February 2022 Issue

CPE Monthly: The Role of Omega-3 Fats in Cancer
By Ginger Hultin, MS, RDN, and Emily Guzman, MS
Today’s Dietitian
Vol. 24, No. 2, P. 44

Suggested CDR Performance Indicators: 8.1.4, 8.1.5, 8.2.1, 10.2.6
CPE Level 2

Take this course and earn 2 CEUs on our Continuing Education Learning Library

The science supporting the health benefits of omega-3 fats throughout the life cycle is abundant, but research is still exploring their efficacy for cancer risk reduction, treatment, and prevention of recurrence. Unfortunately, many studies are riddled with inconsistencies and limitations that make it difficult to establish evidence-based recommendations.

Dietitians in all areas of practice can benefit from a deeper understanding of the emerging research surrounding omega-3s given the wealth of media coverage around this topic and the widespread use of omega-3 supplements. According to an online survey conducted in three countries (n=3,030), 45% of study participants in the United States, 29% in the United Kingdom, and 24% in Germany reported using omega-3 supplements.1

Omega-3 fatty acids provide structure, stability, and fluidity to cell membranes, facilitate cell-to-cell communication, regulate blood clotting, and support the normal growth and development of the nervous system, brain, and retina.2 They may regulate inflammation through several mechanisms related to changes in cell membrane composition and gene expression. Studies on the effects of various ratios of omega-6 to omega-3 fats in the diet have found that a lower ratio was associated with increased telomere length, which is noteworthy because telomere shortening occurs in many cancers.3-5

The anti-inflammatory functions of omega-3s are a focus of cancer researchers because cancer can fuel chronic inflammation, a decrease in lean body mass, and functional impairment during treatment—all of which are major drivers of malnutrition and cancer cachexia.6 Omega-3s also may influence signaling pathways that inhibit cell proliferation and induce apoptosis, functions that may suppress the growth and proliferation of tumors. These anti-inflammatory and potential anticancer functions have been confirmed in many animal and in vitro studies, but results are mixed in humans.7

This continuing education course reviews the role of omega-3 fats from both dietary and supplement sources in cancer risk reduction, treatment, and prevention of recurrence.

Omega-3 Fatty Acid Biochemical Review
Omega-3s are polyunsaturated fatty acids (PUFAs) the body needs for normal health and development. The three main types are alpha-linolenic acid (ALA), EPA, and DHA. These are further classified into two groups based on chain length: long-chain EPA and DHA, which are the more biologically active forms, and short-chain ALA. Omega-6s are the other major class of PUFAs that must be obtained from the diet and include linoleic acid (LA) and arachidonic acid (AA).

Of the three types of omega-3s, ALA is the only essential fatty acid because it can be converted to EPA and DHA in the liver. This conversion isn’t very efficient, though, because ALA and LA compete for the same enzymes required for their metabolism into longer-chain fatty acids. The conversion from ALA is estimated to be 5% to 15% for EPA and 1% or less for DHA, though it varies by age, sex, genetics, health status, and diet, especially fat composition.8,9 For example, cross-sectional data suggest the conversion is more efficient in women than in men.10,11 However, other factors, including conditions such as diabetes and hypertension as well as diets high in omega-6 LA, may interfere with this conversion.8,11

While some individuals may be able to meet their total omega-3 needs with ALA intake alone, many people, including men, with increased needs (eg, some vegetarians, vegans, and pregnant or lactating women) or those with health conditions that interfere with the conversion, may benefit from a direct source of EPA and DHA from foods or supplements.11

Both omega-3 and omega-6 fats serve as precursors to signaling molecules called eicosanoids, but those derived from omega-6s, such as leukotrienes, prostaglandins, and thromboxanes, are associated with a mostly proinflammatory response.8,9 Omega-3-derived eicosanoids, including resolvins, protectins, and maresins, help resolve inflammation.

Because omega-3s and omega-6s compete with each other for incorporation into cell membranes, the ratio of omega-6 to omega-3 fats in the diet may be a risk factor for inflammatory conditions, including cancer.9 The optimal ratio is likely 3:1, but standard Western diets are characterized by relatively low intakes of omega-3s and a dietary ratio closer to 17:1.12,13 This imbalance allows for the production of more proinflammatory eicosanoids that may contribute to adverse health outcomes.8

Omega-3 Intake Recommendations
The Adequate Intake (AI) for omega-3 fats is 1.6 g/day for men, 1.1 g/day for women, and 1.4 g/day and 1.3 g/day during pregnancy and lactation, respectively. This applies to ALA only, as ALA is the only essential omega-3. Individuals on vegetarian and vegan diets may benefit from higher intakes of ALA because they commonly have lower blood levels of EPA and DHA.11

Because conversion of ALA to EPA and DHA is inefficient, individuals also are encouraged to consume direct sources of EPA and DHA. Even though an official daily recommended intake hasn’t been established, various organizations and guidelines, including the American Heart Association (AHA), American Cancer Society, American Institute for Cancer Research (AICR), and the 2020–2025 Dietary Guidelines for Americans, concur that an average of 250 mg/day of combined EPA and DHA is adequate for general health.14-17 To meet this goal, individuals should consume a variety of low-methylmercury seafood, such as salmon, anchovies, herring, sardines, trout, and Atlantic and Pacific (but not king) mackerel, at least twice per week (for a total of 8 oz).17

For cancer protection, the AICR and American Cancer Society encourage intake from whole foods rather than supplements. In addition, the AHA discourages omega-3 supplement use unless an individual is at high risk of CVD.16,18,19 For those with coronary heart disease, the AHA recommends 1 g/day of combined EPA and DHA and suggests taking a 4 g/ day prescription of combined DHA and EPA for reducing triglycerides. However, it recommends consulting a physician before taking these supplements.19

Food Sources of Omega-3s
Foods highest in ALA include flaxseeds and flax oil, chia seeds, hemp seeds, and walnuts.2,20 Smaller amounts are found in canola oil, soybean oil, and mayonnaise, but a standard serving of any of these foods will still provide most or all of the ALA someone needs in a day. Other foods with low amounts of ALA per serving include bread, ground beef, milk, and beans.2

EPA and DHA are found in fatty fish, fish and krill oil supplements, and marine plants such as algae and seaweed. It’s worth noting that fish don’t produce these long-chain fatty acids on their own; it’s the microalgae at the bottom of the food chain that synthesize EPA and DHA endogenously in their chloroplasts, which are the organelles responsible for photosynthesis and other processes such as fatty acid synthesis.2,21 Fish begin to accumulate omega-3s only when they consume the phytoplankton that feed on the microalgae, which is why people who don’t eat fish still can obtain adequate amounts of EPA and DHA through food and/or supplemental sources of algae.2,11

Saltwater fish contain the highest levels of EPA and DHA because they have access to these marine algae. These include wild and farmed salmon, wild herring, sardines, wild mackerel, canned pink salmon, sea bass, and wild rainbow trout. EPA and DHA levels are lower in shrimp, lobster, crab, cod, scallops, and freshwater fish such as bass, trout, catfish, and tilapia.2,22

Individuals who don’t eat seafood may be able to obtain adequate amounts of EPA and DHA from algae foods such as seaweed, kelp, nori, spirulina, and chlorella, though amounts may vary between products.23 A growing number of foods are now fortified with omega-3s, including some brands of eggs, fruit juice, dairy and nondairy milks, tofu, yogurt, cooking oils, breads, pastas, nut butters, vegan butter substitutes, and spreads.8,22 Food companies often include this information on the front of packages so it’s easy for consumers to know that a product has been fortified.

Research is mixed on whether food or supplement sources are more effective at raising omega-3 levels in the body, and many of the available studies were done using supplements. The Academy of Nutrition and Dietetics’ position statement on dietary fats highlights that the difference between the two remains unclear, while many major heart health and cancer organizations do suggest a food-first approach.8,14-16

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Omega-3 Supplements
It’s common for omega-3 supplements to contain DHA, EPA, or a combination of the two rather than ALA because those needs are more easily met with a standard serving of vegetable oil. Most Americans will more than meet their ALA needs with a standard diet.2 Omega-3 supplements originate from both plant and animal sources and are found in oil, capsule, and gummy form.

Supplements that provide a direct source of EPA and DHA include fish oil, krill oil, cod liver oil, and algal oil, which often is labeled as vegan omega-3. Most fish oil supplements provide 180 to 300 mg EPA and 120 to 200 mg DHA per capsule, whereas most algal oil supplements contain 100 to 300 mg of DHA and very little, if any, EPA.2,24,25 Limited research suggests the bioavailability of algae-based EPA and DHA supplements is comparable to that of fish and krill oils.25,26

Even though some fish may contain traces of methylmercury, contamination of omega-3 supplements generally isn’t a concern because the contaminant often is removed during processing.2 However, consumers should be counseled on the potential side effects of higher-dose fish and cod liver oil supplements, as these contain varying amounts of vitamins A and D, which could be problematic or toxic in high amounts. Note the Tolerable Upper Intake Level for vitamin A is 3,000 mcg for people older than 19, and, for vitamin D, is 4,000 IU for people older than 9 years.27,28

The FDA warns that EPA and DHA supplementation above 3 g/day may lead to gastrointestinal side effects such as nausea, diarrhea, and heartburn, which may exacerbate similar symptoms that occur during cancer treatment.2 It’s also unknown whether fish oil supplements cause adverse reactions in people with seafood allergies. Food allergies typically result from a reaction to a protein, while supplements are purely fat based. Some studies have shown that individuals with fish allergies can safely tolerate fish oil supplements, but they should work with their allergists and use extreme caution before supplementing.29

It’s also important to educate clients on FDA regulation of dietary supplements. Because of the 1994 Dietary Supplement Health and Education Act, the FDA regulates dietary supplements differently than it does drugs and conventional foods.30 Supplement labels that carry structure or function claims have the following disclaimer on the label: “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.”31 Advising patients to purchase products that have an external third-party quality testing certification can help ensure the supplements they choose are of high quality and contain what’s listed on the label.

Omega-3s and Cancer Risk Reduction
Interest in the association between omega-3s and cancer originated from reports that Japanese and Inuit (Indigenous peoples of Alaska, Canada, and Greenland) populations had very low incidence of breast, prostate, and other cancer risk and mortality before the second half of the 20th century.32,33 The traditional diets of these cultures included large quantities of fats from fish and other marine sources of omega-3s.33

Researchers also began to observe a growing prevalence of breast cancer in Western populations with low intakes of omega-3s and high intakes of omega-6s.32 Although the body of literature has grown substantially since these initial observations, inconsistencies in the data and variabilities in research methods make it difficult to declare a blanket statement about omega-3s and cancer risk.

Observational studies suggest an association between omega-3s and reduced risk of certain cancers such as breast and colorectal, but experimental studies haven’t always confirmed these findings. Most of the evidence comes from fish oil supplementation trials, so less is known about the effects of whole foods, ALA, and algal supplements.

Studies also face challenges in teasing out the differential effects of individual fatty acids alone vs combined. Few studies have investigated the method of fish preparation or the type of fish consumed, which matters because omega-3 levels vary considerably between fish species.2 Given these limitations, it’s unsurprising that studies have long reported mixed results on omega-3s and cancer risk. Evidence that has emerged in the last few years points to an overall neutral effect for omega-3s regarding most cancers, with a few key exceptions.

The role of omega-3 supplements in prostate cancer risk is difficult to assess because findings from systematic reviews and meta-analyses don’t follow a clear trend, and there continues to be much debate around this topic. The debate stems, in large part, from a well-known and controversial case-cohort study (n=834) published in 2013 in the Journal of the National Cancer Institute, which found an increased risk of aggressive prostate cancer in men with high plasma levels of omega-3s.34 However, the authors didn’t collect information on fish intake or supplements—they only tested blood levels of omega-3s—and the study didn’t offer a possible explanation for their results. Because the ensuing media attention left many consumers worried, critics from both the research and medical communities spoke out to provide context to the study and evidence that fish intake may be associated with a decreased risk of prostate cancer.35,36

More recent research shows that omega-3 supplementation doesn’t affect prostate cancer incidence.37-39 A 2019 randomized, double-blinded, placebo-controlled trial published in the New England Journal of Medicine found that taking 1 g/day fish oil in capsule form (840 mg EPA and DHA) didn’t lower the risk of developing cancer in a racially diverse cohort (n=25,871).40

A 2020 systematic review and meta-analysis of 47 randomized controlled trials (n=108,194) published in the British Journal of Cancer found that increasing long-chain omega-3 fatty acid intake had little or no effect on cancer diagnosis or cancer death (including for breast cancer). Researchers also found a slight increase in prostate cancer risk with increasing total PUFA, ALA, and long-chain omega-3s, but the evidence was low quality due to limited data and highly variable doses.39 It’s worth noting that most of these studies were supplementation trials, so the effect of food sources of intake remains unknown.

Emerging research on the link between omega-3 supplements and breast cancer risk looks more promising. Much of the research on this topic dates back to a 2010 cohort study (n=35,106) that found a 32% reduction in breast cancer risk among postmenopausal women who took fish oil supplements for an average of 10 years.41 Then, in 2013, The BMJ published a meta-analysis that found marine-derived EPA and DHA were associated with a 14% decreased risk of breast cancer.42

Other studies have revealed similar benefits with a higher dietary ratio of omega-3s to omega-6s.43 However, more research is needed given that earlier studies are mixed and a recent meta-analysis suggested omega-3 supplementation has little or no effect on breast cancer risk.32,39

Cancer Treatment and Survivorship
Omega-3s have emerged as a promising adjunct to conventional cancer treatments, most notably as a nutritional approach to improve treatment-related side effects such as weight and muscle loss.6 EPA and DHA have improved treatment outcomes in many in vivo animal studies. Now, researchers are conducting clinical trials to test their effects in humans. Some research has shown that omega-3s may enhance the efficacy and tolerance of chemotherapy drugs, reduce the size of tumors, and lower the risk of recurrence in some cancers.6,44,45 Although inconsistencies have emerged and research is ongoing, studies generally have demonstrated that omega-3s are a safe complement to standard therapies.6

There’s strong evidence to support the use of omega-3s to preserve or prevent weight loss and loss of lean body mass. It’s common for patients to experience weight and body composition changes during treatment because of side effects such as taste and smell alterations, nausea, vomiting, diarrhea, fatigue, and anorexia.6 Omega-3 foods such as fatty fish and some nuts and seeds provide a concentrated source of calories, protein, vitamins, and minerals that can aid in weight maintenance and improve the body’s response to treatment.

The Academy of Nutrition and Dietetics’ Evidence Analysis Library found that supplementing with fish oil resulted in weight gain or maintenance in adult oncology patients experiencing weight loss, but more research is needed to determine the optimal dose because intake ranged from 0.26 to 6 g/day of EPA.46 Although the Evidence Analysis Library didn’t evaluate algae-based supplements for weight maintenance, limited research suggests they’re nutritionally equivalent and their bioavailability is comparable to fish and krill oils.26

Omega-3s also may improve tolerance to chemotherapy in a range of cancers, including breast, lung, and colorectal.32,33 A 2011 clinical trial published in the journal Cancer found that supplementing with 2.5 g/day of EPA and DHA increased the efficacy of chemotherapy without affecting treatment toxicity in patients undergoing first-line chemotherapy for non–small cell lung cancer. The researchers also reported that one-year survival was higher in the fish oil group compared with controls, but this trend wasn’t statistically significant (p=0.15), which may be due to the small sample size (n=46).47

In patients with breast cancer, studies show that EPA and DHA intake improves survival, reduces cancer recurrence, and reduces chemotherapy-associated side effects such as cachexia, cardiac events, bone density loss, insulin resistance, and cognitive dysfunction.32,45,48 In patients with colorectal cancer, omega-3s can improve tolerability to chemotherapy, delay tumor progression, reduce tumor size, and improve survival.45,49,50

A 2016 randomized controlled trial found that men and women with colorectal cancer (n=30) who supplemented with 2 g/day of fish oil for the first nine weeks of chemotherapy had a significantly longer time to tumor progression.49 Another systematic review reported a decrease in symptoms of fatigue and pain during chemotherapy and radiotherapy, but no reduction in tumor size nor improved survival.51

Additional studies are needed to confirm the beneficial effects of omega-3s on cancer outcomes after diagnosis and determine the optimal dose. Even then, dietitians should continue to assess the benefits of omega-3 supplements on an individual basis. Recommendations should consider the individual’s dietary omega-3 intake, degree of inflammation, and medication and treatment regimens.

Breast Cancer
Although the research is less abundant on the role of omega-3s after a breast cancer diagnosis, several animal studies and some clinical trials have shown that EPA and DHA may improve symptoms and survival.

A 2011 cohort study published in the Journal of Nutrition found that women diagnosed with early-stage breast cancer (n=3,081) who had higher dietary intakes of EPA and DHA experienced a dose-dependent decrease in risk of all-cause mortality and a 25% reduction in breast cancer recurrence.52 More recently, in 2019, a double-blinded randomized controlled trial found that supplementing with 1 g/day of fish oil improved survival in 48 Indonesian women with locally advanced breast cancer receiving standard chemotherapy.53

Omega-3s also may improve treatment side effects and enhance quality of life in breast cancer survivors. In a 2019 double-blinded, placebo-controlled clinical trial of 53 women diagnosed with locally advanced breast cancer, supplementing with 2.4 g/day of omega-3s (1.6 g EPA and 0.8 g DHA) showed no effects on body composition or toxicity but a significant improvement in xerostomia.54

Less research exists on the effects of flaxseed (a food source of ALA) in breast cancer, but the evidence suggests it may be an effective strategy to improve treatment outcomes.55 Animal and biomarker studies suggest that flaxseed in the diet can induce cancer cell apoptosis and decrease the proliferation of tumor cells, but larger and more rigorous intervention trials are needed to confirm these findings.56,57 Cohort studies have observed a reduction in tumor tissue with 25 g/day flaxseed supplementation, and a 2013 meta-analysis of 10 studies showed 25 g/day of flaxseed may reduce mortality. Most studies have investigated the effects of supplementation with ground flaxseed, flaxseed oil, and isolated lignin rather than whole flaxseed. In studies that do look at whole flaxseed, it’s difficult to extract the effect of ALA alone from other components such as fiber and lignans.57 More research is needed in this area.

Prostate Cancer
Omega-3 supplementation is common among men with prostate cancer. Data from a 2019 study of self-reported complementary and alternative medicine use found that 24% of newly diagnosed patients (n=7,989) supplemented with omega-3s.58 Despite this widespread use, evidence around omega-3s in the secondary prevention of prostate cancer is scarce. Animal and in vitro studies show that EPA and DHA can increase cancer cell death, slow tumor growth, inhibit metastasis, and increase survival, all of which are likely related to the anti-inflammatory effects of omega-3s.59,60 However, human studies across all study designs offer conflicting results that suggest little or no benefit on prostate cancer prognosis.61,62

Systematic reviews on the secondary prevention of prostate cancer are in overall agreement that no association exists between omega-3s and prostate cancer prognosis, although few studies have investigated marine and algae foods or ALA supplements. A 2017 meta-analysis of 54 studies published in Integrative Cancer Therapies found that, in some intervention trials, fish oil supplementation (1,600 to 2,400 mg of EPA and DHA) reduced inflammatory markers such as cyclooxygenase-2 and leukotrienes but had no impact on levels of prostate-specific antigen, which is used to monitor disease progression in men with prostate cancer. Results from observational studies have been inconsistent, but cohort studies have found that higher intakes of fish and omega-3 supplements are associated with a significantly lower risk of prostate cancer mortality.62 The results of these and other studies suggest there may be an association between omega-3s and decreased mortality, but more research is needed.

Inconsistencies in this area likely exist because of variability in research methodology. Studies use different methods to assess exposure, outcomes, and biomarkers, and very few collect information on the type of fish consumed and method of preparation. More data are required before researchers can draw a definitive conclusion about the role of omega-3s in prostate cancer treatment or recurrence, but intervention studies to date suggest that dietary intake of fish and fish oil supplements doesn’t pose harm when used during treatment.35,62

Clinical Considerations for Omega-3 Supplementation
Because fish oil is a natural blood thinner, there’s some concern that high doses of fish oil supplements (above 2 to 4 g/day of EPA and/or DHA in different sources) may interact with anticoagulants and antiplatelet drugs such as aspirin and warfarin, as well as vitamin C, vitamin E, and turmeric/curcumin supplements. Clinicians also have raised concerns that taking high doses of fish oil supplements before surgery can increase the risk of bleeding. Early case reports revealed an increase in the international normalized ratio, a measure of how long it takes the blood to clot, after omega-3 supplementation, but later studies offered contradictory evidence that showed fish oil with warfarin didn’t affect this ratio or bleeding.6,63-65

Omega-3s have been shown to significantly reduce platelet aggregation, but a 2017 systematic review of 52 randomized controlled trials found that fish oil supplementation ranging from <0.1 to 6 g/day didn’t increase the risk of bleeding during or after surgery.66 The authors of this research didn’t support the recommendation to discontinue the use of fish oil supplements before surgery. Other experts agree, citing evidence from randomized controlled trials that show no clinically significant increase in bleeding during surgery, even in patients on anticoagulants.67 It should be noted that the AHA and various cancer centers around the country continue to warn about the use of high-dose fish oil supplementation, including in patients taking anticoagulants, because of the risk of excess bleeding.19,68,69

Putting It Into Practice
There are many unknowns around omega-3s and cancer risk, treatment, and survivorship, but the general and cardiovascular health benefits are better established. Dietitians should encourage clients to regularly consume a variety of foods that contain omega-3s, regardless of their impact on cancer outcomes. Helping clients identify sources of omega-3s from plant, animal, and fortified foods is a useful strategy to address relatively low intakes of omega-3s compared with omega-6s.

Dietitians should advise clients to consume direct sources of EPA and DHA from fish or algae because conversion from ALA may be low. Not all fish are high in EPA and DHA, so dietitians can guide clients toward fattier types, such as salmon, tuna, sardines, and anchovies, including canned varieties. RDs can point vegetarian and vegan clients toward foods and supplements containing algae and convey the limited evidence that suggests they’re comparable in nutritional value and bioavailability to fish and krill oils.

The AICR doesn’t recommend the use of omega-3 supplements to treat or reduce cancer risk, but there’s strong evidence to support omega-3 supplementation for changes in weight and body composition during cancer treatment. Clients who are in active treatment should work with their care team to ensure that omega-3s won’t interfere with other medications or cause adverse effects.

The research around omega-3s and cancer is promising for some types of cancer, but the evidence remains limited and studies offer conflicting results. As the body of literature continues to grow, clients should be encouraged to consume a diet that includes omega-3 foods from a variety of plant and/or animal sources to support their general health.

— Ginger Hultin, MS, RDN, is a Seattle-based integrative oncology nutrition specialist and owner of private practices Champagne Nutrition and Seattle Cancer Nutritionist. Emily Guzman, MS, is a Chicago-based freelance nutrition writer.

Learning Objectives

After completing this continuing education course, nutrition professionals should be better able to:
1. Counsel clients on the unique function of omega-3 fatty acids in the body and their role in health promotion.
2. Distinguish three potential positive clinical outcomes of omega-3 fatty acids in the oncology setting.
3. Determine clinical considerations in cases where omega-3s may pose a risk during cancer treatment.

CPE Monthly Examination

1. What are the three main types of omega-3s?
a. Alpha-linolenic acid (ALA), EPA, and DHA
b. Arachidonic acid (AA), EPA, and DHA
c. Gamma-linolenic acid, AA, and ALA
d. EPA, DHA, and linoleic acid

2. Which is true of the conversion of ALA to long-chain omega-3s?
a. It’s higher in men than women.
b. It’s estimated to be <15%.
c. It’s higher in older adults than younger.
d. It’s estimated to be around 50%.

3. Why are fish high in EPA and DHA?
a. They accumulate them when they feed on seaweed and kelp.
b. Ocean temperatures cause fish to accumulate them from the water.
c. Their diets are rich in the mineral precursors to the omega-3s.
d. They accumulate them when they feed on phytoplankton.

4. Which of the following are food sources of ALA?
a. Flax oil, chia, and lamb
b. Hemp seeds, walnuts, and broccoli
c. Flaxseeds, walnuts, and ground beef
d. Chia, hemp seeds, and tomatoes

5. What are the daily intake recommendations for EPA, DHA, and ALA?
a. EPA and DHA have not been established; ALA is 1.6 g for men and 1.1 g for women.
b. EPA and DHA is 2.7 g for men and 2.4 g for women; ALA is 1.6 g for men and 1.1 g for women.
c. EPA and DHA is 1.6 g for men and 1.1 g for women; ALA has not been established.
d. EPA, DHA, and ALA combined should be 1.5 g for men and 1.2 g for women.

6. During cancer treatment, there’s strong evidence that omega-3s may do which of the following?
a. Reduce side effects such as taste and smell alterations
b. Reduce tolerance to chemotherapy
c. Improve neuropathy in the hands and feet
d. Preserve weight or prevent weight loss and loss of lean body mass

7. In patients with breast cancer, studies show that EPA and DHA reduce which of the following?
a. Red blood cell counts
b. Chemotherapy-associated side effects such as cachexia and cardiac events
c. Diarrhea associated with chemotherapy and radiation
d. The need for antinausea medications

8. Studies on omega-3 fats and prostate cancer have found which of the following about fish oil supplementation?
a. Did not affect inflammatory markers but did help lower levels of prostate-specific antigen (PSA)
b. Reduced inflammatory markers but increased levels of PSA
c. Reduced inflammatory markers but had no impact on levels of PSA
d. Reduced inflammatory markers and levels of PSA

9. A systematic review on fish oil supplementation and bleeding during surgery found which of the following?
a. Fish oil supplements increased the risk of bleeding during or after surgery.
b. Fish oil supplements did not increase the risk of bleeding during or after surgery.
c. Fish oil supplements increased the risk of bleeding during or after surgery in some cancers.
d. Fish oil supplements increased the risk of bleeding during or after surgery in patients taking anticoagulant medications.

10. What is one reason omega-3s may be helpful for oncology patients?
a. They offer antioxidant support.
b. They induce apoptosis.
c. They commonly contain vitamin D.
d. They help lower inflammation.


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14. Dietary fats. American Heart Association website. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/dietary-fats. Accessed February 22, 2021.

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16. Fish and cancer risk: 4 things you need to know. American Institute for Cancer Research website. https://www.aicr.org/news/fish-and-cancer-risk-4-things-you-need-to-know/. Published April 2, 2015. Accessed February 6, 2021.

17. US Department of Health & Human Services; US Department of Agriculture. Dietary Guidelines for Americans 2020–2025. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf. Published December 2020.

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20. Senila L, Neag E, Cadar O, Kovacs MH, Becze A, Senila M. Chemical, Nutritional and Antioxidant Characteristics of Different Food Seeds. App Sci. 2020;10(5):1589.

21. Harwood JL. Algae: critical sources of very long-chain polyunsaturated fatty acids. Biomolecules. 2019;9(11):708.

22. FoodData Central. US Department of Agriculture, Agricultural Research Service website. https://fdc.nal.usda.gov/. Updated February 21, 2020. Accessed December 15, 2020.

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