Omega-3 fatty acids are important nutrients involved in many body activities, especially immune system responses. Your body doesn't produce omega-3 fatty acids and must get them from the food you eat. The highest concentrations of omega-3 fatty acids are found in coldwater fish, such as sardines, salmon, herring, tuna, cod, mackerel, halibut, and shark. These fatty acids are also found in lower concentrations in plant foods such as flaxseed, walnuts, Great Northern beans, kidney beans, navy beans, and soybeans.
A study suggests that omega-3 fatty acids may reduce the risk of breast cancer in obese postmenopausal women.
The research was published in the February 2016 issue of Cancer Prevention Research. Read the abstract of “Influence of obesity on breast density reduction by omega-3 fatty acids: Evidence from a randomized clinical trial.”
The researchers think the reduction in risk is caused by the omega-3 fatty acids’ anti-inflammatory properties.
Obese women have a higher risk of breast cancer than women who maintain a healthy weight, especially after menopause. Researchers think this is partially because being overweight can lead to chronic inflammation. In chronic inflammation, the immune system is working overtime and may not know when to stop. The overload of certain cells and proteins can damage cells and tissues and change the way they function. This includes changes that may cause normal cells to turn into cancer cells.
In this study, 266 postmenopausal women with dense breasts who had never been diagnosed with breast cancer were randomly assigned to one of five treatments:
- no treatment
- Evista (chemical name: raloxifene), 60 mg per day
- Evista, 30 mg per day
- Lovaza (chemical name: omega3-acid ethyl esters), 4 gm per day
- 4 gm of Lovaza plus 30 mg of Evista per day
Evista is a type of hormonal therapy medicine used to reduce the risk of breast cancer in high-risk postmenopausal women. Evista also is used to treat and prevent osteoporosis in postmenopausal women.
Lovaza is a prescription form of omega-3 fatty acids. It contains both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the omega-3 fatty acids found in cold water fish.
Dense breasts have less fatty tissue and more non-fatty tissue compared to breasts that aren't dense. Dense breasts have more gland tissue that makes and drains milk and supportive tissue (also called stroma) that surrounds the gland. Research has shown that dense breasts:
- can be twice as likely to develop cancer as nondense breasts
- can make it harder for mammograms to detect breast cancer; breast cancers (which look white like breast gland tissue) are easier to see on a mammogram when they're surrounded by fatty tissue (which looks dark)
Of the 266 women:
- 50% were at a healthy weight
- 30% were overweight
- 20% were obese
The researchers measured the women’s breast density at the beginning of the study and then again 2 years later, at the end of the study.
The results showed that as levels of omega-3 fatty acids in the blood went up, breast density went down, but only in women with a body mass index (BMI) higher than 29. The U.S. National Institutes of Health says a BMI of 25 to 29.9 is overweight and a BMI of 30 and higher is obese.
Although Lovaza contains both EPA and DHA, only DHA blood levels were linked to lower breast density.
“Omega-3 fatty acids have an anti-inflammatory effect, so that's one of the reasons why we suspected it may be particularly effective in obese women," said Dr. Andrea Manni, professor and division chief of endocrinology, diabetes, and metabolism at the Penn State College of Medicine. Dr. Manni was the lead author of the study.
Some earlier research supports the idea that omega-3 fatty acids protect against breast cancer, but the results have been mixed. Dr. Manni theorized that results from normal-weight women were clouding the results.
The researchers plan to test the effect of just DHA in obese women, possibly in combination with a weight loss program, in a future study.
"The finding supports the idea that omega-3s, and specifically DHA, are preferentially protective in obese postmenopausal women," Dr. Manni said. "This represents an example of a personalized approach to breast cancer prevention."
If you’ve gained quite a bit of weight after menopause and have dense breasts, you may want to talk to doctors about this study and whether an omega-3 fatty acid supplement may be right for your unique situation. You also may want to talk to your doctor about developing a safe and sensible plan to lose weight.
Losing weight can be harder as you get older, but it can be done with careful changes to your diet and regular exercise. The first thing to do is to talk to your doctor about a healthy weight for you based on your age, height, body type, and activity level. Next, talk to your doctor about a safe and sensible plan to lose weight designed specifically for you and your needs.
Once you have the OK from your doctor and a weight goal, you can create a healthy eating plan that meets your nutritional needs. You may want to talk to a registered dietitian about how to create a healthy eating plan that's tailored to your specific needs and likes.
If you're unable to work directly with a registered dietitian, you have some other options. Computer programs and online tools can help you further analyze what you eat. They go beyond whether or not you're getting enough of a specific nutrient. Some of them might even make recommendations about how much of specific foods you should eat per day and track your eating and nutrient patterns over time.
Exercise is such an important part of daily life that the United States Department of Agriculture said that all people should meet the Physical Activity Guidelines for Americans in the Appendix of the 2015-20 Dietary Guidelines for Americans. Regular exercise helps reduce breast cancer risk.
There's no magic bullet or single food that will make you lose weight quickly. In fact, the safest way to lose weight is to do it slowly -- about a pound a week.
The United States Department of Agriculture 2015-20 Dietary Guidelines for Americans recommend:
- getting less than 10% of calories per day from added sugars
- getting less than 10% of calories per day from saturated fats
- eating less than 2,300 mg per day of salt
The guidelines also recommend eating a variety of nutrient-dense foods across all food groups, including:
- a variety of vegetables from all of the subgroups: dark green, red and orange, beans and peas, starchy, and others
- fruits, especially whole fruits
- grains, at least half of which are whole grains
- fat-free or low-fat dairy, including milk, yogurt, cheese, and/or fortified soy beverages
- a variety of protein foods, including seafood, lean meats and poultry, eggs, beans and peas, nuts, seeds, and soy products
For more information, visit the Being Overweight page in the Breastcancer.org Breast Cancer Risk Factors section.