Re-used Cooking Oil May Trigger Breast Cancer Spread

Nutritionists have long discouraged the re-use of cooking oil including vegetable oil, soybean oil, and others, raising alert that such practice could be harmful to health. Now, a recent study in mice showed that reheated cooking oil might trigger cell changes that could promote late-stage breast cancer growth. These findings have been reported in the journal ‘Cancer Prevention Research’ to this end. The American Cancer Society (ACS) recommends that women at average risk for breast cancer should start having annual routine mammograms at the age of 45 years. Even if a person has no signs or symptoms, mammograms can help detect breast cancer at an early stage, which is when treatment is most likely to be successful.

According to the researchers from the University of Illinois at Urbana- Champaign, United States (US), who tested “thermally abused frying oil,” which is cooking oil that has undergone reheating to high temperatures multiple times, in laboratory mice, they found that it increased metastatic breast cancer growth. Metastatic breast cancer (also called stage IV) is breast cancer that has spread to another part of the body, most commonly the liver, brain, bones, or lungs. Breast cancer is a disease in which cells in the breast grow out of control.

There are different kinds of breast cancer. Most breast cancers begin in the ducts or lobules. Breast cancer can spread outside the breast through blood vessels and lymph vessels. Cancer cells can break away from the original tumour in the breast and travel to other parts of the body through the bloodstream or the lymphatic system, which is a large network of nodes and vessels that works to remove bacteria, viruses, and cellular waste products.

Breast cancer can come back in another part of the body months or years after the original diagnosis and treatment. Nearly 30 per cent of women diagnosed with early-stage breast cancer will develop metastatic disease. Some people have metastatic breast cancer when they are first diagnosed with breast cancer (called “de novo metastatic”). This means that the cancer in the breast wasn’t detected before it spread to another part of the body. In the current study, the scientists fed all of the lab mice a low-fat diet for a week. Then, they gave some of the mice unheated fresh soybean oil for 16 weeks while the rest ingested thermally abused oil instead.

They chose to use soybean oil because the restaurant industry commonly uses it for deep frying. To simulate breast cancer, they injected 4T1 breast cancer cells into a tibia of each mouse. These breast cancer cells were very aggressive and have a high rate of metastasis to multiple distant sites. As a result, they often appear in the lymph nodes, liver, and lungs.