To be healthy, diets need to be: x adequate: providing enough essential nutrients to prevent deficiencies and promote health, without excess; x balanced: in energy intake and energy sources (i.e. fats, carbohydrates and proteins); x diverse: including a wide variety of nutritious foods within and across food groups to favour nutrient adequacy and consumption of other health-promoting substances; and x moderate: in consumption of foods, nutrients or other compounds associated with detrimental health effects. The exact makeup of a diet will vary depending on individual characteristics, preferences and beliefs, cultural context, locally available foods and dietary customs.

y According to WHO, a healthy diet is one that provides enough essential nutrients to prevent deficiencies and promote health, without excess; is balanced in energy intake and energy sources (i.e. fats, carbohydrates and proteins); is moderate in consumption of foods, nutrients or other compounds associated with detrimental health effects; and includes a wide variety of nutritious foods within and across food groups to favour nutrient adequacy and consumption of other health-promoting substances. The exact makeup of a diet will vary depending on an individual’s characteristics, preferences and beliefs; the cultural context; locally available foods; and dietary customs. y In the context of dementia risk reduction, the following dietary patterns (all of which are compatible with WHO general guidance) have been studied: x MeDi emphasizes minimally processed, plant-based foods, with fresh fruits consumed daily and olive oil serving as the primary source of fat. It includes moderate portions of fish, seafood, poultry and dairy products, but limits sugary foods and red meat (98). Although rooted in Mediterranean food traditions, the core principles of MeDi can be adapted to diverse cultural and regional dietary patterns. x DASH focuses on reducing salt, added sugars and saturated fats, and promotes the eating of plenty of fruits, vegetables, whole grains, legumes, nuts, lean proteins and low-fat dairy products (105). x MIND – a hybrid dietary approach that integrates principles from both MeDi and DASH – prioritizes the consumption of predominantly plantbased foods while restricting the intake of animal-derived products and items high in saturated fats. A distinctive feature of MIND is its targeted emphasis on the inclusion of berries and green leafy vegetables (106). y Dietary patterns are complex models that encompass multiple dietary guidelines related to various dietary components. This differs from individual food dietary guidance, such as the WHO nutrition guidelines, which provide advice on the intake of salt, potassium, carbohydrates, saturated fatty acids and trans-fatty acids or the use of non-sugar sweeteners (87,90,92-94), and overall are compatible with WHO recommendations for a healthy and balanced diet. The present review did not identify any evidence for the effects of specific nutrients on the risk of cognitive decline and/or dementia. y Dietary habits are closely associated with socioeconomic status; thus, it is essential to establish equitable approaches that enable all individuals to access and maintain a healthy diet. Additionally, dietary intake should aim to ensure adequate consumption of nutrients that are of increased importance in older age, such as protein. y Adherence to a healthy, balanced diet should be supported through fiscal policies (95) and by implementing individual dietary guidance (87,92). y The recommendation against supplementing vitamins B and E, omega-3 PUFA and multivitamin/mineral complexes applies to individuals who do not have a diagnosed nutrient deficiency. y Healthy dietary patterns such as MeDi are feasible and adaptable when they are culturally tailored. Programmes should prioritize the adaptation of core principles of these dietary patterns – such as emphasizing vegetables, legumes, whole grains, healthy fats and reduced processed foods – to locally available ingredients and traditional eating practices. This approach supports implementation across diverse cultural, economic and geographical contexts. y Equity should be central to implementation, especially in low‑resource settings where availability and affordability of recommended foods may be limited. Adherence to a healthy diet is not always in the control of the individual; therefore, programmes may need to identify locally accessible, lower cost alternatives that still align with recommended dietary patterns. y Interventions should emphasize whole‑diet approaches rather than focusing on single nutrients, because overall patterns appear to be more relevant for long‑term health. y Longer term interventions and sustained behaviour‑change strategies are likely to be more effective, and should be built into programme design and delivery. y Dietary guidance should balance scientific complexity with practical applicability. In some settings, it may be helpful to translate broader dietary patterns into simple food-based messages.

A healthy, balanced diet should be recommended to all adults, in line with WHO guidance. Clinical practice: y Carbohydrate intake for adults and children: WHO guideline (21,22) y Guideline: sugars intake for adults and children (23) y Use of non-sugar sweeteners: WHO guideline (24) y Total fat intake for the prevention of unhealthy weight gain in adults and children: WHO guideline (25) y Saturated fatty acid and trans-fatty acid intake for adults and children: WHO guideline (26) y Guideline: sodium intake for adults and children (27,28) y Guideline: potassium intake for adults and children (28) Service delivery and care pathways: y WHO package of essential noncommunicable (PEN) disease interventions for primary health care (11) Public health and policy: y Healthy diet (12) y Fiscal policies to promote healthy diets: WHO guideline (29) y Tackling NCDs: best buys and other recommended interventions for the prevention and control of noncommunicable diseases (12)