NSHD: key findings

The participants of NSHD lived through a time of post-war austerity in their early years which directly affected their dietary intake.

By 1950, the number of foods available was still in short supply. More information about rationing during this period in relation to NSHD has been discussed by Prynne et al. [35, 36].

Three studies examined the diet of NSHD participants in 1950 [35, 36, 45]. In comparison to children in the 1990s, children in 1950 ate a more homogenous diet which contained more bread and vegetables but less sugar and soft drinks [35]. Their diets were higher in fibre and vitamin K but also higher in fat compared to children in the 1990s [35, 45].

Food sources of major nutrients were also different. For example, in 1950, iron came from red meat, but in 1992 it mainly came from fortified breakfast cereals [35]. Rationing was designed to reduce inequalities in food intake, but despite this, there was some evidence of small social and regional differences remaining [36].

Consumption of fruit and vegetables, which were not rationed, was higher among children whose father was classified as being in a non-manual occupational social class compared with manual social class.

Some rationed foods (bacon, orange juice and tea) were also associated with social class, but meat and spreading fats were not. Children in Scotland tended to have a lower energy intake and vitamin K than other regions and retained traditional Scottish diets such as porridge and soups [36, 45].

At 36 years, higher educational attainment was associated with better dietary habits, but in women, this was also associated with higher intakes of fat and alcohol [39]. Disadvantaged social class and low educational attainment were associated with the worst dietary habits [39].

In the 17-year period between 36 and 53 years, there were changes in key nutrient intakes [46]. For example, fat, sodium and iron intakes have fallen while calcium, carotene, folic acid, vitamin C and fibre intakes have increased [46, 47]. Total haem and non-haem iron rose from 36 until 43 years then decreased at 53 years [48]. There was a decline in haem iron from beef with an increase in that from poultry, possibly reflecting the bovine spongiform encephalopathy (BSE) outbreak from 1990 [48, 49].

Similarly, over a 30-year period between 36 and 60-64 years, white bread was replaced by granary and wholemeal bread, while there was a reduction in the consumption of red and processed meats and an increase in the consumption of vegetables [44]. These changes could be due to ageing, cohort effects or a response to government dietary recommendations and greater availability of foods such as wholegrain bread in the UK.

Five distinct dietary patterns (DPs) were identified using factor analysis on the 48-hour recall at 43 years:

• “health aware”
• “dinner party”
• “traditional”
• “refined”
• “sandwich” [50].

Social class in childhood was associated with the DPs at 43 years, however, social mobility also had an impact. For example, participants who made the transition from manual to non-manual social class partly adopted the “health aware” and “dinner party” DPs of the non-manual SEP [50]. Change in other DPs between 43 and 53 years were also observed [51].

Three DPs among women (“fruit, vegetable and dairy”; “ethnic foods and alcohol”; “meat, potatoes and sweet foods”) and two in men (‘”ethnic foods and alcohol”; “mixed”) were identified from factor analysis of 126 food groups at 43 and 53 years [51]. There was an increase in adherence to the DPs over time with only the “meat, potatoes and sweet foods” DP in women showing a decline.

The dietary diary data at 43 years was used to develop an index to discriminate healthy and unhealthy foods; the Eating Choice Index (ECI) [52]. The index consists of information about breakfast and fruit consumption and type of bread and milk.

Higher scores on the ECI are positively associated with protein, carbohydrate, fibre, vitamin C, iron, calcium and folate and negatively associated with fat. Participants with a lower ECI were also more likely to be in a lower social class, obese and less active [52].

Since diet diaries were used to collect the dietary data, NSHD provides a unique opportunity to examine a new discipline termed “chrononutrition” which investigates the timing and regularity of food intake [53-57].

Results from these studies have found that the proportion of energy and macronutrients consumed at lunch declined between 36 and 53 years, with greater intakes occurring in mid-afternoon [55]. There was an association between increasing carbohydrate intake in the morning while simultaneously reducing fat intake at 43 years with metabolic syndrome [53] and diabetes [54] at 53 years.

Irregular energy intakes at and between meals decreased with increasing age between 36 and 53 years [57]. There was a cross-sectional and longitudinal association between meal irregularity and cardio-metabolic risk [56, 57].