Fish oil linked to increased risk of colon cancer in mice

October 5, 2010, Michigan State University

Fish oil – long encouraged by doctors as a supplement to support heart and joint health, among other benefits – induced severe colitis and colon cancer in mice in research led by Michigan State University and published this month in the journal Cancer Research.

Jenifer Fenton, a food science and human nutrition researcher at MSU, led the research that supports establishing a dose limit for (DHA), one of the omega-3 fatty acids present in fish oil, particularly in people suffering from chronic conditions such as inflammatory bowel diseases.

"We found that mice developed deadly, late-stage when given high doses of fish oil," she said. "More importantly, with the increased inflammation, it only took four weeks for the tumors to develop."

Specifically, the research team found an increase in the severity of the cancer and an aggressive progression of the cancer in not only the mice receiving the highest doses of DHA but those receiving lower doses as well. The mice used in the study were prone to inflammatory-like bowel disease; inflammation is an important risk factor for many types of cancers, including colon cancer.

"Our findings support a growing body of literature implicating harmful effects of high doses of fish oil consumption in relation to certain diseases," Fenton said. "Currently, there is a call by academics and the food industry to establish dietary guidelines for omega-3 consumption. This is primarily motivated by the fact that most Americans are deficient in omega-3 fatty acids, and there is substantial evidence supporting the beneficial effects of the consumption."

The findings were surprising, specifically because DHA has been shown to have some anti-inflammatory properties, according to Fenton: "We hypothesized that feeding fish oil enriched with DHA to mice would decrease the cancer risk; we actually found the opposite. These mice were less equipped to mount a successful immune response to bacteria that increased colon tumors."

Fenton cautions people may not need to avoid fish oil; what the research shows is needed are guidelines on dosing. With any nutrient, there is a "bell curve" effect. On the left of the curve are those deficient in a nutrient; on the right are those in excess.

She said people already receiving enough omega-3 fatty acids through their normal diet and foods have no need for added supplementation.

"With , we don't yet know how much is appropriate," said Fenton, also a researcher with the Michigan Agricultural Experiment Station. "There are many examples of taking supplements, nutrients or chemicals in excess that can promote cancer (for example, beta-carotene supplementation in smokers). Supplementation is most useful when the person taking them is deficient in that specific nutrient."

The research team's findings could have an important preventive health impact, specifically in light of the high rates of colon cancer in the United States. Individuals with inflammatory bowel disease have an increased risk of developing colon cancer, and when the cancer metastasizes it can be fatal.

The next step, Fenton said, is to test omega-3 fatty acid levels in people with inflammatory bowel disease. To that end, she is continuing to build relationships – via MSU's College of Osteopathic Medicine campus in Macomb County – with gastrointestinal specialists to develop a cohort of patients.

"To help develop guidelines, we need to see how these findings correlate to human populations," she said.

Related Stories

Recommended for you

Researchers create a drug to extend the lives of men with prostate cancer

March 16, 2018
Fifteen years ago, Michael Jung was already an eminent scientist when his wife asked him a question that would change his career, and extend the lives of many men with a particularly lethal form of prostate cancer.

Machine-learning algorithm used to identify specific types of brain tumors

March 15, 2018
An international team of researchers has used methylation fingerprinting data as input to a machine-learning algorithm to identify different types of brain tumors. In their paper published in the journal Nature, the team ...

Higher doses of radiation don't improve survival in prostate cancer

March 15, 2018
A new study shows that higher doses of radiation do not improve survival for many patients with prostate cancer, compared with the standard radiation treatment. The analysis, which included 104 radiation therapy oncology ...

Joint supplement speeds melanoma cell growth

March 15, 2018
Chondroitin sulfate, a dietary supplement taken to strengthen joints, can speed the growth of a type of melanoma, according to experiments conducted in cell culture and mouse models.

Improved capture of cancer cells in blood could help track disease

March 15, 2018
Tumor cells circulating throughout the body in blood vessels have long been feared as harbingers of metastasizing cancer - even though most free-floating cancer cells will not go on to establish a new tumor.

Area surrounding a tumor impacts how breast cancer cells grow

March 14, 2018
Cancer is typically thought of as a tumor that needs to be removed or an area that needs to be treated with radiation or chemotherapy. As a physicist and cancer researcher, Joe Gray, Ph.D., thinks differently.


Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (1) Oct 05, 2010
"We found that mice developed deadly, late-stage colon cancer when given high doses of fish oil,"
What was the dose and how does that translate to human dosage? Just about anything can be shown to cause cancer in a high enough dose.
not rated yet Oct 05, 2010
wow it would be so much better if they gave us some numbers and data to work with. this is definitely something I will be following being that I know a lot of people that take this daily including my mother.
not rated yet Oct 06, 2010
Fish oil is known to be high in steroid "D" (vitamin D) which downregulates the VDR gene which controls the immune system, so no real news here.

"The findings were surprising, specifically because DHA has been shown to have some anti-inflammatory properties,"
Not really when you read it with this article -
not rated yet Oct 06, 2010
Why in the world isn't there a link to the original article? Or at least the abstract? Have I missed it?
not rated yet Oct 06, 2010
PS--the mouse immune system is pretty significantly different from the human immune system.
not rated yet Oct 06, 2010
So it is, and that's why most of the articles you read hereabouts come to nothing!
The sad part is that the researchers involved know this but still keep banging away on mice!
I guess it's just a job to most of them.
not rated yet Oct 07, 2010
Here is the link (but only the abstract is free):
not rated yet Oct 07, 2010
Here is the quote from the abstract, but not sure if it helps:
"Mice were fed isocaloric diets modified to include corn oil, safflower oil, or DFO (doses ranging from 0.75% to 6.00%) as the fatty acid source for 8 weeks."
not rated yet Oct 07, 2010
DFO means dietary fish oil
not rated yet Oct 10, 2010
doses ranging from 0.75% to 6.00%

If of diet, then the amounts were not absurdly high.
not rated yet Oct 12, 2010
Yeh...because mice evolved eating fish and everything...pointless, ultra specific nonsense. "Lemur shows unhealthy complications when given high doses of barracuda blood" must be bad

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.