A helping hand? Vitamins may be dangerous for cancer patients

Cancer patients need to think twice before adding vitamins to their treatment. shannonkringen/flickr

Previously unthinkable questions about vitamin use by cancer patients are being asked following a series of recent clinical studies.

Is it time for cancer patients’ love affair with vitamins to end? Might vitamins actually be harmful for cancer patients?

It’s well known that many cancer patients – perhaps a majority – supplement treatment recommended by their cancer specialists with so-called complementary and alternative medications, also known as CAM.

CAM can include a wide range of treatments such as special diets, meditation and herbal preparations. The term also embraces wacky treatments such as coffee enemas and energy zapping machines.

Until now, vitamin supplements have generally been thought to be at the benign end of the CAM spectrum. Many patients and their doctors subscribe to the notion that at least they can do no harm. But is this really so?

Vitamins are components of our diet required in tiny quantities to guarantee good health.

Most were discovered in the first half of the twentieth century when it was found that lack of individual vitamins led to specific debilitating illnesses.

Deficiency of vitamin C causes scurvy, for example, and deficiency of vitamin B1 (thiamine) causes beriberi. These diseases are rarely seen nowadays in prosperous countries such as Australia, due to general knowledge of the need for vitamins and the ready availability of fresh fruit, vegetables and dairy products.

But the apparently magical properties of vitamins in rapidly relieving the symptoms of their respective diseases has naively led to them being used – without evidence and often in big doses – to treat conditions for which modern medical science lacks answers.

Their use among cancer sufferers was spurred in the 1970s by a report from the double Nobel Laureate Linus Pauling, a biochemist, who together with a Scottish physician Dr Ewan Cameron, observed a group of patients with advanced cancer being given high doses vitamin C. The researchers claimed that these patients survived much longer than expected.

This study has since been severely criticised on the grounds that the treated group and the comparison group were quite dissimilar and that comparing them was invalid.

To check Pauling’s claims, a series of high-standard scientific comparisons were carried out by the world famous Mayo Clinic in the United States.

The result: no benefit whatsoever was found for patients given high doses vitamin C compared with those who were not.

The Mayo Clinic studies were randomised controlled trials – the highest standard of medical evidence – in which the treated and untreated or control groups were comparable in all respects other than their treatment.

Nonetheless, the idea that high doses of vitamins might be beneficial for cancer patients had taken hold. In addition to vitamin C, minerals and antioxidants and other vitamins (A, E and those of the B complex) are often combined in the hope that their use will help control the patient’s cancerous growth.

But let’s look at history. Way back in the late 1940s, a famous Boston children’s cancer specialist, Dr Sidney Farber, noted that children with leukaemia who were given folic acid – one of the B group of vitamins – had more rapid growth of leukaemia cells and died more quickly than those who did not receive the vitamin.

This led him to seek out a group of anti-folate drugs which, remarkably at the time, brought about a temporary remission in many of these children. Leukaemia remission was almost unheard of until then.

One of these drugs, methotrexate, is still used as a component of the successful multi-drug treatment that can bring about cure in 80% to 90% of childhood leukaemia cases.

Shouldn’t this experience have been a warning?

The scientific literature concerning the possible benefit of vitamins on cancer growth is bedevilled by the types of unfair comparisons of which Pauling and Cameron were guilty.

Only in recent years have proper high-standard scientific randomised controlled trials been carried out, and the results have surprised those who thought vitamins could only do good.

The first shock came from a study in Finland carried out in the 1990s. This was designed to find out whether giving vitamins and antioxidants – in this case vitamin E and beta-carotene – could prevent lung cancer in a group of nearly 30,000 male cigarette smokers.

Unexpectedly, not only did the treatment not prevent cancer, the group given beta-carotene had a higher rate of lung cancer than those not given it.

Subsequently, a series of high-standard scientific studies were carried out on the value of various vitamins – often in high dosage – to prevent, and in some cases to treat, a variety of cancer types particularly bowel cancer and prostate cancer.

These studies often involved tens of thousands of subjects. No benefit was found and, like the Finnish study of lung cancer, several of the studies have shown the treatments to be harmful.

To be fair, one study did show some benefit from a vitamin/mineral complex. This was a stomach cancer prevention trial carried out in subjects from rural China.

But many of these subjects were likely to have been borderline vitamin deficient to start with due to a poor baseline nutritional status. So their experience is probably not relevant to patients from developed countries.

Vitamin D might be another exception – there are a number of recent studies suggesting that lack of vitamin D can increase the risk of succumbing to various diseases including some cancers.

But we do not yet have proof that giving additional vitamin D can prevent cancer nor that it is useful in cancer treatment.

So, is it plausible that vitamins A, C, E and vitamins from the B complex for cancer treatment could be harmful? Undoubtedly yes.

Just consider what vitamins do – they are chemicals in the diet whose role, as a generalisation, is to help cells grow and they stimulate healthy cell growth and multiplication.

Isn’t it likely then that vitamins, particularly if given in larger than necessary doses, could stimulate the growth of cancer cells along with normal body cells?

Cancer patients need to think twice before adding vitamins to the treatment program recommended by their cancer specialists. They might be doing themselves more harm than good by taking vitamin supplements.