The health benefits of olives and associated natural products like olive oil have long been recognized and touted by proponents of the Mediterranean diet. Now, a Virginia Tech research team has found that the olive-derived compound oleuropein helps the body secrete more insulin, a central signaling molecule in the body that controls metabolism.
Little was previously known about what specific compounds and biochemical interactions in the fruit contribute to its medical and nutritional benefits such as weight loss and prevention of type 2 diabetes.
The Virginia Tech scientists discovered that the olive-derived compound oleuropein helps the body secrete more insulin, a central signaling molecule in the body that controls metabolism. The same compound also detoxifies another signaling molecule called amylin that over-produces and forms harmful aggregates in type 2 diabetes. In these two distinct ways, oleuropein helps prevent the onset of disease.
The findings were recently published in the journal Biochemistry as a Rapid Report, which is reserved for timely topics of unusual interest, according to the journal.
“Our work provides new mechanistic insights into the long-standing question of why olive products can be anti- diabetic,” said Bin Xu, lead author. “We believe it will not only contribute to the biochemistry of the functions of the olive component oleuropein, but also have an impact on the general public to pay more attention to olive products in light of the current diabetes epidemic.”
The discovery could help improve understanding of the scientific basis of health benefits of olive products and develop new, low-cost nutraceutical strategies to fight type 2 diabetes and related obesity.
Next steps include testing the compound in a diabetic animal model and investigation of additional new functions of this compound, or its components, in metabolism and aging.
Olive Oil Consumption to Fight Dementia and Alzheimer’s Disease?
In a separate study, researchers at the Lewis Katz School of Medicine at Temple University showed that the consumption of extra-virgin olive oil protects memory and learning ability and reduces the formation of amyloid-beta plaques and neurofibrillary tangles in the brain — classic markers of Alzheimer’s disease.
The Temple University scientists also identified the mechanisms underlying the protective effects of extra-virgin olive oil. “We found that olive oil reduces brain inflammation but most importantly activates a process known as autophagy,” explained senior investigator Domenico Praticò, MD. Autophagy is the process by which cells break down and clear out intracellular debris and toxins, such as amyloid plaques and tau tangles.
“Brain cells from mice fed diets enriched with extra-virgin olive oil had higher levels of autophagy and reduced levels of amyloid plaques and phosphorylated tau,” Dr. Praticò said. The latter substance, phosphorylated tau, is responsible for neurofibrillary tangles, which are suspected of contributing to the nerve cell dysfunction in the brain that is responsible for Alzheimer’s memory symptoms.
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.
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.”
Olive Oil Consumption Lowers Stroke Risk
In yet another European study, researchers looked at the medical records of 7,625 people ages 65 and older from three cities in France: Bordeaux, Dijon and Montpellier. Participants had no history of stroke. Olive oil consumption was categorized as “no use,” “moderate use” such as using olive oil in cooking or as dressing or with bread, and “intensive use,” which included using olive oil for both cooking and as dressing or with bread. Study participants mainly used extra virgin olive oil, as that is 98 percent of what is available in France.
After a little over five years, there were 148 strokes.
After considering diet, physical activity, body mass index and other risk factors for stroke, the study found that those who regularly used olive oil for both cooking and as dressing had a 41 percent lower risk of stroke compared to those who never used olive oil in their diet (1.5 percent in six years compared to 2.6 percent).
Olive oil has been associated with potentially protective effects against many cardiovascular risk factors, such as diabetes, high blood pressure, high cholesterol and obesity.
Olive Oil Consumption Associated with Lower Risk of Cardiac Arrest
In a separate study, researchers in Spain randomly selected 296 people at high risk of cardiovascular disease participating in the PREvención con DIeta MEDiterránea study. Blood samples were taken from the participants at the beginning of the study and again at the end.
Participants, average age 66, were randomly assigned to one of three diets for a year: a traditional Mediterranean diet enriched with virgin olive oil (about 4 tablespoons) each day, a traditional Mediterranean diet enriched with extra nuts (about a fistful) each day, or a healthy “control” diet that reduced consumption of red meat, processed food, high-fat dairy products and sweets. In addition to emphasizing fruit, vegetables, legumes, such as beans, chickpeas and lentils, and whole grains, both Mediterranean diets included moderate amounts of fish and poultry.
The study found that only the control diet reduced total and LDL cholesterol levels. None of the diets increased HDL levels significantly, but the Mediterranean diets did improve HDL function. The improvement in HDL function was much larger among those consuming an extra quantity of virgin olive oil.
Fitó and her team found that the Mediterranean diet enriched with virgin olive oil improved key HDL functions, including:
- Reverse cholesterol transport, the process by which HDL removes cholesterol from plaque in the arteries and transports it to the liver where it is used to produce hormonal compounds or eliminated from the body.
- Antioxidant protection, the ability of HDL to counteract the oxidation of LDL, which has been found to trigger the development of plaque in the arteries.
- Vasodilator capacity, which relaxes blood vessels, keeping them open and blood flowing.
Researchers said they were surprised to find that the control diet, which like the Mediterranean diets was rich in fruits and vegetables, had a negative impact on HDL’s anti-inflammatory properties. A decrease in HDL’s anti-inflammatory capability is associated with cardiovascular disease. Participants on the Mediterranean diets did not experience a decline in this important HDL function, the authors wrote.
Researchers said the differences in results between the diets were relatively small because the modifications of the Mediterranean diets were modest and the control diet was a healthy one. They added that study results are mainly focused on a high cardiovascular risk population that includes people who can obtain the most benefits from this diet intervention.
Still, Fitó said, “following a Mediterranean diet rich in virgin olive oil could protect our cardiovascular health in several ways, including making our ‘good cholesterol’ work in a more complete way.”