BDNF is a protein that is responsible for many important brain functions. Severe alterations in BDNF levels may contribute to many different psychiatric disorders such as epilepsy, autism, schizophrenia and depression. Animal studies have shown that different dietary factors can affect brain levels of BDNF. Diets rich in omega-3 fatty acids, vitamin E or flavonols from colorful fruits can increase BDNF levels and improve cognitive function and mood. In contrast, diets rich in saturated fatty acids or total fat actually lower BDNF levels and are associated with impaired memory, brain atrophy and mood disorders. But this is true for rats; would a similar dietary change benefit us humans?
A recent study published in Nutritional Neuroscience by a group of scientists from the University of Las Palmas de Gran Canaria in Spain determined the effect of the classic Mediterranean diet (with some slight modifications) upon levels of BDNF in patients who suffer with major depression and in those who did not. The subjects were randomly assigned to three groups: a control (but low-fat) diet, a Mediterranean diet supplemented with virgin olive oil or a Mediterranean diet supplemented with nuts (an equal mixture of walnuts and almonds).
The Mediterranean diet is characterized by the consumption of fruits and nuts, vegetables, legumes, olive oil, cereals and fish, with a low consumption of dairy products and meat, and a moderate intake of alcohol. The nuts chosen for this study are rich in monounsaturated (almonds) and polyunsaturated (walnuts) fatty acids as well as many different antioxidants. Fruits, vegetables, and red wine are rich in polyphenols that exhibit antioxidant and anti-inflammatory properties. Although the individual components of the diet are clearly beneficial, the overall Mediterranean diet is believed to be beneficial due to the synergistic interactions between its components.
The patients were followed for three years! The reason is that dietary changes often affect brain function rather slowly and the full impact of any diet may take many months to be realized. Patients with prevalent depression who consumed the Mediterranean diet supplemented with nuts showed the greatest increase in blood levels of BDNF. Participants who were not clinically depressed showed no change in their blood levels of BDNF. These results were consistent with prior epidemiological reports of an inverse relationship between a healthy diet and the prevalence of depressive symptoms.
Thus, if you are depressed, eating a typical Mediterranean diet supplemented with nuts might improve your mood; if you are not depressed, eating a typical American diet rich in saturated fats will likely induce more depression (and a larger waistline); if you are not depressed and you are already eating a typical Mediterranean diet supplemented with nuts – nothing is likely to happen, except that you’ll be healthier overall.
© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford University Press)