Understanding how people eat: a dietary pattern approach

Table filled with a variety of food types

Dr Kathryn BeckDr Kathryn Beck is an Associate Professor in Human Nutrition and Dietetics at Massey University in Auckland, New Zealand. Dr Beck is a World Cancer Research Fund Academy Fellow and principal investigator of the REACH study, which is funded by a New Zealand Health Research Council Emerging Researcher Grant. 

Dietary pattern analysis seeks to understand how people are eating. Traditionally, nutrition research has focused on whether individual nutrients and foods are linked with health outcomes or disease.; for example, whether vitamin C intake is linked to iron deficiency. Investigating nutrition using this approach has a number of limitations. People don’t eat individual nutrients and foods in isolation, people eat meals and snacks which contain a variety of ingredients that interact.

Well-known examples of this are the enhancing effect vitamin C has on iron absorption, while tea and coffee decrease iron absorption when consumed with food. Furthermore, an analysis based on nutrients alone may be confounded by the type of dietary pattern a person follows. By using a dietary pattern approach we overcome these limitations, by considering how foods (and nutrients) are eaten in combination.

Determining dietary patterns

Dietary patterns are typically derived using two main approaches. The first is an a-posteriori approach whereby dietary data collected from participants is analysed statistically to generate the combinations of foods (dietary patterns) people are eating. Alternatively, using an a-priori approach, people are given a score based on whether they are following a particular dietary pattern (such as a Mediterranean diet) or particular dietary guidelines. World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR) recently developed a standardised scoring system to assess people’s adherence to their Cancer Prevention Recommendations.

What is the REACH study?

Here in New Zealand, my team are exploring the dietary patterns of adults aged 65–74 years old and their association with cognition, body composition and metabolic syndrome. This work is known as the REACH (Researching Eating Activity and Cognitive Health) study.

More than 360 adults have taken part and we have collected in-depth dietary data, as well as measuring different domains of cognitive function including memory and attention. We have also measured body fat and muscle mass using Dual X-ray Absorptiometry (DEXA), physical activity levels, blood pressure, and taken a blood sample to measure cholesterol, blood glucose and the ApoE ԑ4 genotype.

The ApoE ԑ4 is a gene that may affect cognitive function, so it is important to consider ApoE ԑ4 when investigating the relationship between dietary patterns and cognitive function. We have identified two main dietary patterns within the REACH population – a ‘healthy’ dietary pattern and a ‘Western’ dietary pattern. The ‘healthy’ dietary pattern is categorised by high intakes of vegetables, nuts and seeds, legumes, wholegrains, meat alternatives, fruit, fish, seafood and spices. The ‘Western’ dietary pattern is categorised by processed meats, sauces and dressings, biscuits and cakes, fast food, confectionary, vegetable oils, cheese and beer.

We have also applied the WCRF/AICR score to the dietary intake of the REACH population. Those participants who had a higher WCRF/AICR score (more closely adhered to the WCRF/AICR guidelines) were more likely to follow the ‘healthy’ dietary pattern and less likely to follow the ‘Western’ dietary pattern (abstract under review).

Why study diet in so much detail?

Exploring these dietary patterns will help us to understand how older adults in New Zealand are eating, and eventually we will be able to look at how these dietary patterns are associated with cognitive function, metabolic syndrome and body composition. Dietary patterns can be investigated in different population groups and across different health outcomes. A previous study I was involved in found iron deficiency in female military recruits to be associated with impaired physical performance. A further understanding of the dietary patterns of these women may help to improve both health and performance outcomes.

Observed dietary patterns represent accessible and familiar foods that people are eating, and the combinations in which these foods are consumed. It may be easier to improve people’s diet by shifting them along the scales of a particular dietary pattern by making small and relevant suggestions for change, rather than large changes to a less familiar dietary intake (or pattern).