Tuesday, December 23, 2014

Health Benefits of a Mediterranean Diet: Cognitive Decline/Dementia Benefits

Mediterranean diet plus olive oil or nuts associated with improved cognitive function

Supplementing the plant-based Mediterranean diet with antioxidant-rich extra virgin olive oil or mixed nuts was associated with improved cognitive function in a study of older adults in Spain  according to an article published online by JAMA Internal Medicine.

Emerging evidence suggests associations between dietary habits and cognitive performance. Oxidative stress (the body's inability to appropriately detoxify itself) has long been considered to play a major role in cognitive decline. Previous research suggests following a Mediterranean diet may relate to better cognitive function and a lower risk of dementia. However, the observational studies that have examined these associations have limitations, according to the study background.

Emilio Ros, M.D., Ph.D., of the Institut d'Investigacions Biomediques August Pi Sunyer, Hospital Clinic, Barcelona, and Ciber Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, and coauthors compared a Mediterranean diet supplemented with olive oil or nuts with a low-fat control diet.

The randomized clinical trial included 447 cognitively healthy volunteers (223 were women; average age was nearly 67 years) who were at high cardiovascular risk and were enrolled in the Prevencion con Dieta Mediterranea nutrition intervention.

Of the participants, 155 individuals were assigned to supplement a Mediterranean diet with one liter of extra virgin olive oil per week; 147 were assigned to supplement a Mediterranean diet with 30 grams per day of a mix of walnuts, hazelnuts and almonds; and 145 individuals were assigned to follow a low-fat control diet.

The authors measured cognitive change over time with a battery of neuropsychological tests and they constructed three cognitive composites for memory, frontal (attention and executive function) and global cognition. After a median of four years of the intervention, follow-up tests were available on 334 participants.

At the end of the follow-up, there were 37 cases of mild cognitive impairment: 17 (13.4 percent) in the Mediterranean diet plus olive oil group; eight (7.1 percent) in the Mediterranean diet plus nuts group; and 12 (12.6 percent) in the low-fat control group. No dementia cases were documented in patients who completed study follow-up.

The study found that individuals assigned to the low-fat control diet had a significant decrease from baseline in all composites of cognitive function. Compared with the control group, the memory composite improved significantly in the Mediterranean diet plus nuts, while the frontal and global cognition composites improved in the Mediterranean diet plus olive oil group. The authors note the changes for the two Mediterranean diet arms in each composite were more like each other than when comparing the individual Mediterranean diet groups with the low-fat diet control group.

"Our results suggest that in an older population a Mediterranean diet supplemented with olive oil or nuts may counter-act age-related cognitive decline. The lack of effective treatments for cognitive decline and dementia points to the need of preventive strategies to delay the onset and/or minimize the effects of these devastating conditions. The present results with the Mediterranean diet are encouraging but further investigation is warranted," the study concludes.

The Mediterranean Diet Has Varied Effects on Cognitive Decline Among Different Race-Specific Populations

While the Mediterranean diet may have broad health benefits, its impact on cognitive decline differs among race-specific populations, according to a new study published in the Journal of Gerontology.

The team of researchers, including Ben-Gurion University of the Negev (BGU Prof. Danit R. Shahar RD, Ph.D, analyzed an NIH/NIA prospective cohort study [Health ABC] conducted over eight years in the U.S. to measure the effects of adherence to a Mediterranean diet. Prof. Shahar is affiliated with the BGU S. Daniel Abraham International Center for Health and Nutrition, Department of Public Health, Faculty of Health Sciences.

 The Mediterranean-style diet (MedDiet) has fewer meat products and more plant-based foods and monounsaturated fatty acids from olive and canola oil (good) than a typical American diet.

To assess the association between MedDiet score and brain function, the researchers used data of several Modified Mini-Mental State Examinations (3MS) on 2,326 participating older adults (70-79).  The 3MS is an extensively used and validated instrument designed to measure several cognitive domains to screen for cognitive impairment and commonly used to screen for dementia.

"In a population of initially well-functioning older adults, we found a significant correlation between strong adherence to the Mediterranean diet and a slower rate of cognitive decline among African American, but not white, older adults. Our study is the first to show a possible race-specific association between the Mediterranean diet and cognitive decline.”

The researchers note that further studies in diverse populations are necessary to confirm association between the MedDiet and cognitive decline, and to pinpoint factors that may explain these results.

Mediterranean diet linked to preserving thinking and memory skills

Those who more closely followed the Mediterranean diet were 19 percent less likely to develop problems with their thinking and memory skills according to research is published in the April 30, 2013, print issue of Neurology®, the medical journal of the American Academy of Neurology.

"Since there are no definitive treatments for most dementing illnesses, modifiable activities, such as diet, that may delay the onset of symptoms of dementia are very important," said Georgios Tsivgoulis, MD, with the University of Alabama at Birmingham and the University of Athens, Greece. Tsivgoulis is also a member of the American Academy of Neurology.

Data came from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study, a national sample of the general population. For the study, dietary information from 17,478 African-American and Caucasian people with an average age of 64 was reviewed to see how closely they adhered to a Mediterranean diet. They were also given tests that measured memory and thinking abilities over an average of four years. A total of 17 percent of the participants had diabetes. Seven percent of the participants developed impairments in their thinking and memory skills during the study.

The study found that in healthy people, those who more closely followed the Mediterranean diet were 19 percent less likely to develop problems with their thinking and memory skills. There was not a significant difference in declines between African-Americans and Caucasians. However, the Mediterranean diet was not associated with a lower risk of thinking and memory problems in people with diabetes.

"Diet is an important modifiable activity that could help in preserving cognitive functioning in late life," said Tsivgoulis. "However, it is only one of several important lifestyle activities that might play a role in late-life mental functioning. Exercise, avoiding obesity, not smoking cigarettes and taking medications for conditions like diabetes and hypertension are also important."

Mediterranean Diet Boosts Ageing Brain

A Mediterranean diet with added extra virgin olive oil or mixed nuts seems to improve the brain power of older people better than advising them to follow a low-fat diet, indicates research published online in the Journal of Neurology Neurosurgery and Psychiatry.

The authors from the University of Navarra in Spain base their findings on 522 men and women aged between 55 and 80 without cardiovascular disease but at high vascular risk because of underlying disease/conditions.

These included either type 2 diabetes or three of the following: high blood pressure; an unfavourable blood fat profile; overweight; a family history of early cardiovascular disease; and being a smoker.

Participants, who were all taking part in the PREDIMED trial looking at how best to ward off cardiovascular disease, were randomly allocated to a Mediterranean diet with added olive oil or mixed nuts or a control group receiving advice to follow the low-fat diet typically recommended to prevent heart attack and stroke

A Mediterranean diet is characterised by the use of virgin olive oil as the main culinary fat; high consumption of fruits, nuts, vegetables and pulses; moderate to high consumption of fish and seafood; low consumption of dairy products and red meat; and moderate intake of red wine.

Participants had regular check-ups with their family doctor and quarterly checks on their compliance with their prescribed diet.

After an average of 6.5 years, they were tested for signs of cognitive decline using a Mini Mental State Exam and a clock drawing test, which assess higher brain functions, including orientation, memory, language, visuospatial and visuoconstrution abilities and executive functions such as working memory, attention span, and abstract thinking.

At the end of the study period, 60 participants had developed mild cognitive impairment: 18 on the olive oil supplemented Mediterranean diet; 19 on the diet with added mixed nuts; and 23 on the control group.

A further 35 people developed dementia: 12 on the added olive oil diet; six on the added nut diet; and 17 on the low fat diet.

The average scores on both tests were significantly higher for those following either of the Mediterranean diets compared with those on the low fat option.

These findings held true irrespective of other influential factors, including age, family history of cognitive impairment or dementia, the presence of ApoE protein--associated with Alzheimer's disease--educational attainment, exercise levels, vascular risk factors; energy intake and depression.

The authors acknowledge that their sample size was relatively small, and that because the study involved a group at high vascular risk, it doesn't necessarily follow that their findings are applicable to the general population.

But they say, theirs is the first long term trial to look at the impact of the Mediterranean diet on brain power, and that it adds to the increasing body of evidence suggesting that a high quality dietary pattern seems to protect cognitive function in the ageing brain.

Potential benefits of adherence to the Mediterranean diet on cognitive health.

A review in the Proceedings of The Nutrition Society Dec 2012 updated available knowledge on the relationship between adherence to the Mediterranean diet (MeDi) and cognitive decline, risk of dementia or Alzheimer's Disease (AD), and analyzed the reasons for some inconsistent results across studies. The traditional MeDi has been recognised by the United Nations Educational Scientific and Cultural Organisation as an Intangible Cultural Heritage of Humanity. This dietary pattern is characterised by a high consumption of plant foods (i.e. vegetables, fruits, legumes and cereals), a high intake of olive oil as the main source of fat, a moderate intake of fish, low-to-moderate intake of dairy products and low consumption of meat and poultry, with wine consumed in low-to-moderate amounts during meals.

Beyond the well-known association between higher adherence to the MeDi and lower risk of mortality, in particular from CVD and cancer, new data from large epidemiological studies suggest a relationship between MeDi adherence and cognitive decline or risk of dementia.

Mediterranean Diet Good For Brain

According to a study in the February, 2012 issue of Archives of Neurology, one of the JAMA/Archives journals, a Mediterranean-style diet (MeDi) may be healthier for the brain. Researchers have discovered that a MeDi diet is associated with reduced damage of small blood vessels in the brain.

White matter hyperintensities (WMHs) are markers of chronic small vessel damage and can be seen using brain magnetic resonance imaging (MRI).

The researchers explain:

"Although diet may be an important predictor of vascular disease, little is known about the possible association between dietary habits and WMHs. Studies have suggested that consumption of a MeDi [Mediterranean Diet] is associated with a reduced risk of the metabolic syndrome, coronary heart disease, stroke and cognitive disorders, but no studies to date, to our knowledge, have examined the association between a MeDi and WMH volume (WMHV)."

To examine this association, data from 966 participants in the Northern Manhattan Study were assessed by Hannah Gardener, Sc.D., of the University of Miami Miller School of Medicine and her team. In order to evaluate dietary patterns during the previous year, the researchers gave participants a food frequency questionnaire. The researchers then used the answers from the questionnaire to determine a MeDi compliance score. The team measured WMHV by quantitative brain MRI.

The researchers found that on a MeDi scale from 0 to 10:

* 11.6% of participants scored 0 to 2
* 15.8% scored 3
* 23% scored 4
* 23.5% scored 5
* and 26.1% of participants scored between 6 to 9

In addition they discovered that men and had higher MeDi scores than women, as well as those who reported moderate to heavy levels of physical activity. Furthermore, results showed that individuals with a MeDi score of 6+ had lower BMI.

Results from the study indicate that among participants, those who consume a MeDi have a lower burden of WMHV. This connection was independent of vascular and sociodemographic risk factors including smoking, blood lipid levels, physical activity, BMI, history of cardiac disease, hypertension, and diabetes. The researchers found that the only component of the MeDi score that was independently linked to WMHV was the ratio of monounsaturated to saturated fat.

Mediterranean Diet Associated With Slower Rate of Cognitive Decline
The Mediterranean diet, rich in vegetables, fish, and olive oil and moderate in wine and alcohol, is associated with slower rates of cognitive decline in older adults, according to researchers at Rush University Medical Center.

The results are published in the American Journal of Clinical Nutrition.

Included in the study were 3,759 older residents of the South side of Chicago who are part of the Chicago Healthy Aging Project, an ongoing evaluation of cognitive health in adults over the age of 65. Every three years, the study participants, age 65 and older, underwent a cognitive assessment that tested such things as memory and basic math skills. Participants also filled out a questionnaire on the frequency with which they consumed 139 food items ranging from cereals and olive oil to red meat and alcohol.

The researchers then analyzed how closely each of the study participants adhered to a Mediterranean diet, which includes daily consumption of such foods as fruit, vegetables, legumes, olive oil, fish, potatoes and nonrefined cereals, as well as wine.

Out of a maximum score of 55, which would indicate complete adherence to the Mediterranean diet, the average study participant scored 28. Those with the higher scores were also the individuals whose cognitive tests showed a slower rate of decline, even when other factors that might account for the result, such as education level, were considered.

The researchers also analyzed how closely study participants adhered to the Healthy Eating Index—2005, which is based on the recommendations from the 2005 Dietary Guidelines for Americans. Higher scores indicating closer adherence to this index, which gives less weight to fish, legumes and moderate alcohol intake, did not correspond with differences in rates of cognitive decline.

Christy Tangney, PhD, lead author of the study and associate professor of clinical nutrition at Rush University, said that the results add to other studies showing that a Mediterranean diet reduces the risk of heart disease, certain cancers and diabetes.

“The more we can incorporate vegetables, olive oil, and fish into our diets and moderate wine consumption, the better for our aging brains and bodies,” Tangney said.

Mediterranean Diet = Slower Cognitive Decline

In an examination of the association between adherence to a Mediterranean-type diet and cognitive performance and risk of dementia, researchers found that high adherence to the diet was associated with slower decline in some measures of cognitive function but was not associated with decreased risk for dementia, according to a study in the August 12. 2009 issue of JAMA.

Higher adherence to a Mediterranean-type diet is linked to lower risk for mortality and chronic diseases, and "might also have protective effects against cognitive decline in older individuals, because it combines several foods and nutrients potentially protective against cognitive dysfunction or dementia, such as fish, monounsaturated fatty acids, vitamins B12 and folate, antioxidants (vitamin E, carotenoids, flavonoids), and moderate amounts of alcohol," the authors write. But its association with cognitive decline has been unclear.

Catherine Féart, Ph.D., of the Université Victor Ségalen Bordeaux 2, Bordeaux, France, and colleagues examined whether adherence to a Mediterranean diet was associated with change in cognitive performance and with lower risk of all-cause dementia or Alzheimer disease. The study included 1,410 individuals (age 65 years or older) from Bordeaux, France, who were part of the Three-City cohort in 2001-2002 (a study of vascular risk factors of dementia) and were re-examined at least once over 5 years. Adherence to a Mediterranean diet (scored as 0 to 9) was computed from a food frequency questionnaire and 24-hour recall.

Cognitive performance was assessed on 4 neuropsychological tests: the Mini-Mental State Examination (MMSE), Isaacs Set Test (IST), Benton Visual Retention Test (BVRT), and Free and Cued Selective Reminding Test (FCSRT). New cases of dementia (n = 99) were validated by an independent expert committee of neurologists.

After adjusting for age, sex, education, marital status, energy intake, physical activity, depressive symptomatology, taking 5 medications/day or more, apolipoprotein E genotype, cardiovascular risk factors, and stroke, the researchers found that higher Mediterranean diet score was associated with fewer MMSE errors. But performance on the IST, BVRT, or FCSRT over time was not significantly associated with Mediterranean diet adherence, especially in those who remained free from dementia over 5 years. Mediterranean diet adherence was not associated with the risk for incident dementia, although the statistical strength of the data to detect a difference was limited.

"The Mediterranean diet pattern probably does not fully explain the better health of persons who adhere to it, but it may contribute directly. A Mediterranean diet also may indirectly constitute an indicator of a complex set of favorable social and lifestyle factors that contribute to better health. Further research is needed to allow the generalization of these results to other populations and to establish whether a Mediterranean diet slows cognitive decline or reduces incident dementia in addition to its cardiovascular benefits," the authors conclude.

Mediterranean diet fights Alzheimer disease

Elderly individuals who had a diet that included higher consumption of fruits, vegetables, legumes, cereal and fish and was low in red meat and poultry and who were physically active had an associated lower risk of Alzheimer disease, according to a study in the August 12, 2009 issue of JAMA.

Research regarding the effect physical activity can have on the risk of Alzheimer disease (AD) or dementia has shown mixed results, as has the effect of dietary habits. Their combined association has not been investigated, according to background information in the article.

Nikolaos Scarmeas, M.D., of Columbia University Medical Center, New York, and colleagues examined the association between physical activity and risk of AD and also the effect of physical activity and adherence to a Mediterranean-type diet on AD risk. The study included 2 groups that consisted of 1,880 community-dwelling elderly residents of New York city without dementia at the start of the study, for whom there was both diet and physical activity information available. Standardized neurological and neuropsychological measures were administered approximately every 1.5 years from 1992 through 2006.

The participants received measurements of their adherence to a Mediterranean-type diet (scale of 0-9; categorized as low, middle, or high) and their physical activity (sum of weekly participation in various physical activities, weighted by the type of physical activity [light, moderate, vigorous]; categorized into no physical activity, some, or much, also low or high), separately and combined. A higher score for diet was obtained with higher consumption of fruits, vegetables, legumes, cereals, and fish; lower consumption of meat and dairy products; a higher ratio of monounsaturated fats to saturated fats and mild to moderate alcohol consumption.

Individuals were followed up for an average of 5.4 years, during which a total of 282 developed AD. In considering only physical activity, the researchers found that more physical activity was associated with lower risk for developing AD. "Compared with physically inactive individuals, report of some physical activity was associated with a 29 percent to 41 percent lower risk of developing AD, while report of much physical activity was associated with a 37 percent to 50 percent lower risk," the authors write.

When considered simultaneously, both physical activity and Mediterranean diet adherence were significantly associated with AD incidence. According to the researchers, "Belonging to the middle diet adherence tertile was associated with a 2 percent to 14 percent risk reduction, while belonging to the highest diet adherence tertile was associated with a 32 percent to 40 percent reduced risk. Similarly, compared with individuals with no physical activity, individuals reporting some physical activity had a 25 percent to 38 percent lower risk for AD, while individuals reporting much physical activity had a 33 percent to 48 percent lower risk for AD."

The authors also write, "Compared with individuals with low physical activity plus low adherence to a diet (absolute AD risk, 19 percent), high physical activity plus high diet adherence was associated with a 35 percent to 44 percent relative risk reduction (absolute AD risk, 12 percent). … Absolute AD risks declined from 21 percent in the group with no physical activity plus low diet adherence to 9 percent in the group with much physical activity plus high diet adherence."

"In summary, our results support the potentially independent and important role of both physical activity and dietary habits in relation to AD risk. These findings should be further evaluated in other populations."

Mediterranean diet may lower risk of brain damage that causes thinking problems

A Mediterranean diet may help people avoid the small areas of brain damage that can lead to problems with thinking and memory, according to a study released today that were presented at the American Academy of Neurology's 62nd Annual Meeting in Toronto April 10 to April 17, 2010.

The study found that people who ate a Mediterranean-like diet were less likely to have brain infarcts, or small areas of dead tissue linked to thinking problems.

The Mediterranean diet includes high intake of vegetables, legumes, fruits, cereals, fish and monounsaturated fatty acids such as olive oil; low intake of saturated fatty acids, dairy products, meat and poultry; and mild to moderate amounts of alcohol.

For the study, researchers assessed the diets of 712 people in New York and divided them into three groups based on how closely they were following the Mediterranean diet. Then they conducted MRI brain scans of the people an average of six years later. A total of 238 people had at least one area of brain damage.

Those who were most closely following a Mediterranean-like diet were 36 percent less likely to have areas of brain damage than those who were least following the diet. Those moderately following the diet were 21 percent less likely to have brain damage than the lowest group.

"The relationship between this type of brain damage and the Mediterranean diet was comparable with that of high blood pressure," said study author Nikolaos Scarmeas, MD, MSc, of Columbia University Medical Center in New York and a member of the American Academy of Neurology. "In this study, not eating a Mediterranean-like diet had about the same effect on the brain as having high blood pressure."

Previous research by Scarmeas and his colleagues showed that a Mediterranean-like diet may be associated with a lower risk of Alzheimer's disease and may lengthen survival in people with Alzheimer's disease. According to the present study, these associations may be partially explained by fewer brain infarcts.

Mediterranean Diet Associated with Lower Risk of Cognitive Impairment

Eating a Mediterranean diet appears to be associated with less risk of mild cognitive impairment—a stage between normal aging and dementia—or of transitioning from mild cognitive impairment into Alzheimer’s disease, according to a report in the February, 2009 issue of Archives of Neurology, one of the JAMA/Archives journals.

“Among behavioral traits, diet may play an important role in the cause and prevention of Alzheimer’s disease,” the authors write as background information in the article. Previous studies have shown a lower risk for Alzheimer’s disease among those who eat a Mediterranean diet, characterized by high intakes of fish, vegetables, legumes, fruits, cereals and unsaturated fatty acids, low intakes of dairy products, meat and saturated fats and moderate alcohol consumption.

Nikolaos Scarmeas, M.D., and colleagues at Columbia University Medical Center, New York, calculated a score for adherence to the Mediterranean diet among 1,393 individuals with no cognitive problems and 482 patients with mild cognitive impairment. Participants were originally examined, interviewed, screened for cognitive impairments and asked to complete a food frequency questionnaire between 1992 and 1999.

Over an average of 4.5 years of follow-up, 275 of the 1,393 who did not have mild cognitive impairment developed the condition. Compared with the one-third who had the lowest scores for Mediterranean diet adherence, the one-third with the highest scores for Mediterranean diet adherence had a 28 percent lower risk of developing mild cognitive impairment and the one-third in the middle group for Mediterranean diet adherence had a 17 percent lower risk.

Among the 482 with mild cognitive impairment at the beginning of the study, 106 developed Alzheimer’s disease over an average 4.3 years of follow-up. Adhering to the Mediterranean diet also was associated with a lower risk for this transition. The one-third of participants with the highest scores for Mediterranean diet adherence had 48 percent less risk and those in the middle one-third of Mediterranean diet adherence had 45 percent less risk than the one-third with the lowest scores.

The Mediterranean diet may improve cholesterol levels, blood sugar levels and blood vessel health overall, or reduce inflammation, all of which have been associated with mild cognitive impairment. Individual food components of the diet also may have an influence on cognitive risk. “For example, potentially beneficial effects for mild cognitive impairment or mild cognitive impairment conversion to Alzheimer’s disease have been reported for alcohol, fish, polyunsaturated fatty acids (also for age-related cognitive decline) and lower levels of saturated fatty acids,” they write.

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