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Fish Oil May Be Dangerous for Some People

 
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Fish oil rich in omega-3 fatty acids have long been encouraged by doctors as supplements to support heart and joint health, among other benefits. But the supplements have a dark side. Michigan State University Researchers found it induced severe colitis and colon cancer in mice.

Jennifer Fenton, a food science and human nutrition researcher at MSU led the research that supported the need to establish a dose limit for docosahexaenoic acid (DHA), one of the omega-3 fatty acids present in fish oil, particularly for people suffering from chronic conditions such as inflammatory bowel disease (IBD).

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

The study findings, published in the October, 2010 issue of Cancer Research, support a growing body of literature implicating harmful effects of high doses of fish oil consumption in relation to certain diseases.

The MSU researchers found an increase in the severity and an aggressive progression of the cancer not only in the mice receiving the higher doses, but also in those receiving lower doses of DHA. The researchers observed the mice were prone to inflammatory-like bowel disease; inflammation is an important risk factor for many types of cancers, including colon cancer and prostate cancer.

The findings were surprising to the researchers who initially hypothesized DHA-enriched fish oil would decrease the cancer risk in the animal models. DHA has been shown in previous studies to have some anti-inflammatory properties.

“We actually found the opposite. These mice were less equipped to mount a successful immune response to bacteria that increased colon cancer tumors,” Fenton said.

Colon cancer rates in the United States are high compared to other nations. The National Cancer Institute estimates that one in 20 people of either sex will be diagnosed with colon cancer during their lifetime.

Individuals with IBD diseases, including ulcerative colitis and Crohn's disease, have an increased risk of developing cancer of the intestinal tract, and when the cancer metastasizes it can be fatal.

Fenton cautioned that people may not need to avoid fish oil entirely as it does have some known benefits. However, individuals already receiving enough omega-3 fatty acids through a well-balanced diet have no need for adding supplements which could increase their risk. But the research community also believe that a substantial number of people are dangerously omega-3 deficient.

The challenge is “with fish oil, we don’t know yet how much is appropriate,” she said.

As such, academics and the food industry have called for establishing dietary guidelines for omega-3 consumption. To accomplish this, Fenton and colleagues plan future tests of omega-3 fatty acids in people with IBD to determine how these findings correlate to human populations and what, if any, amount is safe.

Lynette Summerill is an award-winning writer who lives in Scottsdale, Arizona. In addition to writing about cancer-related issues for EmpowHER, she pens Nonsmoking Nation, a blog following global tobacco news and events.

Add a Comment13 Comments

EmpowHER Guest
Anonymous

There are a couple of factual issues in this article. First, the study did not find that omega-3s induced colitis, the mice were intentionally induced with colitis (a highly inflammatory bowel condition) and THEN given fish oils to see what the effect was in mice that already had the condition. If you have colitis, you are going to be under special care of a doctor and should not be taking high doses of anything the doctor doesn't ok. Auburn asked how much is a "high dose," which is another issue. These mice consumed the human equivalent of 10-30 capsules of fish oil per day...on top of having baseline omega-3 blood levels that were already three times higher than the Japanese (who eat more seafood than any other group).

The study is valuable for colitis patients and doctors treating them, but until more research is done the results should not be extrapolated to the general population.

Full Disclosure: I work for an association that tries to educate consumers and doctors about omega-3s.

January 21, 2011 - 10:11am
EmpowHER Guest
Anonymous (reply to Anonymous)

So I'm wondering what really is a safe dosage, you hear differently depending on who you ask & what you read.

April 8, 2011 - 8:23am

How much is a "high dose"?
What would a comparable dose be for a 160 male?
Were these mice genetically unique?
What happened to the mice given a "low dose"?

January 21, 2011 - 8:56am
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