Advanced Mediterranean Diet

For years I’ve been recommending measures to help prevent mental the decline and dementia associated with advanced age.  Measures immediately coming to mind are the Mediterranean diet, exercise, not smoking, avoiding obesity, eating cold-water fatty fish regularly (for the omega-3 fatty acids), and keeping the mind active.

Turns out there’s not much good evidence ( but there’s some) in support of that advice, according to a study commissioned by the National Institutes of Health and published this month in Annals of Internal Medicine.

The investigators did a literature review of the best-designed studies looking for associations between about 45 factors and the risk of cognitive decline in later life.  It’s a little unclear, but this report seems to focus on mild cognitive impairment rather than dementia such as Alzheimer disease.  Mild cognitive impairment is often a precursor to dementia such as Alzheimer disease.  The review included 127 observational studies, 22 randomized controlled trials, and 16 systematic reviews.

The list of cognitive decline risk factors (and protective factors) included the apoliprotein E epsilon-4 gene, smoking, diabetes, physical activity, alcohol consumption, obesity, Mediterranean diet, omega-3 intake, and many others.

For all of the factors, the investigators found insufficient evidence from which to draw firm conclusions.  They are fairly confident that statin drugs and aspirin are not associated with cognitive decline.

They found high-quality evidence for only one factor that protects against cognitive decline: cognitive training (involving memory, reasoning, and speed).

They noted that overall quality of the scientific evidence is low [so there’s hope they missed some protective effects?].

Another report in the same issue of Annals focused on Alzheimer disease and was similarly disappointing in terms of action we can take now to prevent cognitive decline and Alzheimer dementia.  Beaucoup experts and thousands of man-hours were devoted to this report.  Here’s a depressing line:

Currently, firm conclusions cannot be drawn about the association of any modifiable risk factor with cognitive decline or Alzheimer disease.

Now What?

Enjoy life while you can, and plan ahead for possible cognitive decline.

Hope and pray the researchers come up with some solutions soon.  There’s a tsunami of dementia in our future.

I still think the Mediterranean diet (and perhaps some of the other factors analyzed) may be brain-protective, and here’s why.  Note that the reviewers of these studies point out we have “no high-quality studies upon which to base firm conclusions.”  The reviewers gave most credence to randomized controlled trials.  And with good reason: such studies are probably the best way to prove that a medical or dietary intervention is effective.  Observational studies, on the other hand, can point to associations, which may have nothing to do with cause and effect.

Here’s how you do a randomized controlled trial to see if the Mediterranan diet has a long-term effect on cognitive function.  Take 5,000 adults aged 3o to 50 and make half of them eat the Mediterranean diet and the other half eat a specific standard diet.  Keep all other variables the same for both groups.  Over the course of 30-40 years, monitor the changes in cognition in all individuals and compare the two groups.  That study has the potential to yield high-quality data and proof.

Problem is, it’ll probably never be done because it’s close to impossible.  It’s hard enough to get a free-living 40-year-old to follow a new way of eating for 12 weeks, much less 30 years.  That’s why so much population-wide nutrition research is observational.  Most, but not all, of the studies supporting the brain-protective properties of the Mediterranean diet are observational.  I’m not aware of a single randomized controlled study on the long-term cognitive effects of the Mediterranean diet.

And one more thing . . .

The NIH reports at hand didn’t look at the synergy among factors that individually may have only tiny positive effects.  For instance, what if you combine the Mediterranean diet with physical activity, non-smoking, mind-stimulating activities, and avoidance of diabetes and obesity?  Could have a winning combo there! 

Sounds like I’m grasping at straws, doesn’t it?

I’m not prepared yet to abandon idea of the brain-protective Mediterranean diet.

Steve Parker, M.D.

References:

Brenda L. Plassman, PhD; John W. Williams Jr., MD, MHSc; James R. Burke, MD, PhD; Tracey Holsinger, MD; and Sophiya Benjamin, MD (2010). Systematic review: NIH state-of-the-science conference: Factors associated with risk for and possible prevention of cognitive decline in later life.

Annals of Internal Medicine, 152

Daviglus ML, Bell CC, Berrettini W, Bowen PE, Connolly ES Jr, Cox NJ, Dunbar-Jacob JM, Granieri EC, Hunt G, McGarry K, Patel D, Potosky AL, Sanders-Bush E, Silberberg D, & Trevisan M (2010). National Institutes of Health State-of-the-Science Conference Statement: Preventing Alzheimer Disease and Cognitive Decline. Annals of internal medicine PMID: 20547888

New York researchers reported in Archives of Neurology this month that a particular eating pattern does seem to lower the risk of Alzheimers Disease, the most common type of dementia.  Manhattanites were significantly less likely to develop dementia if they had . . .

Higher consumption of:

• salad dressing
• nuts
• tomatoes
• fish
• poultry
• cruciferous vegetables (e.g., cabbage, radish, broccoli, kale, collard greens, cauliflower, turnips, brussels sprouts)
• fruits
• dark and green leafy vegetables

Lower consumption of:

• high-fat dairy products
• red meat
• organ meats
• butter

The study involved over 2000 people over age 65 who were followed for the onset of dementia for four years.  The researchers used a sophisticated analytic technique called “reduced rank regression.”  See the original article for details.

The study authors note similarities of this anti-dementia dietary pattern to the Mediterranean diet, long associated with lower risk of dementia.  They also document (again) the strong association of moderate alcohol consumption with lower dementia risk, although it was not part of their predetermined anaylytic technique.

Alzheimers Dementia has a strong tendency to run in some families.  As lifespans increase, we’re going to be seeing lots more of it.  If you make it to age 85, your odds of having dementia are 50:50.

If you worry about developing Alzheimers, perhaps because of family history, you may be doing yourself and others a favor by adopting either the dietary pattern above or the Mediterranean diet.

On the other hand . . .

MedPageToday on April 28, 2010, reported the conclusions of a panel convened by the (U.S.) National Institutes of Health:

The independent panel . . . determined that the causes of Alzheimers disease are still unknown and that no reliable evidence has shown that anything can prevent the disease or stop it from progressing.

Steve Parker, M.D.

Disclaimer:  All matters regarding your health require supervision by a personal physician or other appropriate health professional familiar with your current health status.  Always consult your personal physician before making any dietary or exercise changes. 

References: 

Gu, Yian, et al.  Food combination and Alzheimer Disease risk.  Archives of Neurology, 67 (2010).  Epub ahead of print.  doi: 10.1001/archneurol.2010.84

Walker, Emily P.  NIH panel provides no help in unraveling Alzheimers disease.  MedPageToday, April 28, 2010.  Accessed online April 28, 2010.

The traditional Mediterranean diet has long been associated with longer lifespans and lower rates of chronic diseases: heart disease, strokes, dementia, and cancer (breast, prostate, lung, uterus).  Recent research has expanded the benefit list.

I ran across a good summary of the health benefits of Mediterranean-style eating at Medical News Today, published online May 6, 2009.  An excerpt:

The following health benefits have been observed by people who have a Mediterranean diet:

• Longer lifespan
• Lower risk of dying at any age
• Lower risk of dying from heart disease
• Lower risk of dying from cancer
• Lower risk of developing Type 2 diabetes
• Lower risk of hypertension (high blood pressure)
• Lower risk of raised cholesterol levels
• Lower risk of becoming obese
• Lower risk of developing Alzheimer’s disease

Not mentioned above is the lower risk of Parkinson’s Disease and chronic obstructive pulmonary disease.  You’ll also find a fair description of the traditional Mediterranean diet.

Steve Parker, M.D.

HealthDay TV has a short video about oleocanthol, a component of olive oil that may help prevent Alzheimer Disease.  Olive oil is the predominant form of fat in the traditional Mediterranean diet.  The Mediterranean diet is associated with lower rates of Alzheimer Disease and longer survival in Alzheimer patients.

 Steve Parker, M.D.

Older adults in low- to middle-income countries seem to have a lower risk of dementia if they regularly eat fish, according to a new study in the American Journal of Clinical Nutrition.

This comes on the heels of another recent study questioning the anti-dementia protective effect of fish consumption.

Almost 15,000 people were surveyed in China, India, Cuba, Domincan Republic, Mexico, Peru, and Venezuela.  As fish intake increased - from never, to some days of the week, to most or all days of the week - dementia prevalence dropped by 19% for each increase of intake.  Data for the effect were less convincing for Indian populations. 

The prevalence of dementia also tended to rise with meat consumption.

Steve Parker, M.D.

Reference:  Albanese, Emiliano, et al.  Dietary fish and meat intake and dementia in Latin America, China, and India: a 10/66 Dementia Research Group population-based study.  American Journal of Clinical Nutrition, 90 (2009): 392-400.

Major media outlets have been reporting in the last 24 hours two new scientific studies regarding dementia, exercise, and the Mediterranean diet.  The story has been covered by the Wall Street Journal, U.S. News and World Report, and Bloomberg. 

Regarding dementia prevention and the Mediterranean diet, the two studies are contradictory, as so often happens in science.  One study suggests that regular exercise coupled with Mediterranean diet reduces the rate of dementia better than either measure alone.

The French study involved 1,410 adults 65 and older followed for at least five years.  Ninety-nine cases of dementia developed.  Adherence to a Mediterranean diet was computed from a food-frequency questionnaire [how accurate is that in demented people?].  Mediterranean diet adherence was not associated with the risk for developing dementia, although the authors note that statistical power to detect a difference was limited.  In other words, with only 1,410 study subjects, there would have to be a fairly large difference in outcomes, for it to be detectable.

In New York, New York, investigators studied the combination of exercise and a Mediterranean-type diet as protection against developing Alzheimer Disease, the most common cause of dementia.  Both exercise and the Mediterranean diet previously had been associated individually with lower rates of dementia.  They studied 1,880 seniors over five years.

They found that high adherence to the Mediterranean diet - not middle-of-the-road adherence - was associated with a 40% lower risk of developing Alzheimer Disease.  MOR got you nowhere.

The higher the degree of exercise, the lower the risk - up to 33% lower - of Alzheimer’s, in a dose-response fashion.

Folks who were sedentary and didn’t adhere to the diet had a 19% risk of developing Alzheimer’s.  Those with high diet adherence and high physical activity had a 12% risk of Alzheimer’s.  So, about a 60% lowered risk if you did everything right.

I covered recently two studies indicating that omega-3 fatty acids and fish consumption may not have the dementia-prevention properties many of us hope for.

Other studies suggest that your risk of dementia can be reduced by:

• ongoing social engagement as you age 
• ongoing intellectual stimulation as you age
• avoidance of overweight and obesity in middle age

Clearly, diet and exercise prescriptions are no panacea for dementia.  We still need better preventative measures and cures.

Steve Parker, M.D.

References: 

Porter, Carrie.  Dementia studies find diet, exercise matter.  Wall Street Journal online, August 12, 2009.

Feart, Catherine, et al.  Adherence to a Mediterranean diet, cognitive decline, and risk of dementia.  Journal of the American Medical Association, 302 (2009): 638-648.

Scarmeas, Nikolaos, et al.  Physical activity, diet, and risk of Alzheimer Disease.  Journal of the American Medical Association, 302 (2009): 627-637.

Dentists are considering a return to an old theory that dietary carbohydrates first cause dental diseases, then certain systemic chronic diseases, according to a review in the June 1, 2009, Journal of Dental Research. 

We’ve known for years that some dental and systemic diseases are associated with each other, both for individuals and populations.  For example, gingivitis and periodontal disease are associated with type 2 diabetes and coronary heart disease.  The exact nature of that association is not clear.  In the 1990s it seemed that infections - chlamydia, for example - might be the unifying link, but this has not been supported by subsequent research.     

The article is written by Dr. Philippe P. Hujoel, who has been active in dental research for decades and is affiliated with the University of Washington (Seattle).  He is no bomb-throwing, crazed, radical. 

The “old theory” to which I referred is the Cleave-Yudkin idea from the 1960s and ’70s that excessive intake of fermentable carbohydrates, in the absence of good dental care, leads both to certain dental diseases - caries (cavities), periodontal disease, certain oral cancers, and leukoplakia - and to some common systemic chronic non-communicable diseases such as coronary heart disease, type 2 diabetes, some cancers, and dementia.  In other words, dietary carbohydrates cause both dental and systemic diseases - not all cases of those diseases, of course, but some.   

Dr. Hujoel does not define “fermentable” carbohydrates in the article.  My American Heritage Dictionary defines fermentation as:

1. the anaerobic conversion of sugar to carbon dioxide and alcohol by yeast
2. any of a group of chemical reactions induced by living or nonliving ferments that split complex organic compunds into relatively simple substances

As reported in David Mendosa’s blog at MyDiabetesCentral.com, Dr. Hujoel said, “Non-fermentable carbohydrates are fibers.”  Dr. Hujoel also shared some personal tidbits there. 

In the context of excessive carbohydrate intake, the article frequently mentions sugar, refined carbs, and high-glycemic-index carbs.  Dental effects of excessive carb intake can appear within weeks or months, whereas the sysemtic effects may take decades. 

Hujoel compares and contrasts Ancel Keys’ Diet-Heart/Lipid Hypothesis with the Cleave-Yudkin Carbohydrate Theory.  In Dr. Hujoel’s view, the latest research data favor the Carbohydrate Theory as an explanation of many cases of the aforementioned dental and systemic chronic diseases.  If correct, the theory has important implications for prevention of dental and systemic diseases: namely, dietary carbohydrate restriction.

Adherents of the paleo diet and low-carb diets will love this article; it supports their choices.

I agree with Dr. Hujoel that we need a long-term prospective trial of serious low-carb eating versus the standard American high-carb diet.  Take 20,000 people, randomize them to one of the two diets, follow their dental and systemic health over 15-30 years, then compare the two groups.  Problem is, I’m not sure it can be done.  It’s hard enough for most people to follow a low-carb diet for four months.  And I’m asking for 30 years?!   

Dr. Hujoel writes:

Possibly, when it comes to fermentable carbohydrates, teeth would then become to the medical and dental professionals what they have always been for paleoanthropologists: “extremely informative about age, sex, diet, health.”

Dr. Hujoel mentioned a review of six studies that showed a 30% reduction in gingivitis score by following a diet moderately reduced in carbs.  He mentions the aphorism: “no carbohydrates, no caries.”  Anyone prone to dental caries or ongoing periodontal disease should do further research to see if switching to low-carb eating might improve the situation. 

Don’t be surprised if your dentist isn’t very familiar with the concept.  Has he ever mentioned it to you?

Steve Parker, M.D.,

author of The Advanced Mediterranean Diet and the Diabetic Mediterranean Diet blog

Reference:  Hujoel, P.  Dietary carbohydrates and dental-systemic diseases.  Journal of Dental Research, 88 (2009): 490-502.

Mendosa, David.  Our dental alarm bell.  MyDiabetesCentral.com, July 12, 2009.

Two recent studies refute the notion that fish and omega-3 fatty acid consumption help prevent dementia.

Most dementias, such as Alzheimer disease, are progressive and incurable.  Observational studies over the last 10 years have suggested that adequate fish intake - possibly related to the omega-3 fatty acids in fish - would prevent at least some cases of dementia.  Fish are the main dietary source of omega-3 fatty acids. 

The Canadian study was relatively small, with 663 participants.  They looked mainly at blood levels of omega-3s, and found no association between blood levels of omega-3s and dementia.  APOE4 status didn’t matter.  For those of you worried about mercury contamination of fish: they found that people with the most mercury in the bloodstream had a lower rate of dementia.  Go figure.

Researchers in Rotterdam studied 5395 subjects over almost 10 years.  They found no association between dementia and total fish intake, type of fish eaten, and intake of omega-3s.

These results are clearly disappointing for those of us who deal with dementia patients and their families.  We’ll see even more dementia as the average age of Western populations creeps higher.  Looking at people over 90, about half of them have dementia, and 70% of those are Alzheimer disease that started years earlier.  

On the bright side, several studied have associated the Mediterranean diet with lower rates of dementia.  It’s looking like that benefit is not related to fish consumption. 

Steve Parker, M.D.

References:

Kroger, Edeltraut, et al.  Omega-3 fatty acids and risk of dementia: the Canadian Study of Health and Aging.  American Journal of Clinical Nutrition, 90 (2009): 184-192.

Devore, Elizabeth, et al.  Dietary intake of fish and omega-3 fatty acids in relation to long-term dementia risk.  American Journal of Clinical Nutrition, 90 (2009): 170-176.

Mild Cognitive Impairment (MCI) is considered a precursor to dementia, although it does not always lead to dementia.

A study published this month in the Archives of Neurology indicates that adherence to the Mediterranean diet reduces both the risk of developing MCI and the risk of MCI conversion to Alzheimer dementia.  The story was reported today and yesterday by US News & World Report, USA Today, Bloomberg, and others.

Methodology

1,393 residents of a multi-ethnic community in New York were enrolled in the study.  They were mentally normal at baseline and followed for an average of 4.5 years.

Another 482 residents were identified as having Mild Cognitive Impairment at baseline, and were followed an average of 4.3 years.

All participants were screened for cognitive impairments and surveyed to get an idea of usual food intake.  Researchers used a 10-point scale to describe an individual participant’s adherence to the Mediterranean diet.  The higher the score, the greater the participant’s adherence.  Participants were then divided into thirds (tertiles) based on whether adherence was low, medium, or high.  Average age of study subjects on entry was 77.

Results

275 of the 1,393 participants who were mentally normal at baseline developed Mild Cognitive Impairment over the 4.5 years of follow-up.  Compared to those participants in the lowest third of Mediterranean diet adherence, those in the middle third had 17% less risk of developing MCI, and those in the highest third had 28% less risk.

Of 482  participants with Mild Cognitive Impairment at baseline, 106 later developed Alzheimer disease.  Compared with participants in the lowest third of adherence, those in the middle third had 45% less risk of developing Alzheimer disease, and those in the highest third had 48% less risk.

Comments From the Study Authors

. . . 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.

The Mediterranean diet tends to improve cholesterol levels, overall blood vessel function, reduce inflammation, and lower blood sugar levels, all of which could help preserve brain function.

My Comments

No surprise here.

The traditional Mediterranean diet has long been associated with lower risk of developing dementia, both Alzheimer and vascular dementia.  Vascular dementia results from multiple strokes or poor blood flow to the brain.  Since Mild Cognitive Impairment precedes Alzheimer dementia, it makes sense that the Mediterranean diet could help prevent both.

The lead author of the study at hand, Dr. Scarmeas, also reported in 2007 that the Mediterranean diet also prolongs life in established Alzheimer patients.

Steve Parker, M.D.

Reference:  Scarmeas, Nikolaos, et al.  Mediterranean Diet and Mild Cognitive Impairment.  Archives of Neurology, 66 (2009): 216-225.

Additional Resource:  Oldways’ Mediterranean diet information

Alzheimer disease is a progressive brain disorder resulting in memory loss, personality change, functional impairments, and a decline in various types of thinking (e.g., math ability, problem-solving, spatial orientation).  It is the most common form of dementia in the eldery, causing about 70% of cases and afflicting four million people in the U.S.

TheBostonChannel.com recently published a news release from Beth Israel Deaconess Medical Center on how to prevent Alzheimers Disease.  It is a Q&A interview with Dr. Daniel Press, neurologist and Alzheimer specialist.

Dr. Press made favorable comments about the Mediterraean diet and pointed out that avoidance of obesity and diabetes may also help prevent Alzheimer disease.  Regular aerobic exercise, 30 minutes daily, also seems to be protective.  The potential protective effect of alcohol consumption was not mentioned.

For details on how to accomplish all this, see the Do-It-Yourself Mediterranean Diet, the Alzheimer disease prevention article at WebMD.com, or The Advanced Mediterranean Diet book.

Steve Parker, M.D.