Historians consider it one of the ‘cradles of civilization,’ but for many scientists today the real value of the Mediterranean basin does not lie in its contribution to history. Home to one of the largest concentrations of built heritage sites, these lands have often been celebrated for their mystic healing power, offering long-sought shelter to harassed minds, mending the damaged lives of writers and artists from all over the world. Whilst the natural landscapes and lifestyle of this region are indisputably linked to the profound sense of contentment that tourists often experience when entering it, an important part of the appeal arises from its much celebrated cuisine.
Indeed, the Mediterranean diet (MeDi) has long attracted extensive media attention due to a growing international taste for the cooking of the lands bordering the inland sea. However, this fascination for all edibles Italian and Mediterranean is also sparked by accumulating evidence for its wide-ranging benefits on the body and, more recently, on the brain.
Indeed, evidence suggests that feeding your brain with the plant-based diet of the Mediterranean regions may reduce the risk of cognitive problems, effectively making you live a longer and healthier life. But what does MeDi consist of? According to Ancel Keys, one of the first scientists to champion the benefits of this diet, MeDi involves a high intake of fruit, vegetables, nuts, cereals and olive oil, limited amounts of meat, and moderate amounts of fish, dairy products and wine. This dietary pattern originated in Greece and Italy and thus, it should come as no surprise that one of the first studies investigating the effects of MeDi on brain health took place in this region almost 30 years ago.
As part of a broader investigation into the prevalence of several diseases in older adults, researchers at the University of Bari in Southern Italy discovered that individual elements of the MeDi are protective against cognitive decline. Their investigation involved the use of a standard clinical test to assess cognitive decline every 3 to 5 years and a dedicated questionnaire to evaluate participants’ dietary choices. This pioneering work demonstrated that a large intake of monounsaturated fatty acids (MUFA), which are abundant in olive oil, is protective against cognitive decline.
“Most experts suggest that the mysterious effects of MeDi could stem from the abundance of antioxidants that it provides.”
Encouraged by these intriguing results, scientist Valls-Pedret and colleagues at the Barcelona’s Institut d’Investigacions Biomèdiques August Pi i Sunyer embarked on the first-of-its-kind clinical trial looking at the association between MeDi and cognitive function in older individuals. Seeking to confirm previous findings, the authors of this study compared the effects of a MeDi supplemented with either extra-virgin olive oil or mixed nuts with a control diet that consisted of advice to reduce dietary fat.
Results were striking. After several years of data (and food) crunching, researchers demonstrated that participants allocated the Mediterranean-style diets displayed improved learning and memory whereas those allocated a normal diet showed signs of cognitive decline. Moreover, later analysis revealed that differences between groups could not be attributed to subjects’ gender, age or education level indicating that the effect was likely driven by their dietary pattern.
So how does MeDi exert its effect on the brain? While various attempts have been made to explain its beneficial effects, mechanisms remain nebulous at best. Most experts suggest that the mysterious effects of MeDi could stem from the abundance of antioxidants that it provides. Oxidative stress is a major cause of cell damage in several age-related brain conditions and is caused by the accumulation of toxic compounds in the brain called free radicals. With time, excessive accumulation of free radicals can lead to the irreversible loss of brain cells, which can profoundly affect learning and memory. Several substances with important antioxidant properties such as olive oil, wine, nuts, fruits and vegetables are found in large amounts in MeDi, leading some to suggest that MeDi may preserve cognitive function by reducing age-related oxidative processes in the brain. In addition, people observing a MeDi pattern have been reported to display reduced inflammation in their brain, shedding light on another potential mechanism explaining the protective effect of MeDi. Chronic inflammation has also been associated with a number of age-related brain conditions, as the build-up of inflammatory substances in the brain appears to facilitate the accumulation of toxic proteins which, with time, lead to cell death.
“A recent Italian study found that the benefits arising from MeDi are only evident in people with higher income or better education.”
Now, since brain cells are continuously attacked by oxidative stress and inflammation as we get older, it should come as no surprise that human brains shrink with age due to cell loss. However, high intake of antioxidant and anti-inflammatory substances should in theory delay or stop this shrinkage by a considerable amount. This idea was recently put to test by neuroscientist Michelle Luciano, who last year analyzed changes in brain structure in hundreds of individuals in their 70s. Their results demonstrated that the brains of those who adhered most closely to a typical MeDi shrank less than those of individuals that did not adhere to the same diet. As tantalizing as it sounds, Luciano specified that differences in thinking and memory between groups were not explored in this study, making it difficult to draw any conclusion on the effect of this well-balanced diet on brain function. In addition, a recent Italian study found that the benefits arising from MeDi are only evident in people with higher income or better education, putting into question the very notion that MeDi benefits everyone. Indeed, the same study suggested that only people with a household income over £35.000 (~$45.700) could benefit from this diet, whereas no benefits were found in less advantaged groups.
In conclusion, while mounting research points to the beneficial effects of MeDi on brain health, more research is needed to prove its effects. Most studies suggest a link between this diet and brain function but little is known about the mechanisms that drive its effects on the brain. In addition, defining minimum quantities of recommended foods remains a priority. Researchers agree that there are lots of benefits and no known downside to following a healthy diet. However, whilst adding olive oil and mixed nuts to your diet may benefit your brain cells, using excessive amounts will only make you gain weight. So… don’t go nuts!
This article originally appeared on Knowing Neurons
About The Author
Marco Travaglio is currently pursuing a PhD in Neuroscience at The University of Cambridge under the supervision of Dr Panman. His research aims to generate novel mechanistic insights into the selective vulnerability of dopaminergic neurons in Parkinson’s disease. His project involves the use of both embryonic and induced pluripotent stem cell based model systems to study the onset of the disease and its subsequent pathological manifestations. He received his MSci in Neuroscience from the University of Nottingham.
Keys A., Aravanis C., Blackburn H.W., Van Buchem F.S., Buzina R.,Djordjevic B.D., Dontas A.S., Fidanza F., Karvonen M.J., Kimura N., et al., (1966). Epidemiological studies related to coronary heart disease: characteris-tics of men aged 40–59 in seven countries, Acta medica scandinavica Supplements, 460:1–392.
Solfrizzi V., Panza F., Torres F., Mastroianni F., Del Parigi A., Venezia A., Capurso A., (1999). High monounsaturated fatty acids intake protects against age-related cognitive decline, Neurology, 52(8): 1563- 1569.
Valls-Pedret C., Sala-Vila A., Serra-Mir M., Corella D., de la Torre R., Martínez-González M.Á., Martinez-Lapiscina E.H., Fitó M., Pérez-Heras A., Salas-Salvadó J., Estruch R., Ros E., (2015). Mediterranean diet and age-related cognitive decline: A randomized clinical trial, JAMA internal medicine, 175: 1094–1103.
Luciano M, Corley J, Cox SR, Valdés Hernández MC, Craig LCA,Dickie DA, Karama S, McNeill GM, Bastin ME, Wardlaw JM, et al., (2017). Mediterranean-type diet and brain structural change from 73 to 76 years in a Scottish cohort, Neurology, 88: 449–55.
Bonaccio M., Di Castelnuovo A., Pounis G., Costanzo S., Persichillo M., Cerletti C., Donati M.B., de Gaetano G., Iacoviello L., (2017). Study Investigators High adherence to the Mediterranean diet is associated with cardiovascular protection in higher but not in lower socioeconomic groups: Prospective findings from the Moli-sani study, International journal of epidemiology, 46(5): 1478-1487.