The study, led by Anna Zimny-Zając of the Jagiellonian University Medical College in Kraków together with colleagues from the Maria Skłodowska-Curie National Research Institute of Oncology, found that 61.8 percent of respondents with a self-reported cancer history had used a dietary supplement or an over-the-counter preparation in the previous twelve months. Daily use was reported by 26.9 percent of the entire group, meaning that more than one in four cancer survivors in the sample was taking at least one non-prescription product every single day. The remaining 38.2 percent reported no use at all during the preceding year. Because the survey assessed dietary supplements and non-prescription medicines jointly in a single question, the researchers could not separate the two categories in their analysis, a limitation they acknowledge explicitly.

What exactly are people taking? Among users, multivitamin preparations dominated the list, selected by 52.5 percent of those reporting any use. Digestive products, hair and skin preparations and sleep products rounded out the most frequently chosen categories. The survey asked respondents to indicate both the type of preparation and its intended purpose, and the authors are careful to describe these as reported product categories or purposes of use rather than motivations, since underlying motivations were not directly measured. Even so, the pattern echoes what has been documented internationally: cancer survivors gravitate toward multivitamins, single-nutrient products such as vitamin D, and preparations marketed for fatigue, immune support or general wellbeing.

The demographic fingerprint of supplement use was equally revealing. In a multivariable logistic regression model, higher educational attainment showed the strongest positive association with use, with university-educated respondents having the greatest odds of reporting supplementation. Women were more likely to use these products than men, and older age was associated with lower odds. More frequent stressful situations also predicted higher odds of use, hinting at a possible link between psychological burden and the search for self-care tools, although the authors stress that such mechanisms were not directly assessed and should be treated as hypotheses. Associations with self-rated mental health were statistically significant but did not increase consistently across progressively poorer health categories, complicating any simple interpretation.

Perhaps the most clinically consequential finding concerned comorbidities. Respondents with coexisting non-cancer conditions had greater odds of using supplements and over-the-counter products, and 85.3 percent of the cohort reported at least one such condition. This matters because interaction risk grows with the number of concomitant agents, and many supplements are taken chronically without ever being reviewed by a clinician. The authors argue that this makes a strong practical case for including non-prescription products in routine medication histories taken in oncology clinics, where incomplete disclosure remains a well-documented problem.

That disclosure gap is real and quantified. Previous research cited in the paper found that only 42.2 percent of users of complementary and alternative medicine had discussed their use with an oncologist, while a Polish study reported that 46.6 percent of such users had never informed their physician. Clinical practice guidelines, including an integrative review by Balneaves and colleagues, recommend that oncology professionals routinely ask about complementary products, document what patients are taking and assess potential interactions as part of ongoing care. The new Polish data suggest that without proactive questioning, a majority of patients may be carrying a substantial pharmacological load that never appears in their medical record.

The pharmacological concern is not theoretical. Herbs, foods and dietary supplements can alter the metabolism of anticancer drugs through the cytochrome P450 enzyme system, particularly the CYP3A4, CYP2D6, CYP1A2 and CYP2C8 isoforms that handle many targeted and cytotoxic therapies. Interactions involving drug transport proteins have also been documented. On the outcomes side, the evidence base is uncertain but troubling: in the MARIE cohort, concurrent antioxidant supplementation during chemotherapy or radiotherapy was associated with higher all-cause mortality and poorer recurrence-free survival, and an ancillary study within the randomized SWOG S0221 trial found point estimates suggesting higher hazards of recurrence and death among antioxidant users, though the confidence intervals there included unity. These observational findings raise a potential safety concern without establishing causation, but they are enough to warrant caution.

Current survivorship guidance, including the American Cancer Society nutrition and physical activity guideline and the NCCN survivorship guidelines, emphasizes healthy dietary patterns and regular physical activity and does not recommend routine supplement use for most cancer survivors. Supplementation may be appropriate in selected circumstances based on individual nutritional or clinical needs, such as correcting a confirmed deficiency. The authors of the new study outline a pragmatic counselling approach for clinicians: elicit a complete list of supplements and over-the-counter products, including dose and brand where possible; clarify the intended purpose and expected benefit; screen for potential interactions and duplication with prescribed therapy; and advise particular caution with high-dose antioxidant preparations during chemotherapy or radiotherapy unless a clear medical indication exists.

The temporal picture added another layer of interest. Use varied significantly across the six survey waves, peaking in 2021 and reaching its lowest point in 2025, with daily use ranging from 23.6 percent in 2020 to 30.2 percent in 2021 before settling at 26.2 percent in 2025. The study period spanned the COVID-19 pandemic and its aftermath, and the authors suggest that changes in health-related behaviours, healthcare circumstances and the composition of respondents to the voluntary online survey may all have contributed to the between-wave variation. Notably, there was no consistent year-to-year decline, indicating that supplement use among this population is a stable and persistent phenomenon rather than a passing trend.

The study’s limitations deserve honest weight. The survey used quota-based, non-probability sampling of adult internet users, so people with limited digital access, very advanced disease or severe functional impairment are likely underrepresented, and the observed proportions cannot be read as true population prevalence. Cancer history was captured by a single self-report checklist item, with no data on tumour type, stage, time since diagnosis or ongoing treatment. All measures were self-reported, the 12-month recall window was broad, and no information was collected on product composition, dose, duration or who recommended the product. Residual confounding is likely, and the repeated cross-sectional design without individual linkage rules out conclusions about causality or within-person trajectories over time.

Even with those caveats, the message for oncology practice is clear and actionable. Non-prescription products are not a marginal habit among people with a history of cancer; they are a mainstream behaviour, patterned by education, sex, age, stress exposure and comorbidity, and largely invisible to treating physicians. The authors conclude that routinely asking about dietary supplements and over-the-counter products as part of medication review, documenting what patients take, assessing intended purposes and potential interactions, and providing evidence-based counselling where appropriate could close a significant safety gap in cancer follow-up care. For a growing population of survivors, the pills taken at home may matter as much as the drugs prescribed in hospital, and the first step is simply asking about them.

Subject of Research: Dietary supplement and over-the-counter product use among adults with a self-reported history of cancer in Poland

Article Title: Use of dietary supplements and over-the-counter products among adults with a self-reported history of cancer in Poland

Article References: Zimny-Zając, A., Kowalska-Bobko, I., Pacholczak-Madej, R., & Püsküllüoğlu, M. (2026). Use of dietary supplements and over-the-counter products among adults with a self-reported history of cancer in Poland. Supportive Care in Cancer, 34(10), Article 1033. https://doi.org/10.1007/s00520-026-11263-z

Image Credits: AI Generated

DOI: 10.1007/s00520-026-11263-z

Keywords: dietary supplements, over-the-counter products, cancer survivors, cancer survivorship, Poland, medication history, drug interactions, cytochrome P450, multivitamins, complementary and alternative medicine, supportive care, cross-sectional survey