Mediterranean Diet and Cognition

The evidence for a beneficial effect of a Mediterranean style diet (MedDiet) on brain health grows on a regular basis.

For those interested in a good summary of the effects of the MedDiet on cognition, I recommend reading the free full text review recently published in Frontiers in Neuroscience.

In this review, Roy Hardman and colleagues searched for research studies on cognition and the Mediterranean diet published between 2000 and 2015.

A figure in the review proposed several mechanisms where components in a MedDiet may contribute to brain function:

• Cardiovascular: effect on blood pressure/blood lipids and arterial stiffness
• Inflammation: lowering of blood inflammatory markers including C-reactive protein and cytokines
• Neurotrophic effects: Increased levels of BDNF, insulin growth factor stimulating neurogenesis
• Cell signalling
• Cellular energy metabilism
• Lowering of oxidative stress

Using a rigorous selection process, Hardman and colleagues identified 18 high-quality recent studies of the MedDiet and adult human cognition. These studies generally demonstrated an positive effect for subjects with higher compliance with MedDiet elements. These positive effects included research supporting:

• A slower rate of cognitive decline with aging
• A reduced risk of developing mild cognitive impairment
• Improved recognition memory and delayed recognition memory
• Improved cognitive reserve on the Mini-mental status examination test (MMSE)
• Improved attention

The authors conclude that evidence to date supports prospective randomized clinical trials of MedDiet nutritional intervention. These studies should included standardized batteries of cognitive function that can be administered via a computer or tablet.

For readers with more interest in the review, you can access the free full-text manuscript by clicking on the PMID link in the citation below.

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Photo in this post of foods found in the Mediterranean diet is from my personal files.

Hardman RJ, Kennedy G, Macpherson H, Scholey AB, & Pipingas A (2016). Adherence to a Mediterranean-Style Diet and Effects on Cognition in Adults: A Qualitative Evaluation and Systematic Review of Longitudinal and Prospective Trials. Frontiers in nutrition, 3 PMID: 27500135

The Brain: Red Meat and Mediterranean Diet

Entorhinal Cortex Highlighted in Blue

Previous posts in this blog have highlighted some the research related to links between brain health and elements of the Mediterranean diet.

I want to inform readers of a new important research study from the Mayo Clinic.

In this study, researchers completed brain cortical thickness analyses on 672 cognitively normal adults. It is generally accepted that greater cortical thickness relates to improved cognitive performance.

The participants completed an extensive dietary history and brain cortical thickness measures were correlated to total and component Mediterranean diet intake. Here are the key findings from the study:

• Higher Mediterranean diet total scores were linked to greater cortical thickness measures in frontal, parietal, occipital and total brain
• Higher legume and fish component intake had the highest links to greater cortical thickness
• Legume intake correlated with greater cortical thickness in parietal, precuneus, occipital and lingual regions
• Fish intake correlated with greater precuneus, parietal and posterior cingulate cortical thickness
• Carbohydrate intake was linked to lower entorhinal cortical thickness
• Red meat intake correlated with greater entorhinal cortical thickness

This study in important for several reasons. First, it highlights specific components (legume and fish) of the Mediterranean diet with thicker brain cortices.

But what I found most interesting was the red meat finding.  Red meat intake was associated with slightly smaller cortices in two parietal regions. However, this association did not reach statistical significance. The association of red meat intake with greater entorhinal cortex thickness did reach statistical significance. 

The authors note some of the epidemiological research linking red meat intake to increased rates of dementia. This made their finding of a positive entorhinal cortex finding with red meat intake unexpected and they note in discussion section:

"The potential mechanism is unclear; we speculate that it could relate to some beneficial components of lean read meat (e.g. iron, protein, MUFA and PUFA) and beneficial effects on increasing satiety and reducing weight gain."

The entorhinal cortex is a key brain region serving as a link between the hippocampus and neocortex. The Wikipedia description of the role for the entorhinal cortex includes important contributions to:

• declarative memory
• spatial memory
• memory consolidation
• memory optimization in sleep

This study is observational in nature and shares weakness with this type of research design. The findings will need replication. Nevertheless, the study suggests fish, legume and lean red meat intake may contribute to preservation of brain cortical health.

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Image is an iPad screen shot of the entorhinal cortex from the 3D Brain app.

To access the study abstract, click on the PMID link below.


Staubo SC, Aakre JA, Vemuri P, Syrjanen JA, Mielke MM, Geda YE, Kremers WK, Machulda MM, Knopman DS, Petersen RC, Jack CR Jr, & Roberts RO (2016). Mediterranean diet, micronutrients and macronutrients, and MRI measures of cortical thickness. Alzheimer's & dementia : the journal of the Alzheimer's Association PMID: 27461490

Top Ten Brain Posts 2015: Mediterranean Diet and Alzheimer's

The Brain Post with the second highest pageview count for 2015 was my review of a study of the Mediterranean Diet and Alzheimer's Prevention.

You can access the original post by clicking:

HERE

This study found a link between adherence to a Mediterranean diet with thicker brain cortical regions in the left brain hemisphere.

The regions with increased thickness are regions known to be affected in Alzheimer's disease.

We are a long way from finding a definitive way to modify diet to reduce the incidence of Alzheimer's dementia. Look for this topic to be a continued focus of significant research attention.

Follow the author on Twitter @WRY999

Photo of great egret is from the author's files.

Mediterranean Diet and Alzheimer's Disease Prevention

There is an urgent need to identify strategies to prevent or delay the onset of Alzheimer's disease and other forms of dementia.

The role of diet as a prevention strategy is controversial. Some research evidence supports a role for a Mediterranean diet in cognitive health and dementia prevention.

A recent brain imaging study adds to this evidence. Dr. Lisa Mosconi and colleagues at New York University School of Medicine completed a cross-sectional study of brain magnetic resonance imaging and diet was completed in 52 older cognitively normal individuals.

The key elements of the design of this study were:

• Subjects: Community subjects participating in a longitudinal brain imaging study with a mean age of 54 years (standard deviation 12 years). Approximately 2/3 of the subjects were women.
• Study measures: Dietary information was collected using the Harvard/Willet food frequency questionnaire and subjects were rated on adherence to a Mediterranean diet using the MeDi. This scale rates intake of fruit, vegetables, legumes, cereal and fish as beneficial with dairy and meat intake rated detrimental. Information on dietary fat and alcohol were also used rated for a nine-item Mediterranean diet score. Subjects scoring greater than 5 were rated as Mediterranean diet adherent. 
• Brain imaging: All subjects completed a cross-sectional brain MRI using a 1.5 Tesla scanner. Volumetric brain measures were calculated using FreeSurfer software.
• Statistical analysis: Multivariate general linear modeling was used to assess the correlation of diet (high vs low Mediterranean diet adherence) with correction for a variety of potential confounding variables including age, gender, family history of Alzheimer's disease, APOE gene status and BMI.

The brain analysis focused on regions of the brain known to show atrophy with Alzheimer's dementia. 

This analysis showed Mediterranean diet adherent subjects with statistically significant greater brain thickness measures in the left brain hemisphere for:

• entorhinal cortex
• orbitofrontal cortex
• posterior cingulate cortex

This effect was found in the uncorrected volumetric data and the relationship remained with correction for age and total intracranial volume measures.

The authors note previous brain imaging studies have linked cognitive decline and dementia with atrophy of the left hemisphere regions of the brain found significantly linked to Mediterranean diet adherence in this study.

An additional brain area of atrophy in Alzheimer's is the hippocampus a region not addressed in the current research study.

The take home message here is that this study:

"provides support for further exploration of dietary behavior as a possible AD (Alzheimer's disease) prevention strategy".

The sample size is this study is relatively small and will need replication in other larger sample sizes. 

There was no correlation with neuropsychological scores and Mediterranean diet in this study. This is not surprising as the subjects were recruited as being cognitively normal.

It will be interesting to see in the longitudinal follow up if Mediterranean Diet adherence relates to neuropsychological performance and brain atrophy over time.

Readers with more interest in this research can find the free full-text manuscript by clicking on the PMID link in the citation below.

Photo of macaw is from the author's files.

Follow the author on Twitter @WRY999.

Mosconi L, Murray J, Tsui WH, Li Y, Davies M, Williams S, Pirraglia E, Spector N, Osorio RS, Glodzik L, McHugh P, & de Leon MJ (2014). Mediterranean Diet and Magnetic Resonance Imaging-Assessed Brain Atrophy in Cognitively Normal Individuals at Risk for Alzheimer's Disease. The journal of prevention of Alzheimer's disease, 1 (1), 23-32 PMID: 25237654

Cognitive Decline and the Mediterranean Diet

I have previous posted on some of the research related to beneficial effects of a Mediterranean style diet on health.  In one post I summarized some of the quantities of food types in those judged to have a high rating for the diet.

A recent study by Tangney and colleagues looked at the rate of cognitive decline in a prospective study of elderly adults in Chicago, Illinois.  The study retrospectively judged the diet of participants for characteristics consistent with a Mediterranean diet.  The exact scoring sheet is not included in the manuscript but based on the data provided and other resources, I have attempted to summarize the rating in the spreadsheet below.

Before looking at the rating system, the study results of note include:

• Subjects were rated on compliance with the Mediterranean Diet and another diet rating for compliance with the USDA food pyramid model
• White subjects scored higher on compliance with the Mediterranean diet while black subjects scored higher on the USDA food pyramid model
• Higher scores on the Mediterranean diet were correlated with a slower rate of cognitive decline over time (cognitive decline was judged based on a composite score of a memory test, the Minimental Status Exam and a digit symbol substitution test)

Looking in more detail at this current study, the highest tertile (highest third) in the Mediterranean diet scored 30-45 on the Mediterranean average weekly diet score. (There was some score adjustment for total calorie intake it the study).  The rating includes 11 categories rated from 0-5 on each item for a maximum of 55 points.  The study looked at two different ratings for alcohol intake.  One looked only at alcohol intake and one looked at total alcohol intake. (Use only one of the two rating for item 11, not both).  Both low and high consumption of alcohol is rated lower on the scale than a consumption of 1-2 drinks per day.  Interestingly, a slower rate of cognitive decline was found in the present study when either red wine or total alcohol was used.

The amount of weekly servings for cereals/whole grains and vegetables looks a little overwhelming.  But four slices of whole grain bread per day by itself would put you in the 4 rated for cereals/pasta/whole grains.  You really only need a top score of 5 in 6 categories to reach what was found as the top third in a U.S. sample.  If you throw in a couple of days per week without red meat you can reach a 3 in the red meat category (I hate to make this recommendation since my father raised cattle in Nebraska). 


So looking at the scoring system used in this study helps put the diet in better perspective.  Many people are probably scoring mid-range on the Mediterranean diet but with a few adjustments could significant improve their compliance with the diet.


Photo of WGC Accenture winner Luke Donald at 2010 PGA Championship courtesy of Yates Photography. 


Spreadsheet summary scale adapted from manuscript by author.


Tangney CC, Kwasny MJ, Li H, Wilson RS, Evans DA, & Morris MC (2011). Adherence to a Mediterranean-type dietary pattern and cognitive decline in a community population. The American journal of clinical nutrition, 93 (3), 601-7 PMID: 21177796

Does Alzheimer's Prevention Research Deserve More Funding?

Three separate items caught my eye recently related to the demographic challenge of aging and clinical neuroscience disorders of old age--primarily Alzheimer's disease and Parkinson's disease.

The first was the TED Talk of Gregory Petsko on the coming neurological epidemic. Here are my notes on the presentation--it is only about 4 minutes in lengh.

• Next 40 years epidemic of neurological illness on global scale
• Map of countries with >20% over 65 expanding
• Lifespan doubled since 1940
• Risk of Alzheimers increases exponentially after age 65
• Alzheimers and Parkinsons Disease key disorders
• Misfolding protein key to the development of Alzheimers
• His research tries to develop drugs to inhibit this folding of tangling of brain proteins
• Alzheimers disease linked to lower cancer risk
• Current research funding by private entities
• Government has dropped the ball
• Caffeine protects against Parkinsons
• Brain injury (concussion) is significant dementia risk factor
• Chronic hypertension also raises risk
• The clock is ticking for all of us

The second item was an editorial in October 27,2010 New York Times by Sandra Day O'Connor, Stanley Prusiner and Ken Dychtwald entitled "The Age of Alzheimer's". Key points in this editorial:

• For every penny spent on research on Alzheimer's the U.S. spends $3.50 on treatment.
• Yearly costs for the treatment of Alzheimer's estimated to increase from current $172 billion per year to $2 trillion in 2020 and $20 trillion in 2050.
• When U.S. research efforts target key illness with sufficient funding results emerge.
• A 10-year commitment to fight AIDS found effective treatments and added $1.4 trillion to U.S. economy. NIH spends about $3 billion per year on AIDS--there are five times as many
• Alzheimer's disease patients and this disease only receives about $469 million per year in NIH research funds.

Congress has a bill to raise annual federal investment to $2 billion per year. The authors endorse pushing this investment through during the lame-duck session of Congress following next week's mid-term election.

The third item is the a scientific research summary manuscript entitled: Promising Strategies for the Prevention of Dementia. Middleton and Yaffe recently summarized the best research evidence for the most promising strategies for prevention of dementia. Although there is no universally endorsed prevention approaches in Alzheimer's disease, the authors note promise in the following areas:

Vascular Risk Factor Reduction:

• Treat hypertension
• Reduce high cholesterol
• Identify and treat diabetes
• Encourage reduction in smoking
• Identify and treat metabolic syndrome (abdominal obesity, hypertriglyceridemia, low HDL cholesterol, hypertension and/or hyperglycemia) 

Cognitive Ability

• Encourage people to get a college degree (or pursue highest level of education possible
• Stay mentally active throughout adulthood 

Physical Activity

• Reduces several vascular risk factors
• Increase  brain neurotrophic factors 

Social Engagement

• Develop and strong social network
• Stay connected with friends and family members
• Watch for the onset of social disengagement as it may be an early sign of dementia

Diet

• No generally endorsed diet
• Mediterranean diet (high in fruits, vegetables, fish, olive oil) may reduce dementia risk through reducing cardiovascular risk factors

Depression

• Depression may be a early symptom or prodrome of dementia
• Depression treatment (and seeking care) in elderly may lead to diagnosis of depression
• Cognitive deficits may induce depressive symptoms

One promising prevention for dementia interfaces with prevention of brain trauma.  Funding brain trauma prevention is likely to also aid in reducing the risk of dementia in later life.

So the clock is ticking and like the national debt, the numbers are scary and growing daily. Promising prevention and treatment approaches are available. What will the research funding response be?

Middleton LE, & Yaffe K (2009). Promising strategies for the prevention of dementia. Archives of neurology, 66 (10), 1210-5 PMID: 19822776