FAT INTAKE - IMPLICATIONS OF CHANGES IN DISTRIBUTION FOR SETTING DIETARY GOALS IN THE UK

Study objective - To examine (a) changes in the shape of the distribut ion of dietary fat intake as the mean dietary fat intake of the popula tion shifts and (b) implications for setting national dietary goals. D esign - Data on the percentage of energy from total fat, saturates, mo nounsaturates, polyunsaturates, and the P:S ratio were analysed for tw o dietary intervention trials and six cross sectional dietary surveys. The nutrient distributions from each study were described in terms of the mean, standard deviation (SD), coefficient of variation (CV), and skewness statistic. For the intervention trials statistical parameter s were compared for groups who received and did not receive dietary ad vice. For the cross sectional studies, statistical parameters were com pared across groups with different levels of mean fat intake. The impl ications of the results for setting dietary goals were considered usin g statistical models. Main results - For most fat fractions there was a positive association between the mean and the SD, and an inverse ass ociation between the mean and the CV, indicating that as the mean shif ts upwards the SD increases but not in proportion to the mean. This is intermediate between a constant SD and a constant CV model. For a pop ulation nutrient goal of a maximum of 15% saturates, the estimated pop ulation mean for British women would be 8.4% using the constant SD mod el and 10.8% using the constant CV model. For saturates and the P:S ra tio, a lower mean intake was associated with a greater positive skew i n the distribution of reported intakes. For saturates, this is consist ent with a group of high fat consumers who fail to reduce their intake as the population mean shifts downwards: a ''rearguard effect''. Find ings for the P:S ratio are consistent with a group of consumers who pr oduced a strong positive skew at low mean intakes, which reduced in si ze as the mean population intake increases: a ''vanguard effect''. Con clusions - These findings provide evidence that the distribution of fa t intake may change with the mean to a degree that the setting and mon itoring of nutritional goals may need to take account of changes in va riance and shape of the intake distribution.