Diet Myths and Cancer: Separating Evidence from Misinformation

For healthcare professionals, addressing diet myths is an important part of cancer prevention as public understanding of nutrition related to cancer risk is often shaped by misinformation, and oversimplified messages (Di Sebastiano et al., 2019). Patients may present with strong beliefs about “anti-cancer foods”, restrictive diets, or fear that specific foods directly cause cancer.

This article explores common diet-related myths surrounding cancer and summarises what the evidence actually shows.

Myth 1: “Certain foods can prevent or cure cancer”

There is no single food or nutrient that can prevent or cure cancer. While dietary patterns influence cancer risk, the evidence does not support claims that specific foods can independently prevent or treat cancer.

Large systematic reviews consistently show that overall dietary patterns, rather than individual foods, are associated with cancer risk (Kamal et al., 2022). There has been no study that has found a specific food causes cancer; however associations have been made. Diets rich in wholegrains, fruit, vegetables and legumes are associated with lower risk for some cancers, but these effects are modest and operate alongside other lifestyle factors.

Clinical implication: Emphasis is needed on improving dietary patterns and sustainability rather than promoting or discouraging specific “superfoods”.

Myth 2: “Sugar feeds cancer and should be completely avoided”

Cancer cells do use glucose for energy, but so do all cells in the body. There is no evidence that dietary sugar selectively fuels cancer growth in humans or that eliminating sugar can treat cancer.

Restricting sugar excessively can lead to unnecessary dietary restriction, weight loss, and poor nutritional status (Cancer Research UK, 2023). The primary concern with high sugar intake relates to excess energy intake, weight gain and obesity, which is an established cancer risk factor, rather than sugar itself (Epner et al., 2022).

Clinical implication: Focus should be on overall diet quality and energy balance, rather than demonising sugar.

Myth 3: “An alkaline diet can prevent cancer”

The idea that cancer thrives in an acidic body environment and can be prevented through an alkaline diet is not supported by scientific evidence. The body tightly regulates blood pH through physiological mechanisms, regardless of dietary intake.

While alkaline diets often encourage higher fruit and vegetable consumption, any potential benefits are due to improved diet quality rather than changes in body pH (Fenton & Huang, 2016).

Clinical implication: Emphasise that dietary patterns rich in plant foods are beneficial, but not because they alter body pH.

Myth 4: “Red meat causes cancer and must be eliminated”

Although evidence has highlighted that high intakes of processed meat, and red meat, have an associated increased risk of colorectal cancer (Farvid et al., 2021), it does not mean that red meat must be completely eliminated.

Cancer risk is influenced but not determined by amount, frequency, and overall dietary context. Processed meat, and red meat have a higher fat compared to lean meat, which can contribute to other non-cancer related health complications like, obesity, and cardiovascular disease (Zhang et al., 2023). Public health guidance recommends limiting red meat intake and minimising processed meat consumption, rather than complete avoidance (World Cancer Research Fund, 2018).

Clinical implication: Support moderation and balance, avoiding overly restrictive or fear-based messaging.

Myth 5: “Certain supplements cause cancer”

Dietary supplements are often perceived as either protective against cancer or harmful. In reality, the relationship between supplements and cancer risk is complex.

Current evidence does not support the routine use of dietary supplements for cancer prevention in the general population (World Cancer Research Fund, 2018). For most individuals, nutritional needs can be met through a balanced diet. High-dose supplementation may pose risks in certain contexts, while offering no clear benefit for improved health, and cancer prevention. Reliance on supplements may detract from addressing broader lifestyle behaviours that have a far greater impact on cancer risk. Evidence consistently shows that combined healthy behaviours like eating a balanced diet, regular physical activity, maintaining a healthy weight, avoiding smoking and limiting alcohol intake, are associated with substantially lower cancer risk (Khaw et al., 2008).

Clinical implication: Supplements should not be promoted as cancer prevention tools, and dietary advice should prioritise overall lifestyle patterns.

Why diet myths persist

Diet myths often persist because they offer simple explanations for complex diseases, providing a sense of control during periods of uncertainty. Misinformation is frequently amplified through social media and commercial interests, allowing unsubstantiated claims to reach large audiences.

Healthcare professionals therefore play a critical role in countering misinformation by providing clear, consistent and evidence-based guidance (Di Sebastiano et al., 2019).

Key messages

• No single food, nutrient or diet can prevent or cure cancer;
• Cancer risk is influenced by overall dietary patterns and lifestyle behaviours;
• Restrictive or fear-based dietary advice may cause harm;
• Healthcare professionals are well placed to challenge misinformation with evidence-based guidance

References

Cancer Research UK. (2023). Sugar and cancer. https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/diet-and-cancer/sugar-and-cancer

Di Sebastiano, K. M., Murthy, G., Campbell, K. L., Desroches, S., & Murphy, R. A. (2019). Nutrition and cancer prevention: Why is the evidence lost in translation? Advances in Nutrition, 10(3), 410–418.

Epner, M., Yang, P., Wagner, R. W., & Cohen, L. (2022). Understanding the link between sugar and cancer: An examination of the preclinical and clinical evidence. Cancers, 14(24), 6042.

Farvid, M. S., Sidahmed, E., Spence, N. D., Mante Angua, K., Rosner, B. A., & Barnett, J. B. (2021). Consumption of red meat and processed meat and cancer incidence: A systematic review and meta-analysis of prospective studies. European Journal of Epidemiology, 36(9), 937–951. https://doi.org/10.1007/s10654-021-00741-9

Fenton, T. R., & Huang, T. (2016). Systematic review of the association between dietary acid load, alkaline water and cancer. BMJ Open, 6(6), e010438. https://doi.org/10.1136/bmjopen-2015-010438

Kamal, N., Ilowefah, M. A., Hilles, A. R., Anua, N. A., Awin, T., Alshwyeh, H. A., Aldosary, S. K., Jambocus, N. G. S., Alosaimi, A. A., & Rahman, A. (2022). Genesis and mechanism of some cancer types and an overview on the role of diet and nutrition in cancer prevention. Molecules, 27(6), 1794.

Khaw, K. T., Wareham, N., Bingham, S., Welch, A., Luben, R., & Day, N. (2008). Combined impact of health behaviours and mortality in men and women: The EPIC-Norfolk prospective population study. PLOS Medicine, 5(1), e12. https://doi.org/10.1371/journal.pmed.0050012

World Cancer Research Fund. (2018). Diet, nutrition, physical activity and cancer: A global perspective. Continuous Update Project Expert Report. https://www.wcrf.org/dietandcancer

Zhang, X., Liang, S., Chen, X., Yang, J., Zhou, Y., Du, L., & Li, K. (2023). Red/processed meat consumption and non-cancer-related outcomes in humans: Umbrella review. British Journal of Nutrition, 130(3), 484–494.