Effects of Antioxidant Dietary Supplement Use upon Response to Cancer Treatment: A Scoping Review of Available Evidence

Abstract

Introduction

The effects of antioxidant dietary supplements on response to biological therapies for cancer is unknown. We conducted a scoping review of the available systematic review evidence on this question.

Methods and analysis

We searched six databases from inception to August 19, 2022 for systematic reviews of randomized controlled trials of antioxidant dietary supplements used by patients receiving curative chemotherapy, radiotherapy, or other biological therapy for cancer and assessing the impact of supplements on survival, treatment response, or disease progression. We focused on results from reviews at high or moderate AMSTAR-2 quality. Records were selected, data extracted, and AMSTAR-2 ratings assessed independently by two authors.

Results

We found 24 systematic reviews with relevant evidence. Reviews were heterogenous in cancers, treatments, and antioxidant dietary supplements assessed. Conclusions across reviews were mixed, ranging from negative to no apparent difference to positive, but always with caveats about the limited size and quality of the evidence. One review was rated ‘moderate’ on AMSTAR-2; it included one small trial of vitamin C and formed no firm conclusions.

Conclusions

We did not find reliable systematic review evidence on the effects of antioxidant dietary supplements upon therapies for cancer. More research is necessary to inform clinical recommendations.

Acknowledgements

We gratefully acknowledge Becky Skidmore, MLIS, for PRESS peer review of the search strategy.

Author Contributions

AE, CLK, and CD jointly conceived the study and developed the research questions. LSW proposed the scoping review methodology, refined the research questions, and developed the protocol with IM and SS. EFG developed the search strategy. SS, IM, AA and LSW screened studies and extracted data. LSW drafted the manuscript. All authors revised the manuscript and approved the final text. LSW is guarantor of the review.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

Data sharing is not applicable as no new data were created or analyzed for this study.

Additional information

Funding

LSW is supported by the National Center for Complementary and Integrative Health of the National Institutes of Health (R24 AT001293). AE and CLK are supported by the University of Maryland Greenebaum Comprehensive Cancer Center Support Grant from the National Cancer Institute of the National Institutes of Health (P30CA134274) and the State of Maryland’s Cigarette Restitution Funds https://health.maryland.gov/phpa/crfp/Pages/home.aspx. The funders had no role in planning or conducting the review.