The discussion regarding what really affects our brains throughout our lives has been ongoing for some time. We know that alcohol and drugs are part of a lifestyle that can damage our brains, and we know that saturated fats can damage our hearts and brains, for example, by potentially causing the development of vascular dementia. We understand many factors that may contribute to certain disorders; however, do we understand how we can maintain cognition at the standard it is at a younger age? Studies often attempt to find the answers by examining effects of various dietary components on our cognition.
The latest in this field of research comes from the Proceedings of the National Academy of Sciences (Alzheimer's UK, 2023; Brickman et al, 2023). The results appear to prove that dietary flavanols can restore hippocampal-dependent memory in older adults with lower diet quality and a diet low in regular consumption of flavanols. It appears that adults who consume less plant-based chemical compounds (flavanols) as a part of their diet may be significantly more likely to develop memory decline as they age (Alzheimer's UK, 2023; Brickman et al, 2023).
The research was carried out in the US and the UK, and involved the study of more than 3500 adults in the US. This formed part of a larger study comprising 21000 adults, which explored the health benefits of flavanols from cocoa (Alzheimer's UK, 2023; Brickman et al, 2023). Cognition, including memory, was examined, and flavanol biomarkers were sought in the urine of participants. One group received a 500mg cocoa flavanol supplement and the other received the placebo. The research took place over the course of 3 years, throughout which the same tests were conducted, and compared to the start of the study (Brickman et al, 2023).
Comparisons showed that those who received the supplement, who had a low-quality diet and the lowest amounts of the biomarker at the start of the study had significantly boosted memory test scores. However, those at the start of the study with high scores on diet assessment showed no difference from taking the flavanol supplement. This could mean that these participants were receiving enough of what was needed for cognition from their varied and healthy diets, but those with significantly poorer diets required the supplement, which then enabled improvement of their memories.
Spencer et al (2017) previously noted the global trend towards obesity and that over one-third of American adults have obesity. It is becoming a significant health issue around the world with a knock-on effect on many areas of a person's health. The authors noted that caloric intake and diet composition have lasting effects on the brain, although the neural mechanisms have not always been very well understood. They highlight that emotions have an impact on cognition, and the desire to overeat, or eat many of the ‘wrong’ things. Therefore, the authors conducted a review examining the link between dietary fat consumption and omega-3 polyunsaturated fatty acid dietary imbalance with inflammation in the brains of those who are young and still developing, those of normal adult age and those considered to have aged brains.
The authors’ commented on the importance of early life. Exposure to stress and early-life diet have lasting impacts on cognition; dysfunctional thinking and dysfunctional emotional responses can be the outcomes of these important early life experiences. This, of course, can impact nutrition and eating behaviours. Hence, the authors noted that there could be potential for early nutritional interventions to prevent such deficits. Spencer et al (2017) noted that an acute consumption of a high-fat diet can change the hippocampus, introducing a neuroinflammatory response to mild immune challenges, resulting in impaired memory. Having a reduce intake of omega-3 may put someone at greater risk of depression due to its impact on endocannabinoid and inflammatory pathways in certain areas of the brain, which causes synaptic phagocytosis by microglia in the hippocampus, thus causing memory loss (Spencer et al, 2017). In plainer terms, this means that neural synapses are destroyed by a mechanism in the brain in certain cells, as a response to mild immune threat, due to this being a primed response caused by the lack of omega-3 in the diet. This cell destruction can lead to impaired memory.
However, Spencer et al (2017) argued in their review that consuming fruits and vegetables high in polyphenolics can prevent and possibly reverse the cognitive issues linked to ageing, due to their actions in lowering oxidative stress and inflammation. Therefore, the authors discussed the complex relationship between diet, the brain's cognition and the its activity with regard to emotion. The key now is to find out ways to uncover the mechanisms responsible for various processes, and how we can prevent neurological problems in people who have obesity or poor diets, given the clear links between neurological functional decline, poor diet and unhealthy lifestyle, and those with eating disorders.
According to the researchers, the most significant finding of their work was that early life overfeeding can lead to the permanent sensitisation of the brain's neuroinflammatory response to any challenging stimuli. Hence, emotions can more easily trigger the feeling of a need to overeat or eat very unhealthy foods in certain people, in turn, causing cognitive problems. There is a metabolic impact and nutritional issues, which can lead to vulnerability to emotional disorders or cognitive problems. These may then cause the diet to worsen even further. Simple dietary interventions at a young age may therefore be a significant step towards avoiding cognitive dysfunction or disorders in later life, as well as emotional issues.
Overall, we are still unaware of all the facts relating to neuropathology and its link to cognition, cognitive decline, and illnesses such as dementia. There are multiple studies presenting clear associations between dietary supplements/nutritional factors, early life eating behaviours and healthy lifestyle factors. A couple of these relating to diet specifically have been delved into in the current article. However, it is important to look at other lifestyle factors as well. Part two of this article will look beyond diet and towards lifestyle in general. With obesity rising across the world, it is hoped that early life interventions and tools for emotional management may help prevent cognitive decline and neurological illness.