Mouse study supports encouraging evidence from population studies 12/12/2019
The so-called “Mediterranean” diet is widely — and wisely — touted as an aid to heart health.
Most of the evidence for that claim comes from epidemiological studies — which cannot prove a cause-effect relationship between a food or nutrient and health outcome.
Nonetheless, the best-designed clinical studies that have tested the Mediterranean diet against other diets show that it beats low-fat/high-carb diets for vascular and metabolic health.
The advantages of the Mediterranean diet over low-fat/high-carb diets likely flow from the fact that it’s very low in sugars and starches and relatively high in fruits, vegetables, nuts, beans — and total fat.
And those relatively high levels of fat appear to also benefit brain health because extra virgin olive oil or EVOO is the Mediterranean diet's chief source of added fat. Before turning to the new brain study, let's examine the evidence that favors higher-fat diets — and EVOO in particular — for cardiovascular health.
Mediterranean diet's cardio benefits linked to fat, especially EVOO
Contrary to decades of mistaken medical advice, clinical trials consistently show that high-fat diets — which lower triglyceride levels and yield higher levels of “good” HDL cholesterol — outperform low-fat/high-carb diets when it comes to reducing cardiovascular risks (Shai I et al. 2008).
Although high-fat diets tend to raise total LDL cholesterol levels, they're a very poor predictor of cardiovascular outcomes, and most of the increased LDL produced by relatively high-fat diets is the large, fluffy, benign form: see Cholesterol Picture Gets Clearer.
There's now overwhelming evidence that dietary sugars and starches, rather than saturated fats, pose a much bigger risk of promoting risky blood fat and cholesterol profiles. This explains why public health authorities’ decades-long promotion of low-fat diets — which caused people to over consume processed foods high in sugars and refined starches — didn’t reduce cardiovascular disease.
The reductions in cardiovascular risk factors that the Mediterranean diet produces in comparison with low-fat/high-carb diets can be attributed in part to four factors: it has fewer refined carbs, it features relatively large proportions of fat, it abounds in fiber and antioxidants, and most of its added fat is antioxidant-rich extra virgin olive oil.
In fact, the abundance of potent, anti-inflammatory antioxidants in extra virgin olive oil (EVOO) explains why it benefits vascular health far more than any other cooking oil — including the two cheaper, refined grades of olive oil known as “virgin” and “pure”: for more on that, see Extra Virgin Olive Oil Confirmed as Best Cardiac Prevention Choice and Olive Oil Benefits Linked to EV Grade's Key Antioxidant.
EVOO also holds significant potential for brain health: see Brain Benefits from Olive Oil?, Brain Aging Delayed by Mediterranean Diet, Antioxidant Unique to Extra Virgin Olive Oil Protects Mouse Brain Cells, and their links to related reports.
Now, the results of a mouse study from Philadelphia’s Temple University support the idea that — in addition to helping cardiovascular health — extra virgin olive oil may help delay or reduce the severity of dementia.
Let’s review the reason why extra virgin grade olive oil stands head and shoulders above other, cheaper grades, and then review the results of the new brain-health study.
EVOO’s uncommon antioxidants
Extra virgin olive oil (EVOO) contains about 30 antioxidant compounds, including secoroids, lignans, and a group of exceptionally beneficial phenols.
Phenols account for many of the health benefits of colorful fruits and vegetables, tea, coffee, and raw cocoa — but only EVOO abounds in a particularly potent foursome: tyrosol, hydroxytyrosol, oleocanthal, and oleuropein.
Importantly, the tyrosol in EVOO surpasses most food-borne antioxidants when it comes to (indirectly) neutralizing the unstable, damaging oxygen compounds called free radicals and reducing the inflammation they stimulate.
Temple University study ties EVOO to reduced dementia risk in mice
New findings from the school of medicine at Philadelphia’s Temple University suggest that extra virgin olive oil (EVOO) may be able to help prevent dementia and/or ease its symptoms.
Two years ago, the same Temple University team found that EVOO preserved memory capacity in mice and protected their brains against Alzheimer's disease (Lauretti E et al. 2017). And those findings supported ones reported by a German team in 2008.
Their previous study involved animals that were bred to develop Alzheimer's disease, and the Temple group found that EVOO protected young mice from memory and learning impairment as they aged.
Strikingly, the brains of mice fed EVOO did not display features typical of cognitive decline, particularly amyloid protein plaques, which impair communication pathways between brain cells (neurons). In fact, the animals' brains looked normal.
Those encouraging results prompted a Temple team led by professor Domenico Praticò, M.D., to conduct the follow-up study recently published in the journal Aging Cell.
And the results of that new study show that EVOO may be of special value in helping prevent aging-related dementia characterized by buildup of an abnormal form of a protein called tau — a syndrome called tauopathy — which leads to a decline in mental function and eventually to dementia.
The new findings in mice are the first to suggest that EVOO may defend people against a specific, uncommon, type of mental decline linked to tauopathy known as frontotemporal dementia or FD — at least in mice.
For the new study, mice predisposed to accumulate tau proteins in their brains were put on a diet supplemented with EVOO at ages corresponding to about age 30 or 40 years in humans.
Six months later, when the mice were the equivalent of age 60 in humans, tauopathy-prone animals experienced a 60% reduction in damaging tau deposits, compared to littermates that were not fed EVOO. And, compared with mice that did not receive EVOO, the mice fed EVOO also performed better on memory and learning tests.
When Dr. Praticò and his colleagues examined brain tissue from EVOO-fed mice, they found healthier synapse function, which in turn was associated with higher-than-normal levels of a protein known as complexin-1, which is known to play a critical role in maintaining healthy synapses.
Encouraging implications for Alzheimer's
The new findings may have implications beyond prevention of FD, because buildup of tau proteins is also a major driver of Alzheimer’s disease, the most common form of dementia.
Like the amyloid plaques that characterize Alzheimer's disease, tau deposits block communication between neurons and thereby impair thinking and memory, resulting in frontotemporal dementia — or Alzheimer's.
The new finding about EVOO is especially notable given the results of a new brain-imaging from the University of California, which adds to growing evidence that tau tangles drive brain degeneration in Alzheimer's disease more directly than amyloid protein plaques (La Joie R et al. et al. 2020).
The UC study revealed that the location of tau-protein tangles predicts the location of future brain atrophy in Alzheimer's patients much more reliably than the location of amyloid plaques, which have been the focus of Alzheimer's research and unsuccessful drug development for decades.
Alzheimer's disease primarily affects the hippocampus, which is the brain’s primary memory storage center. And, excepting the minority of people with “early-onset” genetic profiles, Alzheimer’s usually appears in old age, not in middle age.
In contrast, frontotemporal dementia (FD) affects the areas of the brain near the forehead and ears, and symptoms typically emerge between ages 40 and 65. Those symptoms include changes in personality and behavior, verbal difficulties, and deterioration of memory and learning capacities.
Findings provide a broader picture of EVOO's brain benefits
Dr. Praticò said their findings place another piece in the puzzle of EVOO's apparent ability to ward off cognitive decline and protect the junctions — known as synapses — where neurons come together to exchange information.
As he said, “The realization that EVOO can protect the brain against different forms of dementia gives us an opportunity to learn more about the mechanisms through which it acts to support brain health.”
His team's new study proved that EVOO benefits mice engineered to develop tauopathy. In these mice, normal tau protein turns defective and accumulates in the brain, forming harmful tau deposits, also called tangles.
Dr. Praticò and colleagues now plan to explore what happens when EVOO is fed to older animals that have begun to develop tau deposits and signs of cognitive decline, which more closely reflects the clinical scenario in humans. “We are particularly interested in knowing whether EVOO can reverse tau damage and ultimately treat tauopathy in older mice,” Dr. Praticò added.
The research was funded in part by a grant from the North Star Charitable Foundation and by a grant from Italy’s Sapienza University.
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