In an ideal world a healthy, varied diet should not need supplementing with additional pills tablets or potions. There are situation where selected supplements may help especially after an illness but it is difficult to know what or how many to take. This page discusses the issues of dietary supplements in relation to cancer

Although the concept of a quick fix supplement is attractive, as we all know, life is unfortunately not that simple, especially when considering the integrate genetic and constantly changing biochemical cancer pathways. 

The evidence  

Several environmental studies have shown a link between selenium, zinc and some vitamin deficiencies and cancer. There have been some studies showing that correcting a deficiency in a population reduces the risk of cancer. For example, in China were the soil is very low in selenium, one village was given selenium and another a placebo - after 4 years there was a significantly lower incidence of liver cancer in the selenium village.

In the west the evidence is more conflicting difference in the  There may be other concerns about supplements compared to concentrating on whole healthy foods.  Some of the large trials have shown that upsetting the dietary balance of nature and taking too much of a good thing, may be harmful both in terms of cancer and other important illnesses such a heart disease and strokes. Although there is still much to learn from ongoing studies, I and many enthusiasts have considerable reservations that supplements, in some situation, could do more harm than good.

Vitamin A. Prostate cancer cells and mice in the laboratory demonstrated an anti-cancer effect after being fed with vitamin A. However, in a study involving 10,472 U.S. men with an adequate diet, no reduction in prostate cancer incidence was demonstrated in those given vitamin A supplements. In this regard they may well be a waste of money and effort but the studies in which they are combined with beta-carotene may have more sinister consequences – see below.

Vitamin E is thought to be linked to the cancer process mainly via an antioxidant effect. The tocopherol forms have also been shown to prevent less aggressive tumours changing to a more aggressive type. A study of vitamin A involving 30,000 male smokers, found that there was reduction in the incidence of prostate cancer, but the incidence of lung cancer was actually higher. Other studies showed that smokers had lower vitamin E levels, but that this correlation was particularly high with the isoform of vitamin E called gamma-tocopherol which is the main vitamin E found in healthy foods, as opposed to the alpha-tocopherol found in manmade supplements. A further study which supplemented women with alpha-tocopherol demonstrated no reduction in cancer, but the incidence of heart disease was slightly worse. Finally, another study of male smokers demonstrated a higher rate of cerebral haemorrhage if they also had high blood pressure.

Vitamin D in the form of calciferol fed to cancer cells and rats in the laboratory, reduced cancer growth, progression and the formation of new blood vessels. Humans with sub-optimal levels of vitamin D have been linked with a high risk of cancer. Clinical studies of high dose calciferol, however, had to be abandoned however because it dangerously increased serum calcium.  

Calcium supplements have been evaluated in two human studies at doses of between 1330-1840 mg/day, and showed no benefit or risk of cancer. Two other large studies at doses >2000 mg/day from food and supplements, actually showed a significantly higher rate of prostate cancer. Five of nine further questionnaire surveys associated high intake of dairy food with an increased risk of prostate and breast cancer, but interpretation of these was complicated by the fact that high dairy consumption was associated with high fat intake. The detrimental effect of excessive calcium is thought to lie in the finding that high dietary calcium can reduce blood and cellular vitamin D levels.  

Calcium and vitamin D supplements are very useful in the maintenance of bone density and preventing osteoporosis. Bones are at risk following a number of cancer therapies.  The paragraph in the ‘cons’ section above, however, summarises the concerns with a high calcium intake on its own. The reasons for the negative effects of calcium are likely to be its associated with food of high fat content and its tendency to lower vitamin D levels.  Combining calcium with vitamin D in a supplement will avoid these factors, and in theory may be safe. Although confirmation of this theory in a clinical trial is required, it provides some reassurance that it is likely to be safe and can be taken if bone loss is a concern.  

Carotenoids These natural pigments have an anti-oxidant effect and people with higher dietary intake tend to have a lower rate of cancer.  A substantial European study gave carotenoid supplements in the form of alpha-tocopherol (vitamin E) and beta carotene to individuals who were either heavy smokers, or who had previously had cancer of the throat. The trial showed an elevated risk of lung and prostate cancer!  
In a laboratory experiment, rats fed with tomato powder, but not those fed with pure lycopene, demonstrated a reduction of their tumour growth. Another large human dietary prevention study combined beta-carotene with retinol (vitamin A). People who started the trial with naturally low blood levels of beta-carotene had lower levels of prostate cancer after years of supplementation. Those people who had adequate blood levels at the start of the study ended up with a higher risk of cancer, particularly prostate. This trial provides a clear take home message, that correcting a natural or acquired deficit is beneficial, but too much of a single anti-oxidant is harmful. 

Zinc is one of the metals needed to produce the superoxide dimutase (SOD) enzyme important to defend the body against the attack of dangerous free radicals. Laboratory experiments have shown that cells deficient in zinc are more likely to become cancerous. The role of zinc supplements in humans was highlighted in a study of 50,000 health professionals, 3348 of which developed prostate cancer. Detailed analysis showed that men who took normal amounts of zinc had the normal incidence of prostate cancer, but those who took supplemental zinc at levels of more than 100mg/day, or for long durations, were more than twice as likely to develop advanced prostate cancer.  

Selenium supplements An eloquent trial,  gave 200 micrograms of dietary selenium or placebo to large group of Americans. After several years, there was a significantly lower level of lung, bowel and prostate cancer in the selenium group. Several large ongoing prevention studies are now underway across the world to try to confirm these findings, and fine-tune the optimal selenium dose required. Many suspect, however, that the people who would benefit from selenium supplements are those with a dietary deficiency in the first place. There is also evidence from studies involving blood / hair samples and toenail clippings, that many areas of the World have populations deficient in selenium, including the UK , Central Europe and China , thought to arise from low indigenous soil levels.

Phytoestrogen supplements. Although foods containing phytoestrogens are generally healthy, concentrating oestrogenic elements of food into a pill can be potentially hazardous. Although chapter 5 explains the lack of evidence for and against this, most cancer doctors would discourage their patients from taking them. This is especially true for individuals with tumours originating from the breast which can be stimulated to grow by oestrogens.

Supplement interaction with chemotherapy In recent years it has become evident that some over the counter remedies can influence chemotherapy drug metabolism leading to reduced effectiveness or increased toxicity. Unfortunately, patients often do not realise that these products may interfere with their treatment as there use is mostly not discussed with their cancer team. Furthermore, as they are usually branded as natural, a possible harmful interaction is usually not considered. This should be regarded as an oversight as other research has shown that up to 84% of patients dabble or regularly take complementary medicines after their diagnosis of cancer.

Amoung the most widely used herbal supplement is St John’s wort (Hypericum perforatum) thought to have anti-depressant properties. Like smoking, mentioned above this interacts with one of the liver enzymes (CYP3A4) decreasing the concentration of the chemotherapy drugs irinotecan, docetaxol and the biological agent imatinib.

 Although the evidence for a number of other complementary therapies is less robust, potential interactions have been reported with echinacea, grape seed and gingko (caution with most chemotherapy drugs), ephedra (increases blood pressure during cancer therapies particularly with sutent and nexevar), kava- kava (increases the risk of liver damage). In short, supplements are chemicals and need the body’s metabolic processes to excrete them. As the body is already under a lot of pressure and there is some evidence that antioxidant, herbal or vitamin they may interfere with the effectiveness of conventional therapies, on balance it is best not to take them as they make matters worse.

Cod liver oil The main components are omega-3 fatty acids but it is also high in vitamins A and D. There is genuine trial evidence for the benefits of cod liver oil on the joints. Not only have well conducted trials shown a reduction in joint discomfort, but they have demonstrated a reduction in the underlying damage to the joint. A trial involving patients with rheumatoid arthritis took 1 g of cod liver oil (one capsule) daily for 3 months. Half reported a reduction in stiffness, and 40% a reduction in pain and swelling. An extremely eloquent study from Cardiff University in 2004, examined the discarded arthritic knees of people who had undergone knee replacement surgery. Some were treated with Omega-3 fatty acids for 24 hours in a laboratory, others were not. A chemical was added to mimic an inflammatory response, and the samples examined four days later. When researchers looked at the cartilage pieces, they found enzymes which are responsible for destroying cartilage in arthritis, present in the untreated group. But they were 'turned off' in those treated with Omega-3 fatty acids, as were the enzymes which cause inflammation and pain in joints. This research, therefore, showed that not only does cod liver oil reduce pain and inflammation in the joints of people with osteoarthritis, but it also turns off the enzymes responsible for destroying cartilage. If you have joint stiffness and pain, it is certainly worth taking cod liver oil.
Cod liver oil is also high in vitamin D which is difficult to take in recommended amounts particularly, in the northern hemisphere. As deficiencies in vitamin D have been linked to cancer, for this reason alone, there may be a place for daily cod liver oil supplements, at least in the winter months.

Probiotics and prebiotics  (healthy bacteria)  The healthy bacteria in our gut have lived with mankind for millions of years. We have learnt to rely on them to help us digest our food. During chemotherapy, radiotherapy, after a prolonged illness, following a course of antibiotics, or for no apparent reason, these healthy bacteria can be damaged, and there is now very good evidence that taking an extra amount in the form of a dietary supplement may be helpful.  
The most numerous probiotic bacteria normally inhabiting the small intestine are a species of lactobacilli. In the colon, the majority are mainly bifidobacteria. Most probiotic products consist of one or more species of bacteria from one or both of these types.

Lactobacillus acidophilus is by far the most well known species of probiotic, which has led many people to refer to probiotics simply as "acidophilus". This strain, amongst other benefits, has been shown to increase levels of interleukin and tumour necrosis factor, which suppress cancerous tumour growth. Other research has shown that L.acidophilus alleviates lactose intolerance by producing significant amounts of the lactose digesting enzyme, and inhibits gastrointestinal pathogens by producing antimicrobial substances such as acidophilin. It has also been shown to help conditions outside the gut such as eczema and other skin inflammatory skin conditions. Chemotherapy agents such as fluorouracil can cause diarrhoea, which cannot only be uncomfortable, but can also lead to dehydration, concentration of the drug in the blood stream and generally greater side effects and risks. A study in 2007 randomly allocated a 100 patients receiving fluorouracil Lactobacillus acidophilus, and another 50 patients no supplements. There were no adverse effects in the probiotic group, but the rate of moderate to severe diarrhoea was significantly better in the lactobacillus group.

Lactobacillus rhamnosus combined with acidophilus, has also been shown to reduce or prevent radiotherapy induced diarrhoea in three separate clinical studies. There a growing amount of evidence that L.rhamnosus can help treat and prevent gut infections. Good controlled trials performed on hospitalised children who had acute diarrhoea showed that L. rhamnosus reduced the duration of diarrhoea. Some placebo controlled studies also suggest that probiotics are of benefit in the treatment of antibiotics-associated diarrhoea, and in the prevention of viral diarrhoea. There have also been a number of studies which suggest a protection against the ‘superbug’ clostridium difficile plaguing hospitals around the World, so a course of probiotics, before coming into hospital for an operation, would be a wise idea.

Lactobacillus bulgaricus. This organism usually passes through the digestive system and leaves the body in the stool, untouched. It has been shown to enhance the digestibility of milk products and other proteins, and to produce natural antibiotic substances that specifically target pathogenic bacteria, whilst sparing friendly species. In another study it was shown to stimulate activity in part of the gut immune system called the Peyer's patches. 

Lactobacillus salivarius has been shown to inhibit the bacteria Helicobacter pylori (H.pylori) which is responsible for the creation of peptic ulcers. It has been discovered that L.salivarius produces large amounts of lactic acid acting as an antibiotic, inhibiting the growth of H.pylori and reducing the associated inflammatory response. The first bacteriocin (natural antibiotic substance) to be isolated and studied at the genetic level, was taken from a strain of L.salivarius.

Lactobacillus probiotics have also been shown to help alleviate food intolerance and allergic conditions. Food intolerance leads to uncommon periods of bloating, wind and colicky indigestion – this is often labelled irritable bowel syndrome. This can develop for no apparent reason at any stage of life, but it is even more likely you have taken had a prolonged illness, taken antibiotics or chemotherapy. Often this is related to the development of a mild intolerance to wheat or yeast, but it may also be caused by other foods. Although this does not usually lead to full blown bowel damage or malabsorption seen with conditions such as Coeliacs Disease, it can be uncomfortable and distressing.  As well as bloating, you can be prone to alternating diarrhoea and constipation, passing offensive wind and an overall sensation of not having a satisfactory bowel movement. As well as identifying the foods which upset you, e.g. bread, beer or wheat pasta, a course of probiotics for a week or so every month, may help to restore the natural balance.

Prebiotics are indigestible carbohydrates known as oligosaccharides, and feed probiotic bacteria and encourage their growth. Oligosaccharides are found naturally in certain fruit and vegetables, including bananas, asparagus, garlic, wheat, tomatoes, artichoke, onions and chicory. Prebiotics can be taken on their own or with a probiotic supplement. The most common types of prebiotics available in supplements are fructooligosaccharides, inulin and galactooligosaccharides.   

Chondroitin and Glucosamine These are complex sugars that are present in the cartilage of joints. They are used widely to treat arthritis, and are often taken in large quantities by body builders who are convinced that they would not be able to lift the weights without extra protection for their joints. Their springy chemical structure provides much of the resistance to compression of cartilage on weight bearing, and its loss is a major cause of joint pain and osteoarthritis  

Chondroitin appears to be made from extracts of cartilaginous cow and pig tissues particularly trachea, ear and nose, although alternative sources include bird and shark cartilage. The dosage of oral chondroitin used in human clinical trials is usually 800–1,200 mg per day. Since chondroitin is not a uniform substance, and is naturally present in a wide variety of forms, the precise composition of each supplement will vary. Chondroitin is under the jurisdiction of the FDA in the U.S. as a dietary supplement as a result, and as there are no mandatory standards for formulation, there is no guarantee that the product is correctly labelled. One report, in the year 2000, analysed 32 chondroitin supplements. Only 5 were labelled correctly, and more than half contained less than 40% of the labelled amount. Fortunately, at least in the US testing standards now exist for the identification and quantification of chondroitin. 

Glucosamine  is a monosaccharide amino sugar found as a major component of the exoskeletons of crustaceans, but is also found abundantly in fungi and higher organisms.  It is produced commercially by crushing crustacean exoskeletons. Like chondroitin, glucosamine is commonly used as a treatment for joint pains, although its acceptance as a medical therapy varies.  

Multiple clinical trials in the 1980s and 1990s, all sponsored by the European patent-holder, Rottapharm, were conducted on patients with a wide variety of arthritic problems. Although these trials were small and not particularly well designed, they did show a clear benefit for glucosamine treatment. There was not only an improvement in symptoms, but also an improvement in joint space narrowing on. This suggested that glucosamine can actually help prevent the destruction of cartilage as well as reduce pain. On the other hand, several subsequent studies, independent of Rottapharm, but again small and poorly designed, did not detect any benefit of glucosamine. As a result of the conflicting evidence both for and against glucosamine's efficacy, there remained a debate amongst physicians about whether to recommend glucosamine treatment to their patients. 

This situation led the prestigious National Institute of Health in the USA to fund a large multi-centre study of people with pain and osteoarthritis of the knee, evaluating both agents. It compared groups treated with, glucosamine, chondroitin or a combination of both, to both placebo and a standard anti-inflammatory pain killer. The results of this 6-month trial found that patients taking glucosamine HCl, chondroitin sulfate, or a combination of the two had no improvement in their symptoms compared to patients taking a placebo. The group of patients who took the standard pain killer, not surprisingly, did have a statistically significant improvement in their symptoms. These results suggest that glucosamine and chondroitin did not effectively relieve pain in the overall group of osteoarthritis patients, although no significant side effects were reported. There still remains, however, some hope for the fate of this supplement. A subgroup analysis suggested that the supplements may have been effective in patients with pain classified as moderate to severe. Also the main commercial manufacturers’ of glucosamine claimed that glucosamine sulfate should have been used in the study instead of HCL, as this is more effective. Although this concern is not shared by pharmacologists, many conclude that the question of these agents efficacy will not be resolved without further updates or trials.  

Summary of concerns with dietary supplements:- 

• They offer an attractive quick fix to health
• May distract people from the real issues of lifestyle.
• Some trials have shown increase risk of cancer and heart disease.
• Other long term risks remain uncertain until more data available.
• Very few trials have actually shown a benefit for cancer.
• Individuals with an underlying deficiency have shown a benefit
• Nutritional deficiencies could be corrected with a balanced diet
• They can add expense to the cost of living

Summary of the potential benefits of dietary supplements

• After illness or intensive treatments supplementation may be helpful, e.g
      -  vitamin and mineral to cover a period of poor nutrition
      -  vitamin B following a period of heavy alcohol intake
      - oral iron following a heavy menstrual period or other bleeding 
• Correcting a known deficiency has been shown to be most beneficial Selenium deficiency is relatively common and may need supplementation in some parts of the world where soil levels are low 
• Cod liver oil has been shown to help arthritis 
• Glucosamine & chondroitin may help arthritis, although more evidence is needed
• Probiotics help with
      - chemotherapy induced diarrhoea
      - protection from infective diarrhoea including C. difficle 
      - protecting the stomach from infective indigestion (H.pylori) 
• Calcium and vitamin D help with bone density, but should be monitored 

Is there a place for dietary supplements? The concerns above do not necessarily insinuate there is no place at all for supplements. Well designed supplements should have a wide range of essential trace minerals and vitamins at low doses which means it is unlikely to accumulate toxic levels of a single mineral. Others such as fish oils area good source of omega 3 and have been proven to help arthritis and help reduce cholesterol. 

The safest way to ensure you take the correct amount and type of dietary supplement is to find out your own bodies current levels and requirements. A number of different tests are available to do this ranging from analysis of blood, urine, saliva, hair or even or toe nails! A number of independent laboratories are now offering tests which can assess your baseline nutritional status.

Test your baseline nutritional status - This will help you decide if supplementts are necessary and if so which types