The study abstract was presented at Discover BMB 2024, the American Society for Biochemistry and Molecular Biology’s annual meeting, and will be published in a virtual supplement to the Journal of Biological Chemistry.

The new study found that rats fed diets with reheated cooking oils exhibited significantly higher levels of neurodegeneration compared to rats consuming a standard diet.

The research suggests that reheated oil may increase neurodegeneration by disrupting the liver-gut-brain axis, which is crucial for maintaining physiological balance and has been linked to neurological disorders.

Heated vs unheated cooking oils

Deep frying is a prevalent cooking method globally, often used in fast-food restaurants, street vendors, and home cooking.

Studies have associated deep-fried food consumption with cardiometabolic conditions and certain cancers. However, few have examined the long-term effects of consuming reheated cooking oils on polyunsaturated fatty acids (PUFAs) metabolism and disease development.

Dr. Kathiresan Shanmugam, PhD, an associate professor at the Central University of Tamil Nadu in Thiruvarur, India, led the research team to explore this issue.

The study team organized female rats into five groups, fed a normal diet (control group) or a normal diet supplemented with unheated sesame oil, unheated sunflower oil, reheated sesame oil, or reheated sunflower oil daily for a period of 30 days.

This approach was designed to mimic the conditions of consuming reused deep frying oil.

Compared with their counterparts on different diet regimens, rats fed diets with reheated oils exhibited heightened oxidative stress and inflammation in liver tissues.

Additionally, significant colonic damage was observed in these rats, which led to altered levels of endotoxins and lipopolysaccharides, indicating the presence of toxins produced by specific bacterial strains.

In secondary experiments, monosodium glutamate (MSG) was used to promote neurotoxicity in offspring. The offspring fed diets including reheated oils showed greater susceptibility to neuronal damage than the control group fed no oils or diets with unheated oils.

In a press release, Shanmugam explained:

“As a result, liver lipid metabolism was significantly altered, and the transport of the important brain omega-3 fatty acid DHA was decreased. 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.”

The study revealed that diets inclusive of reheated oils led to escalated levels of cholesterol, LDL cholesterol, triglycerides, AST and ALT, and inflammatory markers, alongside considerable damage to liver and colon structures, pointing to potential cardiometabolic and organ harm.

Consumption of reheated oils also resulted in specific brain damage, especially in areas crucial for regeneration, highlighting the neurological risk of reheated oil consumption.

In contrast, rats fed unheated oils showed better markers for brain health compared to rats in reheated oil groups.