Show 1420: The Cooking Oil Controversy Spotlights Cancer (Archive)

This week, we dig into the cooking oil controversy. For decades, we’ve heard that we should be using vegetable oils rather than butter, lard or other fats (possibly even olive oil). Oils from corn, soybeans, sunflower or safflower seeds are rich in polyunsaturated fatty acids. Consequently, people consuming them may have lower cholesterol levels than those primarily using saturated fats. But could there be a downside? We hear from scientists who have found these seed oils may be linked to certain cancers.

The Cooking Oil Controversy:

The more we learn about fats, the more it seems that focusing on just one aspect may be too simplistic. In the 1990s, health experts told Americans to avoid all fat. When it became clear that low-fat diets were not necessarily making everyone healthy, we got the message that we needed to stick with polyunsaturated fatty acids (PUFAs) like those in corn or canola oil. There are, however, different types of PUFA. Chemists classify them as omega-3, omega-6 and omega-9 fatty acids. Only omega-3 and omega-6 are considered essential fatty acids.

Current cooking oils have a preponderance of omega-6 fatty acids. As a result, the ratio of omega-6 to omega-3 in our blood has risen from a pre-industrial average of an estimated 4:1 to our current ratios of 20:1 (Missouri Medicine, Sep-Oct. 2021).  This could have biological consequences.

Dietary Fat and Cancer:

Dr. William Aronson has asked how different types of dietary fat affect the progression of prostate cancer. Laboratory studies show that a diet high in corn oil accelerates the growth of human prostate cancer tumors implanted under the skin of mice. That inspired him and his colleagues to conduct a randomized controlled trial (Journal of Clinical Oncology, Dec. 13, 2024).

Fish Oil vs. Prostate Cancer:

For their trial, they recruited 100 men diagnosed with prostate cancer who opted for active surveillance rather than immediate surgery or radiation. They assigned these volunteers to different diets for one year. One group followed their usual diet and did not take fish oil. The researchers instructed the other group in avoiding omega-6 fats in their diet, increasing the amount of omega-3 rich fish and taking fish oil supplements. Minimizing omega-6 fats meant staying away from fried foods, cooking oils, bottled salad dressing and mayonnaise. At the end of the year, there was a significant difference in an important prostate cancer biomarker called Ki-67.

Does the Cooking Oil Controversy Extend to Other Cancers?

We spoke with Dr. Timothy Yeatman about his research on colorectal tumors. His research was published in Gut, a leading journal for gastroenterologists (Dec. 20, 2024). He and his colleagues used a technique called lipidomics for their analysis. They found that the lipid profile of the tumors and their micro-environments is pro-inflammatory. They seem to lack the resolving mediators (“resolvins”) that should normally accompany healing. The balance has been disrupted.

Dr. Yeatman suspects that some of this disruption may be due to changes in the microbiome that constitutes a lot of the immediate environment for colorectal tumors. He suggests that extensive use of seed oils high in pro-inflammatory omega-6 fatty acids may contribute to the imbalance. You can find soybean oil, for example, in many foods where you might not expect it, such as breads, cakes, cookies, crackers, chips and even hummus. Cooking at home allows people to avoid seed oils, but it takes time, skills and resources that are not available to everyone.

Can We Resolve the Cooking Oil Controversy?

Neither of the studies we discuss during this episode is definitive. Scientists need more research to be able to make solidly evidence-based recommendations. However, both our guests would suggest we need not wait for the final word to reduce the inflammatory potential of our diets. Reading labels carefully is a good first step to avoiding some of the seed oils that provide excess omega-6 fats and gravitate more toward omega-3 fats.

This Week’s Guests:

William Aronson, MD, is Professor in the Department of Urology of the David Geffen School of Medicine at the University of California, Los Angeles. He is also Chief of Urologic Oncology at the West Los Angeles Veterans Affairs Medical Center and Chief of Urology at the Olive View-UCLA Medical Center.

Dr. William Aronson, UCLA

Timothy Yeatman, MD, FACS, is Professor in the Dept of Surgery at the University of South Florida. He is also Associate Center Director for Translational Science and Innovation Tampa General Hospital Cancer Institute. His website is https://phenomehealth.org/c-suite/tim-yeatman-md-facs

Timothy Yeatman, MD, University of South Florida

Debora Melo vanLent, PhD, is Assistant Professor at the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health in San Antonio, TX. Her interview is part of the podcast.

Listen to the Podcast:

The podcast of this program will be available Monday, March 3, 2025, after broadcast on March 1. You can stream the show from this site and download the podcast for free. In addition to what you heard in the broadcast, the podcast also includes our discussion with Dr. Melo vanLent on her research into the link between dietary inflammation and dementia.

Download the mp3, or listen to the podcast on Apple Podcasts or Spotify.

Citations

• DiNicolantonio JJ & O'Keefe J, "The importance of maintaining a low omega-6/omega-3 ratio for reducing the risk of autoimmune diseases, asthma, and allergies." Missouri Medicine, Sep-Oct. 2021.
• Aronson WJ et al, "High omega-3, low omega-6 diet with fish oil for men with prostate cancer on active surveillance: The CAPFISH-3 randomized clinical trial." Journal of Clinical Oncology, Dec. 13, 2024. DOI: 10.1200/JCO.24.00608
• Soundararjan R et al, "Integration of lipidomics with targeted, single cell, and spatial transcriptomics defines an unresolved pro-inflammatory state in colon cancer." Gut, Dec. 20, 2024. DOI: 10.1136/gutjnl-2024-332535