An adequate diet has important effects on brain functions and brain health. Excess or lack of specific nutrients differently affect cognitive processes, emotions, behaviour, neuroendocrine functions and synaptic plasticity with protective or harmful effects on neuronal physiology. In particular, lipids play structural and functional roles in neurons, actively participating in the formation of the cellular membrane and myelin; as well as cellular signalling pathways in the brain, which include lipid intermediates, that regulate cell differentiation, cerebral processes and synaptic transmission [Chianese 2018]. Therefore, good lifestyle and adequate nutrition can represent an effective therapeutic approach to maintain and preserve brain health throughout life.
Foods contain different types of fatty acids, which are distinguished in saturated and unsaturated fatty acids. Saturated fatty acids, because of their structure, are difficult to metabolize and tend to accumulate in the blood. They can cause an increase in total cholesterol and LDL (the “bad cholesterol”) with the natural consequence of an increased predisposition to cardiovascular disease. Unsaturated fatty acids are divided into monounsaturated fatty acids and polyunsaturated fatty acids (PUFA). The last one can be widely divided into two classes, omega-3 and omega-6. The ω-6 are contained in dried fruit. The ω-3 are contained in fish, nuts and oily seeds such as flaxseeds. An interesting observation is that nuts and flaxseeds are short-chained PUFA and a low-carb environment is required to metabolize them at best.
PUFAs are widely present among food lipids and actively mediate the inflammatory process. The ω-3 lead to the production of anti-inflammatory prostaglandins, which participate in the “resolution” of inflammation by directing neutrophils to migrate to the site of inflammation and exercising anti-inflammatory and protective actions through multiple mechanisms, such as the elimination of inflammatory chemokines and stimulation of the anti-microbic defence mechanism [Bazinet 2014]. Therefore, the ω-3 regulate the immune response through the action of their derivatives. On the contrary, an excess of ω-6 generates pro-inflammatory prostaglandines. In the brain, the bioavailability of PUFA and their bioactive derivatives depends heavily on the composition of the diet with an ideal ratio of 4 (ω-6): 1 (ω-3). However, diet is often unbalanced and high consumption of ω-6 have been associated with neurological disorders with inflammatory outcomes.
Endocannabinoids (eCBs) in PUFA derivatives deserve special attention; they link dietary lipids to synaptic activity, neuronal plasticity and neuroendocrine functions. Recent studies show that eCBs derived from arachidonic acid also modulate synaptic transmission [Lafourcate 2011; Thomazeau 2017]. This highlights the importance of dietary lipids in preserving and maintaining the specific molecular systems and mechanisms that regulate neuronal functions and the ability to prevent neurodegenerative diseases through an adequate diet.
Arachidonic acid (ARA) and docosaesanoic (DHA) and eicosapentaenoic (EPA) acids, the first deriving from ω-3 and the other from ω-6, have essential roles in the physiology of the brain as they regulate fundamental neurobiological processes, especially in cognition. It is supposed that the neuroprotective activities of DHA and EPA are powerful for protection from cognitive decline and dementia [Salem 2015]. Dietary supplementation with DHA and EPA has also shown to improve cognitive performance in several animal studies affected by Alzheimer’s Disease (AD). Previous human studies have also reported promising effects on cognition in individuals receiving DHA, EPA, or a combination of the two. The mechanisms, by which DHA supplementation can affect AD, may be related to the deposition of the β-amyloid protein in the brain [Cole 2010]. Therefore, the right intake of fatty acids can prevent different neuroinflamatory diseases.
Neuroinflammation involves the brain’s immune system, mainly microglia. In the healthy brain, these cells modulate synaptic functions and protect neurons from infection or damage. The deregulation of microglia, due to aging or neurodegenerative processes, participates in the synaptic loss observed not only in AD, but also in conditions of chronic stress or dietary lipid imbalance. In addition, neurodegenerative diseases are accompanied by pro-inflammatory factors, which participate in neuronal death, neuropathological processes and promote cognitive deficit. A recent study has shown that the consumption of foods rich in ω-3 has potential neuroprotective effects at the microglia level [Nadjar 2017].
In particular, several related epidemiological studies have revealed the positive association between ω-3 and cognitive performance in the elderly and/or in patients with neurodegenerative diseases such as AD. These observations have led to frequent clinical studies to assess whether dietary supplementation with EPA and DHA can restore cognitive function in the elderly and in patients suffering from AD or at risk of cognitive decline, psychosis or mood disorders. Some clinical studies report improved knowledge in subjects with mild cognitive decline [Palacios-Pelaez 2010; Dyall 2015; Hamilton 2017].
All these studies make us understand that an appropriate nutrition and the right balance between nutrients can have preventive effects for neurodegenerative diseases.
Dr. Rosjana Pica
In collaboration with Cerebro® Staff
Cerebro®, Start-Up in High-Tech and Innovative Neuroscience aims to help and support patients in associated studies and clinics through different methods and approaches to improve the perception and quality of life of each individual