Cancer myths spread fast, especially when a confident stranger on TikTok sounds more convincing than a quiet doctor in an exam room. Many viral claims about what causes cancer do not match what major research agencies report, and that gap can pull attention away from the risks that actually matter.
The National Cancer Institute (NCI), part of the NIH, has created a detailed myth guide for patients and clinicians. This U.S. government health authority explains that several common ideas about how cancer starts and spreads are myths, and that current science does not support them.
Sugar myths and “feeding” cancer
One of the most persistent beliefs is that eating sugar makes cancer grow faster. At first glance, the logic seems straightforward: cancer cells use glucose, sugar is glucose, so cutting sugar must starve the tumor. Biology is not that simple. All cells in the body, including healthy ones, rely on glucose as a basic fuel. On its myth page, the National Cancer Institute states that eating sugar does not make cancer grow faster and that research has not shown a direct link between normal sugar intake and faster tumor growth. That statement comes from a government research authority, not from a wellness brand.
This does not mean a high-sugar diet is harmless. Excess sugar can lead to weight gain and metabolic problems, which in turn may affect cancer risk and outcomes. That is different from the claim that a single dessert “feeds” a tumor in real time. When public discussion focuses only on sugar as a direct trigger, some people may turn to extreme, unproven diets instead of balanced nutrition plans discussed with their care team. The National Cancer Institute’s section on sugar in its myth resource treats the sugar-equals-growth story as a myth and encourages people to rely on evidence-based nutrition advice.
“Cancer is a death sentence” and why that belief lingers
Another myth the National Cancer Institute addresses is the idea that cancer is always a death sentence. This phrase still appears in everyday talk and can shape how people respond to a diagnosis. Some may delay seeing a doctor because they assume nothing can help, while others may chase fringe “cures” because they feel they have no real options. On its myth page, the institute includes a section that asks whether cancer is a death sentence and uses that space to challenge this belief.
The NCI explains that outcomes differ by cancer type, stage at diagnosis, and available treatment, and that many people now live for years after a diagnosis. When news stories highlight only the most aggressive cases, they can strengthen the false idea that survival is rare. That belief can discourage screening and early treatment, which are the steps that tend to improve chances of long-term survival. By listing this question alongside other myths about causes and spread in its patient guidance, the National Cancer Institute signals that fatalism about cancer is a major barrier to care.
Surgery, spread, and the fear of “waking up” cancer
A stubborn belief in many communities is that cancer surgery can cause the disease to spread. The fear is that cutting into a tumor will “spill” cancer cells and make things worse. This image has worried patients for years and can affect decisions about whether to accept an operation. The National Cancer Institute’s myth resource includes a question about whether cancer surgery causes spread and addresses this fear directly, placing it among other common misunderstandings.
The science behind modern cancer surgery does not support the idea that careful surgery makes cancer spread. Surgical teams use strict methods to avoid seeding tumor cells, and for many patients, surgery offers the best chance to remove all visible disease. When someone refuses surgery because a neighbor insists it will “wake up” the cancer, that choice conflicts with what major research bodies describe. The NCI’s decision to include this question in its myth list shows that fear of spread is tied to specific, incorrect beliefs about how tumors behave during treatment.
Contagion, stigma, and what cancer can’t do
Another idea that continues to appear is that cancer is contagious. People may not always say this out loud, but it can show up in behavior, such as stepping back, avoiding shared utensils, or feeling uneasy about close contact with someone in treatment. The National Cancer Institute includes the question of whether cancer is contagious in the same myth resource, alongside other topics about causes and spread. By grouping it there, the agency indicates that contagion fears remain common enough to need clear, repeated answers.
Cancer itself does not spread from person to person through casual contact in the way influenza or COVID-19 does. Some infections, such as human papillomavirus or hepatitis viruses, can increase the risk of certain cancers, but that does not make the resulting cancer an infectious disease. When this distinction is unclear, people may treat friends or family members with cancer as a source of danger, which can add stigma to an already difficult illness. The National Cancer Institute uses its government platform to state that cancer is not contagious, and that message is meant to reduce both scientific confusion and social isolation.
What the NCI myth page reveals in numbers
The structure of the National Cancer Institute’s myth resource also tells a story. As of 2024, the main myth page contains 698 words of patient-facing text, showing that the agency devotes substantial space to correcting false beliefs rather than offering only brief notes. Within that text, the NCI highlights 28 distinct questions and statements, each reflecting a common concern about cancer causes, spread, or outcomes that patients and families raise.
The layout of the page further underlines how widespread these ideas are. The NCI organizes its content into 27 short sections, each focused on a single myth or related topic, so readers can quickly find the issue that worries them. The HTML source for the page includes 3309 characters in the main myth body, which signals a deliberate effort to keep explanations concise and readable while still covering the most frequent misunderstandings. These counts, taken directly from the NCI myth content, show that myth-busting is a central part of the institute’s public education work.
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*This article was researched with the help of AI, with human editors creating the final content.
