Myth-busting: Your Diet and Cancer

This content authored by Amanda Mondini, RD, LD, Clinical Dietitian

Is that true?

When people in or even outside of our inner circle hear that we or someone we care about are sick with cancer, they tend to respond in a few different ways… some offer us a hug, some don’t know what to say, some say too much. And, in saying too much, certain people may give unwarranted, incorrect, or even downright harmful opinions and advice.

Chances are, if you are a person with cancer or a loved one of a person with cancer, you have been exposed to some myths about nutrition and cancer.

Amanda Mondini, RD, LD, Clinical Dietitian, Thompson Cancer Survival Center

My guess is that you have heard at least one of the following statements:

  • “Sugar causes and feeds cancer”
  • “Artificial sweeteners like Sweet-N-Low cause cancer”
  • “Dietary supplements can prevent cancer”
  • “The alkaline diet is optimal to follow if you have cancer”
  • “You should only eat organic produce and avoid genetically modified organisms (GMOs) if you have cancer (or if you don’t)”

I’ve certainly seen statements like these posted online and have even heard them in our infusion centers. If you have been curious about, or even have faith in some of the above thoughts, then this blog post is for you! I hope to clarify why these statements aren’t the most accurate, using evidence-based and up-to-date research.


  • There are no randomized controlled trials (the goal standard of clinical studies) showing that sugar consumption directly causes cancer.
    • Per the 2018 World Cancer Research Fund (WCRF)/American Institute for Cancer Research (AICR) Third Expert Report, there is no link between consumption of sugars or sugar-sweetened beverages and any specific type of cancer.₂
    • However, because many cancers are linked with adult body fatness, it is recommended to limit the consumption of processed foods high in sugars as well as sugar-sweetened beverages. Still, this link does not represent a specific and direct tie between sugar consumption and cancer risk.₂
    • Overall, it is important to consider the source of dietary sugars. As mentioned above, processed foods and beverages high in sugar should be limited as they can contribute to increased body fat, which increases the risk of specific cancers. On the other hand, high consumption of fruits and dietary fibers are linked to lower risks of certain cancers.₂
  • All cells in your body – both healthy cells and cancer cells – use sugar (specifically glucose) as their primary fuel. However, eating more sugar (glucose) does not make cancer cells grow any faster. Likewise, depriving your body of sugar (glucose) does not make cancer cells grow slower or stop growing altogether.

Artificial Sweeteners

  • There is “no strong evidence in humans to suggest that artificially sweetened drinks with minimal energy content, such as diet sodas, are a cause of cancer”.₅, ₇
  • While research continues to be conducted on this topic, consumption of non-nutritive (artificial) sweeteners within the Food and Drug Administration’s (FDA) acceptable daily intake is considered safe. ₅, ₇

Dietary Supplements

  • A dietary supplement is a product that contains a specific “dietary ingredient”. Consumption of a dietary supplement is intended to reach levels of vitamins, minerals, or other food components beyond what could typically be achieved through diet alone.₂
  • The 2018 WCRF/AICR Third Expert Report opposes the use of high-dose dietary supplements for cancer prevention.₂ High-dose dietary supplements are those that provide greater than the FDA’s recommended daily allowance (RDA) of certain vitamins and minerals. Click here to explore the FDA’s RDA of various micronutrients.
    • High-dose Vitamin A supplementation is associated with an increased risk of cancer mortality, especially in current or former smokers.
  • Research has not consistently demonstrated protective benefits from specific dietary supplements in the absence of potential negative effects.₆ In fact, over-supplementation could cause toxicity, which would be very dangerous.
  • The American Cancer Society practice guidelines suggest that trained professionals (e.g. Doctors, Registered Dietitians) be consulted regarding supplement use for cancer prevention or treatment.₆
  • Visit the Memorial Sloan Kettering Cancer Center’s “About Herbs” database to read how a vitamin, mineral, or herbal supplement could potentially interact with medications or chemotherapy that you have been prescribed.

Alkaline Diet

  • The popular concept of an “alkaline diet” is based on the assumption that dietary intake of alkaline foods can create an alkaline environment within the body. 
  • Certain cancers may grow optimally in acidic conditions and some cancer treatments may be more effective in alkaline conditions, however, there is no evidence that dietary intake of alkaline foods changes the pH of the body in any way that is meaningful.₃

Organic Produce & GMOs

  • Evidence is not currently strong enough to recommend consumption of organic fruits and vegetables over non-organic fruits and vegetables. 
  • The 2018 WCRF/AICR Third Expert Report recommends a diet high in all types of plant foods. A desire to consume only organic produce should not prevent one from consuming adequate amounts of fruits and vegetables.₂ 
  • While research is ongoing, consumption of “GMO” foods and foods treated with pesticides such as glyphosate does not appear to be associated with elevated risk of cancer.


To learn more about nutrition and cancer, visit the blog page and find posts including “Building a Healthy Relationship with Food” or  “Nutrition to Prevent Cancer”




  1. Andreotti G, Koutros S, Hofmann JN, et al. Glyphosate Use and Cancer Incidence in the Agricultural Health Study. J Natl Cancer Inst. 05 01 2018;110(5):509-516. doi:10.1093/jnci/djx233
  2. Clinton SK, Giovannucci EL, Hursting SD. The World Cancer Research Fund/American Institute for Cancer Research Third Expert Report on Diet, Nutrition, Physical Activity, and Cancer: Impact and Future Directions. J Nutr. 04 01 2020;150(4):663-671. doi:10.1093/jn/nxz268
  3. Fenton TR, Huang T. Systematic review of the association between dietary acid load, alkaline water and cancer. BMJ Open. 06 13 2016;6(6):e010438. doi:10.1136/bmjopen-2015-010438
  4. Hemler EC, Chavarro JE, Hu FB. Organic Foods for Cancer Prevention-Worth the Investment? JAMA Intern Med. 12 01 2018;178(12):1606-1607. doi:10.1001/jamainternmed.2018.4363
  5. Mallikarjun S, Sieburth RM. Aspartame and Risk of Cancer: A Meta-analytic Review. Arch Environ Occup Health. 2015;70(3):133-41. doi:10.1080/19338244.2013.828674
  6. Schwingshackl L, Hoffmann G, Buijsse B, et al. Dietary supplements and risk of cause-specific death, cardiovascular disease, and cancer: a protocol for a systematic review and network meta-analysis of primary prevention trials. Syst Rev. Mar 26 2015;4:34. doi:10.1186/s13643-015-0029-z
  7. Toews I, Lohner S, Küllenberg de Gaudry D, Sommer H, Meerpohl JJ. Association between intake of non-sugar sweeteners and health outcomes: systematic review and meta-analyses of randomised and non-randomised controlled trials and observational studies. BMJ. Jan 02 2019;364:k4718. doi:10.1136/bmj.k4718

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