Neuronal dysfunction in the brains of mammals is theorised to be caused by oxidative stress. The cell membranes of neurones in the central nervous system contain high concentrations of long chain polyunsaturated fatty acids because these fatty acids facilitate membrane fluidity and improve the efficiency of action potential propagation. However, polyunsaturated fatty acids are particularly susceptible to free radical damage because of the presence of multiple reaction sites for oxygen on the numerous double bonds they possess. Oxidation in uncontrolled conditions therefore leads to lipid peroxidation, which means that the polyunsaturated fats of the brain become rancid and as structure is lost so follows function. High levels of oxidative stress can also damage nucleic acids, mitochondria and proteins in the neurones and accessory cells of the central nervous system and this can cause further deteriorations in the efficiency of the neuronal pathways leading to disease and cognitive decline.
The accumulation of oxidative damage in the brains of mammals is manifest as a slow decline in cognitive function. To a certain extent this decline is inevitable, but there is no reason to assume that the development of degenerative diseases are a foregone conclusion because certain groups of individuals in the World maintain their cognitive function into old age and are not encumbered with the same risk of dementia as those living in other areas. The reason for the discrepancy in the risk of serious cognitive deterioration has been studied and evidence supports a role for diet in the protection against cognitive decline. For example, while rates of dementia are high in the developed Western nations as a whole, age-related cognitive decline is not so apparent in populations within these nations who still consume traditional plant based diets. For example, studies looking at aged populations living in Sicily who consume a traditional Mediterranean diet show that such individuals maintain normal mental function into old age.
Poor diet is an important driver of cognitive decline because low quality foods induce oxidative stress. In contrast, high quality diets based on whole plant foods provides high levels of antioxidant nutrients that may inhibit the oxidative stress that leads to cognitive decline. Plant foods are rich in both water and fat soluble antioxidant phytochemicals and current understanding is that these non-essential nutrients including flavonoids, terpenes, polyphenols, stilbenes, chalcones, isoflavones and carotenoids are protective of systemic oxidative stress including that within neuronal tissues. The ability of antioxidants to protect the brain from cognitive decline has been extensively tested by researchers and in one study1 that was widely publicised in the media, rats were fed diets that included acetyl L-carnitine and R-α-lipoic acid in their drinking water. Using a number of established tests the researchers showed that acetyl L-carnitine and lipoic acid were effective at improving spatial and temporal memory in the rats.
The combination of acetyl L-carnitine and lipoic acid was the more effective at improving memory in the rats compared to either treatment in isolation, suggesting that synergism between the nutrients was occurring. The researchers also measured oxidative stress in the rats by analysing the degree of oxidation in the nucleic acids of the rats. Both lipoic acid and acetyl L-carnitine were effective at reducing the oxidative damage to the nucleic acids with the combination of both nutrients being the most effective treatment. Both acetyl L-carnitine and lipoic acid also decreased the age-related decline in the function of the mitochondria in the hippocampus. Therefore it is likely that through their ability to inhibit oxidative stress, these two nutrients were effective at improving the memory of the rats. Since this study was published other studies using humans have corroborated these findings. High quality diets containing high amounts of antioxidant nutrients therefore appear to prevent mental deterioration.
Dr Robert Barrington’s Nutritional Recommendation: Acetyl L-carnitine and lipoic acid both appear to inhibit some of the memory impairments seen through natural ageing. The mechanism by which they are affective is likely through prevention of oxidative stress, which maintains the efficiency of the neuronal pathways. However, it is clear that high quality diets produces similar effects because of the antioxidant phytochemicals they contains. Those eating a high quality plant based diet may not therefore derive the same benefit from these supplements as those eating a more typical Western style diet.
RdB
