Diet
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Diet has also received considerable attention, with researchers focusing on whole diet styles to specific micronutrients. The relationship between diet and physical health has been widely reported in the literature, and this relationship is generally appreciated amongst the lay public (although this does not mean that they will act on this knowledge, an issue that we address specifically below in section \ref{225494} on behavioural change). For example, the vegetarian diet has been associated with a reduced risk for disease development, including coronary heart disease and type 2 diabetes, compared with a diet containing red and processed meat \citep*{McEvoy2012}, while insufficient fibre has been associated with colon cancer, high blood cholesterol, diabetes, coronary heart disease and obesity \citep*{cowbrough2005}. Diet is also associated with all-cause mortality, with one study reporting findings based on a sample of 2000 individuals, finding that those adhering the most to a Mediterranean diet had an all-cause mortality risk that was 34% lower than those with adhering the least to the diet \citep{Limongi2017}
However, diet is also associated with mental wellbeing, with a healthier diet predicting better mental health and wellbeing \citep{Dimov2019,Kulkarni2015,Emerson2019,Rooney2013}. Focusing on whole diets, the Mediterranean diet has proven useful in slowing age-related deterioration, including improvements in cognitive function and reducing risk of cognitive impairment and dementia \cite{Petersson2016,Aridi2017}, with B-vitamins and antioxidants playing a key role \citep{Moore2018,Castelli2018}. The Mediterranean diet has also proven effective in reducing depression symptomology (according to an RCT) \citep{Parletta2019}. Based on the evidence, dietary recommendations for the prevention of depression have been proposed; adopting "traditional" diets, such as the Mediterranean diet, increasing consumption of fruits, vegetables, legumes, wholegrain cereals, nuts, seeds, foods rich in omega-3 polyunsaturated fatty acids and limit consumption of processed foods \citep{Opie2017}.
Dietary habits not only impact on physical and mental health; there is now increasing concern about associated impacts on the wider environment, which will subsequently have further impacts on individual wellbeing. We will return to this topic below in section \ref{479675}. We now turn to the role of sleep as a contributor to individual wellbeing.