Introduction

According to the World Health Organization (WHO), dementia has affected more than 55 million people globally and quite alarmingly, every year, 10 million more cases get added to this statistic. It is not as surprising, then, to know that dementia is the seventh leading cause of death around the world.  While there is currently no cure for dementia, there are many interventions and self-management strategies individuals with dementia can adopt, including healthy diets that maintain and promote brain function.

Dementia is not a disease in itself but rather a broad term to describe several diseases that are characterised by the loss of cognitive functioning, such as decision-making, memory, and reasoning. 

Some types of dementia include:

• Alzheimer’s - one of the most common types of dementia
• Vascular dementia
• Dementia with Lewy body
• Frontotemporal dementia 

This list is by no means exhaustive and it is possible for individuals to have a combination of two or more types of dementia – known as mixed dementia. According to Alzheimer’s Society UK, “at least 1 in 10 people with dementia is diagnosed as having mixed dementia”. 

Dementia is progressive in nature, which means the symptoms usually worsen over time, especially if early diagnosis and intervention are missed. On an individual level, dementia affects a person’s mental capabilities, on top of bringing about a loss of interest in activities that were previously enjoyable, aspects of personality change, and difficulty navigating social situations. This leads to a loss of independence, which means external help from family, friends, or healthcare professionals is inevitable at a certain stage of this disease. 

Within the United Kingdom, the annual care cost (social care and unpaid care combined) for someone with mild dementia is £28,700 per person, while that figure rises to £80,500 for individuals with severe dementia. 

While this signifies what an urgent economic challenge this is nationwide, it is individuals and families faced with dementia that bear the majority of these care costs. Similarly, close to 50% of people with dementia completely fund the whole of their own nursing and residential care. 

This brief overview of dementia's prevalence and its individual and societal impact highlights the urgent need to understand effective management and prevention strategies. It is important for the public to receive the latest information on dementia research and prevention methods. The connection between dementia and diet is well-established, with certain foods contributing to healthy brain function. However, ongoing review and development of research in this area are essential to improve our understanding of diet's role in dementia prevention. This article aims to present recent insights from 2020 onwards on several diets and nutrients that show promise in combating dementia's effects.

Latest insights on diet and dementia management (from 2020 onwards)

The mediterranean diet 

One of the most well-known diets to help prevent dementia or reduce its progression is derived from Mediterranean eating habits, emphasising plant-based foods like fruits, vegetables, whole grains, legumes, and nuts. Olive oil is the primary fat source, supplemented by moderate fish and poultry intake for omega-3 fatty acids. 

Dairy and red wine are consumed in moderation, while red meat and processed foods are limited. Herbs and spices are usually the seasonings of choice, reducing salt intake. This diet is linked to improved cognitive function and reduced risks of heart disease and cancer.

Recent studies have tried to bridge the gap in longitudinal follow-up:

• One study of a traditional Mediterranean population found that only 62 out of 1,046 participants developed dementia over the years. Those who followed the diet the most had a 72% reduced risk compared to those who adhered the least.¹
• A meta-analysis of 11 studies concluded that consistently adopting a Mediterranean-rich diet significantly reduced the risks of developing mild cognitive impairments and Alzheimer’s disease.²
• A UK Biobank study found that consuming fish 2-3 times a week and 1-2 servings of fruit daily was linked to a reduced risk of dementia compared to non-consumers.³

The MIND diet

The Mediterranean-DASH (Dietary Approaches to Stop Hypertension) Intervention for Neurodegenerative Delay (MIND) diet is designed to promote brain health and reduce neurodegenerative disease risks such as Alzheimer's disease by supporting heart and blood vessel function. It focuses on anti-inflammatory foods such as green leafy vegetables, berries, nuts, whole grains, fish, poultry, olive oil, and wine. Unlike the Mediterranean diet, the MIND diet emphasises specific brain-healthy foods and limits red meat, butter, cheese, pastries, and fried or fast food to reduce cognitive decline.

Several recent studies have explored the association between the MIND diet and brain function:

• A study on older adults in a French population concluded that following a MIND diet was linked to a lower chance of dementia. Brain images showed that individuals adhering to the MIND diet had more preserved brain structures ⁴
• A 2023 review found that, in the 11 studies reviewed, there was a positive association between following the MIND diet and some forms of cognitive function, but not all specific cognitive functions had a positive correlation. It also suggested the MIND diet may be a useful long-term treatment strategy though more research was required for those with onset dementia.⁵
• A review of 13 MIND diet articles found a positive link between diet and specific brain functions, with 78% supporting overall mental capabilities. This review suggests the MIND diet is better for improving cognition than other plant-rich diets like the Pro-Vegetarian or Baltic Sea diets.⁶

The ketogenic diet and brain health 

Another frequently discussed diet linked to improving brain health is the ketogenic diet. This high-fat, low-carbohydrate diet shifts the body's metabolism into ketosis, where fat is used as the primary energy source instead of carbohydrates (and glucose). This diet is believed to provide protection to the brain and improve cognitive function. Key components include a high intake of healthy fats, moderate protein, and even less carbohydrates. Foods such as avocados, nuts, seeds, fatty fish, and oils are emphasised, while grains, sugars, and starchy vegetables are restricted.

Recent research has explored the potential benefits of the ketogenic diet for individuals with dementia. Key findings include:

• A 2021 study investigated the ketogenic diet's impact on Alzheimer's patients, comparing daily cognitive function results to those on a low-fat diet. Participants on the 12-week (modified) diet experienced better daily function and quality of life.⁷
• Researchers at the University of California, Davis found that a ketogenic diet delayed early stages of memory loss in mice, symptoms that are comparable to mild cognitive impairment prior to developing Alzheimer’s disease in humans.⁸

Nutrient-specific insights

Omega-3 fatty acids are known to regulate our immune system by reducing inflammation. A recent review on incorporating high omega-3 diets concluded that omega-3s are associated with reduced risk of cognitive impairment and are most effective at doing so when introduced before or during the appearance of early cognitive decline.⁹

However, a recent study in 2024 analysed how several factors that differ from person to person, such as metabolism rates, hormone levels, and effectiveness of the immune system, can have an impact on how much omega-3 is metabolised. Therefore, there is a push for further research on high omega-3-rich diets and promoting brain health, as well as further consideration being given to personalising this supplementation by taking into account a person’s health history.¹⁰

Antioxidants, commonly found in vegetables and fruits, help protect our cells from damage. There are mixed results from previous studies that looked at the effects of antioxidants on brain health, which usually take self-reports to determine participants' food consumption. 

One study that looked at the correlation between antioxidant levels in blood samples and the probability of developing dementia found that individuals who had higher blood levels of antioxidants had a reduced risk of dementia onset. However, other lifestyle factors, such as smoking and overall diet, reduced this correlation.¹¹

Vitamin B - especially B6, B9 (i.e. folic acid), and B12  have been suggested as important nutrients in dementia management and cognitive maintenance. This is because B vitamins help reduce levels of an amino acid that has been linked to damaging blood vessels in the brain and inducing the risk of cognitive decline. However, a few studies in recent years have found inconclusive evidence for this.^{12, 13}

Summary

Dementia poses significant global health challenges and currently has no cure. However, one of the most important strategies to promote cognitive function and reduce the risk of developing dementia is adopting an appropriate diet with nutrient-specific foods that are known to aid brain health. Diets like the Mediterranean, MIND, and Ketogenic have shown promise in improving cognitive function and potentially slowing dementia's progression. It is important to understand that personalised nutrition, considering genetic, metabolic, and lifestyle factors, is essential for optimising these diets' effectiveness. Combining dietary strategies with ongoing research is crucial for comprehensive dementia management. Adopting a brain-health diet and staying informed on the latest research are proactive steps individuals can take to support their cognitive health.