Assessing dietary intake and its relation to growth in British children.

Attempts to relate the quality of diet to growth in British children are plagued by two persistent anomalies. In the first, workers have found no consistent relationship between individual intake and growth. The biggest eaters are not necessarily the biggest individuals. As Widdowson said in 1947, ‘the present study has been unable to bring to light the laws which relate the height, weight, size and surface area of any one person to his calorie intake or calorie requirement’. We are still very much in the dark. The second anomaly relates to groups of individuals from different social classes. The average energy and nutrient intakes amongst children from the manual social classes (111 manual, IV and V) tends to be higher than that of children from non-manual classes (I, I1 and 111 non-manual) (Widdowson, 1947; Bransby & Fothergill, 1954; Department of Health and Social Security, 1975; A. E. Black, unpublished results), while at the same time manual workers’ children are on average shorter than non-manual workers’ children (Durnin et al. 1974; Department of Health and Social Security, 1975; A. M. Thomson, unpublished results). It is this second anomaly that I wish to try and resolve. Briefly, the limited information available in Britain suggests that the quality of the social and physical environment mediates the effectiveness of diet in promoting growth and health. The use of a common standard (e.g. the recommended dietary intake; RDI) to assess dietary adequacy in different environments does not take into account these differences in dietary effectiveness. By dividing the population into two subgroups using a suitable parameter of environmental quality (e.g. social class), and by assessing diet and growth in these two groups independently, the second anomaly can be resolved, as we shall see. First we must consider how diet and growth are best assessed.