ALSPAC: estimation of nutrient intake

Food Frequency Questionnaires

Estimated nutrient intake from the FFQs were calculated by multiplying the weekly frequency of consumption of each food item by the nutrient content (from McCance and Widdowson’s ‘The Composition of Food’s’ and it’s supplement reports) of a standard portion of that food item [26] and summing for all food/drinks in the questionnaire.

Portion sizes were allocated according to the age of the participants. For children, there was no differentiation between boys and girls; however for adults the portions were larger for men than women [94].

Using information from the diet diaries collected when the children were 3.5 years old, Bristol-based nutritionists refined the proportion of individual foods to use when estimating the nutrient intake of each food group [94]. They also contacted schools to obtain copies of menus and serving sizes [94].

Diet diaries

At each age from 18 months, the diet diaries were coded using DIDO as described in the NSHD section of this guide [37].

Where appropriate, portion sizes were based on average portion sizes for children from previously published data [99-101] or based on manufacturers’ information or by adapting adult portion sizes [26].

Once coded using DIDO, it is possible to categorise foods based on their industrial food processing and calculate the consumption of processed and ultra-processed foods (UPFs), as in Chang et al [102] and Handakas et al [102, 103].   

Estimates of average nutrient, energy, and food group intake were calculated from the diet diaries collected during Children in Focus (10% subsample) clinic visits at ages 4 months, 8 months, 18 months and 3.5 years and 5– years. 

Estimated nutrient and energy intake were calculated from diet diaries collected during the Focus @ clinics (full sample) at age 7– years and 10– years.