Baked Fish May Lower Colon Cancer Risk by 26%

According to the Centers for Disease Control and Prevention, there were nearly 148,000 new cases of colorectal cancers reported in the U.S. in 2022. More than 50,000 people in the U.S. died from colorectal cancer in 2023. Black Americans have the highest rates of colorectal cancer in the U.S., and they are more likely to die from it than other ethnicities and racial groups in America.

We know that diet plays a role in cancer risk. For example, there is evidence that people who follow plant-based diets have lower cancer risk than those who eat meat. Eating certain foods, such as broccoli, walnuts, and legumes, has been linked to a lower risk of colorectal cancer. And we know that eating more fiber can also help lower your risk of colorectal cancer.

Researchers from Boston University were curious about fish, polyunsaturated fatty acids (PUFAs) and CRC. Could eating more fish and PUFA-rich foods lower your risk? They published their findings in The Journal of Nutrition. Let’s break down what they found.

How Was This Study Conducted?

For this study, researchers were especially interested in Black American women and their risk of colorectal cancer, since Black Americans have the highest rate of colorectal cancer in the U.S. They drew their data from the Black Women’s Health Study (BWHS), a long-term study that ran from 1995 to 2021. From the BWHS, 52,690 women, ages 21 to 69, met the criteria researchers were looking for. Out of this population, 687 women developed colorectal cancer over the average follow-up time of 24 years. 

Researchers also had typical demographics that would be adjusted for during the statistical analyses. These included age, total energy intake (kcal/day), type 2 diabetes, BMI, smoking status, alcohol intake, red and processed meats (servings/day), fruits and vegetables (servings/day), education level, family history of colorectal cancer, aspirin and non-steroidal anti-inflammatory (NSAID) use, walking as exercise, vigorous physical activity, menopausal status and menopausal hormone use.

In addition, participants had completed two food frequency questionnaires: one in 1995, which included 68 food items, and a second one in 2001 that included 85 food items. From these questionnaires, researchers compiled information about participants’ intake of foods suspected to reduce colorectal cancer risk, and those believed to increase it, like processed meats. 

Based on participants’ responses, researchers divided them into four quartiles based on grams of fish eaten per 1,000 calories, with quartile one being the lowest intake of fish and quartile four the highest. And because colorectal cancer can be located in different parts of the colon and rectum, researchers also considered the type of colorectal cancer and its location in the gut. 

What Did This Study Find?

After running several statistical analyses, including adjusting for demographics and health and family history, researchers found that a high intake of baked fish—those who fell into quartile 4—was associated with a 26% decrease in colorectal cancer risk. The key here is that the fish was baked; interestingly, they did not find an association with total fish intake and a reduced colorectal cancer risk, probably because total fish intake includes all types of fish, including those low in PUFAs, and all types of cooking methods, including frying.

When looking at site-specific colorectal cancer, high baked fish intake was associated with a 44% decrease in proximal colon cancer. The proximal colon is the first part of the large intestine. It sits in the right upper abdomen. 

Researchers also found that higher intake of omega-3s in general, and having a healthy omega-3-to-omega-6 ratio, were associated with a 39% to 53% lower proximal colon cancer risk. 

There are several limitations to this study. First, anytime food frequency questionnaires are used, there is always a chance of recall bias; in other words, participants are essentially estimating how much of each food they eat and how often. Also, while researchers feel these results are generalizable to most Black American women, they can’t say if they apply to other populations. Lastly, there’s always a chance of error in statistical analysis and factors not taken into consideration skewing the results.

How Does This Apply to Real Life?

The American Institute for Cancer Research provides several diet-related recommendations for preventing cancer in general. They include:

• Eating a diet rich in whole grains, vegetables, fruits and legumes
• Limiting consumption of “fast foods” and other processed foods that are high in fat, starches or sugars
• Limiting consumption of red and processed meats
• Limiting consumption of sugar-sweetened drinks
• Limiting or avoiding alcohol

The AICR also recommends being physically active and trying to maintain a healthy weight. 

Omega-3s are a type of PUFA that most of us don’t get enough of. Including fish and seafood a couple of times a week is a good way to get this essential fatty acid. And it doesn’t have to be difficult or fussy. Crack open a can of tuna or salmon and toss it onto your salad, or make a tuna salad sandwich with it. We’ve even got a recipe for the best tuna salad if you’ve grown tired of your version. And if you’re looking to switch your tuna salad sandwich to salmon, we’ve got a recipe for that, too.

One thing we know about cancer and other diseases is that there is a connection to chronic inflammation. So eating more foods believed to be anti-inflammatory—like plants and baked fish—and avoiding or limiting those that are known to increase inflammation—like sugar, processed meats and alcohol—may help. If you’re ready to dive in, try our 30-Day No-Sugar Anti-Inflammatory Meal Plan. 

It’s also important to pay attention to which cooking method is most frequently used with your seafood. While having it fried now and then is fine, eating it baked or broiled appears to have more health benefits. According to these study authors, this is partly due to how baking better retains seafood’s omega-3s compared to frying or grilling. Researchers also note that frying fish in cooking oil can oxidize or degrade omega-3s in the seafood, and it can even add high amounts of fat and omega-6s, which most of us already get enough of. 

Our Expert Take

Colorectal cancer rates are highest among Black Americans. This study suggests that Black American women with the highest intake of baked fish may have the lower rates of colon cancer. It’s important to know the symptoms of colon cancer, including abdominal pain, fatigue and bloody stool, and get the recommended screenings for colorectal cancer. The current recommendation is that anyone with an average risk for colorectal cancer and no symptoms get a baseline screening at age 45. This may include an at-home test that involves sending in a stool sample for examination or a colonoscopy. 

Preventing cancer includes eating a diet high in fruits, vegetables, nuts, seeds, legumes, lean proteins, fish and seafood, and limiting or avoiding sugar, processed meats, highly processed foods and alcohol. Move your body more often and try to get to and maintain a healthy weight. Managing your stressors, getting plenty of quality sleep and spending time with loved ones round out a whole-health approach to disease prevention and quality of life.