Diet revealed?: Semiparametric estimation of nutrient intake age relationships

Smoothed estimates of the complex relationships between age and intakes of energy, fat, calcium and vitamin C are obtained for Males and females from British National Food Survey data covering the period 1974-94. Since the data record household food acquisitions during a survey week, not food consumption by individuals, a model is constructed in which average nutrient intakes by sex at each completed year of age are parameters which are estimated by roughness penalized least squares. Income per head and region of residence are controlled for in a non-linear extension of the model. The sensitivity of the estimates to variations in eating out and the incidence of visitors is examined. Age-and sex-specific estimates of the proportion of energy from fat, a key health indicator, are derived and compared across a 21-year period.