The Brain Benefits of a Mediterranean Diet

A 2011 study by Gu & Scarmeasfound participants whose dietary pattern included a higher intake of fruits, vegetables, fish, nuts, and legumes, as well as a lower intake of meats, high fat dairy, and sweets reduced their risk of developing Alzheimer’s disease (AD) and age-related dementia (ARD).  Similarly, a literature review by Demarin, Lisak, & Morovic (2011), found people following a Mediterranean diet enjoyed a reduced risk for a wide range of neurodegenerative diseases such as AD, Parkinson’s, and other cognitive impairments.  Solfrizzi et al. (2011), found that the MedDiet reduced both the risk of Alzheimer’s disease and the rate of progression from the beginning stages of dementia to moderate-to-severe dementia.

A substantial amount of well-documented, quantitative evidence has been collected from numerous studies detailing test score improvements.  Scarmeas et al. (2009), found participants who closely followed the Mediterranean diet had a 28% lower risk of developing cognitive impairment over a 4.5-year period than those who didn’t follow the diet.  Also, volunteers suffering from some form of cognitive impairment at the start of the study who followed the Mediterranean diet had a 48% lower risk of developing full-blown Alzheimer’s disease than those who didn’t follow a Mediterranean diet by the end of the study.

The Mediterranean diet also appeared to increased life expectancy for people already suffering from AD.  Scarmeas et al. (2009), found that AD patients who followed the MedDiet very closely for a period of 4.4 years were 76% less likely to die than those who followed it the least.  Even a loose adherence to the MedDiet increased life expectancy.  AD patients who followed the Mediterranean diet to only a moderate degree lived an average 1.3 years longer than those who adhered to the diet to the least degree.

Inflammation is a well-known cause of many chronic diseases; including cardiovascular diseases, type 2 diabetes, cancer and AD (Nield, 2016).  A growing number of epidemiological studies have found that following a MedDiet can reduce inflammation.  Close adherence to a MedDiet has been shown to cause a decrease in both white blood cell and platelet counts, two common measures of low-grade inflammation.

Martinez-Lapiscina et al. (2013), found that the MedDiet was significantly better at preserving brain function than a low-fat diet.  The researchers studied 522 male and female volunteers between the ages of 55 and 80 who were healthy, but were at a higher risk for AD and dementia because of risk factors such as high blood pressure, family history, or being overweight.

The participants were split into three groups.  The first group followed a MedDiet and consumed at least a half-liter of extra virgin olive oil each week.  The second group followed a MedDiet plus a daily serving of nuts. The third control group ate a modern low-fat diet.  All study subjects took extensive cognitive tests at baseline and again 6 1/2 years later.  The tests gauged higher cognitive functions such as language skills, time and place orientation, abstract thinking and memory.

95 participants had developed either AD or MCI by the end of the study. 30 of the participants who consumed a MedDiet plus olive oil developed AD or MCI, while 25 who had followed the MedDiet plus nuts developed dementia, and 40 participants who followed the low-fat diet had either MCI or AD.  The follow-up cognitive function test showed that, on average, those who followed either one of the MedDiets scored substantially higher than those following the low-fat diet.

Martinez-Lapiscina et al. (2009), double-checked their findings by following up with 285 people. Participants averaged 67 years old at the start. Once again, participants were split into three equivalent and random groups; a MedDiet plus olive oil group, a MedDiet plus nuts group, and a low-fat diet control group. Their diets were documented using a self-report food questionnaire.

Study subjects cognitive acuity was tested at baseline and four years later. Again, the researchers found that olive oil was especially good for cognition. The group that ingested additional olive oil was 66% less likely to develop cognitive impairment at the conclusion of the study as the low fat diet control group.

Because of the relatively small sample size, results from both studies were not definitive. However, Martinez-Lapiscina et al. said it was one of the first times improvements in cognitive function have been linked to adherence to a Mediterranean diet in a randomized trial.

A study for the American Academy of Neurology by Luciano et al. (2017) found that older adults who followed a traditional MedDiet retained more grey matter as they get older than those who didn’t follow a MedDiet.  The study measured changes in brain volumes of 562 mentally healthy participants for 6 years from a large group of Scottish people designated as the “Lothian Birth Cohort.”  The study subjects were all born in 1936 and had taken standardized health assessments throughout their lives, including a mental ability test when they were 11 years old.

Around the time they reached 70, participating Lothian Birth Cohort members filled out dietary frequency forms that informed researchers what kinds of foods they ate and which kinds of foods they avoided.  Luciano et al. (2017), used the dietary surveys to split the volunteers into two groups; those who followed a Mediterranean-style diet and those who did not.  Using magnetic resonance imaging (MRI) scans, researchers gave participants a baseline brain scan
at age 70, and then again three and six years later to measure any changes in brain volume.  Other key factors taken into consideration were body mass index, diabetes, high blood pressure, cardiovascular disease history, IQ and years of education.

The MRI scans found that the brains of participants who followed the Mediterranean diet shrank about half as much as those who didn’t.  Even individuals who only loosely followed the Mediterranean diet had significantly less brain shrinkage.  The study also found that participants with a wide range of IQs and educational backgrounds benefited from the diet.  This suggests that the Mediterranean diet did not just help more educated or intelligent individuals who, generally speaking, tend to have larger brain volumes.  Luciano et al. (2017), said the study’s lengthy seven-year duration helped establish scientific evidence that the brain-shrinkage rates were tied to dietary patterns, and weren’t just flukes or casual associations.

Another important question concerning dietary interventions is what time of life should you start and when is it too late to start?  Evidence from a couple of recent studies suggest when it comes to making better dietary choices the sooner, the better.  But just about anyone, regardless of age or physical condition, can benefit from better nutrition at any age.

In a large cohort study of more than 10,000 healthy women, Samieri et al. (2013), found that women who followed a healthy Mediterranean diet in their 50s and 60s were 40% more likely to be cognitively healthy and live disease-free past the age of 70.

Researchers recorded each participants diet and overall health in the mid 1980s, then checked back with them 15 years later.  They found that women who ate balanced, healthy diets were 34% more likely to age healthily than women who ate less-healthy diets.  Women following a Mediterranean diet fared even better, they were 46% more likely to live disease free well past the age of 70; avoiding chronic illnesses such as heart disease, diabetes, and Parkinson’s disease.  They also showed far less cognitive impairment compared to the less healthy control group.

Researchers reported that women who ate more plant-based diet were healthier than those who didn’t.  They said a plant-based Mediterranean diet rich in whole grains, legumes, fruit, and vegetables is filled with fiber that helped reduce oxidative stress, slow digestion and control blood sugar.

While sooner may be better, a randomized controlled Scandinavian trial found that it’s never too late to benefit from a dietary change.  Kivipelto et al. (2015), recruited a group of 1,260 people in Finland considered at risk of dementia who were between the ages of 60 and 77.  Half of the participants followed a standard diet while the other half ate a modified Mediterranean diet and took part in a low-impact exercise plan.

Participants in the Mediterranean diet intervention group ended up doing substantially better on standardized cognitive tests.  Participants in the intervention group scored 25% higher on a neuropsychological test compared to the control group.  The differences in memory improvement was even greater. The intervention group scored 83% higher in executive memory tests, and processing speed was 150% faster that the control group.  Best of all, researchers said those improvements became apparent within just two years.

Kivipelto et al. (2015), said while previous research showed causal links between cognitive decline and lifestyle factors, theirs was the first large randomized controlled trial to show that an intensive program aimed at addressing these risk factors might be able to prevent cognitive decline in elderly people.

Olive oil, a central component of the MedDiet, was found to improve brain health in a French study conducted by Berr et al., (2009). Researchers followed 6,947 people ages 65 and over living in 3 French cities for 5 years.  Study subjects were split into three groups; no olive oil use at all, moderate use for cooking, and intensive use for both cooking and dressing. 23% of study participants used no olive oil, 40% used it moderately, and 37% were intensive users.  Outcomes were adjusted for overall health, lifestyle behaviors, socio-economic factors and other dietary considerations.

Participants in the Berr et al. (2009), study were given a series of cognitive tests at baseline and then again 4 years later.  The tests measured visual memory, verbal fluency, and overall cognitive function.  The researchers found that intensive use of olive oil resulted in a 17% reduction in cognitive decline and a 15% reduction of verbal fluency decline.

Several additional confounding factors could have influenced the findings. Intensive olive oil users were three times more likely to eat fish at least twice a week and two times more likely to have three or more vegetable servings a day than participants who used no olive oil.  Berr et al. (2009), wrote that olive oil in-and-of itself could most likely help improve cognition later on in life.  But overall diet, especially fruit and vegetable intake, were critically important for long-term health benefits.

A significant drawback of Berr et al.’s (2009), research, besides being a cohort and not a controlled study, was that researchers defined the moderate use category as “cooking only.”  Many of the nutrients in olive oil are heat sensitive. The “cooking only” category could have ruined many nutritional components, including monounsaturated fats and other cell-protecting antioxidants.  Only the “intensive” category participants used olive oil in salad dressings and drizzled it over their vegetables, which would preserve the heat-sensitive nutrients.  The researchers recommended a follow-up study to adjust for this line of inquiry.

Olive oil is considered to be so healthy because olives contain a large number of medicinal phytonutrients.  A principal phytonutrient is oleuropein, with is an antioxidant proved to reduce blood pressure and inflammation.  Other olive oil phytonutrients include hydroxytyrosol, tyrosol, and verbascoside (Mercola, 2016).

Extra virgin olive oil is the healthiest method of producing the oil. Extra virgin has the most antioxidants because the olives are processed naturally and crushed with a mechanical press.  Lesser grades of olive oil use chemical solvents or hot temperatures to extract the oil, methods that degrade the oil’s polyphenol content.

In addition of olive oil, fruits and vegetables are primary sources of healthy antioxidants, which help prevent damage to the brain and body by stabilizing rogue molecules known as free radicals.  Free radicals can damage cells and other genetic materials (Moeller, 2002).  Two types of extremely toxic free radicals already mentioned are tau tangles and beta-amyloid plaques.

A 2002 study by Engelhart et al., followed the dietary habits of more than 5,000 women and men who were at least 55 years old for an average of 6 years to examine the long-term effect of antioxidants on cognitive function.  All study subjects were healthy at the beginning of the study with no signs of AD or ARD.  The researchers analyzed the participant’s diets for antioxidant consumption at baseline, then gave them medical examinations and cognitive assessments every year after that to look for signs of dementia throughout the duration of the study.  Six years later, 197 study subjects had developed AD or ARD.

Researchers found that smokers who regularly ate foods rich in antioxidants were 70% less likely to develop AD than smokers who did not have high antioxidant diets. Smokers seemed to gain the most benefit from vitamins C and E, as well as from beta-carotene.  Nonsmokers did not gain same level of benefits from antioxidants.  The researchers noted that smoking could dramatically increase the body’s production of free radicals.

A study by Morris (2009), found that food rich in vitamin E appeared to decrease rates of cognitive decline and help a significant number of study subjects reduce their risk for AD and ARD.  Researchers recruited 815 older adults ages 65 and older.  They used self-report food frequency questionnaires to determine how much vitamins C, E and beta-carotene participants consumed at baseline and for 4 years after that.  131 people developed AD during the four-year study period.

Morris noted that increased levels of vitamin E for participants in the highest percentile resulted in a 43% decreased risk for AD.  However, this decreased risk was only found in participants who didn’t have the APOE-4 allele, a protein associated with an increased risk for AD.

A potential drawback with both the Morris (2009), and Engelhart et al. (2002), studies was that participants with cognitive problems might not be able to accurately report their diet or supplement use.  Also, both researchers noted that anyone who was concerned they were suffering from memory loss might start eating more healthily or taking more vitamin and mineral supplements.

It’s also been noted that the closer you follow a traditional Mediterranean diet, the better your chances are of preventing AD.  A study from Columbia University Medical Center in New York City by Scarmeas et al. (2006), followed 2,258 older people for four years, focusing on how a close adherence to a traditional Mediterranean diet influenced the brain health of study subjects developing AD. It was one of the first studies focusing on the Mediterranean diet’s effect on AD and cognitive decline as a whole, and not just individual types of food.

To make sure they were healthy and lacked cognitive impairment, participants were given a baseline standard medical and neurological examinations.  The neurological exam consisted of short and long-term memory tests, orientation, abstract reasoning, language and comprehension.  Participants were split into three groups according to their Mediterranean diet adherence using two seven-day food records.  The results were adjusted for age, sex, ethnicity, and education, smoking, comorbidity index, and body mass index.

After four years, 262 participants developed AD or dementia.  Scarmeas et al. (2006), found that participants who closely followed a traditional Mediterranean diet were 40% less likely to develop Alzheimer’s than people who only loosely followed the MedDiet.  And, as a general rule, study subjects who developed dementia were older, less educated, and had lower body mass indexes.

The ratios between Mediterranean diet and developing AD remained constant, even after adjusting for potential confounders such as age, sex, ethnicity, education, and body mass index.  Scarmeas et al. (2006), said a high intake of fish, fruits, and vegetables rich in antioxidants, plus an emphasis on unsaturated fats combined to lower the risk for developing AD.  The biggest drawback of the study is that it didn’t stop to consider the possible additive and interactive effects of all the different types of nutritional components working together.

Results from several prospective studies cited here suggest that the Mediterranean diet can reduce the risk of developing AD and ARD.  However, the results are not all consistent, which could be caused by differences in populations of study participants.  The Health, Aging, and Body Composition study (Health ABC) was a longitudinal cohort study that (Atkinson et al., 2007). The Health ABC study began in 1997 and followed 2,326 older adults in Memphis, TN and Pittsburgh, PA for 10 years.  Researchers used food-frequency questionnaires to determine how closely participants followed the Mediterranean diet as regards race and gender.  38.2% of participants were African-American, 51.3% were females aged 70-79 at the beginning of the study.

Atkinson et al. (2007), say the study found that a closer adherence to the Mediterranean diet reduced the rate of cognitive decline among African-American seniors, but not white senior citizens.  Researchers said the differences may be explained by socioeconomic factors which can be associated with both diet and cognitive performance.  The highly complex relationship between socioeconomic factors and race may cause some residual confounding. The discrepancy in outcomes might also be influenced by cardiovascular disease.  Researchers cite the example that African-Americans are known to be more sensitive to sodium intake and prone to high blood pressure.

The research indicates that a Mediterranean diet can help reduce both oxidative stress and inflammation and is made up of several dietary components thought to improve overall brain health.  It can also improve vascular risk factors such as diabetes and hypertension.  Researchers found that African-American who followed the Mediterranean diet closely declined significantly less on follow-up cognitive tests than those who didn’t follow it as closely. The difference was 22 points per year after adjusting for external factors like age, sex, education, physical activity, depression, diabetes and socioeconomic status.  Participants in the highest adherence group also had 15% lower homocysteine levels (Atkinson et al., 2007).

Limitations of the study include not distinguishing between different types of food categories, frequencies of food intake.  Additional randomized controlled trials with more diverse populations are needed to help confirm the association between the Mediterranean diet and cognitive decline.  If race does play a significant factor, additional studies using multiethnic cohorts can help discover whether a cognitive benefit is due to genetic or environmental factors.  Atkinson et al. (2007), conclude by saying regardless of any potential confounding race effects, following a MedDiet is still recommended for its many health benefits.  It is also likely that a lower adherence to a Mediterranean diet could be a consequence and not a cause of AD or ARD.

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