Diet quality and environmental impact changes with age

Many aspects of diet change with age and an understanding of this is important when seeking to promote health and environmental sustainability through changes to diet.  Study of a nationally representative set of diet records shows that diet quality declines through childhood, improves during adulthood and declines again in old age.

The diet people eat changes as we grow through childhood and reach maturity, and changes further throughout adult life and ultimately, as we age.  Exploring these changes is important in understanding many aspects of health and can help inform strategies for how we can influence people to move to diets which are healthier and more environmentally sustainable.  

The National Diet and Nutrition survey (NDNS) is a rolling programme that annually records 4 days of food consumption in a nationally representative sample of about 1000 UK individuals, with oversampling of children and of individuals in the devolved countries.  As well as looking at specific aspects of diet, we can summarise the overall properties in terms of diet quality and environmental impact.  A diet quality index can be obtained by accounting for several aspects of diet that are recommended, such as limiting sugar and saturated fat, and quantifying the adequacy of fruit, vegetable and fibre intake.  Environmental impact can be measured using various criteria, but one of the most important is measurement of the CO2 emissions associated with the production and consumption of food.  

The NDNS data show that diet quality declines throughout childhood, until about age 18-20, while CO2 emissions increase, mostly due to increased overall intake.  Typical quality improves until individuals reach their mid-30s, remaining unchanged until the early 50s, when an improvement resumes and continues until their mid-60s, after which average quality declines again.  This decline in the more elderly is associated with a reduction in CO2 emissions.  The pattern during life is similar in men and women, apart from the midlife dietary quality improvement which is accompanied by a reduction in CO2 emissions only in males.  

Further study of these patterns will enable us to better understand what aspects of diet are driving these broad changes and how we might encourage better and more sustainable diets.  An important caveat is that this is a repeated cross-sectional survey collected over the past decade, and so patterns may reflect cohort effects (the preferences of groups of people who are all of much the same age, whose current preferences may not be the same as other groups when, in future, the latter reach a given age) as well as reflecting longitudinal changes with age.

Scatter plot showing DQI and CO2 changes with age. Males and females follow the same pattern, but on average males have a lower DQI and a higher mean CO2 than females.

This work was done in collaboration with the Rowett Institute and was funded under the Scottish Government's Strategic Research Programme for environment, agriculture and food.

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