By Dr Rebecca Pradeilles, School of Health and Related Research, University of Sheffield; Dr Emily Rousham and Dr Paula Griffiths, Centre for Global Health and Human Development, Loughborough University.
As part of a SIID funded project on changing urban diets in Africa, Rebecca Pradeilles (SIID Fellow) will be analysing the Birth to Twenty Plus data to explore dietary patterns in relation to socio-economic status. She is doing this in collaboration with Michelle Holdsworth (SIID Fellow, University of Sheffield); Paula Griffiths and Emily Rousham (Loughborough University); Alison Feeley and Shane Norris (University of the Witwatersrand).
In our recent blog “Nutrition transition in South African cities-not the same experience for everyone” published in February 2016, we discussed findings from my PhD work looking at socio-economic and gender differences in anthropometric patterns in urban adolescents living in the area of Johannesburg/Soweto. Another important component of my PhD work was to assess dietary patterns of these adolescents living in this rapid transitioning environment, which will be discussed in this blog.
South Africa is at an advanced stage of the nutrition transition
Diet-related chronic diseases such as diabetes and cardiovascular diseases are increasing rapidly in low-and middle-income countries (LMICs), especially in urban areas, partly due to changes in diet and physical activity. LMICs are transitioning to ‘modernised’ lifestyles. Popkin (2006) highlights that the diets in many LMICs are transitioning from a traditional diet (e.g. consumption of starchy staples, low fat, low variety, water, high fibre) to a ‘modern’ diet high in fat, sugar, processed food, sugary drinks and less fibre.
Economic growth and rapid urbanisation lead to an increased access to energy-dense products, convenience foods, and processed foods. South Africa is an upper-middle income country, at an advanced stage of the nutrition transition compared to other countries in the region.
Food environments in the area of Johannesburg/Soweto
What do adolescents currently eat in urban South Africa?
Adolescents spend more time outside of their home, with peers and are therefore influenced by neighbourhood food environment. Therefore, this is a crucial time for the development of nutrition behaviours.
In the area of Soweto/Johannesburg, there are numerous affordable food outlets (i.e. commercial or informal (e.g. tuck shops, street vendors) selling fast food items. Previous studies conducted in South Africa have shown that a large proportion of urban Black South African adolescents consume fast food items, most days of the week, which may contribute to more than 50% of their daily energy intake. The three most common fast food items consumed were ‘quarters’ also called ‘kota’ (i.e. traditional South African sandwich composed of a quarter loaf of white bread, fried chips, processed cheese and meats/sausages, a fried egg and sauces); chips and vetkoek (i.e. traditional South African fried dough bread (fat cakes) either filled with mincemeat or syrup/honey/jam). Research shows that adolescents tend to choose local, energy dense, fast food products instead of food prepared at home, resulting in poor-quality diet.
‘Kota’ traditional South African sandwich including bread, chips, sausages, cheese, eggs and sauces. This product is energy-dense and can bring up to 800 kcal.
Dietary patterns as a way of defining the whole diet
The above research shows that adolescents are eating modern foods. But how do we define these changes in diet? Recently, dietary pattern analysis has emerged as a popular way of summarising the whole diet. Dietary patterns give an idea of how foods are combined and related to one another and capture complex behaviours.
Two main patterns of consumption are commonly described in the literature; the ‘prudent’ and the ‘western’ pattern. The ‘western’ pattern was defined by Slattery et al. (1998), as a diet characterised by high consumption of red meat, processed meat, fast food, refined grains and sugar, alongside a low consumption of vegetables and fruit. The ‘prudent’ pattern was defined as a diet characterised by a high consumption of healthier food items such as fruit and vegetables, fish and poultry alongside a low consumption of red meat, processed meat and sugar (Slattery et al. 1998).
Our study of South African adolescents
The aim of our study was to explore dietary patterns in urban South African adolescents aged 17-19 years.
Our study was conducted in Johannesburg-Soweto, which is the largest urban area in South Africa. The sample of adolescents comes from an internationally renowned dataset called the Birth to Twenty Plus (Bt20+) cohort study. Bt20+ is a longitudinal cohort study (sample size of 3273) of births occurring between April-June 1990 to mothers who were permanent residents of Johannesburg-Soweto.
Birth to Twenty logo – The children enrolled in the cohort are known as Mandela’s Children as they were born in the seven weeks following Nelson Mandela’s release from prison on the 11th of February 1990.
For our study, 656 adolescents completed a food frequency questionnaire (FFQ) which provided information on the food items consumed in the past seven days, their frequency, and estimated quantity. The FFQ allows an estimation of the frequency of consumption of food or food groups within a given time-frame and thus captures perceived habitual intake. Dietary patterns were generated using a data driven reduction technique (known as Principal Component Analysis). This technique identifies the most important patterns of consumption and the most important foods in the diet.
Interview room for the Food Frequency Questionnaire, Soweto
What we found in our study
Three main dietary patterns were identified in the analysis:
– The first dietary pattern was characterised by a high consumption of high fat dairy products, poultry, processed meat, red meat, chips, biscuits and pastries, vegetables and sauces. This dietary pattern showed similar features to the “western” pattern described above (i.e. diet characterised by a high consumption of red meat, processed meat, fast food, refined grains and sugar, alongside a low consumption of vegetables and fruit). We decided to label this pattern of food consumption as the “modern” pattern.
– The second dietary pattern comprised high consumption of tea, nuts, whole grains, sugar and low consumption of beverages, desserts, pizzas, high fat dairy products, and fried battered chicken. This pattern of consumption seemed to reflect low-cost and filling food options and we therefore decided to label it the “low-cost food” pattern.
– The third dietary pattern was defined by a high consumption of processed fruit, vegetables, legumes, fresh fish, processed fish, canned fish, savoury tarts, legumes and low consumption of soft drinks, refined grains, chips, sweets, pizzas and margarine. This pattern seemed to reflect a balanced, diversified and relatively high-cost diet. It showed similar features to the ‘prudent’ diet described above (i.e. diet characterised by a high consumption of fruit and vegetables, fish and poultry alongside a low consumption of red meat, processed meat and sugar. We labelled this pattern the “healthy” pattern.
To our knowledge, this study is the first to assess dietary patterns, using this method, among urban adolescents in Sub-Saharan Africa. Our analysis allowed us to provide a summary of the complex nature of the dietary information and identify the different patterns of consumption within this cohort of adolescents.
Three main dietary patterns were apparent in this cohort of adolescents: i. the modern pattern; ii. the healthy pattern and iii. the low-cost food pattern. The ‘modern’ dietary pattern which comprised energy-dense products, processed foods and high fat, high sugar products provides evidence of a nutrition transition among adolescents from relatively low socio-economic backgrounds, similar to that seen in high income countries. These findings support the expected dietary changes suggested by the nutrition transition model.
The fact that dietary patterns are shifting from traditional to modern during adolescence highlights that the adolescent period represents a window of opportunity for obesity prevention intervention at a time when individualised behaviours develop. Interventions aiming to improve nutrition behaviours in adolescence can also be effective for obtaining long-term health benefits via a mechanism in which healthy dietary patterns track through the life course. In this context, it is essential to identify the factors that influence changes in dietary patterns.
Our next step is to explore socio-demographic characteristics related to the three dietary patterns described above. More specifically, we want to look at the impact of household socio-economic status across early life and adolescence on dietary patterns and shed some light on the drivers of dietary patterns in this context.
This work is currently being prepared for publication and will be presented at the International Society for Behavioral Nutrition and Physical activity (ISBNPA) held in Cape Town, South Africa in June 2016.