A new study is creating fresh excitement about the abundant health benefits of eating fish such as salmon. According to recently published research, an omega-3 fatty acid that’s abundant in seafood uses complex chemistry to essentially poison tumor cells and slow their growth (Dierge et al., 2021).

Seafood fans have long appreciated the health benefits of wild-caught salmon and other fish. From antioxidants to minerals and healthy fats, seafood is a bountiful source of many vital nutrients our bodies need. Among the most valued are omega-3 fatty acids, which are so-called “essential fats.”

Healthy fats may sound like an oxymoron, but omega-3s aren’t just good for you, they’re critical to many of your body’s functions. Our brains use omega-3s as a fundamental building block (Horrocks and Yeo, 1999). Our eyes use them to protect vision (Dornstauder et al., 2012). And our immune system depends on them.

docosahexaenoic acid DHA molecular structure
The unique chemical structure of DHA appears to have a unique effect on tumorous cells – in at least some contexts, it can destroy them from the inside.

But omega-3 fatty acids have to be consumed; our bodies can’t make enough on their own. That’s where seafood comes in. Two of the most important omega-3 fatty acids are DHA, or docosahexaenoic acid, and EPA, or eicosapentaenoic acid (Swanson et al., 2012). Both come primarily from eating marine life, especially fish like salmon. (Read more: DHA is More Important Than DNA)

Now a new study shows that in addition to its other superpowers, DHA appears to actually kill tumor cells. Scientists had long known that DHA had cancer-fighting abilities, but this latest research is the first to show just how it works. These fresh insights may prove to be pivotal in unlocking omega-3 fatty acids for use in cancer treatment.

The results were published in the journal Cell Metabolism on June 11.

DHA and Cancer

For several decades, researchers have examined how a wide range of species suffering from all manner of cancers responds when treatments include fatty acids (Appel et al., 1994) (Bai et al., 2019). Those studies have generally shown positive results when those treatments include fatty fish and fish oil.

For example, back in 2000, researchers gave DHA to dogs with lymphoma that were undergoing chemotherapy (Ogilvie et al., 2000). They found a direct correlation between how much DHA was in a dog’s blood and the number of disease-free intervals the animal experienced.

In 2009, an experiment in rats found that tumors shrank faster in animals given DHA alongside chemo drugs (Elmesery et al., 2009). Similar work in mice showed that giving DHA to rodents with colon cancer resulted in a 93 percent inhibition in the growth of their tumors (Kato et al., 2007). Research in humans has proven promising as well, and an ongoing clinical trial is giving omega-3 supplements to women with breast cancer for several months during chemo treatments to monitor their response ahead of surgery (Newell et al., 2019).

All this work has increased scientists’ confidence that DHA can make cancer cells more sensitive to chemo treatments, while also slowing the growth of tumors.

But a couple of mysteries have persisted. It remains unclear whether people who eat lots of fish don’t get cancer as often. There does appear to be some evidence that omega-3 intakes reduce risk of breast and colorectal cancers, but more investigation is needed (U.S. Dept. of Health and Human Services, 2021).

And while scientists generally accept that omega-3 fatty acids are actually helping stop the growth of cancer, they’ve had an exceptionally hard time proving exactly how that happens.

Omega-3 Poisons Tumors

This latest research explores and explains the biochemistry at work when omega-3s meet tumor cells, and it’s being hailed as a major advance in the field. Most tumors have a compartment full of acid that scientists call the acidic tumor microenvironment. This compartment is generally considered to be a pivotal engine driving tumor progression (Feng et al., 2017).

salmon fish on white background
The fatty acid known as DHA is abundant in salmon, good for overall human health, and, research suggests, appears to offer anti-cancer effects.

Back in 2016, a team of cancer researchers at the Dutch university UCLouvain noticed that cells inside a tumor’s acidic compartment seem to multiply in an interesting way, using fatty acids for energy instead of sugar. Then, several years later, another team at the same school realized that these particular tumor cells were actually the most aggressive spreaders. So, the two research groups teamed up to study how tumors reacted when offered different fatty acids.

In just weeks, they started spotting surprising behavior. While some fatty acids would slow tumor growth, others could actually speed it up, stimulating the cells to spread. But when the tumors were exposed to DHA, it was as if the cells had been poisoned, the researchers said.

The researchers used special kind of tumor-cell culture system known as spheroids. In the presence of DHA, spheroids grew, but then imploded. To test the idea in a more complex living system, the team also fed a DHA-rich diet to mice that had tumors. They found the treated mice had significantly slower tumor development than did mice fed a conventional diet.

Ultimately, they found that DHA’s cancer cell-killing effect happens through a complex process called oxidation, where a compound loses electrons. Cells in a tumors’ acidic compartment typically store fatty acids in droplets, which protects them from oxidation. But DHA overwhelms that storage system, creating oxidation that can kill the cells.

Their hope is that having a better understanding of the complicated chemistry at play will ultimately lead to better treatment combinations. But in the meantime, the researchers also point out that regardless of whether or not we have cancer, most of us aren’t eating enough omega-3 fatty acids each day anyway. Experts recommend consuming some 250 mg of DHA each day, yet the average person gets just 50 to 100 mg (Papanikolaou et al., 2014) (Dierge et al., 2021).

Increasing your DHA intake isn’t hard. You can consider using omega-3 supplements, or you could also simply eat seafood like wild-caught salmon a few times a week (following the lead of famed pediatrician William Sears, M.D., who enjoys a total of 18 ounces of salmon weekly). It’s delicious as well as nutritious — and while the cancer-preventative power of DHA-rich foods is still under investigation, there’s no risk and much potential reward in putting salmon on the family dinner table.

 

Sources:

  • Emeline Dierge, Elena Debock, Céline Guilbaud, Cyril Corbet, Eric Mignolet, Louise Mignard, Estelle Bastien, Chantal Dessy, Yvan Larondelle, Olivier Feron. Peroxidation of n-3 and n-6 polyunsaturated fatty acids in the acidic tumor environment leads to ferroptosis-mediated anticancer effects. Cell Metabolism, 2021; DOI: 10.1016/j.cmet.2021.05.016
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