Fish Oil Lowers Risk of Breast Cancer By 32 Percent

"This study is one of the largest studies that have come out showing that there may be a role for fish oil in the prevention of cancer, specifically breast cancer," said Lorenzo Cohen, of the M.D. Anderson Cancer Center at the University of Texas-Houston.

The researchers followed 35,016 post-menopausal women between the ages of 50 and 76 who were taking part in the 10-year Vitamins and Lifestyle (VITAL) study, an investigation into the effects of non-vitamin supplements on male and female cancer risk. All participants were residents of Washington state and had no history of breast cancer.

After an average of six years, the researchers found that women who regularly took a fish oil supplement were 32 percent less likely to develop invasive ductal breast cancer than women who did not take the supplements. No information was available on what doses of fish oil the study participants were taking.

Invasive ductal breast cancer, in which tumors form in the breast's milk ducts, is the most common form of the disease. In contrast, lobular breast tumors form in the organ's milk glands.

The researchers also looked for a breast cancer-preventive effect of the menopause-relieving supplements black cohosh, dong quai, soy, and St. John's wort, but found none.

Scientists remain unsure what role fish oil might play in reducing cancer risk. Since some research has implicated inflammation in cancer risk, the anti-inflammatory properties of fish oil may explain part of the effect.

"Fish oil, in general, is a very good anti-inflammatory agent, and inflammation plays a role in cancer development," fish oil researcher Peiying Yang of M.D. Anderson said.

Fish oil's high content of omega-3 fatty acids may also play a role. Although previous studies have found no connection between consumption of fatty fish and lowered cancer risk, fish oil supplements typically contain a higher omega-3 concentration than fish itself.

Omega-3s are known to play an essential role in inter-cell communication, inflammation control, and the formation of cell membranes. They have also been linked to lower trigylceride levels, higher HDL ("good") cholesterol levels, and a lower risk of heart attack and death in people who suffer from heart disease. They may also decrease the risk of dangerously abnormal heartbeat.

Additional research is underway to determine whether omega-3s and fish oil can help prevent or treat cancer, dementia, and other mental health conditions.

A growing body of research suggests that the typical Western diet is far too low in these essential oils, which can be found in fatty fish (such as salmon and sardines), canola oil, soybeans and flaxseeds. However, because the oils may cause an increased risk of bleeding if combined with certain medications including over-the-counter NSAIDs, they should be used only in consultation with a health professional.

For those wishing to take fish oil supplements, the wide variety of options can be overwhelming. In addition, these products are not regulated by the FDA.

"Some products may be contaminated with heavy metals," Cohen said. "If you are not going to get fish oil from the fish itself, do appropriate homework to make sure you choose a reputable product."

Good Morning America recommends that consumers look for oils that are of high purity and are certified by U.S. Pharmacopeia, the official NGO that sets standards for healthcare products sold in the United States. Many over-the-counter brands meet these standards just as well as name brands, at a significantly lower price.

A physician or other health practitioner may also be able to help consumers select a reputable product.