What are alternative therapies?

Alternative therapies, also known as alternative medicine,  are different from complementary therapies. They are used instead of cancer treatments. They may claim to actively treat or even cure cancer. But there is no scientific proof to support these claims.

False claims about alternative therapies have sometimes led people to refuse cancer treatments that could have helped.

No alternative therapies have ever been proven to cure cancer or slow its growth.

Why do people consider alternative therapies?

Some people try alternative therapies because they feel that cancer treatments cannot help them, or could be harmful.

The idea of having cancer treatments and unpleasant side effects can be frightening. However, many people with an early-stage cancer can be cured by cancer treatments.

If you have been told by your doctors that the cannot be cured, you may find it hard to accept. Some people in this situation think about using an alternative therapy. However, if a cancer cannot be cured by cancer treatment, it will not be cured with an alternative therapy. Using some alternative therapies may not do any harm, but others could be very harmful.

Even when a cancer is advanced, cancer treatments can help control it and help people live longer, often for many years.

Find information about making treatment decisions

Why can alternative therapies sound convincing?

  • Misleading advertising

    Alternative therapies are sometimes very cleverly marketed. This means that when you read about them or are told about them, they sound very effective.  

    Therapists may use scientific language to make their claims sound more convincing. But many are based on unproven or disproven theories of how cancer develops or stays in the body.

  • Unreliable evidence

    Claims about an alternative therapy may be based on the results of tests that were done on cancer cells in a laboratory. But the human body is much more complicated than the controlled conditions of cells in a laboratory. 

    Most treatments that seem to work when tested in the laboratory do not work when used for people with cancer. This is why it takes so long to develop new cancer treatments.

  • Individual stories

    Many alternative therapies rely on individual stories or testimonials as evidence that they work. This is the least reliable type of evidence. 

    This is because there is no way of checking whether the effect someone has described is because of the alternative therapy or something else. It is also not usually possible to check whether the person’s story is reliable, or even that they existed or had cancer.

Getting a second opinion

If your doctor tells you that further treatment will not help control the cancer, you may find it very hard to accept. This is understandable. In this situation, you might find it helpful to get a second medical opinion.

The second doctor may be able to offer you another type of cancer treatment. Or they may confirm what you have already been told.

This may help you to accept that your doctors have tried everything. If you still want to have treatment, you could ask if there are any cancer research trials that might be suitable for you.

Getting advice and support before using an alternative therapy

If you are considering using alternative therapies, talk to your cancer doctor for advice and support. Doctors are generally supportive of people using any complementary therapies that may help them cope better with their illness. But they usually advise against using alternative therapies.

If you decide to use an alternative therapy, it is important to check it is safe. Always check the credentials of the therapist. Alternative therapies can be expensive, and some can cause serious side effects. They can also make you feel unwell and be harmful to your health.

Types of alternative therapy

There are many types of alternative therapy. In this information we explain the alternative therapies that are most well-known to people with cancer. These include:

  • amygdalin (Laetrile®, Vitamin B17)
  • Essiac® (Vitaltea®, Flor-essence®)
  • cannabis oil or CBD oil
  • metabolic therapy
  • diets that claim to treat cancer
  • megavitamin therapy.

If you would like to talk to someone about alternative therapies, you can call the Macmillan Support Line on 0808 808 00 00. They are available to speak to 7 days a week, 8am-8pm.

You can also chat online to a Cancer Information Nurse Specialist.

Amygdalin (Laetrile®, vitamin B17)

Amygdalin is a compound found in bitter almonds, peach stones and apricot stones. When amygdalin is processed by the body, it changes to cyanide. Cyanide is a type of poison.

A man-made form of amygdalin is called Laetrile®. Some suppliers call it vitamin B17. But it is not actually a vitamin.

Why some people use laetrile

Many websites that sell Laetrile claim it can slow or stop the growth of cancer. They also claim it can poison cancer cells, without damaging normal cells and tissues. But there is no medical evidence to support this. There has been a review of studies that were looking at the outcomes for people with cancer taking Laetrile. The review found no evidence to show that it can control or cure cancer.

Possible side effects of laetrile

Laetrile can have serious side effects. Some people have had cyanide poisoning while taking it, and a few people have died as a result. The sale of Laetrile has been banned by the European Commission and by the Food and Drugs Administration (FDA) in the USA. Unlike conventional medicines, the manufacture of Laetrile is not controlled. So if you buy Laetrile, there is no way of knowing what it contains or if it is contaminated with other substances.

If you are thinking about taking Laetrile, it is best to discuss this with your cancer doctor.

Essiac® (Vitaltea®, Flor-essence®)

Essiac comes as a drink and is sold as a nutritional supplement.

It is important not to take Essiac during cancer treatment, or with any other medicines, without checking with your cancer doctor first.

Why some people use Essiac

Some websites claim Essiac can slow down the growth of cancer, or even cure it. But there is no medical evidence to show that taking Essiac helps treat cancer or improves your quality of life.

Possible side effects of Essiac

Essiac affects an enzyme in the body that regulates hormones and vitamin D. It also affects how the body deals with toxins. This means that taking Essiac with other cancer treatments could make them less effective or increase side effects.

Cannabis oil and CBD oil

Cannabis is made up of substances called cannabinoids. Two of the main cannabinoids are:

  • THC (delta-9-tetrahydrocannabidiol) – it is illegal to use this in the UK
  • CBD (cannabidiol) – it is legal to use this in the UK.

Many types of cannabis oil are sold online. CBD oil is also sold in some shops, such as health food shops.

Cannabis oil can contain different amounts of THC and CBD.

There is no reliable, medical evidence to show whether cannabis in any form can effectively and safely treat cancer in humans.


If you are thinking about using cannabis oil or CBD oil, there are some important things to consider:

  • THC and products that contain THC are illegal in the UK.
  • THC in cannabis oil can cause side effects, such as an increased heart rate, dizziness, hallucinations, paranoia and feeling stoned.
  • CBD and THC can affect how some medicines work.

Metabolic therapy

Metabolic treatments vary from one therapist to another. One of the most well-known therapies is called Gerson therapy. This may include:

  • a diet of raw fruit and vegetables
  • a diet with no processed foods or salt
  • taking vitamin and mineral supplements
  • taking enzymes or chemical supplementss
  • having coffee enemas.

These are said to flush toxins out of the body. But there is no medical evidence to show that they help treat cancer.

If you have any questions about alternative diets or are thinking of following one, get advice from your cancer doctor, specialist nurse or dietitian.

Why some people use metabolic therapies

Metabolic therapists think cancer is caused by a build-up of toxic substances in the body. They claim they can treat it by removing toxins and strengthening the immune system.

One study compared the effects of using a metabolic therapy with the effects of chemotherapy. The metabolic therapy included enzymes, nutritional supplements, detoxification and organic foods. The study found that the patients who had the chemotherapy lived three times longer and had a better quality of life than those who had metabolic therapy.

Possible side effects of metabolic therapy

Possible side effects of metabolic or Gerson therapy include nausea, vomiting, stomach cramps, a high temperature and headaches. The high levels of hormones and extracts used can sometimes make people feel unwell. The risks of using coffee enemas include infections and serious damage to the large bowel.

Diets that claim to treat cancer

There are a number of diets, in addition to the Gerson diet , that claim to treat cancer.

It is understandable that some people are attracted to diets that seem to offer hope. But there is no medical evidence to show that these diets can cure cancer, or help people with advanced cancer live longer.

Talk to your cancer doctor, specialist nurse or dietitian before cutting out any food group from your diet.

Why some people use diets to treat cancer

Some diets claim to remove toxins from the body. Many of these diets are vegetarian or vegan. They involve eating food that is raw, sugar-free and low in salt. Sometimes vegetable or fruit juices, and high doses of vitamins, minerals or enzymes are used. Other diets are based on claims that some foods feed cancer, or affect the pH levels (acidity) of the body.

Possible side effects of diets that claim to treat cancer

If you choose to follow a diet that cuts out some food types, it is important to make sure you are not missing out on important nutrients. For example, if you follow a dairy-free diet it is important to replace the calcium that you would usually get from dairy products, with other calcium-rich foods.

Diets that are high in fibre and low in calories and protein, are not suitable if you have problems maintaining your weight because of cancer or its treatment. If you are underweight, you need protein and calories from any source of food.

Megavitamin therapy

This type of alternative therapy involves taking very large doses of vitamins as a way of preventing and treating cancer. However, there is no evidence that taking large doses of vitamins is helpful in treating cancer. Some vitamins can be harmful in high doses.

It is important to tell your cancer doctor before having high doses of vitamin C during, or within a few weeks of, cancer treatment.

Possible side effects of megavitamin therapy

High-dose vitamin C is one of the most common types of megavitamin therapy. High-dose vitamin C can make many cancer treatments less effective. This includes:

  • cisplatin
  • doxorubicin
  • imatinib
  • and vincristine.

It may also affect how radiotherapy works. High-dose vitamin C may also interact with some complementary and alternative therapies.

High-dose vitamin C is not suitable for people who have:

  • kidney problems
  • a condition that causes iron overload (haemachromatosis)
  • a G6PDH deficiency.

About our information

  • References

    Below is a sample of the sources used in our complementary therapies information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    Cassilieth B. The Complete Guide to Complementary Therapies in Cancer Care: Essential Information for Patients Survivors and Health Professionals. 2011. 

    Ernst E, et al. Oxford Handbook of Complementary Medicine. 2008. 

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Dr Saul Berkovitz.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Information about coronavirus

We understand that people are worried about coronavirus (COVID-19). You may have questions about the different vaccines, or you may be worried about how the pandemic will affect your cancer treatment. We have detailed information about coronavirus and cancer treatment here.

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We know cancer throws a lot your way, and right now, the coronavirus pandemic is making it even tougher. If you're worried about something, and you need to talk to someone, whatever is on your mind, we're here to listen.

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Date reviewed

Reviewed: 31 October 2019
Next review: 31 October 2022

This content is currently being reviewed. New information will be coming soon.

Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

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