Reused Cooking Oils Accelerate Neurodegeneration

It’s medical cannon by now: Fried food is bad for you. It adds empty calories to whatever you’re frying. Those extra calories come packed with trans fats. And multiple studies have shown that diets high in fried foods increase the risk of chronic disease. Now, as if that wasn’t enough, new research shows that foods fried in reused oils present the threat of neurodegeneration.

The results, which researchers presented at Discover BMB 2024, the American Society for Biochemistry and Molecular Biology’s annual gathering, also appeared in a supplement to the March issue of The Journal of Biological Chemistry.

Taking a Second Look at a Common Practice

Home cooks and professional chefs alike have been reusing cooking oil for years. It saves money, cuts down on waste, and makes life easier for food trucks and street vendors.

Besides, we love our fried foods. One study, for example, revealed that anywhere between 25 percent and 36 percent of Americans consume some type of fried food every day.

But while scientists have long wondered about – and studied – fried foods, no one’s taken as close a look at the recycled oil used to fry those foods.

“Deep-frying at high temperatures has been linked with several metabolic disorders, but there have been no long-term investigations on the influence of deep-fried oil consumption and its detrimental effects on health,” Kathiresan Shanmugam, associate professor at Central University of Tamil Nadu in Thiruvarur, India, and research team lead, said. “To our knowledge, we are first to report long-term deep-fried oil supplementation increases neurodegeneration in the first-generation offspring.”

Methodology

To better understand the long-term consequences of reused deep-fried frying oil, Shanmugam and his team, segregated a group of female rats into five groups. The scientists then fed each group something a little different for 30 days. Their diets included:

• Standard chow.
• Standard chow with 0.1 ml of unheated sesame oil daily.
• Standard chow with 0.1 ml of unheated sunflower oil daily.
• Standard chow with 0.1 ml of reheated sesame oil daily.
• Standard chow with 0.1 ml of reheated sunflower oil daily.

The group used the reheated oils to replicate reused frying oil.

The rats fed the reheated sesame or sunflower oil showed higher levels of oxidative stress and liver inflammation. These rats also showed notable colon damage that spawned changes in endotoxins and lipopolysaccharides.

“As a result, liver lipid metabolism was significantly altered, and the transport of the important brain omega-3 fatty acid DHA was decreased,” the researchers wrote. “This, in turn, resulted in neurodegeneration, which was seen in the brain histology of the rats consuming the reheated oil as well as their offspring.”

Following Up

The researchers added that they’re already planning more research. For starters, the team expressed their intent to examine the effects of deep-frying oil on specific neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. They also plan to explore its impact on anxiety, depression, and neuroinflammation.

They also shared plans to investigate the link between gut microbiota and the brain to “identify potential new ways to prevent or treat neurodegeneration and neuroinflammation.”

In the meantime, the study’s authors advise that omega-3 fatty acid supplements and nutraceuticals – such as curcumin and oryzanol – might prove beneficial in mitigating liver inflammation and neurodegeneration.

Finally, they added that someone should promote a study like this one to include humans. It could offer clearer insight into how this study might translate to humans. Especially those prepared with repeatedly reused oils.

Further Reading

The Diagnostic Challenge of Psychiatric Symptoms in Neurodegenerative Disease

Schizophrenia: A Neurodevelopmental or a Neurodegenerative Disorder

Multidisciplinary Approach to Dementia Unspecified