Nutritional Supplement Know-How

What to Consider When Contemplating Dietary Supplements

People around the world are spending over 140 billion dollars every year on nutritional supplements, with the well-intentioned effort to improve their health.(1) The Dietary Supplement Health and Education Act of 1994 defines a dietary supplement as a product taken by mouth that may contain contain dietary ingredients such as: “vitamins, minerals, herbs or other botanicals, amino acids, and substances such as , organ tissues, glandulars, and metabolites.” (2)  Aside from the money being spent, the greater concern is the safety factor in using these supplements with no guidance from a medical professional.

Some important points to consider regarding dietary supplements:

  • Products you purchase may differ from the supplements tested in studies; for instance, they may contain unsafe ingredients that are not listed on the label (3)
  • Sources of nutrients or herbs may pose a food safety risk, meaning they could contain bacteria or fungus if manufactured in an area outside of the United States that is unregulated for these conditions
  • Unsafe food-drug interactions with a prescription drug someone is taking could possibly occur (3)
  • An allergy to an unknown substance, whether the main dietary supplement ingredient or an additional ingredient (for instance, a filler or binder) could occur

The United States Food and Drug Administration (FDA) oversees regulation of dietary supplements; however, the rules for manufacturing and distributing supplements are less strict than those for prescription or over-the-counter drugs.(4) Terms such as “organic” or “natural” on a product label do not necessarily equate to safe. The United States Pharmacopeia Convention (USP) is a non-profit scientific organization which establishes standards for helping ensure quality in pharmaceutical development and manufacturing. A product with a USP Verified Mark means that it is a safer option as it signals to the public that what is on the product label is what the bottle contains.(5)

Wherever you may be on the cancer spectrum- prevention, treatment, or survivorship- dietary supplement information should always be evaluated by a healthcare provider with cancer-related expertise so that the efficacy, safety, and practical application of any nutritional supplements in question may be carefully considered.(6)

What is the Best Way to Prevent Cancer?

There is no stronger nutrition-related force relating to cancer prevention than a whole-foods, plant-based (WFPB) diet pattern. Simply put, the WFPB approach contains its power in its food “packages”, where a unique package of nutrients works together synergistically, as a team, in ways that the nutrients are not entirely capable of working when alone. It’s like trying to score a touchdown (achieve cancer prevention) against a ferocious football team (cancer) all alone – it’s just not how things were designed to work – there is more effective power in a well-designed system (whole food).

Careful consideration should be given to taking single nutrient supplements. Most often, they are not needed unless a person has a nutrient deficiency that is clinically determined by a healthcare provider upon blood test results and physical signs/symptoms. Sometimes, taking one nutrient or component in isolation can throw other related nutrients out of balance.

Additionally, certain nutrient supplements can potentially increase a person’s risk for cancer. This seems to be most prevalent with antioxidant-related vitamins such as vitamin A and vitamin E, likely due to activation of cell pathways that can create cancerous cells.  Many herbal supplements touted for cancer prevention can affect the liver and kidneys in adverse ways. (7)

In essence, more of something is not always necessarily better.

The Impact of Supplement Use on Cancer Treatment

Antioxidants are safe when consumed in lower to moderate amounts from food sources as they are more naturally recognized and absorbed this way.  Foods rich in antioxidants include, but are not limited to, blueberries, nuts, broccoli, and sweet potatoes. High doses of antioxidants, particularly from man-made forms as well as high-dose whole foods can potentially interfere with a person’s cancer treatment.(8)

Many herbs can block cancer treatments, including and radiation treatment, from working properly and to their full potential.(9) For instance, turmeric supplements can potentially interfere with certain chemotherapy agents and lessen their effects; these include doxorubicin (Adriamycin; Rubex) and cyclophosphamide (Cytoxan; Neosar). (10)

A study published in February 2020 revealed that cancer survivors reported significantly higher nutrient intakes from dietary supplements than from foods, in comparison with individuals without cancer. (11) The American Institute for Cancer Research offers that a WFPB diet pattern is the safest and most effective way to attain valuable nutrients needed and that nutritional supplements should only be considered when clinically necessary and should be managed by a patient’s oncology care team. (12, 13)  

If certain foods are not well-tolerated during treatment, it is important to let your oncology care team know so that a consultation with the team’s Registered Dietitian may be arranged for you.

In conclusion, the long-standing phrase “food as medicine” continues to ring true, as a whole-food, plant-based diet is safely packed with the nutrients our bodies need. Please remember it is important to discuss all the dietary supplements you may be interested in taking with your healthcare provided, even a daily multivitamin/mineral supplement.

  1. Dietary Supplements Market Size, Share & Trends Analysis Report By Ingredient (Vitamins, Proteins & Amino Acids), By Form, By Application, By End User, By Distribution Channel, And Segment Forecasts, 2021 – 2028. February 2021.
  2. Dietary Supplement Health and Education Act of 1994. Public Law 103-417. 103rd Congress.
  3. Dietary Supplements Wisely. NIH National Center for Complementary and Integrative Medicine. January 2019.
  4. Dietary Supplements. United States Food and Drug Administration. August 2019.
  5. Dietary Supplements & Herbal Medicines. United States Pharmacopeia. Accessed March 2021.
  6. Dietary Supplements: What Is Safe? Accessed March 2021.
  7. American Society of Clinical Oncology Educational Book 34. May 15, 2014.
  8. Dietary Supplement Use During Chemotherapy and Survival Outcomes of Patients With Breast Cancer Enrolled in a Cooperative Group Clinical Trial. Journal of Clinical Oncology. March 2020.
  9. Herbs and Chemotherapy. Academy of Nutrition and Dietetics. February 2014.
  10. About Herbs, Botanicals & Other Products. Memorial Sloan Kettering Cancer Center. February 2021.
  11. Dietary Supplement Use among Adult Cancer Survivors in the United States. The Journal of Nutrition. February 2020.
  12. What about Dietary Supplements? Cleveland Clinic Chemocare. Accessed March 2021.
  13. Study Suggests Supplements During Breast Cancer Chemotherapy May be Harmful. American Institute for Cancer Research. October 2020.