Study links dietary fat ratios to slower prostate cancer growth

A hundred men with early prostate cancer sat in a peculiar kind of limbo. Their tumors grew so slowly that surgery or radiation would cause more damage than benefit. So they waited, undergoing regular tests, living with the knowledge that cancer was inside them but doing nothing about it. This state of watchful waiting—called active surveillance—makes medical sense but weighs heavily on patients. The question that haunts them is always the same: Is there anything I can do?

A team at UCLA's David Geffen School of Medicine decided to test whether the answer might lie in something as ordinary as cooking oil. The hypothesis was straightforward: the fats we consume influence how quickly cancer cells divide. Most Americans eat a diet wildly skewed toward omega-6 fats, found in vegetable oils and fried foods, while consuming far too little omega-3, abundant in fish like salmon and sardines. The typical ratio is roughly 15 to 20 parts omega-6 for every part omega-3. Scientists believe a healthier balance would be closer to 4 to 1. This imbalance may trigger inflammation that creates conditions favorable for cancer cell growth.

Dr. William Aronson and his team recruited 100 men already on active surveillance and split them into two groups. One half continued eating as they normally did. The other half worked with a dietitian to reduce omega-6 intake and increase omega-3, adding daily fish oil supplements. No one was asked to count calories or lose weight. The intervention was deliberately modest—a shift in the types of fat consumed, nothing more.

To measure whether this dietary change actually affected cancer growth, the researchers needed a precise biological marker. They chose Ki-67, a measure of how rapidly cells are dividing. High Ki-67 means cancer cells are multiplying quickly; low Ki-67 indicates slower division. Each man received a biopsy at the start of the study and again one year later. Crucially, the researchers used MRI guidance to sample the exact same spot in the tumor both times, a methodological refinement that earlier studies had often overlooked.

After twelve months, the results diverged sharply. In the group that modified their diet, Ki-67 levels dropped—cancer cells were dividing more slowly. In the group eating their regular diet, Ki-67 levels rose. The cancer cells were multiplying faster. Other measures, like PSA levels and tumor grades, remained largely unchanged in both groups, which was not surprising; these markers rarely shift over a single year.

The findings carry important caveats. Some participants dropped out due to gastrointestinal side effects from fish oil supplements. Fish oil can interact with blood thinners and other medications, making medical supervision essential. More fundamentally, this study does not prove that dietary changes will keep someone out of the operating room. It shows an association between adjusted fat intake and slower cell division in tumor tissue—a meaningful first step, but not clinical proof. The research was small, conducted at one institution, and lasted only a year. Larger, longer studies are needed before medical guidelines change.

Yet for men living under the stress of active surveillance, the practical takeaway is clear enough. Cut back on fried foods and ultra-processed snacks. Eat salmon or sardines twice a week. Consider eggs from hens fed flaxseed. Sprinkle chia seeds on breakfast. These are small adjustments, but they accumulate. Before starting fish oil supplements, talk to your doctor. Product quality varies; choose brands that have been third-party tested to minimize contamination with heavy metals.

Science advances in stages. First, researchers show how something works. Then clinical trials determine whether it actually helps patients. This study addressed the first stage—demonstrating that adjusting dietary fat intake was associated with slower cancer cell proliferation in actual tumor tissue. The next stage, proving that it prevents cancer spread or delays the need for aggressive treatment, remains ahead. In the meantime, improving diet is unlikely to cause harm. Unlike radiation or surgery, changing what you eat carries minimal side effects. Even if the cancer benefit proves modest, cardiovascular and cognitive health may improve as well. For men on active surveillance, taking constructive action—any action—can ease the psychological burden of waiting. The sense of control itself may matter as much as the biology.