) 0.76 (0.64; 0.87) 0.62 (0.04) 0.56 (0.05)
Energy-adjusted values by regression residuals of observed values on energy (observed residuals)
 Protein, g/d 73.5 (10.3) 77.9 (14.2) 0.20 −5.6 0.35 (0.30; 0.40) 0.33 (0.28; 0.38) 0.75 (0.63; 0.86) 0.49 (0.04) 0.46 (0.04)
 GHGE, kgCO2e/d 3.33 (0.61) 3.63 (1.24) 0.12 −8.3 0.26 (0.20; 0.31) 0.23 (0.17; 0.28) 0.66 (0.50; 0.81) 0.52 (0.06) 0.48 (0.06)
 FE, MJ/d 28.82 (4.21) 30.98 (6.77) 0.22 −7.0 0.39 (0.34; 0.43) 0.35 (0.30; 0.40) 0.76 (0.65; 0.86) 0.62 (0.04) 0.59 (0.05)
 LU, m2*year/d 3.80 (0.71) 4.14 (1.56) 0.13 −8.2 0.30 (0.24; 0.35) 0.27 (0.21; 0.32) 0.73 (0.58; 0.88) 0.65 (0.06) 0.60 (0.06)
 pReCiPe, 0.39 (0.07) 0.43 (0.14) 0.14 −9.3 0.30 (0.24; 0.35) 0.26 (0.21; 0.32) 0.71 (0.57; 0.85) 0.61 (0.06) 0.56 (0.06)
Energy-adjusted values by regression residuals of densities on energy (density residuals)
 Protein density, % 14.9 (2.0) 15.9 (3.1) 0.20 −6.3 0.37 (0.31; 0.41) 0.35 (0.29; 0.40) 0.78 (0.66; 0.89) 0.57 (0.04) 0.54 (0.04)
 GHGEdensity,kgCO2e/d 3.38 (0.60) 3.73 (1.30) 0.19 −9.4 0.28 (0.23; 0.33) 0.25 (0.20; 0.30) 0.59 (0.46; 0.71) 0.61 (0.06) 0.57 (0.06)
 FE density, MJ/d 29.31 (4.09) 32.14 (7.62) 0.30 −8.8 0.39 (0.34; 0.44) 0.36 (0.31; 0.41) 0.66 (0.56; 0.74) 0.73 (0.05) 0.69 (0.05)
 LU density, m2*year/d 3.83 (0.70) 4.24 (1.72) 0.21 −9.7 0.30 (0.24; 0.35) 0.27 (0.21; 0.32) 0.59 (0.47; 0.71) 0.73 (0.07) 0.67 (0.07)
 pReCiPe density 0.40 (0.06) 0.44 (0.15) 0.22 −9.1 0.31 (0.26; 0.36) 0.28 (0.22; 0.33) 0.59 (0.48; 0.71) 0.70 (0.06) 0.65 (0.07)
  1. ICC, intra class correlation coefficient; GHGE, greenhouse gas emissions; FE, fossil energy use; LU, land use; pReCiPe, a weighted summary score for GHGE, FE, and LU; % bias, group-level bias calculated as (mean intake FFQ /mean intake 24hR)×100; 100; correlation coefficient (95%CI) estimated as the Pearson correlation coefficient; de-attenuated correlation coefficient (95%CI) estimated as the Pearson correlation coefficient/√ICC24hR; Attenuation coefficient λ1 (SE) estimated as the slope in the linear regression of the 24hR on the FFQ using linear mixed models to account for within-person day-to-day variability
  2. aMean values with their standard deviations, correlation coefficient with its 95% confidence intervals, attenuation coefficient with its standard error
  3. bAdjusted for age, gender and BMI