Nature Versus Nurture – Studying the Relationships Between Diet and Depression in Older Adults

Abstract

ObjectivesPrior work suggests that higher fruit and vegetable consumption may protect against depression in older adults. By better understanding the influence of genetic and environmental factors on fruit and vegetable intakes, more effective interventions could be designed to increase intakes in older adults to reduce and/or assist with the treatment of depression in older adults. The aim of this heritability study is to estimate the genetic and environmental influences on the consumption of fruit and vegetables in older adults and to investigate if there are shared influences between fruit and vegetable intakes and depression.MethodsParticipants (n = 374 twins, 67.1% female; 208 identical; 166 non-identical, ≥ 65-years) were drawn from the Older Australian Twins Study. Data on diet (validated food frequency questionnaire) and depressive symptoms (15-item Geriatric Depression Scale) were collected. The contribution of genetic and environmental influences on fruit and vegetable intake were estimated by comparing identical and non-identical twin intakes using structural equation modelling. A trivariate model was used to estimate the genetic and environmental correlation between total fruit and vegetable intakes and depression.ResultsIn this study, vegetable intake was moderately influenced by genetics (heritability = 36%) with the remaining 64% due to the unique environment. Heritability was highest for brassica vegetables (40%), while intake of starchy vegetables was not heritable. Genetics did not significantly influence the intake of fruit. No significant genetic or environmental correlations were detected between fruit or vegetable intakes and depression. The number of participants meeting Australian Dietary Guidelines for fruit and vegetable intake was low (fruit 46.5%; vegetables 2.9%).ConclusionsConsumption of vegetables, particularly bitter tasting brassica vegetables, was significantly influenced by genetics. These findings provide novel insights into the drivers of fruit and vegetable consumption in older adults and may help shape interventions to increase intakes, with the view of reducing the burden of depression.Funding SourcesThe Older Australian Twins Study was funded by the National Health & Medical Research Council and Australian Research Council.