Eating onion rings and French fries could raise your risk of dementia, according to a new study highlighting the potential harms of deep-fat frying. For those who love deep-fried foods, (myself Included) making them at home might be a safer alternative.

Researchers investigated the effects of food cooked with large amounts of reused cooking oil, a common practice in many restaurants. They discovered that reused oil can contain brain-damaging impurities, which ultimately make their way into the food. Rats fed a diet high in reused oils showed more signs of bodily inflammation, known to damage blood vessels and accelerate cognitive decline. Additionally, these rats exhibited more signs of brain damage compared to a control group.

The scientists from the University of Chicago stated: “Deep-frying at high temperatures has been linked with several metabolic disorders. To our knowledge, we are the first to report that long-term deep-fried oil supplementation increases neurodegeneration.”

The findings were presented at the annual meeting of the American Society for Biochemistry and Molecular Biology in San Antonio, Texas.

Restaurants frequently reuse cooking oil in deep-fat fryers to prepare a variety of foods, including vegetable fritters, donuts, and shrimp tempuras. This practice can lead to the buildup of impurities such as peroxides, which can damage the brain, and acrylamide, a chemical compound produced in deep-fat fryers that has been linked to cancer.

In the experiment, scientists divided rats into five groups. One group, the control, ate only a standard chow diet for 30 days. The other four groups consumed a diet with oils mixed in for the same period. These groups received a standard chow diet with 0.1 ml of either unheated sesame oil, unheated sunflower oil, reheated sesame oil, or reheated sunflower oil.

Results showed that, compared to the other groups, rats consuming reheated sesame or sunflower oil had increased inflammation in the liver. They also showed significant damage in the colon and the proliferation of bacteria that release harmful toxins and damage cells. When examining the rats’ brains under a microscope, researchers found a pattern of damage indicative of dementia in those who consumed the reheated oils.

While these tests would need to be carried out in humans to confirm the findings, the results are concerning. Researchers are planning a follow-up study to investigate the effects of deep-frying oil on the risk of neurodegenerative diseases such as Alzheimer’s and Parkinson’s, as well as anxiety, depression, and neurodegeneration.

For those who enjoy deep-fried foods, making them at home can be a safer option. Home cooks can control the quality and freshness of the oil used, reducing the risk of harmful impurities. By using fresh oil and changing it regularly, you can enjoy your favorite deep-fried treats with less worry. Moderation is still key, as deep-fried foods should not be a frequent part of your diet, but mindful preparation can help balance enjoyment and health risks.