NSHD: dietary data collection

In 1950, diet was assessed during the home visit using a 24-hour recall. The mother or carer of the child was asked “What did this child have for each meal yesterday” with specific reference to breakfast, dinner, tea or high tea, and last thing at night. The quantity of food consumed was not recorded.

There was a further question “Do you give this child food between meals” with a yes or no response [35]. It is likely that recorded energy intake may be lower than total energy intake if the child had taken their personal ration of 5oz of sweets per week [35].

The majority of the visits took place in summer (94%) and on a weekday (96%). Therefore, seasonally available fruit and vegetables, e.g. strawberries and lettuces, were probably consumed in greater quantity. Further details about how diet was assessed in 1950, including detailed information about rationing at that time, is outlined by Prynne et al. [35, 36].

Between 1982 and 2006-2010, dietary intake was recorded using 5-day prospective estimated food diaries.  In 1982 and 1989 the research nurse gave the participants detailed instructions on how to fill out the food diary and completed an additional 48-hour recall with them. The participant then completed the remaining five days of the food diary and returned it by post.

If the participant did not send the diary back by post in 1982, the 48-hour recalls were lost. Therefore in 1989, a copy of the 48-hour recall was left with the nurse. In 1999 and 2006-2010, only the 5-day food diary was completed by the participants.

In these food diaries, all food and drink (including alcohol) consumed both at home and away was recorded using household measures to estimate portion sizes. There were detailed guidance notes of how to describe foods and, from 1989 onwards, photographs of portion sizes provided at the beginning of the diary to assist the participant.

In the diaries there were seven spaces for each day to record meals and between-meal snacks, and a reminder section about any other snacks and space in which to write recipes. The food diary in 2006-2011 was slightly different in that it had space to record the specific time the food or drink item was consumed. The Clinic Study Pre-Assessment booklet also asked diet-related questions during the 2006-2010 follow-up.

There was no food diary collected in 2014-2015, but there were a number of diet-related questions asked during the postal questionnaire (see the table below). In the three COVID-19 sweeps (2020-2021), questions were asked about consumption of fruits and vegetables before and after the COVID-19 outbreak.