Cancer prevention and treatment, ranked by how well it's proven.
Every option here, from broccoli to radioligand therapy, sits on an evidence rung from 5 (established in large trials and guidelines) down to 1 (lab-only or untested). Every rating links to its sources.
Reviewed 31 October 2026 · Options graded and Foods rated rated · How we score
The evidence ladder
Choose a rung to see what sits on it. Ideas that were tested and failed aren't on the ladder; they're under What to avoid.
Lowering your risk: six steps with the strongest evidence
The highest-graded steps you can take. They lower risk across many cancers at once, and most also help people already living with cancer. Open any card for the evidence and sources.
Every rating answers two questions
What did the studies find, and how sure is the science? The two are separate. Something can sit on rung 5 because we're certain of a small effect, or on rung 3 because the reassurance is solid but not final.
- Verdict
- What the studies found: lowers risk, raises risk, no link found, and so on.
- Rung 1 to 5
- How strong the human evidence is, from 1 (unproven) to 5 (established). Never how big the effect is.
Go deeper by topic
Eating to lower cancer risk
The strongest diet evidence is about overall patterns, not single superfoods. Four rules cover most of it; the food finder below rates individual foods.
Fill up on plants
Colorful vegetables and fruit, whole grains and beans. Together they probably lower risk of colorectal, mouth, throat and esophageal cancers.
Limit red and processed meat
Processed meat is a known cause of colorectal cancer, rising about 16% per 50 g a day. Red meat probably raises risk too.
Drink less alcohol
Linked to seven cancers. The American Cancer Society says not drinking is best.
Cut sugary drinks and highly processed food
The American Cancer Society advises limiting them, along with refined grains, mainly because of their link to weight gain.
Build your plate
- Half: vegetables and fruitGreens, crucifers, tomatoes, berries
- A quarter: whole grainsOats, barley, brown rice
- A quarter: plant or fish proteinBeans, lentils, tofu, oily fish
- Alongside: water, coffee or teaLet hot drinks cool first
- LimitProcessed and red meat, alcohol, sugary drinks
Food finder
Exercise and cancer: how much movement, and what it does
Exercise is one of the few self-care steps with randomized-trial proof in people who already have cancer. The targets below come from the American Cancer Society's prevention guideline and the 2019 international guideline for cancer survivors.
Check your week
Example week filled in. Change the numbers to your own; vigorous minutes count double.
What exercise is proven to do
| Goal | Evidence | What the studies found | What to do |
|---|
Cancer myths: what raises risk at home and work, and what doesn't
Claims about phones, deodorant, sugar and the like spread fast. Each one here gets a verdict on what the human evidence shows, plus an evidence rung from 1 to 5 for how sure that verdict is. They're the same rungs used everywhere on the site.
For hundreds more everyday claims, Harvard's Cancer FactFinder is an excellent companion resource.
Living with cancer: what the evidence supports
If you or someone close to you has been diagnosed, these are the steps and supports with the strongest human evidence. Use them to plan with your care team, not in place of it.
Standard treatment comes first
The surgery, radiation and drug treatments your oncology team recommends are the ones proven in large trials. Using an alternative remedy instead is a documented harm: people with curable cancers who used alternative medicine alone were far more likely to die within five years.
Know exactly what you have
Ask for the cancer's exact type and stage, and whether tumor biomarker testing should be part of your care. It looks for genes and proteins in the cancer that show which targeted drugs or immunotherapy may work, and which won't. It is routine for some cancers, including non-small cell lung, breast and colorectal cancer, and is usually suggested when cancer has spread or come back.
A second opinion is your right
It's worth considering if the cancer is rare, test results are unclear, doctors recommend different treatments, or you're unsure between options. Doctors are usually glad to help arrange one, you can get one after treatment has started, and you still choose who treats you.
Ask whether a clinical trial fits you
Trials are how today's standard treatments were proven, and some give access to newer ones. Ask your oncologist whether one suits your situation. The National Cancer Institute's information service (1-800-4-CANCER) can search for trials with you for free, or you can use its trial search.
Support during and after treatment, by evidence
Options for side effects, fitness and wellbeing, grouped by how strong the evidence is. Open any one for what the studies found and the catch. Check each with your care team, since some interact with treatment.
Tell your team about every supplement
- Antioxidant pills during chemotherapyIn a breast cancer chemotherapy trial, taking vitamins A, C or E, carotenoids or CoQ10 before and during treatment was linked to about 41% higher recurrence risk (borderline significance).
- St. John's wortCut levels of the active form of the chemotherapy drug irinotecan by 42% in a small study. It can make some cancer drugs work less well.
- Herbs and "natural" productsSome damage the liver or interact with treatment. See What to avoid for the full list.
Questions to bring to your care team
- What are my options for this type and stage, and which do you recommend for me and why?
- What are the benefits and risks of each, and how will we know the treatment is working?
- Should my tumor have biomarker testing?
- Is there a clinical trial that fits me?
- Which side effects should I call you about right away, and could any last?
- Could treatment affect my ability to have children?
- Can you help me get a second opinion?
- Here is every medicine and supplement I take. Could any of them interfere?
By type of cancer
The prostate cancer pathway, step by step
Prostate cancer is common and usually slow, so the biggest decisions are about finding the cancers that matter and not over-treating the ones that don't.
Decide about PSA testing, ideally in your mid-to-late 40s
The longest-running screening trial shows a lasting drop in prostate cancer deaths with regular PSA testing, along with real overdiagnosis. U.S. Task Force guidance (2018, under revision) calls screening an individual decision from 55 to 69 and advises against routine screening at 70 and older. The American Urological Association's 2026 guideline says doctors may offer a baseline PSA between 45 and 50. Men with a family history and Black men face higher risk and have more reason to start the conversation early.
If PSA is high, confirm before a biopsy
The 2026 AUA guideline advises repeating a newly raised PSA before further markers, imaging or biopsy. MRI before biopsy helps reduce detection of harmless cancers. Ask whether an MRI or a secondary blood or urine test fits your situation.
Low-risk cancer: active surveillance is a proven choice
In the ProtecT trial, men with PSA-detected localized prostate cancer were randomly assigned to monitoring, surgery or radiation. At 15 years about 97% in every group had not died of prostate cancer. Monitoring led to more progression, but not more deaths, and a quarter of monitored men never needed treatment. Today's MRI-based surveillance is more precise than the version tested.
While on surveillance: what men can do themselves
None of these has yet been shown to change survival in a large trial, but each is low-risk and several show measurable effects on the cancer's biology. In rough order of evidence: keep a healthy weight (strongly linked to advanced prostate cancer), exercise hard and regularly (lowered PSA and PSA velocity in a randomized trial), eat mostly plants (linked to 47% less progression in a large cohort), favor cooked tomatoes and unfermented soy, and ask your urologist before trying a high-omega-3, low-omega-6 diet with fish oil (lowered a tumor growth marker in a small trial).
Skip high-dose vitamin E and selenium pills: no benefit, and vitamin E raised risk. Watch dairy and calcium: the World Cancer Research Fund rates evidence of higher prostate risk as limited.
Higher-risk or advanced disease: ask about genetics and PSMA
Standard care is surgery or radiation, often with hormone therapy, and for advanced disease newer hormone drugs and chemotherapy. Three 2025–26 FDA approvals reward testing the tumor: the PSMA-targeted radioligand Pluvicto now covers metastatic hormone-sensitive as well as castration-resistant disease, capivasertib is approved for PTEN-deficient metastatic cancer, and talazoparib with enzalutamide is approved for HRR-mutated metastatic cancer that still responds to hormone therapy. Ask for a PSMA PET scan and tumor plus inherited genetic testing.
Every cancer prevention, treatment and support option we rated
Filter by what you need, then open any option for what the studies found, the catch, what to do, and the sources.
Ayurveda and cancer: traditional remedies, held to the same standard
We graded Ayurvedic herbs and practices exactly like everything else. Some have modest human evidence for easing treatment side effects or improving quality of life. None has been shown in human trials to treat or prevent cancer, and product quality is a real safety issue. Many other herbs, such as Sanjeevani and mangosteen, have only lab and animal results so far.
Buying Ayurvedic products safely
When researchers bought 193 Ayurvedic medicines online, about one in five contained lead, mercury or arsenic, and every one of those exceeded at least one daily safety limit. U.S.-made products were as likely to be contaminated as Indian-made ones. Rasa shastra formulas, which add metals on purpose, were more than twice as likely to contain them.
The risk shows up in people too: in a 2015 U.S. study of 115 people using Ayurvedic products, 40% had raised blood lead levels.
No U.S. state licenses Ayurvedic practitioners. In the UK, Cancer Research UK suggests choosing products registered under the Traditional Herbal Registration scheme.
Before taking any herb during treatment, tell your oncology team. Herbs can interact with chemotherapy, hormone therapy and surgery.
Prefer single-herb products with independent third-party testing. Avoid metal- or mineral-based formulas entirely, and products such as Carctol that claim to cure cancer.
Skip panchakarma cleansing during treatment. Its purging, enemas and bloodletting can cause infection and mineral imbalances, especially with low blood counts.
Yoga and meditation, from the same tradition, have better support for symptom relief than the herbs do.
What to avoid: proven to backfire, or tested and didn't hold up
Kept out of the rankings. First, things with evidence of harm. Below them, popular ideas that were put to a fair test and failed.
Evidence of harm
- Replacing standard treatment with alternative medicinePatients with curable cancers who chose alternative medicine alone had 2.5 times the risk of death within five years; more than 5 times for breast cancer and 4 times for colorectal cancer.
- High-dose vitamin E (400 IU a day)Raised prostate cancer risk by 17% in the 35,000-man SELECT trial.
- Beta-carotene pills for smokersTwo large trials (ATBC and CARET) found more lung cancer, not less, in smokers taking beta-carotene supplements. Food sources are fine.
- Apricot seeds, laetrile or amygdalinRelease cyanide in the body. A Cochrane review found no reliable evidence of benefit and called the balance of risk clearly negative.
- Metal-containing Ayurvedic formulasSome contained lead or mercury at levels 100 to 10,000 times acceptable limits.
- Ashwagandha with existing liver diseaseCase series describe herb-induced liver injury; three patients with prior liver disease died of liver failure.
- Giloy (Tinospora) with liver diseaseLinked to liver injury in 43 people at 13 Indian hospitals; four with existing liver disease died.
- Antioxidant pills during chemotherapyIn 1,134 women in a breast cancer chemotherapy trial, taking vitamins A, C or E, carotenoids or CoQ10 both before and during treatment was linked to about 41% higher recurrence risk (borderline significance). Iron and B12 were also linked to worse outcomes; multivitamins were not.
- Graviola (soursop) capsules, extracts and daily leaf teaNever tested against cancer in people. In Guadeloupe, heavy use of the fruit and leaf tea was linked to an unusual Parkinson's-like illness, and lab studies show its compounds can damage nerve cells. The occasional fruit is unlikely to cause harm.
- St. John's wort during cancer treatmentIn a small crossover study it cut levels of the active form of the chemotherapy drug irinotecan by 42%. The National Cancer Institute warns it can make some cancer drugs work less well.
- Black salve and other corrosive skin pastesSold to "draw out" skin cancer, these bloodroot and zinc chloride pastes destroy healthy tissue, leave scars and can leave cancer behind.
- Gerson therapy and coffee enemasReviews found no anticancer effect. Repeated coffee enemas have caused deaths from fluid and mineral imbalance, and serious infections.
- Panchakarma purging and bloodletting during treatmentAyurvedic enemas, laxatives and induced vomiting can cause infection and dangerous mineral imbalances, and bloodletting is risky when blood counts are low.
Tested, didn't hold up
- Pomegranate extract for rising PSAA large placebo-controlled trial found no difference in PSA doubling time, because PSA slowed in the placebo group too.
- Selenium pills to prevent prostate cancerNo benefit in SELECT.
- Green tea extract (EGCG pills) for men at high riskA one-year randomized trial did not significantly reduce prostate cancer diagnoses. Drinking green tea is fine.
- Metformin added to hormone therapy in non-diabetic menNo overall survival benefit in the STAMPEDE trial of about 1,900 men, though it eased metabolic side effects.
- Extra vegetables alone to slow early prostate cancerThe MEAL trial raised intake to 7 or more servings a day for two years; progression was unchanged.
- Large monthly or yearly vitamin D dosesInfrequent big doses did not lower cancer deaths in pooled trials; daily dosing did.
How we rate the evidence: what each rung means
Every rating on Rung Five answers one question: how strong is the human evidence? The answer is a rung from 1 to 5, and rung five is the strongest. It reflects the quality of the studies, not how popular, natural or expensive something is, and the same substance can sit on different rungs for different uses. Rungs measure certainty only, so there are no negative rungs. Whether something helps or harms is shown separately, as a verdict.
| Rung | Name | What it takes | How to read it |
|---|
Reading ratings on foods, myths and exposures
Treatments and habits elsewhere on the site are all things that might help, so a rung is all they need. Foods and everyday exposures can lower risk, raise it or make no difference, so each one gets two separate labels.
1Verdict
What the studies found: lowers risk, raises risk, no link, and so on. It's written in words, with green for lower risk and red for higher.
2Evidence rung
How sure we can be of that verdict, on the same 1 to 5 scale in the table above. On foods and exposures it's shown in grey, so color only ever means direction.
Three examples
Every verdict we use
Where the evidence comes from
Clear answers about cancer, held to one honest standard
Anyone facing cancer, or hoping to prevent it, meets a flood of advice: miracle foods, frightening headlines, supplements that promise too much. Rung Five sorts it by a single question: how strong is the human evidence?
Rung Five began close to home, with someone we love who is living with cancer and wanted to help other people find what's real. It's a free public resource, built and kept up by volunteers.
The name comes from our five-rung evidence ladder. Rung five is reserved for what large trials and major guidelines have settled. Everything below it is rated honestly, including ideas that are promising but unproven, and the popular ones that didn't hold up.
What we stand for
How Rung Five is made
Rung Five is an independent, volunteer-run project. It isn't a medical organization, and its ratings aren't reviewed by a doctor. Each rating summarizes published research, drawing on guidelines and reviews from bodies such as the World Cancer Research Fund, the National Cancer Institute, the American Cancer Society and Cochrane, along with individual trials. Every rating links to the studies behind it.
Ratings are our editorial judgments of that research, made with care, and research moves on. The date each page was last reviewed is shown at the bottom of the page. See how we score, or browse every source.
Rung Five is educational information, not medical advice. Please talk with your own doctor or care team before changing treatment, starting a supplement or deciding about screening.
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