Many common cooking oils are now being linked to certain types of cancer

If you’ve ever wondered whether changing your cooking oil could affect cancer growth, you’re not alone. New research shows that the types of fats we eat might influence the rate at which cancer cells multiply. However, it is not as simple as avoiding certain foods.

Picture this: you have cancer, and your doctor advises doing nothing for now. Not yet. That may sound counterintuitive. But that’s exactly what happens to thousands of men with prostate cancer every year.

Their tumors grow so slowly that surgery or radiation would hurt more than help. So they wait and undergo regular tests to monitor for changes.

This approach, known as “active surveillance,” makes medical sense but can be stressful for patients. Men in this situation often ask the same question: Can I do anything to help myself?

A recent study reports part of an answer, and it involves dietary fats found in common cooking oils.

Fats, cooking oils, and cancer cells

In the typical American diet, we consume too much of one type of fat and not enough of another.

Omega-6 fats are common in vegetable oils, fried foods, and many packaged products. Omega-3 fats are abundant in salmon and sardines.

Most Americans eat 15 to 20 times more omega-6 than omega-3. Scientists think a ratio closer to 4:1 would be healthier. This imbalance may increase inflammation, creating conditions that allow cancer cells to grow.

How the study was done

Dr. William Aronson, a urology professor at UCLA’s David Geffen School of Medicine, tested whether modifying dietary fat intake could slow cancer growth.

“This is an important step toward understanding how diet can potentially influence prostate cancer outcomes,” said Aronson.

His team enrolled 100 men with early prostate cancer who were already on active surveillance, then they assigned the men to two groups.

Half ate their regular diet. The other half worked with a dietitian to eat less omega-6 and more omega-3, and to take fish oil supplements daily. No calorie counting or weight loss was required.

“Many men are interested in lifestyle changes, including diet, to help manage their cancer and prevent the progression of their disease,” Aronson explained.

“Our findings suggest that something as simple as adjusting your diet could potentially slow cancer growth and extend the time before more aggressive interventions are needed.”

Tracking tumor growth

The researchers needed a way to measure whether cancer cell growth was slowing. They used a marker called Ki-67, which indicates how quickly cells are dividing. High Ki-67 means cells are multiplying rapidly. Low Ki-67 indicates slower cell division.

Each participant received a biopsy at the start and another one year later. Notably, they used MRI guidance to sample the same spot in the tumor both times. Earlier studies often sampled non-targeted areas, making comparisons less precise.

After one year, the results diverged. Ki-67 levels dropped in the diet change group but rose in the regular diet group.

In other words, cancer cells in the diet change group were dividing more slowly, while cells in the regular diet group were dividing faster.

However, some measures did not change: PSA levels and tumor grades remained similar in both groups. That is not unexpected; these measures rarely change over one year.

Fish oil and cancer cells

Some participants left the study due to gastrointestinal side effects from fish oil. Fish oil can interact with blood thinners and other medications. Use fish oil only under medical guidance.

More importantly, this study does not prove that eating fish will keep you out of the operating room.

“This significant difference suggests that the dietary changes may help slow cancer growth, potentially delaying or even preventing the need for more aggressive treatments,” Aronson continued.

This is a suggestion, not proof; larger, longer studies are needed.

The study was small and conducted at one hospital. That is enough to prompt interest but not to change clinical guidelines. Still, the researchers examined tumor tissue rather than relying solely on blood tests.

For those on active surveillance, the practical advice is straightforward. Cut back on fried foods and ultra-processed snacks. Eat salmon or sardines twice a week. Consider eggs from hens fed flaxseed. Add chia seeds to breakfast. Small changes can add up.

Talk to your doctor before starting fish oil supplements. Product quality varies by brand; choose third-party tested products to minimize contaminants such as heavy metals.

First step of many to come

Scientific progress is gradual. First, research shows how something works; then clinical studies determine whether it helps patients.

This study addressed the first step – showing that adjusting fat intake by changing oils in your diet was associated with slower cancer cell proliferation in tumor tissue.

The next step – demonstrating that it prevents cancer spread or delays treatment – remains to be shown.

In the meantime, improving diet is unlikely to cause harm. Unlike radiation or surgery, adjusting fat intake generally carries fewer side effects. Even if cancer benefits are modest, cardiovascular and cognitive health may also improve.

For men on active surveillance, taking constructive steps can feel better than inaction. The psychological boost of taking control might be just as valuable as any biological benefit.

Diet isn’t magic, and it won’t replace your regular cancer monitoring. According to this research, what you put on your plate may matter more than previously assumed.

The full study was published in the Journal of Clinical Oncology.

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