Research by the University of Reading has found that couples with children have a poorer diet than those without. On average, statistics showed that childless couples ate 2kg more fruit and vegetables than families over a fortnight. The results formed part of a study that looked at the uneven distribution of unhealthy diets in the population. It also showed that regional variation in the demand for fruit and vegetables is pronounced, with the highest demand in London and the South East and the lowest in Scotland and Northern Ireland.
Professor Richard Tiffin, Director of the Centre for Food Security at the University, said: “There are clear distributional implications for dietary health that arise from these patterns of consumption and also for the health of children. They suggest that targeted interventions are necessary in order to reduce the incidence of diet-related health problems in the future.” The study revealed that the presence of children in a household leads to a lower level of demand for fruit and vegetables and meat, and an increased demand for milk and dairy, cereals and potatoes.
The results also emphasised the role played by low incomes and socio-economic circumstances in poor dietary choices. Comparing an unemployed individual with an otherwise identical individual living in a household of two, the former consumed over 3kg less fruit over a period of two weeks. Similarly, for two identical households, a difference in income of 10 per cent can be expected to lead to a difference in demand for fruit and vegetables of around 500g.
Professor Tiffin said: “Our results imply that households which have a higher level of expenditure will tend to consume proportionately more meat and more fresh fruit and vegetables. Households in London and the South East have higher levels of fruit and vegetable consumption while it is reduced by the presence of children. “The dietary components that we have analysed have important implications for policy-makers in tackling diet-related chronic disease, which represents one of the most significant public health challenges of the 21st century.”
The paper, 'The demand for a healthy diet: estimating the almost ideal demand system with infrequency of purchase, by R. Tiffin (University of Reading) and M. Arnoult (Scottish Agricultural College), is published this month in The European Review of Agricultural Economics – http://erae.oxfordjournals.org/content/current
Researchers used the UK government's Expenditure and Food Survey (EFS) for 2003-2004. Participating households voluntarily record food purchases for consumption at home for a two-week period using a food diary. The sample is based on 7,014 households in 672 postcode sectors stratified by Government Office Region, socioeconomic group and car ownership. It is carried out throughout the UK and throughout the year in order to capture seasonal variations.
The paper directly compared findings from two separate studies: 'The Diets of British Schoolchildren' conducted by the Department of health (DH) in 1983 (Department of Health 1989); and the National Diet and Nutrition Survey (NDNS) from 1997 (Gregory & Lowe, 2000).
Gibson's analysis found that total sugar intake averaged at 115g/day in 1983, compared with 113g/day in 1997. Allowing for exclusions of low and high energy reporters, intake levels were 122g/day (1983) and 127g/day (1997), showing a marginal and insignificant increase over the study period. Contrastingly, mean body weight increased significantly during the period of the DH and NDNS surveys, showing a rise of 1.9kg for 10-11 year olds and 3.4kg among 14-15 year olds. BMI increased from 17.9 to 18.6 units in the younger group, and 20.2 to 21.3 units in the older group. According to these calculations, the prevalence of being overweight (plus obesity), as defined by the International Obesity Taskforce (IOTF) cut-offs (91st percentile) rose from 13% to 21-22% between surveys. Gibson concluded that the slight increase in consumption of total sugars did not account for the significant increase in BMI, equivalent to 2-3 kg over the review period.
During the same period, Gibson found that mean energy intake (EI) was 3% lower in 1997 than in 1983, mainly as a result of lower fat intake. This change in overall energy consumption meant that sugars represented a higher proportion of daily energy intake in 1997 (23.6% versus 22.3%), despite total sugar consumption remaining relatively static in comparison. The review surmises that the most likely cause for the increased BMI is a decline in energy expenditure.
In addition, Gibson's paper found that basal metabolic rate (BMR) increased by approximately 3% between surveys as a result of higher body weights, and it is estimated that EI in relation to basal requirements was even lower at 6%. Gibson found that the paradox of rising BMI, despite a 2-3% rise in BMR and an EI that is static or falling, pointed to declining energy expenditure as an important factor in the change.
The Gibson analysis showed that the key sources of sugars in the diet have changed with a marked shift away from table sugar and smaller falls in consumption of sugars through milk, biscuits and cakes, counterbalanced by a significant increase in sugars consumed in soft drinks and, to a lesser extent, fruit juice and breakfast cereals.
A conclusion of Gibson's reanalysis of data from the DH and NDNS studies, that consumption of total sugars remained relatively static during the period, providing an estimated 22% of energy, is supported by findings from a repeated cross sectional study of children's food and drink intake, conducted in Northumberland in 1989, 1990 and 2000 which looked at trends in children's food and drink intake.
Sigrid Gibson, the paper's author, said: “There are very few studies that have assessed trends in sugar intake over time and particularly over such an extended period. The findings of the reanalysis strongly contradict widespread assumptions that sugar levels in the diet are responsible for rising obesity levels. With dietary sugar intakes relatively static, and overall energy consumption showing decline, increased BMI levels cannot be attributed to sugar consumption.”