Updated 04 April 2017

Eating when you have cancer

Good news for cancer patients is that you do not necessarily have to give up the food you love in your fight against disease, according to a leading local dietician.

Good news for cancer patients is that you do not necessarily have to give up the food you love in your fight against disease.

But it makes good sense to reduce known bad foods for everyone’s health especially saturated fats, alcohol and smoked or cured meats. Also coffee and tea do not seem to have an effect on cancer development – so enjoy these in moderation too. And take in just enough calories to maintain your ideal body weight.

This is what Mrs Rene Smalberger, president of the Association of Dietetics, told doctors, dieticians, researchers and nurses at the 9th Biannual Nutrition Congress held in Port Elizabeth this week.

Beware unscientific advice
“Beware of unscientific advice on cancer diets,” said Smalberger, a dietician at the Oncology Unit at St George’s Hospital in Port Elizabeth. “There are many eating regimes but it is best to stick to a proven healthy balanced diet – fruit, vegetables and whole grains with a little lean meat and chicken. It is not good to exclude any group of nutrients.”

The congress was held under the auspices of the Nutrition Society of South Africa and the Dietetics Association.

She said that nutrition alone has not been proven to cure or reverse any malignant process, but it has been estimated that 35% of cancer deaths may be related to dietary factors as well as the typical Western style diet.

“People often believe that cancer could have been prevented and is now curable by following a particular diet and lifestyle. These treatments give them a sense of hope and allow patients to feel as if they have an active role in their treatment,” she said.

But evidence is accumulating that food, or its component bioactive substances, offers benefits beyond basic nutrition.

Alternatives widely used
According to Smalberger, about 25% of cancer patients turned to alternative solutions because conventional cancer treatments - chemotherapy and radiation – are perceived as having severe side effects and were often viewed as causing more harm than good. Some patients used the alternative therapies before, during or after their conventional treatment.

The most common alternative treatments include various lifestyle diet therapies, megavitamin supplementation, and herbal treatments – and it was middle-aged, well-educated patients who were the highest users.

“To treat disease with a diet is one of the oldest and most commonly used alternative treatments,” she said. “Many people understand the role diet plays, that various nutrients may have a role in cancer prevention and a potential role in curing or reversing the carcinogenic process.”

Vegan diets, and variations of these, are often used as part of a metabolic programme to help clear the body of toxins with or without conventional cancer treatment. “Natural” or “organic” foods are encouraged and all animal products eliminated. But there is no scientific evidence of a curative effect. In fact nutritional health concerns are around deficiencies in protein, vitamin B12, calcium, magnesium, zinc and folic acid. A vegan diet should be coupled with proper education and careful meal planning. Patients with no difficulty eating, or experiencing few treatment-related side effects, find such a diet acceptable, but those having trouble eating may not get adequate nutrition.

The theory behind a macrobiotic diet is that most physical ailments experienced today are a result of poor nutrition and an unhealthy, unnatural lifestyle. Very similar to a strict vegetarian diet, it excludes all meat and dairy – but soy-based food is included - in the belief that cancer has developed because of “bad” foods consumed and the body’s unsuccessful attempts to rid itself of the waste products that caused the disease.

Concerns over nutrition
Nutritional concerns include deficiencies in protein, vitamin B12 and calcium – with the potential for dehydration plus a strong emotional burden for the patient and family. Soy products are high in genistein – which has shown some anti-cancer potential - but there is no scientific evidence that the macrobiotic diet has a curative effect.

Metabolic therapies assume that cancer and other diseases result from a build-up of toxins and waste products in the body. When the immune system, respiratory system, liver and pancreas can no longer rid the body of these toxins, the body’s normal metabolic processes are interrupted and chronic disease may occur. Metabolic therapy regimens vary but all follow the traditional three-step process of detoxification, fasting and rejuvenation. They use “natural” and “organic” foods, vitamins, minerals, hormones, enzymes, enemas and various other treatments in their detoxification and rejuvenation process.

No proof it works
It is very important to note that none of these commonly followed dietary regimens have been proven to have any curative effect. In fact, if they are not followed very carefully, planning the adequate intake of all nutrients, they can be very harmful to the body.

The most active and commonly “self-prescribed” area of medicine is nutrient supplementation. The problem with megavitamin therapy alone or in combination with other treatments is that there is little research done to evaluate how it affects health.

Patients should also be cautious about vitamin supplements. Loading the system with a good multi-vitamin and mineral could be better than using large doses of selected vitamins. Patients rarely think of these products as being potentially harmful because they are purchased over the counter – but that is not true. Megadosis of calcium, vitamin D, A, C, E, selenium and beta carotene are sometimes recommended individually but there is no scientific proof that this helps and some can be harmful. Side effects include nausea, vomiting, diarrhoea and nervousness.

Smalberger warned cancer patients on chemotherapy to beware of antioxidant supplements (Vitamins A, D, E and K as well as selenium). Vitamin and mineral supplements should not be taken on the days of receiving chemotherapy treatment.

“We must understand the various alternatives and potential health concerns around each therapy as well as the individual’s decision to use these treatments,” she said. “It is best to stick to the international recommended dietary allowances of vitamins and minerals for healthy people as the increased needs of cancer patients are not known.”

Most herbs useless
Regarding herbs, no anti-cancer effect has been noted in hoxey, essiac, chaparral, echinacea, ginger, kombucha tea, peppermint, pokeroot, garlic or herbal tea mixtures. But milk thistle (a potent antioxidant), and mistletoe (an immune stimulator) were two herbs with potential cancer protective properties.

“For cancer patients, a balanced diet is recommended daily. That includes protein based on body weight (approx. 0.8g per kg ideal body weight per day), 50% of energy intake from carbohydrates and approximately 30% of daily energy intake from fats. Fat intake should preferably be from poly and mono-unsaturated fats.

“The most important aspect is that what you put in your mouth should do no harm! Rely on scientific medical research and not empty promises,” she added. – (Nutrition Society of South Africa and the Dietetics Association)

Source: Press release from the Nutrition Society of South Africa and the Dietetics Association

Read more:
Cancer Centre
Nutrition basics

October 2006


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