Originally published in Spring 2016


 

We are advised that a healthy diet can prevent cancer, but can nutrition be used to fight the disease too? By Louise Wates and Dimitrios Velis

Cancer, its cause and cure, is a subject for continuing debate. In early 2015, a US study created a seismic reaction when it claimed that around two thirds of cancer cases were down to chance or bad luck — although critics argued that the headlines didn’t tell the whole story and had overlooked the research’s large margin for error.[1] Then by autumn, cancer was front page news again when the World Health Organization announced that processed meats such as bacon were carcinogenic; leading to diners at cafes across the UK being quizzed by roving reporters on how they now felt about their fried breakfasts. And finally, by the end of 2015, fresh headlines claimed that cancer wasn’t just down to luck as had previously been reported, and that environment had a part to play.

No wonder we find it confusing — but, understandably, we want to know how to avoid the disease. Or if we become ill, we want to know what will make us well again.

Although a healthy diet and getting our five-a-day is invariably touted as a means to avoiding cancer, lack of empirical evidence on the benefits of individual nutrients has held back any lab-to-bedside practice in treating the disease with diet and nutrition. Although some well-documented research exists on the effects of nutrients and specific foods on different types of cancer, it is not part of standard clinical care. So even if patients would like to incorporate a nutritional approach into their treatment, they may not be advised on where to start.

Journalist Sheila Dillon, a presenter on Radio 4’s Food Programme, wrote in an article for the BBC: “..unless you are very lucky, you will not be told about any of the latest food-related research when you enter the parallel universe that is cancer treatment”.[2] This is despite research showing that there could be a role for diet and nutrition in the fight against cancer — both in terms of prevention and treatment.

One nutritional approach that is currently provoking interest is the ketogenic diet: a low-carbohydrate, medium-protein, high-fat diet which has produced interesting results in the laboratory. The theory behind it stems from our understanding of the peculiarities of energy metabolism in cancer cells. All cells, including healthy ones, use glucose for fuel, whether from sugar in our tea or from a tomato. But in what was dubbed the ‘Warburg Effect’, after Nobel laureate Otto Warburg, it was observed that cancer cells seemed to thrive on anaerobic breakdown of glucose — the bottom line taken from this being that cancer cells feed on sugar.

This has led to fears that sugar actually causes cancer, something Cancer Research argues is “an unhelpful oversimplification of a highly complex area that we’re only just starting to understand”.[3] Currently, in the relationship between sugar and cancer cells, there is no evidence to confirm that it is one of causation.
Following Warburg’s research, it was also proposed that cancer cells had defective mitochondria which — if the glucose supply were shut off — would prevent them from obtaining energy from other sources; in effect, starving them. It’s still emerging science, and some researchers argue that the mitochondria in cancer cells is not defective as previously thought. But the theory has paved the way for research into the ketogenic diet as a potential aid to treatment.

In 2012, a team led by Professor Adrienne C Scheck, Associate Professor in Neuro-Oncology and Neurosurgery Research at Barrow Neurological Institute, USA, administered to mice with brain cancer, in conjunction with radiation treatment, a commercially-available ketogenic formula normally used in the treatment of paediatric epilepsy. The team concluded that the ketogenic diet significantly enhanced the anti-tumour effect of radiation, and stated that the diet “may be useful as an adjuvant to the current standard of care for the treatment of human malignant gliomas [brain cancer]”.[4]

Professor Scheck explained to Optimum Nutrition the biological mechanisms behind the research: “Cancer cells use glucose differently than normal cells — in addition to making energy, they must make building blocks to form more cells. The dogma is that tumour cells are not as ‘metabolically flexible’ as normal cells and therefore they require a large amount of glucose. In contrast, normal cells can use ketones — the products of fat breakdown — for energy, but tumour cells may not be able to do this.”

The potential for the ketogenic diet doesn’t stop with brain cancer... “The available preclinical (laboratory) data suggests that it could be effective in many different cancers”


But the effects of a ketogenic diet go beyond simply depriving cells of an energy source; ketones have also been found to be beneficial even when glucose is present. “We — and others — have found that ketones can inhibit growth and sensitise tumour cells to radiation and chemotherapy, even in the presence of normal glucose levels,” she says. “This provides additional support for the fact that a ketogenic diet is doing many things to help reduce tumour growth. Some are likely to involve energy deprivation for the tumour cell, and some involve other mechanisms that inhibit tumour cell growth. Our belief is that the two together are like a ‘one-two punch’ to cancer.”
This is exciting news, but one of the current setbacks to the treatment becoming mainstream is lack of empirical data from human studies. However, Professor Scheck and her team are now hoping to move forward with a clinical trial. “We plan to accrue 40 patients for the study,” she says. “But we are helping many other people that are not eligible for the actual study in the hope that we can collect data sooner. We are also working with colleagues in the UK that are doing a similar study, with the goal of getting enough data to convince the medical community of the utility of this approach as an adjuvant therapy.”

And the potential for the ketogenic diet doesn’t stop with brain cancer. “The available preclinical (laboratory) data suggests that it could be effective in many different cancers,” says Professor Scheck. “It has a wide variety of effects on the cancer cell and the tumour as a whole, including growth inhibition, inhibition of inflammation and oedema [swelling] in and around the tumour, reduction of the formation of new blood vessels in the tumour (angiogenesis), and it may reduce the tumour’s ability to evade the immune system. We have shown that it also seems to enhance the efficacy of radiation and chemotherapy.”

She adds that because the ketogenic diet mimics fasting in some ways, others have suggested that short-term fasting before therapy may have a similar effect.

However, despite the potential, Professor Scheck does not recommend the diet be used on its own. “I do not feel that the data is currently available to prove that a ketogenic diet alone should be used to treat cancer. Many of the physicians I have spoken to have said that their experience is that while on the diet, tumour growth may slow or even stop. When the diet is discontinued, tumour growth starts again.”

She also says that the diet does not work for everyone, adding: “We do not yet know why this is, or if it can be made more effective by tailoring it to each individual.”

But she believes that if the ketogenic diet were added to the current standard of care for each cancer type, patients would benefit from the fact that it is likely to make other therapies work better and may slow the growth of the tumour. “If it does not work in a particular patient, they have not lost the potential benefit of standard therapy,” she says.

She does caution, however, that it is not a standard ‘diet’. “It is a therapeutic diet that should be done under the direction of a trained dietetic professional and with the knowledge of the patient’s healthcare team for the maximum chance of efficacy.”


A nutritional therapy approach to cancer

From a nutritional therapy perspective, a typical, tentative dietary model targeting cancer prevention would include plenty of vegetables (particularly cruciferous such as broccoli, kale, etc., and those in the onion/allium family) as well as fruit, fibre, a lot less red meat, and balancing the dietary ratio of omega-3s to omega-6s. There may also be a special role for supplementary nutrients, examples of which may include folic acid, vitamins B12, C, D and E, folic acid, selenium, oral enzymes and probiotics.[5]

Yet the roles of single nutrients are not clear cut and sometimes can be contraindicated — in other words, beneficial nutrients may cause harm in certain circumstances. For example, while a higher intake of folate may help prevent deficiency-mediated carcinogenesis, supplementation can be problematic for people with concealed neoplasms (abnormal tissue growth) because folate’s biological effect is to enhance cellular proliferation.[6]

Such problems were highlighted recently in the case of antioxidants, when a US scientist said that he would avoid supplementing his diet with large amounts of antioxidants if he had cancer. The comment by Sean Morrison, director of the Children’s Medical Center Research Institute at UT Southwestern, followed mice studies which found that antioxidants may actually help cancer cells to thrive.[7,8]

Protecting cells against oxidative stress from free radicals, antioxidants are considered a valuable part of the armoury against cancer — which is why so many products are marketed on the strength of their antioxidant properties. However, the UT Southwestern research found that as well as boosting healthy cells, antioxidants also extended the life of cancer cells. The report’s authors stated that while solid cancer cells enter the bloodstream and disseminate systemically, they are “highly inefficient” at forming distant metastases [the ability to spread from one part of the body to another part that is not directly connected]. Oxidative stress plays a part of this, because it causes cells — healthy or cancerous — to die. Yet when human melanoma were implanted into mice, antioxidants were found to give a boost to cancer cells as well as healthy cells and, as a result, promote distant metastasis and the spread of the cancer.

Clearly, because of their potential benefits, the antioxidant story is complex. But what this does tell us is that, currently, there is no silver bullet.

So what might a cancer patient expect from a nutritionist?

A nutritional therapist should offer an approach to accompany standard medical care, with the aim of optimising outcomes or easing anticipated side effects of treatment. But — a word of caution — this should be done without making claims of a cure or claims to replace established medical care.

A nutritional therapist should also aim to personalise appropriate dietary changes to ensure the diet matches the health needs, while appreciating the underlying biochemical factors involved in the pathogenesis of the disease, and how different nutrients can impact on disease prevention, development, progression or recurrence.

One problem with which a nutritional therapist may try to assist is dysgeusia, when food tastes different or unpleasant. This is a common side effect of treatment that is often due to depleted zinc levels in the taste buds. Clinical research has not yet identified a single approach, either drug-based or nutritional, to prevent dysgeusia, but zinc supplementation or administration of a prophylactic (radioprotective) drug such as amifostine have been shown to reduce its severity — although not always offering complete relief. They may also advise on appropriate dietary adjustments such as reducing certain foods with, for example, metallic or bitter tastes, or suggesting a variety of milder-flavoured foods, while taking nutritional intake into consideration.

Cancer treatment can also impact the body’s ability to break down and absorb nutrients. But for the patient, it might seem all too challenging to try to make sense of what is best to eat. For instance, it might help to give up or cut down on sugar, but this could be unhelpful when a patient is trying to combat weight-loss, or if all they want to eat is cake. It may also seem too difficult to work out what to eat and in what proportion.

This is when a nutritional therapist can provide step-by-step guidelines. Eating should mean choice and pleasure, but food also provides for building units of cell components, tissues, and nerve signalling chemicals. So nutritional intervention should help someone feel better in both body and mind while on the road to a full recovery. Enjoying life is an important part of cancer-free survival, and patients should know that there are options and a helping hand for both.


Cancer and treatment

Tilly and Bob have both undergone treatment for cancer; Tilly for breast cancer and Bob for bowel cancer. Tilly tells us how treatment affected their ability to eat

When you were having treatment, were your eating habits affected?
“The chemotherapy chemicals, being invasive, affect your appetite and taste buds quite significantly. The steroids to help prevent throwing up and nausea also increase your appetite. Depending upon where I was in my three-week cycle of chemotherapy, I was either hungry all the time or didn’t feel hungry! My taste buds were so badly affected that I could not imagine what I wanted to eat — plain, spicy, sour, sweet? The only food I can remember ‘craving’ was baked or mashed potatoes with lots of butter and cheese.”

What advice did you receive from your oncology team/health workers about diet?
“None — I am not sure if that was because I didn’t ask or whether in 2005 it wasn’t part of advice being offered. When my husband got bowel cancer in 2013 and we visited the oncology department, I noticed there was a lot of literature on diet during treatment and even a cookery book — though the food in it was so fancy that I am not sure when I was getting treatment that I would have had the motivation to cook any of it! It looked very tasty but I think I would have needed someone else around who could prepare it for me.

“Bob was offered some advice, especially emphasising that he had to increase his fibre intake and the best way to do that was via eating fruit and vegetables. Bob was given steroids too and his appetite doubled. He was very partial to carbohydrates — pasta being the most preferred.

“For both of our experiences — Bob and myself — the advice relating to diet was the general advice we hear or read about. There was nothing special in terms of the cancer itself or how best to support our bodies during treatment.”

Is there anything that you would have found helpful?
“In hindsight, I think what would have been useful is some practical advice like if you are looking after yourself alone (in other words no partner/family/friend living with you) then when you do cook, make extra and freeze [it] for another day. When a friend asks what they can do to help, ask them to supply a cooked dish or ask them to come round and cook you a meal — even beans on toast when you just haven’t got the motivation would be very helpful.

“During my treatment one of the things I couldn’t do was suggest what I wanted to eat, so it was a relief when I ate out that I was presented with a list and I could just pick something! Perhaps diet sheets listing a variety of meals — like you get when you follow a weight loss diet where breakfast/lunch/dinner/snacks for each day are listed — would be helpful.”

If you had known about nutritional therapy at the time, would you have considered using it?
“Yes I would have. I was lucky in that I had my mum around for a lot of my treatment and she is not only a very good cook but is also interested in the nutritional value of different foods. She used to make me a smoothie every morning which had beetroot, spinach, apple, carrot, celery, and anything else that took her fancy to get my ‘blood back to normal’. Years later I found out that there had been a study saying beetroot during chemotherapy helped with the increase in red blood cells after treatment.

“Also one of the side effects of the treatment is fungal infections, so a diet where probiotics were also included would help lessen how rubbish you feel. Generally I think seeing a nutritionist may help with all the side issues which in some ways make life more miserable than it needs to be.”

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References

  1. Bazian. Are most cancers down to ‘bad luck’? NHS (ed). www.nhs.uk/news/2015/01January/Pages/Are-most-cancers-down-to-bad-luck.aspx
  2. Dillon S (2013). Cancer and diet: Why is nutrition overlooked? www.bbc.co.uk/food/0/22567354
  3. Cancer Research. Don’t believe the hype — 10 persistent cancer myths debunked. http://scienceblog.cancerresearchuk.org/2014/03/24/dont-believe-the-hype-10-persistent-cancer-myths-debunked/
  4. Scheck AC et al (2012). The Ketogenic Diet is an effective adjuvant to radiation therapy for the treatment of malignant glioma. PLoS One. 2012; 7(5): e36197.
  5. Donaldson MS (2004). Nutrition and cancer: A review of the evidence for an anti-cancer diet. Nutr J. 3(19).
  6. Coppedè F (2014). Epigenetic biomarkers of colorectal cancer: Focus on DNA methylation. Cancer Lett. 342, 238-247.
  7. Eunjung Cha A (2015). The latest study about antioxidants is terrifying. Washington Post. 16.10.2015. www.washingtonpost.com/news/to-your-health/wp/2015/10/14/antioxidants-may-give-a-boost-to-cancer-cells-making-them-spread-faster-study-suggests/
  8. Piskounova E et al (2015). Oxidative stress inhibits distant metastasis by human melanoma cells. Nature. doi:10.1038/nature15726.