A new study carried out by the University of Granada revealed that frying vegetables typical to the Mediterranean diet in EVOO, as opposed to boiling, is a much better method of cooking in terms of nutrient value.

There has been much debate on the pros and cons of different cooking methods for vegetables and how certain cooking techniques affect phenolic compounds.

This latest study aimed to put domestic cooking techniques to the test and determine how they affect or enhance the antioxidant qualities as well as the quantities of phenolic compounds found in a Spanish Mediterranean diet which typically contains high volumes of potato, pumpkin, eggplant and tomato.

The Mediterranean diet in Spain is also characterized by high consumption of EVOO which, alongside vegetables, are sources of certain compounds that have been linked to the prevention of chronic degenerative diseases like cancer, diabetes and macular degeneration, a condition that causes blindness.
SEE MORE: The Health Benefits of Olive Oil
During the study three cooking methods were employed; 120 gram cubes of the vegetables were fried in EVOO, or boiled in water, or boiled in a mix of water and EVOO.

All tests were carried out under controls with close analysis of the cooking methods and storage of the vegetables in optimum conditions so as to accurately measure factors like moisture, fat, dry matter, phenol content and antioxidant capacity, said the university.

In what they described as a “breakthrough in food science,” the researchers found frying in EVOO produced higher levels of natural phenols.

Professor Cristina Samaniego Sanchez
“While comparing the total phenol content of the fresh vegetables, we found both increases and decreases in their levels, depending on the cooking method employed,” said one of the authors of the work, Professor Cristina Samaniego Sanchez.

“As a heat transfer medium, the EVOO increases the amount of phenols in the vegetables, in contrast with other methods such as boiling, which use a water-based heat transfer medium.”

According to the results of the study, the overall quality of the vegetables was significantly improved when fried in EVOO because the produce becomes enriched with EVOO phenols transferred from the oil.

“We conclude that frying in EVOO was the technique with the highest associated increases of phenols and can therefore be considered an improvement in the cooking process, although it also increases the calorie density of the food because of the amount of oil absorbed,” Sanchez added.

“If the concentration of phenols found in the raw ingredients is high to start with, the overall concentration level is further increased if EVOO is employed during the cooking process, while boiling does not significantly affect the concentration levels.” Boiling is recommended if the vegetables are to be consumed together with the cooking medium (i.e. the water).

A recent study has shown that a diet rich in olive oil has a positive effect on the development of the unborn child and may also affect her adult life.

“During the gestation, there is a great incorporation of fatty acids into the fetal brain, in order to maintain the adequate development,” explained one of the authors of the study, Prof. Marilise Escobar Burger. “Since olive oil is consumed in the Mediterranean diet with great results, the idea was that the olive oil, with a favorable fatty acids profile, could be good as well in the prenatal period.”

The joint study was conducted by researchers from the Department of Physiology and Pharmacology of the Federal University of Santa Maria (UFSM) and from the Department of Pharmacological and Biomolecular Sciences of the University of Milan (DiSFeB).

Olive oil during perinatal period seems to be able to prevent oxidative damage and improve the expression of protective neurotrophins in the adult brain.
– Camila Simonetti Pase, Federal University of Santa Maria
The researchers evaluated the influence of different diets on rodent pups: a group of female rats received a diet enriched with 20 percent olive oil (OOED) and one group was subjected to a standard diet (CD). They monitored their pups at various times — pregnancy, lactation, and after weaning until the pups’ adulthood — and measured oxidative and molecular brain parameters and weight during their lives, achieving very positive results for levels of prefrontal cortex and hippocampus.

At adulthood, animals in the group OOED showed less brain lipid peroxidation and higher levels of glutathione sulfhydryl groups in the prefrontal cortex and lower brain levels of reactive species in the hippocampus.

Interestingly, the group of animals whose diet was changed from a CD to OOED 21 days after birth showed a greater weight than the group that remained the same original diet (OOED) to adulthood.

It was also interesting that the consumption of OOED during pregnancy and lactation significantly increased the prefrontal cortex expression of trophic molecules that play an important role in neuronal plasticity and cognitive function.

“The new fact about this study is that olive oil diet during perinatal period seems to be able to prevent oxidative damage and improve the expression of protective neurotrophins in the adult brain,” researcher Camila Simonetti Pase (UFSM) explained. “The neurotrophins evaluated in our work (BDNF and FGF-2),” added Verônica Tironi Dias, are related to cellular survival, plasticity and protection from neurodegenerative and psychiatric diseases.”

The idea of the study and the joint collaboration started when Dr. Angélica Martelli Teixeira, who used to work with fatty acids in Brazil, got in touch with the Italian researchers of the University of Milan during an exchange program in Italy for her PhD.

Marco Andrea Riva works in a laboratory dedicated to psychiatric disorders and factors that may affect the risk of developing them in the pre- and perinatal period. “There is a clear evidence that exposure to stress makes the individual more vulnerable and more susceptible to develop diseases, such as depression or schizophrenia, later in life especially if they are exposed to stressful events during early life. Different factors can affect brain structure and function, not only those related to the environment but also nutritional elements,” he explained.

The study adds to a body of research that show how diets rich or poor in fats or in sugar may have effects on the mechanisms of brain function and functional recovery after traumatic injuries.

“This research supports the evidence that a diet rich in monounsaturated fats, already during the prenatal period, make the brain more plastic, more dynamic and therefore, probably, more resistant to any negative environmental stresses in adult life,” Prof. Riva concluded.

The results open a line of pioneering research on feeding and adjuvant therapeutic strategies and on the potential of healthy eating habits to prevent neonatal conditions and their influence on adult life.