Omega-3 and Omega-6 and Cancer

Tuesday, January 9, 2007 - 3:56pm

By Erin Dummert RD, CD

Recent studies suggest that the type of dietary fat impacts certain cancers more than the total amount of fat in the diet. In this article we will explore the role of omega-3 and omega-6 fats and their relationship to various cancers.

Omega-3 fats are important nutrients that are involved in many bodily processes. They are responsible for reducing blood clotting, swelling and inflammation. Omega-3 fats are essential, meaning the body cannot make them. They must be obtained from the diet.

Good sources of omega-3 fats are:

  • Fish (especially sardines, wild salmon, herring, mackerel, halibut, tuna and cod)
  • Flaxseed
  • Walnuts
  • Canola oil
  • Enriched eggs

Omega-6 fats are also essential in the diet and play an important role in many bodily processes. They are responsible for increasing blood clotting, swelling and inflammation. While these effects may sound negative, they are extremely important in the healing process. Imagine what would happen if you cut your hand and the blood didn’t clot – you would eventually bleed to death. Unlike omega-3s, omega-6s are quite plentiful in the typical American diet. Sources of omega-6 fats are:

  • Processed foods (especially crackers, cookies, chips and other convenience foods)
  • Hydrogenated or partially hydrogenated oils
  • Corn oil, Soybean oil
  • Margarine and other processed fats

In addition to the individual roles of omega-3 and omega-6 fats, researchers are focusing on how the ratio of these fats in the diet impacts health. Throughout history, people around the world ate a ratio of about 2-to-1 omega-6-to-omega-3 fats. This created a healthy balance of fats, which allowed the body to work efficiently. In the past 50 years, the American diet has shifted, and whole grains, beans, seeds, nuts and seafood have been replaced with highly processed foods. This shift has brought the typical American diet to a ratio of up to 20-to-1, meaning most Americans eat up to 20 times more omega-6 fats than omega-3. This imbalance is thought to contribute to a host of diseases including heart disease, arthritis and many types of cancer.

Link to cancer
Research has intensified in the area of omega-3 and various cancers. Although research is ongoing, some interesting correlations have been identified. Researchers have found that people eating more food sources of omega-3, such as fish, have a lower risk of breast cancer, prostate cancer, Non-Hodgkin’s lymphoma, multiple myeloma and leukemia. A reduction in recurrence of colon cancer has also been noted. In a number of these studies, the ratio between omega-6 to omega-3 has also been shown to be an important factor affecting cancer risk.

Since omega-3 is thought to play a role in cancer prevention, and making dietary changes takes work, why not opt for an omega-3 supplement, such as fish oil or flaxseed oil? While omega-3 supplementation may have its place in other areas, such as heart health, many studies have failed to show a benefit in cancer prevention. Therefore, changing your ratio of omega-6-to-omega-3 fats by eating more omega-3 fats and reducing omega-6 fats is the best way to reap the potential cancer prevention rewards.

Fish is one of the richest dietary sources of omega-3. However, some fish have become contaminated with mercury and other toxins, making frequent consumption dangerous for certain people. The benefits of eating fish are clear, however, to minimize exposure to toxins experts recommend that adults vary the type of fish eaten. Young children, and women who are pregnant, trying to get pregnant, or are nursing should not eat highly contaminated fish such as tuna steak, albacore tuna, orange roughy, shark, swordfish, Chilean seabass or fish from known contaminated waters. They should also limit their intake of the moderately contaminated fish such as farm raised salmon and canned chunk light tuna.

For middle-aged and older adults, including women after menopause, experts agree that the benefits of eating fish may outweigh the risks of mercury or other contaminants. Despite this, experts suggest limiting intake of the most-contaminated fish to one serving per week.

Tips for increasing Omega-3 and decreasing Omega-6 fats in your diet

  • Add walnuts to salads, muffins and cereal.
  • Eat 1-3 tablespoons of ground flaxseed daily.
  • Cook with canola, olive, peanut or walnut oil instead of vegetable, corn or soybean oil.
  • Replace store-bought salad dressings, which are usually made with soybean oil, with your own blend of olive oil and flavored vinegar.
  • Snack on nuts and dried fruit instead of crackers or processed foods.
  • Eat fish at least once weekly, with an emphasis on wild salmon or other rich sources of omega-3. (Most studies showed the most benefit when people ate fish 2 – 4 times per week.)
  • Choose eggs that say “high in omega-3”. These eggs come from chickens that eat flaxseed. More omega-3 is deposited in the egg yolk, making them a rich source of this beneficial fat.
  • Avoid all foods with hydrogenated or partially hydrogenated oils in the ingredient list.