Many people with cancer consider vitamins, herbal products, traditional Chinese medicine (TCM), acupuncture, massage, or other complementary therapies. Some may help with symptoms or well-being. Others have little evidence of benefit, may interact with cancer medicines, or may even cause harm.
The most important rule is simple: tell your cancer doctor about anything you are taking or planning to use during cancer treatment.
Getting vitamins from a healthy, balanced diet is very different from taking high-dose supplements. Vitamins may be appropriate when you have a deficiency or another medical reason, but unnecessary high-dose supplements should generally be avoided during cancer treatment.
Vitamin D3 is important for healthy bones, muscles, and the immune system. There is also considerable interest in its possible role in cancer. Some studies have found that people with higher vitamin D levels have a lower risk of certain cancers, particularly colorectal cancer. However, this does not prove that vitamin D prevents cancer. Large clinical trials have generally not shown that vitamin D supplements reduce the overall risk of developing cancer. There are some encouraging findings that vitamin D3 may reduce the risk of dying from cancer or developing advanced cancer in certain groups.
If you are vitamin D deficient, your doctor may recommend Vitamin D3 to correct the deficiency. Taking extra Vitamin D3 simply to treat or prevent cancer has not been proven to work. Very high doses can also be harmful.
Normal vitamin C from food or ordinary supplements is very different from high-dose intravenous (IV) vitamin C, which has been studied as a cancer treatment.
Laboratory studies and some early clinical studies have produced interesting results. A 2024 randomized study in metastatic pancreatic cancer reported longer survival when IV vitamin C was added to chemotherapy. However, other studies have not found a benefit; a 2024 study in metastatic prostate cancer found that adding IV vitamin C to chemotherapy did not improve outcomes. Therefore, high-dose IV vitamin C is promising but remains experimental. It is not an established cancer treatment and should not replace proven treatment. It can also be unsuitable for people with certain kidney problems, G6PD deficiency, or other medical conditions, and may interact with some cancer medicines.
Vitamin E is an important nutrient found naturally in foods such as nuts, seeds and vegetable oils. However, high-dose vitamin E supplements have not been shown to prevent cancer. Indeed, there was a large clinical study, involving more than 35,000 men, which found that those taking 400 IU of vitamin E daily had a 17% higher risk of prostate cancer than those taking placebo. This was unexpected because earlier studies had suggested that vitamin E might protect against prostate cancer. The reason for the increased risk remains unclear.
This does not mean that vitamin E in normal foods is harmful. The lesson is that high-dose vitamin supplements should not automatically be assumed to be beneficial.
Despite its name, Vitamin B17 is not a recognised vitamin. The term is commonly used for amygdalin or laetrile, compounds found in apricot and other fruit pits. “Vitamin B17” has been promoted as a natural cancer treatment, based partly on the theory that it can release cyanide and selectively kill cancer cells. However, this has not been shown to work in people. A major clinical study published in 1982 treated 178 patients with cancer with amygdalin (Laetrile) together with a programme of diet, enzymes and vitamins. The study found no meaningful benefit in cancer shrinkage or stabilisation, cancer-related symptoms, or survival. Several patients also developed signs of cyanide toxicity, with some having blood cyanide levels approaching the lethal range. A later systematic review likewise found no sound clinical evidence that amygdalin or laetrile benefits cancer patients and concluded that the risk of cyanide poisoning makes the risk–benefit balance unfavourable.
Turmeric used in normal cooking is different from concentrated turmeric or curcumin supplements. There is not enough evidence to recommend curcumin supplements as a cancer treatment. Concentrated products may interact with medicines and may increase the risk of bleeding.
If you are considering turmeric or curcumin supplements during cancer treatment, discuss them with your cancer doctor first.
TCM includes Chinese herbal medicine, acupuncture, Tui Na and cupping. These should not all be considered the same because their potential benefits and risks are different.
Studies are looking at Chinese herbal medicine alongside chemotherapy. Some have reported better control of chemotherapy side effects, improved quality of life and, in some cases, better tumour response or survival. However, different studies use different herbal preparations, and the quality of the evidence varies. Herbal medicines can also interact with cancer medicines. More high-quality research is needed before we can say that Chinese herbal medicine improves survival or should become standard cancer treatment.
If you use Chinese herbal medicine, tell both your cancer doctor and your TCM practitioner, and bring the product packaging or a photograph of the ingredients and doses.
Acupuncture may help with some cancer-related symptoms, including chemotherapy-related nausea and vomiting, and some types of pain or fatigue.
Extra care is needed if you have low blood counts, an increased risk of bleeding or infection, skin problems, lymphoedema, or have recently had surgery or radiotherapy. Use a properly trained practitioner experienced in treating people with cancer, with sterile, single-use needles.
Gentle massage may help relaxation and muscle tension. Avoid deep or forceful massage if you have weakened bones, low platelets, a blood clot, lymphoedema, recent surgery, a medical device, or areas affected by cancer or radiotherapy.
Cupping can cause bruising and skin injury. Wet cupping, which breaks the skin, also increases the risk of bleeding and infection. Extra caution is needed if your blood counts are low, you take blood-thinning medicines, or your skin is fragile or damaged.
Ivermectin is a medicine used to treat certain parasitic infections. It is not a vitamin, supplement, or approved cancer treatment. Interest in ivermectin comes partly from laboratory and animal studies suggesting that it may affect cancer cells and the immune system. These findings are interesting, but results in the laboratory or animals do not mean that the treatment works in people. Early clinical research is continuing, but there is currently no reliable evidence that ivermectin can shrink cancers, prolong survival, or make standard cancer treatment work better. Ivermectin can also cause side effects, serious toxicity when used incorrectly or at high doses, and drug interactions.
Ivermectin should not be used to treat cancer outside a properly conducted clinical trial.
Yes. Supplements and herbal products can affect how cancer medicines work or increase side effects. Not every possible interaction has been studied. This is particularly important with chemotherapy, targeted therapy, immunotherapy, hormone therapy and oral cancer medicines.
Tell your cancer team about everything you take or plan to use, including vitamins, herbal medicines, turmeric, medicinal mushrooms, health tonics, acupuncture, Tui Na, massage and cupping. For supplements, bring the packaging or a clear photograph showing the ingredients and dose.
Simple rules to remember are:
Some complementary therapies may have a useful role in helping people manage cancer and its treatment. But they should be used alongside and NOT instead of evidence-based cancer treatment.
Contributed and written by
Senior Medical Oncologist
OncoCare Cancer Centre (Singapore)
