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Dietary patterns for population and planetary health: opportunities and challenges for older adults
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Date
2024
Authors
Leydon, Clarissa Louise
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Publisher
University College Cork
Published Version
Abstract
Introduction: The foods we consume and the foods we produce are intertwined with our health and the health of the planet. The current global food system no longer supports public health or ecological integrity, leading to adverse outcomes for both people and the environment. In the face of overlapping challenges such as climate change, biodiversity loss, and the rising burden of diet-related diseases, recognising food as a cornerstone for fostering human and planetary health is crucial. The concept of sustainable diets has emerged as one potential solution, characterised by their ability to be simultaneously healthy, less environmentally impactful, socio-culturally acceptable, and economically fair. However, adopting these diets necessitates significant changes from the prevailing dietary patterns observed in the population. Amid the rising population of older adults, whose unique nutritional needs are critical for preventing age-related diseases, it is increasingly important to investigate how sustainable diets can be tailored to this demographic. Given that their eating habits are often deeply rooted in cultural traditions and long-established practices, transitioning to new dietary patterns presents distinct challenges. Therefore, the aim of this thesis is to examine how the dietary patterns of middle- to older-aged Irish adults align with the health, environment, and cost dimensions of a sustainable diet.
Methods: This thesis presents four distinct but interrelated studies examining the dimensions of a sustainable diet. The research began with a systematic literature review, conducted in line with a registered protocol, to explore how adherence to a priori healthy dietary patterns affect health, environmental, and financial cost outcomes. The review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, providing a solid evidence base for the subsequent studies. Three original research investigations were conducted using data from the Cork and Kerry Diabetes and Heart Disease Study (Phase II – Mitchelstown cohort), which consisted of middle- to older-aged adults recruited from a single primary care centre in Mitchelstown, County Cork, Ireland, between 2010 and 2011. With a rescreening of this cohort carried out between 2015 and 2017. Dietary intake data were collected using a validated food frequency questionnaire (FFQ). Three a priori dietary patterns; Dietary Approaches to Stop Hypertension (DASH), Mediterranean (MED) diet, and the Healthy Eating Index (HEI), were derived from the dietary intake data for analyses. Following an examination of the literature, an appropriate food life cycle assessment (LCA) database for the Irish context was selected and applied to the data. The environmental impact of dietary patterns was assessed using two indicators; greenhouse gas emissions (GHGE) and blue water use (BWU). The adequacy of nutrient intakes in the cohort was evaluated using globally harmonised dietary reference values (DRV). Both cross-sectional and longitudinal analyses were conducted to assess the associations between adherence to these healthy dietary patterns and the same outcomes of interest; health, environmental impact, and cost and affordability.
Results: Adherence to a priori healthy dietary patterns, as reflected by diet quality scores, varied within the population at both time points. Notably, dietary patterns among older adults are not aligned with current dietary recommendations, particularly regarding the consumption of discretionary foods and beverages. Adhering to some healthy dietary patterns is linked to lower BMI and other metabolic risk factors. In relation to the prevalence of inadequate nutrient intakes, deficiencies in vitamins D and E were persistent concerns across both time points, regardless of adherence levels. Additionally, some adherence groups exhibited inadequate intakes of vitamin C, riboflavin, calcium, magnesium, and fibre. While the overall percentage of individuals not meeting protein requirements was low, this proportion increased at higher assessed values, especially among males.
The environmental impacts of dietary patterns were assessed, reflecting existing cultural eating habits. The synthesis of the evidence from the systematic review found that while adhering to healthy dietary patterns can reduce diet-related environmental impacts, these diets are not innately more sustainable. Similarly, for the investigations on the Irish cohort, linear regression analyses revealed that greater adherence to the Dietary Approaches to Stop Hypertension (DASH) and Mediterranean (MED) diets was associated with higher blue water use (BWU), though no such association was found for the Healthy Eating Index (HEI). Univariate analysis indicated significantly higher BWU when comparing extreme adherence groups (low vs. high) for all three dietary patterns. Furthermore, longitudinal analysis of DASH adherence showed that individuals who improved their adherence from low or maintained high DASH adherence exhibited higher BWU compared to baseline assessments. Conversely, the findings related to greenhouse gas emissions (GHGE) were less consistent; while lower GHGE were observed cross-sectionally, no significant differences were noted with improved adherence or sustained high DASH adherence over time.
Adhering to a healthier dietary pattern entailed a higher monetary cost, but the limited studies assessing this outcome in the review prevented definitive conclusions. For the Irish cohort, high DASH adhering dietary patterns was associated with increased spending, with the high adherence group allocating more to positively scored food groups while spending less on negatively scored items compared to their low adherence counterparts. Despite these differences, both groups allocated the most to non-scoring food categories in the DASH diet, including fish, poultry, and eggs, alcohol, and caffeinated beverages. While the high DASH diet demonstrated greater cost efficiency in terms of GHGE, it significantly increased BWU per euro spent compared to the low DASH diet.
Discussion: One of the pillars of healthy ageing is diet, and this thesis has underscored the need to improve the dietary quality of older Irish adults and sustain healthy dietary patterns to ensure that increased longevity is accompanied by good health. The DASH diet is associated with a reduced risk of many chronic diseases, particularly relevant for older adults. While it has shown potential for reducing GHGE, the associated increase in blue water use raises concerns about environmental sustainability. The assumption that healthy dietary patterns are inherently more sustainable is not robust, as the challenge lies in the differing definitions and purposes of "health" and "sustainability." However, by further adapting the DASH diet to the Irish food system and incorporating a stronger plant-based foundation, it has the potential to become a healthier, lower-impact, and culturally acceptable diet for older adults. Coordinated government action across food environments and food systems can help address adoption challenges, particularly affordability, ensuring alignment with all dimensions of sustainable diets. Integrating these dimensions into new, sustainability-focused national dietary guidelines for older adults will provide an evidence-based framework from which specific dietary patterns can be tailored, while also acknowledging the need for further research to address identified knowledge gaps.
There is no doubt that ensuring healthy diets for all while protecting our natural environment is an unprecedented challenge that requires a paradigm shift, achievable only through collective action – where diverse stakeholders collaborate, innovate and commit to building a sustainable food system. This complex, systemic challenge necessitates interconnected actions from both public and private sectors across multiple fronts of the food system, extending beyond agriculture. Ultimately, prioritising sustainable healthy ageing is crucial for cultivating a healthy planet, as it aligns human well-being with the need for environmental stewardship. This approach supports a future in which everyone can age well and thrive in harmony with the planet.
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Keywords
Dietary patterns , Sustainable diets , Environmental impact , Life cycle assessment , Food system , Older adults , Public health
Citation
Leydon, C. L. 2024. Dietary patterns for population and planetary health: opportunities and challenges for older adults. PhD Thesis, University College Cork.