CANCER PATIENTS AND THEIR DIETARY APPROACHES
Patients frequently adopt unusual dietary approaches. Often, the underlying rationale, if there is one, will mix cause and effect. The logic underpinning these diets often runs something like this: the risk of getting a number of cancers may be increased by a lack of X in the diet (possible), therefore taking X will restore balance and treat cancer. This leads to patients taking, for example, vitamin or mineral supplements. As a proposal, this is at least testable – we can do a trial with the supplement in question and see whether it impacts on the outcomes experienced by patients. Another common theme in anticancer diets is to pick a particular component of the diet, such as animal fat – the underlying logic being that a number of common cancers have been linked to an excess of animal fats in the diet, therefore giving up animal fats will treat cancer (unlikely). Substituting the word ‘smoking’ for ‘animal fats’ in lung cancer illustrates the futility of this – if all you had to do to treat lung cancer was stop smoking, far fewer would die from it. Sadly, stopping smoking has very little impact on the grimly predictable outcome of most lung cancer. Similarly, evidence, that these sorts of ‘subtraction’ diets impact cancer survival, is also conspicuous by its absence. Another more recent example I have observed in patients turning up in my clinics is the claim that eating sugar is bad, as this ‘fuels’ cancer. As all complex carbohydrates are digested down to sugars in the gut before being absorbed, this is highly unlikely to be a good therapy, especially as organs such as the liver and pancreas very tightly regulate sugar levels in the blood.
Despite the flawed logic and lack of evidence, patients will often adopt new diets in response to a diagnosis of cancer, frequently giving up foods enjoyed for decades to adopt a diet with alleged ‘detoxification’ or ‘healing’ properties, or adding supplements to ‘boost’ the body’s defence mechanisms. At the extremes, both practitioners and adherents often promote these approaches with a fervour approaching the religious. Indeed, adherence to these doctrines in many ways parallels religious observance, with denial and self-sacrifice being potentially rewarded by improved wellbeing. Like religious observance, direct evidence of efficacy is not required – the belief that it works is sufficient. Furthermore, failure of the technique to work can be interpreted as an indication of insufficient diligence in the application of the regime rather than an indication of lack of efficacy.
In 1990, a team of three of us (two oncologists and a psychiatrist) visited the Gerson Centre in Tijuana in Mexico. The Gerson plan is based on a curious mix of a ‘detoxifying’ diet (vegan, crushed fruit and vegetable juices, no added salt) and the frankly odd (regular fresh coffee enemas). Dr Max Gerson developed the diet to treat various ailments, including diabetes (he treated Albert Schweitzer) and tuberculosis. Ironically, he was driven from the USA for advocating the diet for diabetes, at the time treated with a high-fat, low- carbohydrate diet. It subsequently turned out that the ‘Gerson’ high-fibre, low-fat diet actually was a good treatment for diabetes, but this was only realized many years later. This does demonstrate the need to evaluate therapies in a scientific way – when this was done; it proved the value of low-fat, high-carbohydrate diets for diabetes. However, after being expelled from the USA, Gerson continued to advocate the therapy for a range of other conditions, including cancer, heart disease, and arthritis. The US National Cancer Institute carried out investigations in 1947 and 1959 to assess whether the Gerson regime had any effect on cancer outcomes, concluding both times that there was no convincing evidence of a treatment effect. Our own review of cases selected by the Centre in 1990 came to the same conclusion, which we published in the medical journal The Lancet. Patients at the centre undoubtedly believed they were benefiting, and in a sense, for the reasons outlined above, they were getting spin-off psychological benefits from feeling more in control of their fate. There is a flip-side to this, however, in that patients who invest a lot of energy and belief in such treatments inevitably feel that they have somehow failed when their disease worsens. This is often painful in itself, but can sometimes drive them to more extreme adherence to a regime in the mistaken belief that, if only they could adhere more perfectly, then improvement would follow.