A healthy diet is crucial to the overall health of humans. Sometimes what we eat decides who we are, and how healthy we are. In the U.S., the most prevalent diet is the Western diet, a diet high in saturated fat and refined carbohydrates. Saturated fats are those in the solid form at room temperature, such as cheese, butter, and red meat. Refined carbs are grain products with dietary fibers and many other ingredients removed from whole grain. Much as we may like these foods for their great taste, we need to be aware of their health risks as well. For a million times, we are told that the Western diet leads to obesity, and we might be told to eat more vegetables even more often. It is true that the consumption of Western diet could lead to (morbidly) increased body weight, but its potential risk extends beyond simply physical and metabolic. In fact, what we eat and how we eat could affect our brain as well.
In order to have a better understanding of how eating patterns can affect our normal brain function, we need to know how our brain normally function first. The brain consumes almost half of the energy produced by sugar intake (in the form of glucose) every day, making it the most energy-thirsty organ in our body. The huge amount of energy is used for fueling all the neurons to fire, allowing them to transmit signals and direct how we behave. When you do not have enough sugars from meals, you break down your glycogen storage to maintain a constant blood sugar level. When that is depleted also, you undergo hypoglycemia, and your hungry brain will make poor decisions for you. But please keep in mind, having too much sugar is not a good idea either, and in fact, it could be an even worse option.
So now we can come back to our discussion on the Western diet. When we eat too much saturated fats and refined carbs, we put our normal brain cognitive functioning at risk. For example, research showed that a high fat intake could make people distracted more easily, while a high refined carb diet can lead to impaired glucose tolerance and insulin resistance, causing cognitive impairments and type 2 diabetes (Edwards et al., 2011; Chui & Greenwood, 2008). The consumption of high fat and refined sugar (or processed food in general) could also cause normal adults to perform worse on memory and executive functioning tests (Akbaraly et al., 2009).
What’s more, consumption of high saturated fat food actually increases the risk for Alzheimer’s disease in adults older than 65, and a prolonged diet pattern with higher than normal sugar intake actually increases the risk for Parkinson’s disease as well (Morris et al., 2003; Abbott et al., 2003). How on earth could this fatty and sugary diet lead to decreased brain health? One mechanism suggested that excessive blood sugar intake increases oxidative stress (where byproducts of the glucose energy production harms your tissues), and the intake of excessive saturated fats exacerbates the stress (Francis & Stevenson, 2013). The stress seems to primarily affect neurons in the hippocampus (mainly in charge of memory) and the prefrontal cortex (mainly in charge of executive functioning), so no wonder the oxidative stress caused Western diet could lead to cognitive issues. Also, oxidative stress is reported to be highly related to neurodegenerative diseases such as Alzheimer’s and Parkinson’s by either harmful material deposition or death of essential brain neurons (Nunomura et al., 2001; Jenner, 2003).
Well, let’s consider some methods of losing weight. Speaking of losing weight, probably the first way coming up in our mind is to eat less, or even by fasting. This method makes so much sense at first glimpse: since obesity is caused by having too much energy intake, fasting or skipping meals would be the most direct and effective way combating the extra energy intake. Yes, it does make sense to have less energy absorption, and it should be advised so, but there may be some problems with fasting. A research by Goldstone and colleagues (2009) showed that fasting could bias our brain reward systems toward foods with higher calorie. In the study, researchers compared the brain activities between fasting and non-fasting states when the participants were shown pictures of high- and low-calorie foods. They found that when shown high-calorie foods, participants in the fasting state would have more significantly increased activities in ventral striatum (reward center), amygdala (emotion center), and prefrontal cortex (executive center) than when the participants were shown low-calorie foods. Therefore, the energy-thirsty brain cries harder for the more energy-efficient high-calorie food, despite its potential threats to health in long term. What this indicates is that fasting may not be the best way to lose weight, so lowering the total amount of fats and sugars is necessary.
So, how should we have a healthy diet? According to the Office of Disease Prevention and Health Promotion, we need to adjust our Western diet patterns so that energy from added sugars and saturated fats each contribute to less than 10% of our daily calories. Of course, for a very healthy diet, we need to eat more fruits and vegetables, more whole grains, at more varieties of meat (Office of Disease Prevention and Health Promotion, 2015). For more information on how to pursue a healthier diet, I am pasting the link to the Office of Disease Prevention and Health Promotion guideline here: https://health.gov/dietaryguidelines/2015/guidelines/.
Hope you can eat healthily and stay healthy!
Abbott, R. D., Ross, G. W., White, L. R., Sanderson, W. T., Burchfiel, C. M., Kashon, M., et al. (2003). Environmental, life-style, and physical precursors of clinical Parkinson’s disease. Recent findings from the Honolulu-Asia Aging Study. Journal of Neurology, 250(Suppl. 3), III30–III39.
Akbaraly, T. N., Singh-Manoux, A., Marmot, M. G., & Brunner, E. J. (2009). Education attenuates the association between dietary patterns and cognition. Dementia and Geriatric Cognitive Disorders, 27(2), 147–154.
Chui, M. H., & Greenwood, C. E. (2008). Antioxidant vitamins reduce acute meal-induced memory deficits in adults with type 2 diabetes. Nutrition Research, 28(7), 423–429.
Edwards, L. M., Murray, A. J., Holloway, C. J., Carter, E. E., Kemp, G. J., Codreanu, I., et al. (2011). Short-term consumption of a high-fat diet impairs whole-body efficiency and cognitive function in sedentary men. FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology, 25(3), 1088–1096.
Francis, H., & Stevenson, R. (2013). The longer-term impacts of Western diet on human cognition and the brain. Appetite, 63, 119-128.
Goldstone, A. P., Prechtl de Hernandez, C. G., Beaver, J. D., Muhammed, K., Croese, C., Bell, G., … & Bell, J. D. (2009). Fasting biases brain reward systems towards high‐calorie foods. European Journal of Neuroscience, 30(8), 1625-1635.
Morris, M. C., Evans, D. A., Bienias, J. L., Tangney, C. C., Bennett, D. A., Aggarwal, N., et al. (2003). Dietary fats and the risk of incident Alzheimer disease. Archives of Neurology, 60(2), 194–200.
Nunomura, A., Perry, G., Aliev, G., Hirai, K., Takeda, A., Balraj, E. K., et al. (2001). Oxidative damage is the earliest event in Alzheimer disease. Journal of Neuropathology and Experimental Neurology, 60(8), 759–767.
Office of Disease Prevention and Health Promotion. (2015). Dietary guidelines for Americans, 8th edition. Retrieved from https://health.gov/dietaryguidelines/2015/guidelines/ on March 1, 2019.
Featured image from http://whatdoctorsknow.com.