Researchers from the Lewis Katz School of Medicine at Temple University (Philadelphia) have identified a specific ingredient in extra-virgin olive oil (EVOO) that protects against cognitive decline. In a study published online in the Annals of Clinical and Translational Neurology, June 21st, 2017, researchers found that EVOO protects memory and learning ability by reducing the formation of classic markers of Alzheimer’s disease in the brain – amyloid-beta plaques and neurofibrillary tangles. The Temple team, led by Dr.Practico, identified the mechanisms by which EVOO is effective: “We found that olive oil reduces brain inflammation but most importantly activates a process known as autophagy.” Autophagy is the process by which cells break down and clear out intracellular debris and toxins, such as amyloid plaques and tau tangles.
Previous studies have suggested that the widespread use of extra-virgin olive oil in the diets of people living in the Mediterranean areas is largely responsible for the many health benefits linked to the Mediterranean diet. "The thinking is that extra-virgin olive oil is better than fruits and vegetables alone, and as a monounsaturated vegetable fat it is healthier than saturated animal fats," according to Dr. Praticò.
The Mediterranean diet, as you probably know, consists of primarily plant-based foods such as vegetables and fruits, whole grains, legumes and nuts. Butter is replaced by olive oil. Herbs and spices flavor foods, so that less salt is used. Red meat is limited to no more than a few times a month, while fish and poultry are eaten at least twice a week. Red wine is used in moderation if desired (not to exceed one glass for women, two for men). In previous studies, this diet has been associated with a decrease in high blood pressure, heart attack and stroke, and intestinal polyps.
In order to investigate the relationship between extra-virgin olive oil and dementia, Dr. Praticò and colleagues used a well-established Alzheimer's disease mouse model. Known as a triple transgenic model, the animals develop three key characteristics of the disease: memory impairment, amyloid plagues, and neurofibrillary tangles. The researchers divided the animals into two groups, one that received a chow diet enriched with extra-virgin olive oil and one that received the regular chow diet without it. The olive oil was introduced into the diet when the mice were six months old, before symptoms of Alzheimer's disease begin to emerge in the animal model.
In overall appearance, there was no difference between the two groups of animals. However, at age 9 months and 12 months, mice on the extra virgin olive oil-enriched diet performed significantly better on tests designed to evaluate working memory, spatial memory, and learning abilities. Studies of brain tissue from both groups of mice revealed dramatic differences in nerve cell appearance and function.
"One thing that stood out immediately was synaptic integrity," Dr. Praticò said. The integrity of the connections between neurons, known as synapses, were preserved in animals on the extra-virgin olive oil diet. In addition, compared to mice on a regular diet, brain cells from animals in the olive oil group showed a dramatic increase in nerve cell autophagy activation, which was ultimately responsible for the reduction in levels of amyloid plaques and phosphorylated tau.
"This is an exciting finding for us," explained Dr. Praticò. "Thanks to the autophagy activation, memory and synaptic integrity were preserved, and the pathological effects in animals otherwise destined to develop Alzheimer's disease were significantly reduced. This is a very important discovery, since we suspect that a reduction in autophagy marks the beginning of Alzheimer's disease."
Dr. Praticò and colleagues plan next to investigate the effects of introducing extra-virgin olive oil into the diet of the same mice at 12 months of age, when they have already developed plaques and tangles. "Usually when a patient sees a doctor for suspected symptoms of dementia, the disease is already present," Dr. Praticò added. "We want to know whether olive oil added at a later time point in the diet can stop or reverse the disease."
Sadja Greenwood, MD, MPH