Focus on Alternative and Complementary Therapies
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Focus Alternat Complement Ther©2005 Pharmaceutical Press
Focus Altern Complement Ther 2006; 11: 91–5
Survey data demonstrate that many cancer patients try dietary approaches to treat their condition.e.g.1 Others consider a dietary regimen in the hope of preventing cancer. In CAM, a bewildering number of cancer diets are being promoted, and an even more bewildering array of claims are made for them. The result is a high level of confusion – experienced both by patients and healthcare professionals. This article is an attempt to summarise the available factual information on CAM diets for cancer.
As the medical literature tells us little about CAM diets, we decided to first conduct an Internet search. The keyword combinations ‘diet’ and ‘cancer’ and ‘prevention’ or ‘cure’ generated about 20 000 000 hits in Google (accessed January 26, 2006). A similar Google search using the keywords ‘cancer’ and ‘diets’ (in combination) produced about 9 160 000 hits (accessed January 26, 2006). The vast majority of these websites were not informative. They contained very little information about specific cancer diets or they were largely based on individual survivors’ experiences of a particular cancer diet, or the website was used to promote a cancer diet book or supplement and therefore revealed little objective information. Three sites stood out as they contained extensive information about a wide range of diets. They also encompassed a variety of attitudes towards CAM cancer diets ranging from deep scepticism to fundamental belief, as revealed in their mission statements:
In addition, we hand-searched our (extensive) departmental files. Based on these searches, we identified several CAM diets and constructed our search terms. We subsequently used these terms for searches in the Pubmed, Embase, Amed and Cinahl databases. We included all clinical trials of any type of CAM diet for cancer. Anecdotal reports and clinical experiences were excludede.g.2 and so were retrospective analysese.g.3 or summaries of either of these,e.g.4–6 or non-clinical studies.e.g.7–9
Our search strategy identified 26 different diets (Tables 1 and 2). Some diets claimed to be curative; others were promoted as a preventative or supportive regimen. Very few of them were supported by any kind of evidence and none was backed up by data from clinical trials.
See Table 1: ‘Alternative’ cancer diets as cures.
See Table 2: ‘Alternative’ cancer diets (not curative).
The claims made for these diets were usually based on some ‘alternative’ concept of cancer aetiology. Many diets were aimed at improving the body’s immune system and/or detoxification of the body (Tables 1 and 2). The dietary regimens varied greatly and occasionally contradicted each other. Nevertheless several themes seemed to recur: fasting, vegan lifestyle, raw and organic food, avoidance of refined sugar, and the use of vitamin and other supplements. The theoretical or known risks of these diets varied. In many cases they were considerable (Tables 1 and 2).
Our findings confirm the observations made previouslye.g.10–12 that a confusing array of CAM cancer diets exist without any scientific evidence in support. There is certainly no proof of effectiveness for any of these approaches. At the same time, there are good reasons for being concerned about their safety. In essence, this means that the risk–benefit balance is not positive for any CAM cancer diet.
Reading the web-based information on these diets, we were struck by the fanatical tone with which some proponents promote or defend them. It seems to us that this level of zeal renders them (even more) dangerous for cancer patients. It seems remarkable that most dietary approaches carry the name of their inventor, and most websites promote books by these individuals. Our impression was that this area of CAM is more akin to religion (or sectarianism) than to nutrition (or science).
This is, of course, not to say that nutrition does not play an important role in cancer. There is a considerable body of epidemiological (and other) data to suggest that diet can reduce the risk of cancer. For instance, the regular intake of vegetables (particularly cruciferous vegetables), fruits, fibre and food with a high phyto-oestrogen content may reduce the risk of some cancers.e.g.13–16 Lowering of fat intake may be useful for primary or secondary prevention of cancer.e.g.17–19 Regular consumption of green tea or garlic may reduce the risk of gastrointestinal cancers.20,21 It should be noted, however, that these dietary adjustments are fundamentally different from CAM diets and that the evidence on which they are based originates not from CAM but from conventional medical research.
Cancer patients require thoughtful nutritional care. During cancer therapy patients may suffer from loss of appetite, taste and smell, as well as suffering from nausea, malabsorption or bowel problems. In the recovery period, patients need to rebuild muscle strength and correct anaemia or organ malfunctions. Invariably maintaining caloric balance is the most important nutritional goal.10 Most of the CAM cancer diets jeopardise this goal and many may lead to overt malnutrition.
The adverse effects of some CAM cancer diets, however, go far beyond simple malnutrition. Some diets are far from palatable. If, as in the case of cancer, appetite, taste and smell are already suboptimal, this could further reduce the quality of life of severely suffering patients. Furthermore, some regimens are hugely difficult to follow. If non-compliance to the regimen occurs, patients are sometimes blamed for it. Similarly, failure of a ‘curative’ diet to achieve tumour regression is often blamed on the patient’s non-compliance with diets that are frequently extremely strict (e.g. www.cancertutor.com). Thus patients are made to feel guilty. This can result in considerable psychological problems, further reducing quality of life. Lastly, most of the diets are not inexpensive. They can require costly materials and food. In some cases, this may result in financial problems for the patient or their families.
Our review has several limitations. We are sure that we are not even close to listing all CAM cancer diets that are being promoted; there are simply too many websites to be all-inclusive. We hope, however, that the most important ones were considered. The field is plagued by the abundance of ‘grey’ literature not listed in any of the electronic databases. We cannot therefore be absolutely certain that we have not missed relevant primary studies. However, any positive trial would be frequently referred to by proponents and would therefore be highly visible. We doubt that such clinical trials of CAM diets exist. Proponents of CAM diets might argue that we lack the understanding or sympathy to comment on their approaches. This may be true, but we would counter that one needs neither of these qualities to verify the total absence of scientific evidence in this area.
A bewildering variety of CAM cancer diets exists with equally bewildering claims. Effectiveness has not been demonstrated for any of them in clinical trials but their risks are substantial. The risk–benefit balance is therefore not positive for any of these diets. Cancer patients should be informed about this and they should be given responsible nutritional guidance by conventional healthcare professionals with adequate expertise in nutrition.
