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Mediterranean diet and Alzheimer’s disease: the scientific connection.
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What is the Mediterranean diet?
The Mediterranean region covers 22 countries including Croatia, France, Greece, Italy, Morocco, Spain, and Turkey. Their dietary habits have evolved over 5000 years and are heavily influenced by cultural interplay. The term Mediterranean diet was first coined in the 1950s by Dr Ancel Keys, who studied 13,000 men and found that those of Italian and Greek origin had better health outcomes due to their eating habits [1]. Since then, the interest in this diet substantially grew and over the last 5 years, more than 5000 research papers were published in this field.
The Mediterranean diet encourages intake of whole grains, beans and legumes, fruits and vegetables, fish and olive oil and limits intake of red meat and sweets. It allows for limited alcohol consumption. The current recommendations of the Mediterranean diet are as follows [2]:
| Every meal | Daily | Weekly | Occasionally |
| 1-2 servings of fruits | 2 servings of low-fat dairy | 2 or more servings of fish/seafood | 2 or less servings of potatoes |
| 2 or more servings of vegetables | 1-2 servings of olives/nuts/seeds | 2 or more servings of legumes | Less than 2 servings of red meat |
| 1-2 servings of grains | Liberal use of herbs and spices | 2-4 servings of eggs | Less than 2 servings of sweets |
| Olive oil | 2 servings of white meat | Less than 1 serving of processed meat |
Positive lifestyle changes at any age can help in Alzheimer’s prevention. Diet has a major impact on health outcomes as well as brain health and brain performance.
Can foods cause Alzheimer’s disease?
A typical Western diet is high in ultra-processed foods. These foods are high in added sugars, saturated fats, and salt, and low in protein and fibre. A 2022 study that followed over 70,000 people in the UK for 10 years, found that high intake of ultra-processed food was linked to high risk of dementia and Alzheimer’s [3] and replacing just 10% of those calories with healthier options reduced the risk by almost 20%. Another decade-long study found that among 10,000 Brazilians,
those who consumed 20% of their total daily calories from processed foods had a 25% decrease in mental functions [4].
Your brain on sugar, fat, and alcohol
Excessive sugar intake contributes to Alzheimer’s disease by affecting brain areas involved in memory and production of new brain cells [5][6]. A study spanning 20 years found that
those who drank more than 7 servings of sugary drinks were almost 3 times more likely to get Alzheimer’s and dementia
than those who avoided sugary drinks [7].
Your brain is 60% fat [8] and the type of fat you consume can make or break its working. A diet high in saturated fats (found in fatty meats, butter, cheese) increases the level of bad cholesterol in your blood. This has been linked to the production of compounds that can clog your brain cells, commonly seen in Alzheimer’s patients, called amyloid-beta and tau proteins.
Those with the highest intake of saturated fat had 70% higher risk of getting Alzheimer’s [9].
These fats also damage the protective barrier of the brain, allowing entry of amyloid-beta from the blood into the brain.
Good fats can protect your brain. 25% of the brain’s fats is DHA [21] (a type of omega 3 fat), which forms the structure of the brain and has protective functions. It must be taken from your diet and is found in fatty fish, seafood, and algae. DHA helps to prevent the production of amyloid-beta. [10]. They also protect against inflammation and help maintain structure integrity of brain areas responsible for thinking and memory skills [11].
Your brain would be happy if you skip that glass of wine. A 20 years’ study found that
heavy drinkers (8 or more drinks per week) had a faster decrease in mental skills than those who abstained from alcohol [12].
Alcohol causes oxidative stress, and prevents production of a chemical messenger for memory and concentration called acetylcholine. Alcohol also promotes accumulation of amyloid beta and tau proteins [13]. Your brain is quick to spring back once alcohol intake is stopped, research has found that the brain starts repair work within 2 weeks of abstinence [14].
Repairing and protecting your brain
Your brain is resilient, and with the right mix of nutrients, it is possible to recover from the damage of unhealthy eating habits. Mediterranean diet benefits have been heavily researched for reducing the risk of dementia and Alzheimer’s since it is packed with brain loving nutrients like protein, fibre, omega 3 fats, vitamins, and minerals and low in sugar, saturated fats, and salt. A 2022 review of 28 high quality studies found that
following the Mediterranean diet can reduce the risk of Alzheimer’s disease by up to 40% and improve mental skills and memory [15].
Another review of 8 studies found that high adherence to the Mediterranean diet was associated with slower mental decline, higher memory scores, and lesser depression. Replacing burgers and fries with plant protein meals could help you stay happier and smarter until old age.
Those who followed the Mediterranean diet for 10 weeks had an improvement in memory, attention, and concentration [16].
Those with higher adherence to the diet were found to have a better structural integrity of brain areas that are involved in information processing [17]. The anti-inflammatory and antioxidant components of the diet contribute to its benefits.
Diving deeper into the diet’s components, the dominant fats are olive oil and omega 3 fats. Replacing vegetable oils with olive oil was associated with better mental skills scores [18]. High intake of fish, which is a good source of omega 3, is protective for the brain.
Those who consumed at least 1 serving of fish per week had higher volume of brain areas responsible for memory [19].
This means adding a portion of salmon cooked in olive oil for lunch could help you score better in your exams. A study of 70-year-olds following a Mediterranean diet, especially those who had a high intake of green leafy vegetables and low intake of meat, scored higher on memory and thinking skills tests [20].
It is evident that your brain is what you eat. Increasing intake of fruits, vegetables, whole grains, nuts, and omega 3 fats and decreasing intake of sugar, saturated fats and salt can bring long lasting benefits to your brain. Research into Alzheimer’s disease prevention is promising. The current research around diet and lifestyle modifications have provided data to reduce the risk of Alzheimer’s disease or delay its onset. Replacing everyday foods with healthier Mediterranean diet approved swaps can substantially improve your diet quality:
|
Western diet (100g) |
Mediterranean diet (100g) | Nutrient change on switch to Mediterranean diet |
| Chocolate cereal | Steel cut instant oatmeal |
|
| Beef steak | Salmon fillet |
|
| Plain pasta | Whole grain pasta |
|
| Canned baked beans | Cooked chickpeas |
|
| Salted butter | Olive oil |
|
| Hard candy | Blueberries |
|
References:
- Dernini, S. et al. (2015). Mediterranean Diet: From a Healthy Diet to a Sustainable Dietary Pattern. Frontiers in Nutrition, 2.
- FUNDACIÓN DIETA MEDITERRANEA. (n.d.). WHAT’S THE MEDITERRANEAN DIET? [online]
- Li, H. et al. (2022). Association of Ultraprocessed Food Consumption With Risk of Dementia: A Prospective Cohort. Neurology.
- CNN, S.L. (n.d.). Cognitive decline linked to ultraprocessed food, study finds. [online]
- Poulose, S.M. et al. (2017). Nutritional Factors Affecting Adult Neurogenesis and Cognitive Function. Advances in Nutrition: An International Review Journal, 8(6), pp.804–811.
- Beilharz, J.E. et al. (2014). Short exposure to a diet rich in both fat and sugar or sugar alone impairs place, but not object recognition memory in rats. Brain, Behavior, and Immunity, 37, pp.134–141.
- Miao, H. et al. (2020). Sugar in Beverage and the Risk of Incident Dementia, Alzheimer’s Disease and Stroke: A Prospective Cohort Study. The Journal of Prevention of Alzheimer’s Disease, pp.1–6.
- Chang, C.-Y. et al. (2009). Essential fatty acids and human brain. Acta Neurologica Taiwanica, [online] 18(4), pp.231–241.
- Konig, J. (2015). Is There a Link between Saturated Fat Intake and Alzheimer’s disease? The Science Journal of the Lander College of Arts and Sciences, [online] 8(2).
- Grimm, M.O.W. et al. (2017). Omega-3 fatty acids, lipids, and apoE lipidation in Alzheimer’s disease: a rationale for multi-nutrient dementia prevention. Journal of Lipid Research, [online] 58(11), pp.2083–2101.
- Weiser, M. et al. (2016). Docosahexaenoic Acid and Cognition throughout the Lifespan. Nutrients, 8(2), p.99.
- Heymann, D. et al. (2016). The Association Between Alcohol Use and the Progression of Alzheimer’s Disease. Current Alzheimer research, [online] 13(12), pp.1356–1362.
- Araujo, I. et al. (2021). Impact of Alcohol Abuse on Susceptibility to Rare Neurodegenerative Diseases. Frontiers in Molecular Biosciences, 8.
- van Eijk, J. et al. (2012). Rapid Partial Regeneration of Brain Volume During the First 14 Days of Abstinence from Alcohol. Alcoholism: Clinical and Experimental Research, 37(1), pp.67–74.
- Fu, J. et al. (2022) Association between the mediterranean diet and cognitive health among healthy adults: A systematic review and meta-analysis. Frontiers in Nutrition. 9:946361.
- Klimova, B. et al. (2021). The Effect of Mediterranean Diet on Cognitive Functions in the Elderly Population. Nutrients, 13(6), p.2067.
- Karstens, A.J. et al. (2019). Associations of the Mediterranean diet with cognitive and neuroimaging phenotypes of dementia in healthy older adults. The American Journal of Clinical Nutrition, [online] 109(2), pp.361–368.
- Mazza, E. et al. (2018). Effect of the replacement of dietary vegetable oils with a low dose of extra virgin olive oil in the Mediterranean Diet on cognitive functions in the elderly. Journal of Translational Medicine, 16(1).
- Raji, C.A. et al. (2014). Regular Fish Consumption and Age-Related Brain Gray Matter Loss. American Journal of Preventive Medicine, 47(4), pp.444–451.
- Corley, J. et al. (2020). Dietary patterns, cognitive function, and structural neuroimaging measures of brain aging. Experimental Gerontology, 142, p.111117.
- Guesnet, P. et al. (2011). Docosahexaenoic acid (DHA) and the developing central nervous system (CNS) - Implications for dietary recommendations. Biochimie, [online] 93(1), pp.7–12.
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