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Harvard researchers found that study participants found combining higher diet quality with higher olive oil consumption may provide an enhanced benefit in protecting against dementia.Lilyana Vynogradova/iStockPhoto / Getty Images

The Mediterranean diet has been tied to numerous health advantages, with evidence particularly strong for its heart health benefits.

A growing body of research also suggests that adhering to the plant-forward eating pattern helps guard against cognitive decline and dementia.

Now, new study findings suggest that a hallmark ingredient of the Mediterranean diet – olive oil – plays a protective role in brain aging.

According to Harvard University researchers, consuming half a tablespoon of olive oil each day can help lower the risk of dying from dementia. Here’s what to know.

The latest research

The study, published May 6 in the journal JAMA Network Open, set out to investigate the association between olive oil intake and dementia-related death.

Participants included 92,383 male and female health professionals who were followed for 28 years. At the study’s outset, participants were aged, on average, 56 and did not have cardiovascular disease or cancer.

Medical history and lifestyle factors were assessed every two years. Dietary information was collected every four years.

Participants’ daily olive oil intake was determined by how often olive oil was used for salad dressing, added to foods or bread and used for baking or frying food.

Dietary data was also used to calculate participants’ overall diet quality score and adherence to the Mediterranean diet.

During the 28-year study period 4,751 participants died from dementia.

Participants who consumed the most olive oil – at least 7 g (one-half tablespoon) each day – were 28 per cent less likely to die from dementia compared to those who never or rarely consumed olive oil.

The findings remained consistent after the researchers accounted for medical, lifestyle and genetic risk factors for dementia.

People who had higher intakes of olive oil had a lower risk of dying from dementia regardless of the quality or their diet or adherence to the Mediterranean diet, suggesting that olive oil has a specific protective role.

This doesn’t mean, though, that diet quality is irrelevant. It’s not.

Participants who consumed the most olive oil and also had the highest diet quality scores had the lowest risk of dementia mortality. Combining higher diet quality with higher olive oil consumption may provide an enhanced benefit.

Strengths, caveats

The study is credited for its large sample size and long duration.

As well, repeated measurements of diet, weight and lifestyle factors allowed the researchers to account for long-term olive oil intake and dementia risk factors.

Limitations include the study’s observational nature. It found an association between olive oil intake and lower risk of dementia death; this does not prove a causal relationship.

The researchers did not assess the use of different types of olive oil, such as extra virgin or regular olive oil, which differ in their content of protective phytochemicals.

The study enrolled mostly white health professionals; the findings might not apply to more diverse groups.

How olive oil might protect brain health

Olive oil, rich in monounsaturated fat and other protective compounds such as vitamin E and polyphenols, may indirectly guard against dementia mortality by improving heart health.

Several clinical trials suggest that olive oil reduces the risk of cardiovascular disease by improving blood vessel function, lowering LDL cholesterol, fending off free radicals and reducing inflammation.

Olive oil may have direct brain benefits too.

Polyphenols in olive oil are thought to cross the blood-brain-barrier and exert antioxidant and anti-inflammatory effects, possibly reducing beta-amyloid plaques, a hallmark sign of Alzheimer’s dementia.

Olive oil 101

Extra virgin olive oil is unrefined, meaning it’s extracted by pressing the olives; heat and/or chemicals are not used. It’s the highest grade of olive oil and has a golden-green colour and fruity flavour and aroma.

Virgin olive oil is also unrefined but is slightly lower in quality than extra virgin olive oil because of its higher acidity.

Extra virgin and virgin olive oils have the highest content of naturally occurring antioxidants and polyphenols.

Regular olive oil, labelled just “olive oil”, is typically a blend of virgin olive oil and olive oil that’s been refined using heat and/or chemicals to remove to remove flaws from the olives. It has a lighter colour and more neutral flavour than extra virgin olive oil.

Light olive oil is refined olive oil that’s lighter in colour (it is not “lighter” in fat or calories) and neutral tasting.

Olive oil has a relatively high smoke point, the temperature at which an oil starts to burn and smoke, making it suitable for cooking and baking.

The smoke point for extra virgin olive oil, regular olive oil and light olive oil is 350 to 410 F, 390 to 468 F and 465 to 470 F, respectively. Stovetop cooking and oven roasting are typically done between 250 and 400 F.

Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD

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