Not So Sweet Part 2: The Effects of High Fructose Corn Syrup

What is the first thing that comes to mind when thinking about sugar? Most people probably do not think of Alzheimer's disease (AD); however, new research shows that the sugars in processed foods may be contributing to the development of Alzheimer's.  

A review published in March 2023 in The American Journal of Clinical Nutrition suggests that high fructose corn syrup (HFCS) may reduce metabolism in brain regions involved in higher cognitive functions, such as reasoning, impulse control, and memory. An earlier study published in June 2022 in the Public Library of Science discovered that when rats consumed HFCS from a young age onward, certain parts of their brains developed deleterious changes. The research showed that memory, emotion, and nervous system functions were damaged, and it was concluded that long-term consumption of HFCS caused reduced metabolic function in those regions. The effects of this reduction in function are degeneration and cognitive decline, which are typical characteristics of AD.  

So, what is HFCS? HFCS is a commonly used sweetener in processed foods, functioning as an inexpensive and more shelf-stable substitute for sucrose (table sugar). HFCS is made from corn starch, which is broken down into two monosaccharides, fructose (55%) and glucose (45%), by enzymes. In the end, the substance is equal to the sweetness of sucrose, which is formed by one molecule of glucose and one molecule of fructose. Consumption of HFCS is increasing with the rise of processed food. Snacks, baked goods, coffee, tea, and soft drinks are just a few foods containing HFCS. Along with the sweetening effects of HFCS is its ability to prompt addictive consumption behaviors, making it a key component of the obesity epidemic.  

Alzheimer's disease is a neurological disorder that slowly progresses, destroying memory and other essential functions. These include simple tasks such as speaking, reasoning, and appropriate social behavior. First, AD attacks neurons and their connections to the entorhinal cortex and hippocampus, which are parts of the brain that are responsible for memory. Later on, it affects the cerebral cortex, which is responsible for language, reasoning, and social behaviors. Over time, other areas of the brain become affected. This concludes why AD progresses gradually over time as it slowly affects areas of the brain until a person loses his ability to function independently and at his full mental capacity. One molecule that is associated with AD is the beta-amyloid protein. It is formed by the breakdown of amyloid precursor protein, becoming extremely harmful to brain function. Increased levels of beta-amyloid are found in AD, which clump together to form plaques and disturb cellular function. There are various forms of beta-amyloid, and researchers are still trying to figure out which forms are present at each stage of AD progression. Tau is another protein found in neurons that maintains the stability of microtubules; however, in AD, tau detaches from microtubules and connects to other tau molecules, which eventually form tangles inside neurons, disrupting synaptic communication.

Although there is still no definitive answer to what causes AD, research shows that HFCS is affecting the areas of the brain responsible for AD. Researchers seem to have found a link between fructose levels and AD. In a review published in The American Journal of 

Clinical Nutrition, lead author Dr. Richard Johnson cited previous research from the Public Library of Science, which found that rats that consumed HFCS for an extended period of time developed tau and beta-amyloid proteins. He then went on to make the statement: "We make the case that Alzheimer's disease is driven by diet." (The Epoch Times 3). Dr. Johnson hypothesizes that excessive consumption of HFCS activates a survival response, which he calls the "survival switch" (The Epoch Times 3). This helps humans survive during prolonged periods of food and water scarcity. He believes this survival switch is stuck in the on position even in times of food abundance. This leads to overeating sugary, processed foods, which therefore leads to excess fructose production in the body. Although more research is needed to understand how fructose metabolism might cause AD, this is a starting point for understanding the effects of HFCS and brain function. 

Alzheimer's is not the only adverse health effect caused by HFCS. Other metabolic disorders, including diabetes, heart disease, obesity, and hypertension, have been linked to large intakes of HFCS. Because excessive intake of fructose leads to the disturbance of metabolic function, it causes metabolic disorders. Claire Sexton, the senior director of the Alzheimer's Association, stated, "Research has suggested Type 2 diabetes can be a risk factor for Alzheimer's disease and other types of dementia, like vascular dementia." (The Epoch Times 4). This link could be because the factors that increase the risk of Type 2 diabetes also increase the risk of AD. This could also result from the effects of fructose metabolism in the brain, which leads to low blood sugar since the brain needs blood sugar for sustenance. Scientists also concluded that AD is more frequent in people with diabetes and that insulin resistance in the brain is a component of cognitive decline. Overall, HFCS affects metabolism, and there seems to be a link between certain metabolic disorders and AD. 

In conclusion, when looking at foods, especially packaged and processed foods, be cautious by checking the label to see whether it contains HFCS. Foods that do not contain it usually say "No High Fructose Corn Syrup" on the packaging. Being conscientious by avoiding and reducing HFCS intake is a healthy choice for the body's function. Overall, the aforementioned research concludes that perhaps, people truly are what they eat.

References

B. C. M. Stephan, J. C. K. Wells, C. Brayne, E. Albanese, M. Siervo, “Increased Fructose Intake as a Risk Factor For Dementia,” The Journals of Gerontology: Series A, Volume 65A, Issue 8, August 2010, Pages 809–814, https://doi.org/10.1093/gerona/glq079. 

“Could Fructose Contribute to the Development of Alzheimer’s?” Medical News Today, 20 Feb. 2023, www.medicalnewstoday.com/articles/could-fructose-contribute-to-the development-of-Alzheimers. 

“Fructose Could Drive Alzheimer’s Disease.” ScienceDaily, https://www.sciencedaily.com/releases/2023/02/230213113345.htm#:~:text=FULL%20STORY-,An%20ancient%20human%20foraging%20instinct%2C%20fueled%20by%20fructose%20production%20in,of%20Colorado%20Anschutz%20Medical%20Campus. 

NIA. “What Is Alzheimer’s Disease?” National Institute on Aging, 8 July 2021, www.nia.nih.gov/health/what-Alzheimers-disease.

“Sugar in Processed Foods and Drinks Linked to Dementia; Experts Explain Possible Reasons.” The Epoch Times, www.theepochtimes.com/health/sugar-in-processed-foods-and drinks-linked-to-dementia-experts-explain-possible-reasons-5098104. 

“Sugary Foods May Be Driving Alzheimer’s, Study Suggests.” Psychiatrist.com, 20 Feb. 2023, www.psychiatrist.com/news/sugary-foods-may-be-driving-alzheimers-study-suggests/ #:~:text=A%20new%20study%20theorizes%20that.

Spagnuolo, Maria Stefania, et al. “Sweet but Bitter: Focus on Fructose Impact on Brain Function in Rodent Models.” Nutrients, vol. 13, no. 1, 22 Dec. 2020, p. 1, www.ncbi.nlm.nih.gov/pmc/articles/PMC7821920/, https://doi.org/10.3390/nu13010001.

“What Happens to the Brain in Alzheimer’s Disease?” National Institute on Aging, www.nia.nih.gov/health/what-happens-brain-alzheimersdisease#:~:text=The%20beta%2Damyloid%20protein%20involved.