Nutrition and dietary patterns
Healthy eating not only influences physical capability but is also important for the central nervous system, with implications for cognitive capability.
Dr Alison Lennox introduces Nutrition and Dietary Patterns
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Why study nutrition and diet?
Studies have shown that poor dietary habits increase the risk of chronic disease, and there are already many policy initiatives to promote healthy ageing through better diet. Few studies have looked at the effects of diet and nutrition on markers of healthy ageing such as physical and cognitive capability. We hypothesised that what you eat may affect cognitive capability, through a long-term effect on the central nervous system.
There are many social factors that affect what we eat and how healthy we are, and several ways of measuring diet. This makes it hard to isolate the effects of diet on ageing, and explains why the results from studies of different types of food or including different groups of people can come up with conflicting results. We wanted to improve on this by undertaking comparable studies using different cohorts and taking account of lifetime factors that determine dietary choices in these cohorts.
How do we study diet?
Some studies have used food frequency questionnaires, where study members report how often they eat particular foods. In others, study members keep a diary for several days recording everything they eat, and from which nutrients can be derived. In some of the HALCyon cohorts both methods have been used so it was possible to identify key foods that that relate to particular nutrient intakes. We used this information to facilitate cross cohort comparisons.
What we are researching
As part of the project, we investigated the factors that influence dietary choice in older age through a review of the literature. This is currently being completed.
Since many of the cohorts collected their dietary information using food frequency questionnaires (FFQs) and these are less reliable for assessment of nutrient and energy intakes than more detailed methods we decided to focus on specific food groups that may be related to physical and cognitive capability. The two food groups studied were meat and, fruits and vegetables. We used the MRC National Survey of Health and Development (NSHD), which has detailed dietary intake information, obtained using 5 day diaries, to harmonise intakes across the cohorts in terms of portion sizes and types of foods consumed. For meat intake, we did this by using the more detailed information available within NSHD to assess the contribution of the various meat types that are contained within the groupings listed in the various FFQs used by other HALCyon cohorts, and applied typical portion sizes for those meat types to the intake frequencies recorded. In this way we obtained total meat intakes for each of the cohorts. Similar methods were also used for fruit and vegetable intake. We have reported on our methods of harmonisation at various conferences (Mulla et al., 2009) and written and submitted a manuscript for publication (Mulla et al., submitted).
We have also reviewed the various diet quality measures that are used in the literature to describe the overall quality of the diet and have determined which of these can be applied to the eight cohorts with dietary information in HALCyon. Many of the diet quality scores available have been developed in the United States and are not readily translatable to dietary information collected in the UK. However, three scores have been defined and their associations with physical and cognitive capability investigated.
We have explored the effect of nutrition on physical and cognitive capability, taking into account the factors that we found to affect dietary choice.
What have we found so far?
- A major challenge for cross cohort work has been that different methods have been used to assess dietary intake in different cohorts. It is therefore important to share the knowledge gained in overcoming these challenges with other researchers. Our harmonisation work has been reported at two conferences and in a paper. In this paper we provide details of the validation work undertaken to ensure comparability of measures of meat and fruit and vegetable intake across cohorts (Mulla et al. submitted).
- In a study using the more detailed dietary data available across adulthood in the NSHD, we found evidence that higher energy and protein intake earlier in adulthood were associated with stronger grip strength at age 53 years, after adjustment for body size and socioeconomic factors. However, there were no consistent relationships between nutritional and energy intakes and the other two measures of physical performance (Mulla et al., Age and Ageing 2013).
- In June 2011, we held a workshop on “Pooling Cohorts - The challenges of different dietary assessment methods” for researchers and health professionals which focused on methods that various teams, including researchers from HALCyon, have used to harmonise dietary data from multiple cohorts.
Please see the Case for Support for a detailed, more technical overview of the work packages.
Kuh D, Cooper R, Hardy R, Richards M, Ben-Shlomo Y (Eds). A life course approach to healthy ageing. Oxford University Press to be published January 9th 2014.
- Chapter 16: Lifetime lifestyles I: diet, the life course and ageing
Professor Gita Mishra, Professor Marcus Richards, Dr Seema Mihrshahi, Dr Alison Stephen