The Skinny on Fatty Foods and Breast Cancer

By: Stacy Kennedy, MPH, RD, CSO, LDN; Reboot Nutritionist

Fat intake and breast cancer has been an ongoing hot button issue full of conflicting research, strong opinions and controversy.  Part of the “flip-flopping” surrounding expert dietary recommendations regarding fats and breast cancer stem from the fact that the nutrition science and research on this subject is evolving.  Early studies looking at population data suggested that women, who ate more fat in terms of a percentage of total calories, had an increased risk of developing breast cancer.  Since many types of breast cancers are estrogen-based, and estrogen is a fat soluble hormone, this theory made sense.  New information has shown that obesity may also influence cancer risk through non hormonal pathways.

Further study over the years has not fully supported the high fat diet-breast cancer connection and rather focused on the type of fats as being more important than amounts.  But it’s not all or nothing.  There is a limited-suggested increased risk of certain types of cancer in persons consuming larger amounts of total fat and animal fats; lung, colorectal and post-menopausal breast cancer, according to the American Institute for Cancer Research/World Cancer Research Fund 2007 report.  And other reports demonstrate that in fact a much stronger link between a high fat diet and breast cancer risk does exist.

Just to add to the story, a study published last year discovered that keeping the total amount of fat low, down to about 20% of total calories, versus the typical recommendation of 25-30%, had a significant survivorship benefit in women with an estrogen receptor negative (or non-hormonal) type of breast cancer.  However, this decreased risk may be related to other factors like overall weight. The women following the low fat diet in this study also lost weight, met with a nutritionist regularly and made other dietary changes that may have accounted for the benefits observed.

Evidence that the type of fat you eat is important for overall health and a lower risk of cancer is growing. Recent European studies have reported lowered breast cancer risk among women with a higher intake of monounsaturated fats like olive oil, nuts and nut butters, avocado and omega 3 fats like oily, wild fish: salmon, sardines, herring, mackerel, bluefish; flax oil, and walnuts. Choosing monounsaturated fats and omega-3 fatty acids has also been shown to be beneficial for heart health (decreasing risk of heart attacks), decreasing inflammation in the body, and improving immune function.

What’s the bottom line?  A little bit goes a long way.  Be mindful of the quality of the fats you include in your day to day diet and use them sparingly.  Like adding avocado slices to a sandwich or salad, almond butter on cut up apples or banana, and sautéing veggies in coconut oil.  These healthy foods not only provide important vitamins and other nutrients but in small amounts they can lend a lot of flavor and satisfaction to your meal!

Fats to Include

Fats to Limit

1.) Non-fried wild fish (salmon, flounder, herring, sardines)

2.) Grass fed beef

3.) Extra virgin olive oil, flax oil, coconut oil

4.) Nuts & nut butters

5.) Wheat germ

6.) Avocado

7.) Coconut milk 

 1.) Trans-fats

2.) Whole milk dairy products

3.) High fat animal meat (marbled beef, bacon, sausage)

4.) Butter & Mmrgarine

5.) French fries & other deep-fried foods

6.) Partially-hydrogenated oils in pastries, crackers, processed foods (Check the ingredients!)


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Stacy Kennedy, MPH, RD, CSO, LDN; Reboot Nutritionist

Stacy is a Board Certified Specialist in Oncology Nutrition and an Integrative Nutritionist. She consults for various companies, focusing on health, wellness and innovative strategies to help increase individual’s fruit and vegetable intake. Stacy is an American College of Sports Medicine Certified Health Fitness Specialist; she holds a BS degree in Dietetics from Indiana University, completed her dietetic internship at Massachusetts General Hospital, and earned a Masters in Public Health from the University of North Carolina at Chapel Hill. She is a Senior Clinical Nutritionist at the Dana Farber Cancer Institute/Brigham & Women’s Hospital, Harvard Medical School teaching affiliates, in Boston, MA, with more than 20 years of experience. Stacy created and now serves as project manager and lead writer for nutrition services content on the Dana Farber website and the affiliated, nationally recognized nutrition app. Stacy is regularly featured on TV, radio, print and social media on behalf of Dana Farber and other organizations. Together with her husband, Dr. Russell Kennedy PsyD, they have a private practice, Wellness Guides, LLC. Stacy is an adjunct professor in Wellness and Health Coaching at William James College, currently teaching a graduate course in Health Coaching. Stacy is featured in the award winning documentary films, “Fat, Sick & Nearly Dead” and “Fat, Sick & Nearly Dead 2,” and serves on the Reboot with Joe Medical Advisory Board. Stacy lives in Wellesley with her husband, two sons and three dogs. She enjoys cooking, yoga, hiking and spending time with friends and family. Stacy is also one of the nutritionists who runs our Guided Reboot programs.

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