Of all the modifiable lifestyle factors for maintaining a healthy brain throughout adulthood, a healthy dietary pattern may be paramount.
Most experts believe that the same diet that promotes cardiovascular health will also optimize brain longevity and resistance to disease. By improving blood pressure and blood lipids, lowering blood sugar, reducing sodium intake, and maintaining a healthy weight, the optimal diet will improve both cardiovascular and brain health. In addition, phytonutrients in a brain-healthy diet can reduce oxidative stress and inflammatory brain injury.
The identification of the world’s Blue Zones, where a great percentage of the local population lives long, healthy lives free of cardiovascular disease and the burden of dementia, led to an intense investigation of the lifestyle factors which may provide these benefits. Many of these factors are intertwined because of the simultaneous effects of a healthy lifestyle on cardiovascular and brain health, sleep, and even mood.
The most studied diet and to date, the most validated for a healthy brain is the Mediterranean Diet (Med Diet). The Med Diet is based on the traditional eating habits of people living in the countries bordering the Mediterranean Sea. While the ethnicity, culture, religion, economy, and agriculture of these people varies widely, certain common factors in their diet can be identified. These include plenty of fruits, vegetables, whole grains, beans, nuts, and seeds, with olive oil as a primary fat source and low to moderate intake of wine, dairy, eggs, fish, and poultry. Compared to the typical American diet, there is much less saturated fat, refined carbohydrates, sugar, red meat, and salt. The benefits of the Med Diet are due to both what is added and what is left out.
Large population-based studies have validated the Med Diet as beneficial in maintaining cognitive function and preventing dementia. (1) For example, the CARDIA study followed 2,621 middle-aged individuals for 30 years, assessing their adherence to the Med Diet and subsequent development of cognitive decline. (2) Persons who followed the Med Diet most closely had significantly less decline in cognitive performance on standardized tests compared to those with less adherence. In another study, 826 elderly participants were found to have slower cognitive decline when closely adhering to the Med Diet. (3)
The Mediterranean Intervention for Neurodegenerative Delay (MIND) Diet is a variant of the Med Diet diet developed at Rush University to provide optimal brain health. There are 15 dietary components to the MIND Diet. Ten of those components are considered “brain super-foods” or “healthy brain” foods. They include green leafy vegetables, other vegetables, nuts, berries, beans, whole grains, fish, poultry, olive oil, and wine. The remaining 5 components are considered unhealthy and include red meats, butter and margarine, cheese, pastries and sweets, and fast food or fried food. Again, the goal is to eat healthy foods and avoid unhealthy ones. Blueberries and strawberries are particularly promoted by the MIND Diet due to their high concentrations of antioxidant flavonols and related cognitive benefits.
Some studies have found the MIND Diet better than the Med Diet in slowing cognitive decline, but long-term large population studies are still lacking. One study followed 923 middle-aged and elderly participants for 4.5 years and found even moderate adherence to the MIND Diet was associated with a reduced risk of Alzheimer’s Disease, while moderate adherence to the Med Diet showed no benefit. (4)
How the Med and Mind diets are able to prevent cognitive decline is probably multi-factorial. These diets are anti-inflammatory, lessen oxidative stress, have beneficial effects on blood lipids, lower blood pressure, prevent obesity, and help control blood sugar. The increased levels of flavonoids found in the MIND Diet may be particularly important in preventing oxidative damage in multiple organ systems including the brain. (5) The anti-inflammatory effects of the dietary components (polyphenols and omega 3 fatty acids) prevent systemic inflammation including brain inflammation.
Flavonoids are abundant in most plants that we eat, especially berries, red wines, tea, cocoa, and green vegetables. They reduce free radicals and oxidative stress and have anti-inflammatory properties. Recently, a large study of 2800 participants followed over 20 years found a reduction in the diagnosis of dementia associated with higher flavonoid consumption. (6)
The omega-3-fatty acids present in fish, walnuts, and soybeans, along with the flavonols in the diet, inhibit inflammation and may be neuroprotective. (7) However, it has been difficult to prove that Omega 3 supplements improve long term brain health or prevent the onset of dementia, but they are still undergoing study and are regularly recommended by cardiovascular specialists.
Extra virgin olive oil, a mono-saturated fat, is an important part of the Med and MIND Diets and has many beneficial effects on brain function and prevention of disease. Olive oil has potent anti-oxidant and anti-inflammatory effects mediated through its polyphenol and flavonoid content.
Sodium in our diet may have direct inflammatory effects on the brain, leading to an increased risk of dementia. Besides contributing to high blood pressure, salt causes the formation of inflammatory substances in the intestines which can travel to the brain and cause inflammation. (8)
Any dietary intervention designed to maintain brain function must address the obesity epidemic. Besides adding to the burden of high blood pressure and diabetes, obesity directly causes brain inflammation. Fat cells release inflammatory mediators such as tumor necrosis factor and interleukin (6), leading to a pro-inflammatory state and oxidative stress with wide-ranging deleterious effects throughout the body and local production of inflammation in the brain. (9) Even teenagers exhibit deleterious brain changes associated with obesity. (10)
In summary, proper nutrition and diet help maintain brain health through multiple pathways. On the one hand, a proper diet can prevent high blood pressure, hyperglycemia, obesity, lipid abnormalities, and the inflammatory effects of excess sodium, while ingesting beneficial nutrients lessens oxidative stress and chronic inflammation.
The Mind Diet
The MIND Diet includes the following components:
- Whole Grains: at least 3 servings/day
- Green Leafy Vegetables: at least 6 servings/week
- Other Vegetables: at least 1 serving/day
- Berries: at least 2 servings/week
- Fish: at least 1 serving/week
- Poultry: at least 2 servings/week
- Beans: more than 3 servings/week
- Nuts: at least 5 servings/week
- Olive Oil: as primary plant oil
- Wine: 1 serving/day
Limit Intake of:
- Butter/margarine: less than 1 pat per day
- Cheese: less than a 1-ounce serving/week
- Pastries/sweets: less than 5 servings/week
- Fast/fried food: less than 1 serving/week
- Red/processed meats: less than 4 servings/week
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- Neurology 2019;92:e1589-e1599.
- Neurology 2014;85:1410-1416.
- Alzheimer’s and Dementia 2015;11:1007-1014.
- Clin Chem Acta 2014;436:332-347.
- Am J Clin Nutr 2020;112:343-353.
- Pharm Rev 2018;70:12-38.
- Cell Cycle 2017;16:785-794.
- Arch Med Sci 2017;13:851-863.
- Science Daily 2019;4:1.