A Mediterranean diet supplemented with dairy foods improves mood and processing speed in an Australian sample: results from the MedDairy randomized controlled trial

Abstract

Background The Mediterranean diet has been linked to improved cognitive function and reduced risk of dementia. However, a traditional Mediterranean diet may not meet calcium requirements for older non-Mediterranean populations, which could limit long-term sustainability in Western countries. The current study therefore aimed to determine the cognitive and psychological effects of a Mediterranean diet with adequate calcium for an ageing Australian population.

Method: A randomized controlled cross-over design trial compared a Mediterranean diet with 3–4 daily serves of dairy food (MedDairy) with a low-fat (LF) control diet. Forty-one participants aged ≥45 years with systolic blood pressure ≥120 mm Hg and at least two other risk factors for cardiovascular disease completed each dietary intervention for 8 weeks, with an 8-week washout period separating interventions. Attention, processing speed, memory and planning were assessed at the start and end of each intervention using the Cambridge Automated Neuropsychological Test Battery. Mood and health-related quality of life were evaluated using the Profile of Mood States (POMS) and Short-Form Health Survey (SF-36). Dementia risk was also measured using the Framingham Vascular Risk and CAIDE scores.

Results Significant improvements were observed for processing speed (P = .04), Total Mood Disturbance (P = .01), Tension (P = .03), Depression (P = .03), Anger (P = .02), and Confusion (P = .004) following the MedDairy intervention. No significant effects were found for attention, memory and planning, or measures of dementia risk.

Conclusion Our study provides evidence that a Mediterranean diet supplemented with dairy foods may benefit cognitive function and psychological well-being in an ageing population at risk of dementia.

Keywords:

• Mediterranean diet
• dairy
• Calcium
• Cognition
• Mental health
• Ageing

Acknowledgements

A. T. W. was supported by an Australian Government Research Training Program (RTP) Scholarship. J. M. H. was supported by a National Health and Medical Research Council Senior Research Fellowship and a Royal Perth Hospital Medical Research Foundation Fellowship. The authors would like to thank the following individuals: Louise Massie, for clinical trials support; Anita Lawrence for assistance in sourcing yoghurt; and research assistants Joe Mandrell and Campbell Davis for their contributions data entry and analysis. We would also like to acknowledge the following organizations for their generous contributions: Almond Board of Australia for the donation of almonds; Cobram Estate for the donation of Australian extra virgin olive oil; Fonterra Australia Pty Ltd. for the donation of cheese; and Simplot Australia Pty Ltd. for the donation of legumes, tuna and salmon.

Disclaimer statements

Author contributions K. J. M., J. M. H., A. T. W. and C. R. D. designed the project. K. J. M. and C. R. D. developed the diet. K. J. M., A. T. W., J. M. H. and C. R. D. developed the cardiovascular measures. R. J. W. contributed to the study design and developed the statistical approach. K. A. D. contributed to the study design. K. J. M., A. T. W., K. A. D. and C. R. D conducted the trial and collected study data. A. T. W. prepared the manuscript. All authors reviewed manuscript drafts s approved the final version.

Data availability Data supporting the analyses and results of this paper are available from the corresponding author, K. J. M, upon reasonable request.

Conflicts of interest The authors declare no conflict of interest.

Ethics This trial was registered with the Australia and New Zealand Clinical Trials Registry (ACTRN12616000309482) on 9 March 2016 and was conducted according to the Declaration of Helsinki guidelines. All procedures involving human participants were approved by the University of South Australia Ethics Committee (#34954). Participants provided written consent for the inclusion of their anonymized data in the following analysis.

Additional information

Funding

This study was funded by Dairy Australia [grant number C100001408]. Dairy Australia had no role in the study design, implementation, analysis or interpretation of data.