Introduction to vitamins and supplements in cancer therapy

Patients undergoing cancer treatment often ask their doctor whether there is anything they can take to reduce the toxic effects of chemotherapy and radiotherapy, and/or help fight their cancer. One of the topics of greatest interest is vitamins and other supplements or herbal remedies. Surveys estimate that about 50% of cancer patients take some form of dietary supplement. While many vitamins have been shown to be beneficial as a part of a healthy diet, it is important to talk with your doctor about using them.

What are vitamins?

The word ‘vitamin’ comes from the joining of two words, ‘vital’ and ‘amine’. Vitamins are organic substances that our bodies need in small amounts for normal metabolic function, cell growth and tissue repair. The majority of these organic chemicals are not made by the body itself and so must be obtained from what we eat. Good sources of vitamins include fresh fruit and vegetables.

Supplements other than vitamins include dietary minerals such as calcium, which is important for healthy bones, and sodium, which is a good electrolyte. Amino acids such as arginine and tryptophan are also supplements that are important in protein production and normal cell function.

The fact that vitamins and supplements can encourage the growth of cells in our bodies makes it seem logical that they could also encourage the growth of cancerous cells. So by taking vitamins and supplements, it is possible that cancer patients are helping the growth of the very cancer cells they are trying to fight.

Why do people take vitamins and supplements?

The main reason that cancer patients choose to take dietary supplements is to enhance their health and chance of a cure. Studies have shown that cancer survivors use supplements to try to strengthen their immune system, help them to feel better, and to cope with stress. Most cancer patients and survivors believe that there is a benefit in taking dietary supplements.

Effective use of vitamins in chemotherapy

Vitamins, supplements and cancerDespite some research suggesting that vitamins may be unknowingly encouraging the growth of cancer cells, it does not mean they can never be taken during chemotherapy. In certain circumstances, careful supplementation with vitamins can help in cancer therapy.

Supplementing the anticancer drug pemetrexed with folic acid and vitamin B12 has been shown to reduce side effects and improve quality of life. Another example is the addition of folinic acid to 5-fluorouracil (5FU) chemotherapy. It is known that folinic acid significantly improves the response rate to chemotherapy with 5FU. In a study investigating the link between supplemental vitamins and minerals and oesophageal cancer, it was found that using multivitamins was associated with a reduced risk of oesophageal cancer.

Combination therapy using retinoic acid (the oxidized form of vitamin A) together with the anticancer drug ketoconazole has been investigated as a treatment for superficial bladder cancer (SBC). The combination was found to effectively reduce the cancer recurrence rate and increase the survival time of SBC patients.

It is understood that there is a link between more tomatoes in your diet and a reduced risk of cancer. The red colour in many fruits like tomatoes and watermelons comes from a chemical called lycopene. Recent studies have also suggested that lycopene has anticancer properties. Though further clinical trials are required, it is thought that the antioxidant properties of lycopene are responsible for its anticancer properties.

The applications of these vitamin supplements are in very specific and controlled circumstances. It is very important that you discuss the use of any vitamins or supplements during cancer treatment with your specialist before you start using them.

The case against vitamins and supplements in cancer therapy

Certain cancer treatments, particularly radiotherapy, rely on the creation of free radicals to damage the cancer cells. Free radicals are toxic molecules that are able to damage both normal and cancerous cells. Radiotherapy often relies on the creation of toxic free radicals within the affected tissues, which are damaging to and can kill the cancer cells. Taking supplements that are free radical scavengers could potentially reduce the amount of free radicals and lower the effectiveness of the cancer therapy. Vitamins C and E are known to be free radical scavengers, able to ‘mop-up’ any damaging free radicals. Research has shown that lung cancer patients given supplemental vitamins A, C and E experienced a faster recurrence of their cancer, which progressed more rapidly and resulted in a sooner death.  Beta carotene, a vitamin A derivative, has been shown to worsen the outcome of patients with mesothelioma and lung cancer. Results from these studies show the need to be aware that vitamins should be taken with care and should always be discussed with a doctor.

Cancer patients will often home-research various herbal remedies and preparations, and then ask their oncologist whether or not it is all right to take them. Often these are obscure herbal remedies from the Asian subcontinent. This can make it difficult to know what they actually contain and how reliable this information is. There have been many reports of lead and other heavy metal poisoning from herbal and mineral supplements. It is difficult to tell whether or not an herbal remedy can be harmful. Very few have been thoroughly studied.

Chemotherapy levels circulating in the body are very important in determining optimal cell damage. A reduction in the effective circulating chemotherapy dose can reduce cancer cell death, potentially decreasing the response and cure rate. One of the country’s most widely consumed herbal remedies, St John’s wort, is known to interact with virtually every prescription drug. St John’s wort can break down the active ingredients in drugs, and it is possible that it can reduce the amount of a circulating chemotherapy drug. While there is no doubt that St John’s wort works reasonably well as an antidepressant, you should consult your doctor before taking it with any prescription medications.

Unproven therapies

Vitamins, supplements and cancerDespite strong belief and support from both practitioners and patients, there are many cancer therapies that remain unproven. The idea that large doses of vitamins and minerals alone are effective cancer treatments is one such therapy. Nobel Laureate Linus Pauling insisted that massive doses of vitamin C could cure cancer. However, these claims were not confirmed by clinical trials published in the late 70s and early 80s. The idea of taking high doses of vitamins in the treatment of cancer remains popular, perhaps due to the simplicity of the approach and easy over-the-counter access to vitamin supplements.

Another unproven therapy is the idea that shark cartilage could cure cancer. It was first suggested in the 1960s and became increasingly popular in the mid 90s. However, research published in 1998 investigating the effectiveness of shark cartilage as a cancer therapy found that no patients showed a positive response to the treatment, and neither did they show an improvement in quality of life.

Many unproven therapies remain popular despite scientific research proving that they provide little or no benefit to the patient. It is very important to discuss any alternative therapies you have heard about or are interested in with a cancer specialist.

Some quick tips for supplement use and chemotherapy

  • Remember that your oncologist wants what is in your best interest, so always engage in an open conversation.
  • Never start on any vitamin or other supplement without first consulting your cancer specialist.
  • Your oncologist can advise about things you can do in addition to chemotherapy and radiotherapy, so don’t be afraid to ask!

More information

For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.


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