Skip to main content

by Women's Health, Medically Reviewed by Dr. C.H. Weaver M.D. 11/2021

Fat and Fiction

Our diets comprise three macro-nutrients: carbohydrates, proteins, and dietary fats. Most dietary fats come from animal sources such as meats, dairy, and eggs, but they may also be found in plant sources, including nuts, seeds, avocados, and flaxseed. Each of these foods contains different types of oils that are associated with a variety of activities in the body, including the suppression or encouragement of cancer.

A Global Effort to Define “Healthy Fats” for Cancer Patients
Conflicting results from research on diet are everywhere in the news, and the research on dietary fats is no exception. Although there appear to be many conflicting studies, a closer look reveals that those conducted on humans produce fairly consistent results. This is because many studies on diet are conducted on animals, and humans differ enough from animals that findings from these may generate misleading results. Once the animal studies were eliminated from this evaluation, the findings on dietary fat were fairly clear.

Over the past 18 months, numerous studies have been
conducted throughout the world that address specific types of cancer and how each of the animal and plant oils affects them.

Omega-3 fats and hormone-sensitive cancers. Research recommends against omega-3 fats for patients with hormone-sensitive cancers such as breast and prostate.1

Fish oils and breast cancer. The benefits of fish oils for people with breast cancer have long been debated. The most recent large-scale studies that looked for a connection between fish oils and breast cancer have failed to find preventive effects.2
Fish oils and hormone-sensitive cancers. Although fish oils are a healthful part of the diet for most of us, they should be minimized in the diets of patients with hormone-related cancers.3 At this point we know that eicosapentaenoic acid (EPA) is good for patients with cancer but not for those with hormone-sensitive cancers such as breast and prostate.

Cancer patients and beneficial fats. A 2005 study reported in the European Journal of Oncology Nursing suggests that many cancer patients may be deficient in EPA due to an increase in nutritional needs when cancer is present. Studies suggest that increasing EPA-containing foods in the diet or supplementing with EPA capsules can reverse EPA deficiency and improve immune function. Studies also found that EPA has been shown to have specific anti-tumor effects.4

EPA also plays an important role in preventing inflammation, and polyunsaturated fatty acids improve immune response. This study also recommends against omega-3 fats for patients with hormone-sensitive cancers such as breast and prostate.5

Extravirgin olive oil and cancer spread. Recent research combined human study reviews and animal studies and found that extravirgin olive oil contains concentrations of polyphenols, which appear to suppress the development and the spread of cancers across the board. This is a very exciting study because it helps answer some questions surrounding conflicting studies on olive oil and cancer. It appears that olive oil that has been extracted with chemical use—meaning oils that are not extravirgin—do not have these anticancer properties because they do not contain the beneficial polyphenols. Extravirgin olive oil retains its polyphenols, however, thus differentiating it from the more highly processed varieties.6

Olive oil also contains monounsaturated fatty acids and specific compounds (squalene, tocopherols, and phenolic) that are associated with its anticancer properties, particularly for colon cancer.7

A compound found in fats that protects. A very recent study in the journal Anticancer Research reports that conjugated linoleic acid (CLA), a compound found in animal fats and sold as a supplement, has a protective effect against breast cancer.8 Because CLA itself is beneficial for breast cancer but animal fats should be minimized, supplementing with just this compound may be more beneficial than trying to derive it from foods.

Scroll to Continue



4 Ways To Maintain Your Standard Of Living Into Retirement

During uncertain economic times, preparing for retirement might feel daunting.


7 Signs You May Be at Risk of Having a Stroke

Over three-quarters of a million people in the U.S. suffer from strokes annually.


How Nurses Can Promote Healthy Lifestyles for Their Patients

Nurses are undoubtedly an influential force among patients, probably because of their close and frequent contact with patients and wide awareness of population-specific health issues.

Defining Fats

  • Saturated Fatty Acids
    Fats from meats, such as sausage and bacon; dairy products, such as butter, cheese, cream, and ice cream; and some plant oils, such as coconut and palm oils.
  • Polyunsaturated Fatty Acids
  • Omega-3 Fatty Acids
    -Alpha-linolenic acid (ALA) from soybeans, walnuts, flaxseed, and their oils
    -Eicosapentaenoic acid (EPA) from fish and fish oils
    -Docosahexaenoic acid (DHA) from fish and fish oils
  • Omega-6 Fatty Acids
    -Gamma-linolenic acid (GLA) from evening primrose oil (EPO), black currant seed oil, and borage oil
    -Linoleic acid (LA) from cottonseed, sunflower oil, safflower oil, EPO, soybeans, wheat germ, and pumpkin seeds
    -Conjugated linoleic acid (CLA) is created in our bodies from ingesting linoleic acid; also found in meats such as beef, lamb, and poultry; dairy products such as eggs, cheese, and yogurt; and plant foods, including
    safflower oil and sunflower oil
    -Archadonic acid (ARA) from meats, eggs, and poultry

Shopping for High-quality Fats
Finding high-quality, healthy fats is fairly simple if you know what to look for. Generally, avoid the low-quality fats such as hydrogenated oils (found in many crackers, chips, and packaged baked goods) and excessive intake of saturated fats from animal products.

The following are shopping suggestions based on a healthy, whole-foods diet.

Beef. Look for organic, grass-fed, lean beef.
Fish. (under 4 feet long) to avoid mercury
Eggs. Buy hormone-free, organic eggs (to avoid pesticide or herbicide residue) from cage-free or free-range hens.
Milk. Choose hormone-free or organic (inherently hormone-free) milk that states it is free of bovine growth hormone or bovine somatotropin.
Nuts and seeds and their oils. Choose organic if possible; be sure they are fresh and smell nutty, not fishy.
Avocados. Eat them when they are ripe (soft); because avocados are not generally sprayed with agricultural chemicals, it’s not necessary to buy organic.
Flax oil. Choose fresh, organic oil and keep it refrigerated.
Olive oil. Buy an extravirgin variety (extravirgin indicates that the oil is from the first press of the olives and that no chemicals were used in the extraction process.

Proper Storage and Use of Oils
Store oils in a dark, cool place because heat, oxygen, and light will chemically change their composition. It is also important that you not heat oils to the point that they start smoking. Excessive heating causes a chemical change in oils that makes them unhealthy to ingest. A recent Japanese study confirmed what many previous studies have also found: oils heated past the smoking point lose their nutritional value, and carcinogens are produced in the process.9 If you are cooking with oil and it starts to smoke, throw it away and start over.

Many labels indicate whether that particular oil is for cooking with low, medium, or high temperatures. For example, you should never heat flaxseed oil because it has a very low smoking point. Instead of cooking with it, use it as a salad dressing base or in smoothies. Olive oil, however, can be used for baking and sautéing.


  1. La Guardia M, Giammanco S, Di Majo D, Tabacchi G, Tripoli E, Giammanco M. Omega 3 fatty acids: biological activity and effects on human health. Panminerva Medica. 2005;47(4):245-257.
  2. Engeset D, Alsaker E, Lund E, et al. Fish consumption and breast cancer risk. The European Prospective Investigation into Cancer and Nutrition (EPIC). International Journal of Cancer. 2006;119(1):175-182.
  3. Christensen JH, Fabrin K, Borup K, Barber N, Poulsen J. Prostate tissue and leukocyte levels of n-3 polyunsaturated fatty acids in men with benign prostate hyperplasia or prostate cancer. BJU International. 2006;97(2):270-273.
  4. Van Bokhorst-de van der Schueren MA. Nutritional support strategies for malnourished cancer patients. European Journal of Oncology Nursing. 2005;9(suppl 2):74-83.
  5. La Guardia M, Giammanco S, Di Majo D, Tabacchi G, Tripoli E, Giammanco M. Omega 3 fatty acids: biological activity and effects on human health. Panminerva Medica. 2005;47(4):245-257.
  6. Fabiani R, De Bartolomeo A, Rosignoli P, et al. Virgin olive oil phenols inhibit proliferation of human promyelocytic leukemia cells (HL60) by inducing apoptosis and differentiation. Journal of Nutrition. 2006;136(3):614-619.
  7. Hashim YZ, Eng M, Gill CI, McGlynn H, Rowland IR. Components of olive oil and chemoprevention of colorectal cancer. Nutrition Reviews. 2005;63(11):374-386.
  8. Wang LS, Huang YW, Sugimoto Y, et al. Conjugated linoleic acid (CLA) up-regulates the estrogen-regulated cancer suppressor gene, protein tyrosine phosphatase gamma (PTPgama), in human breast cells. Anticancer Research. 2006;26(1A):27-34.
  9. Kawai K, Matsuno K, Kasai H. Detection of 4-oxo-2-hexenal, a novel mutagenic product of lipid peroxidation, in human diet and cooking vapor. Mutation Research. 2006;603(2):186-192.