Dietary patterns in the context of ageing and cognitive and physical functions

Dietary research has shifted focus from nutrients to dietary patterns in recent years, recognising that people consume combinations of foods with synergistic nutrients’ effects. Defined as the combination, frequency, and variety of food intake, dietary patterns provide a more holistic understanding of the diet's impact on health outcomes and improve translation into public health recommendations [1]. They can be derived through index-based approaches, which assign numerical scores based on dietary guidelines (e.g., The Dietary Approach to Stop Hypertension—DASH), or through exploratory methods like principal component analysis, which statistically identify patterns from dietary data. While index-based methods offer structured, replicable assessments, they may lack cultural adaptability, whereas exploratory methods provide flexibility, but require subjective interpretation [1].

With this shift, studies began to be carried out to understand the role of different dietary patterns in ageing processes. Healthier dietary patterns, such as the Mediterranean diet (MedDiet), are shown to modulate genomic instability, telomere attrition, and cellular senescence, contributing to the delay of biological ageing [2]. Fadnes et al. estimated a lifespan gain of 6–10 years when changing the typical country-specific dietary patterns to longevity-related dietary changes (i.e., more whole grains, legumes, and nuts, and less red/processed meats and sugars and sugar-sweetened beverages) in 7 culturally varied countries (China, France, Germany, Iran, Norway, the United Kingdom, and the United States) [3].

Although not consensually defined, a healthy dietary pattern can be translated as a diet delivering sufficient–but not excessive–amounts of macronutrients and micronutrients to proper physiological body functions [4]. It is fundamental, however, to consider that as physiological needs change according to life stage, recommended healthy dietary patterns may vary according to age. Not only age, but also sex, disease status, physical activity level, and cultural context may impact the definition of a healthy dietary pattern [4]. In the study of Lengelé et al., the adherence to dietary patterns driven by an exploratory method changed according to age and sex as well as their associations with body composition and physical function [5]. For example, higher adherence to the “Animal products” diet (i.e. meat, poultry, lunch meat, butter, and refined cereals) was associated with higher lean mass in middle-aged women (50–64 years). However, among young (20–49 years) and middle-aged men, greater adherence to this diet was associated with higher fat mass and lower grip strength, respectively [5]. These results highlight the importance of exploring dietary patterns for subgroups (Fig. 1).

Fig. 1.

Summary of the role of healthy dietary patterns in ageing.

Dietary patterns are known to be related to cognitive and physical functions. In this issue of The Journal of Nutrition, Health and Aging (JNHA), two meta-analyses found a protective effect of adhering to a “healthy dietary pattern” or avoiding an “unhealthy dietary pattern” to the risk for neurodegenerative disorders [6,7]. Among 314,603 people, Zhao et al. found that higher adherence to the MedDiet (i.e. rich in plant-based foods and olive oil, moderate in fish, eggs, dairy, and red wine, and restricted to red meat) was associated with a 25% lower risk for Parkinson’s disease (PD), and a 33% lower risk for the prodromal PD (latent phase) [6]. This study expands the findings from van Soest et al. that demonstrated a reduced risk for all-cause dementia and Alzheimer’s disease (AD) with higher adherence to the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet—a hybrid dietary pattern, based on the MedDiet recommendations but emphasising the intake of neuroprotective foods, such as berries and green leafy vegetables [8]. Prospectively, however, these associations are less evident, with higher adherence to the MedDiet not changing the risk for mild cognitive impairment (MCI), dementia, and AD [8,9].

On the other hand, Fang et al. found that a more pro-inflammatory diet at baseline (estimated through the Dietary Inflammatory Index or the Total inflammation) increased the risk for overall cognitive impairment, MCI, dementia, and AD after 2–20 years of follow-up [7]. This meta-analysis with prospective cohorts included 266,169 adults with mean ages of 56–77 years [7]. Pro-inflammatory diets are characterised by being rich in ultra-processed foods, sugars, and saturated fats, and poor in fruits, vegetables, and whole grains (sources of antioxidants) [10]. They are suggested to increase systemic inflammation, endothelial dysfunction, blood-brain barrier permeability, and neuroinflammation [11].

In terms of physical function, cross-sectionals studies show a positive association between MedDiet and better performance in walking speed and strength tests [9,12]. As observed for cognitive function, these associations are also less consistent in longitudinal studies [9]. Such inconsistency raises two points for discussion. First, as previously mentioned, is the potential lack of cultural adaptability when assessing adherence to a pre-defined dietary pattern as the MedDiet. This becomes more evident when looking at the results from the longitudinal study of Strujik et al., in which the Mediterranean Diet Adherence Screener (MEDAS score), but not the Mediterranean Diet Score (MDS), was associated with physical function among older adults [13]. In this study, the increment of the MEDAS score was associated with a lower likelihood of impaired agility, mobility, and overall function, even after adjustments for physical activity and cognitive impairment. The MEDAS score was developed considering the Spanish MedDiet, which, although also focuses on the intake of fruits, vegetables, fish, and unsaturated fats, differs in the weight attributed to nuts, olive oil, and white meat, and in the items considered as unhealthy (dairy and all meat types in the MDS vs. red meat, butter, sugary-beverages, and baked goods in the MEDAS) [14].

The second point is the difficulty of distinguishing whether dietary patterns themselves can successfully reverse or prevent age-related function loss and whether they are components of strategies that can synergically act for this purpose – particularly physical activity, which promotes neuromuscular stimulation and favours good cognitive and physical function [15,16]. Furthermore, people following healthier diets usually present healthier overall lifestyles [13,17], limiting the assessment of the isolated effect of a specific dietary pattern.

Assessing dietary patterns is a very promising approach when exploring how nutrition interacts with ageing (in both prevention and care), with several studies suggesting a positive relationship between plant-based dietary patterns with limited intake of red meat, ultra-processed foods, and sugars, and several age-related outcomes, including cognitive and physical function. Future research should address potential distinctions among subgroups, longitudinal effects, and local cultural adaptations to deepen the understanding of the role of dietary patterns in ageing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.