In addition to genetic causes, many environmental factors can increase the risk of developing a cancer. These include diet that can play an important role in preventing cancer, during cancer treatment and after cancer.
There are many recommendations on diet and cancer, often very divergent and sometimes without any supporting studies. To shed some light on the subject, we invite you to consult our Frequently Asked Questions section below. Note that this information does not replace the individual advice that must be given by a dietitian or doctor specialising in nutrition. For any questions of a personal nature please contact the Jules Bordet Institute's Dietetics and Nutrition Support Department.
Be sure to stay hydrated throughout the day (1.5 litres). Water is the best choice and sugary drinks (sodas and fruit juices) should be avoided. Also limit your alcohol consumption to a maximum of 1 to 2 glasses a day, a maximum of 10 glasses a week and do not drink alcohol 2 days in a row.
- Fruit and vegetables
Eat up to 250 gr of fruit and a minimum of 300 gr of vegetables every day, opting for variety and produce that is in season.
- Whole grains
Eat whole grains (rich in fibre and micronutrients), at least 125 gr a day.
Eat legumes at least once a week as an alternative to meat/poultry or fish. Legumes (chickpeas, soya, red beans, etc.) are a source of protein and are rich in fibre.
- Red meat
Limit your consumption of red meat (beef, pork, veal, lamb, mutton, etc.) to less than 500 gr per week and a maximum of 50 gr of charcuterie a day.
Fish is rich in omega 3. Eat fish once or twice a week and alternate lean fish (cod, pollock, whiting, etc.) and oily fish (herring, salmon, sardines, etc.).
- Dairy products
Eat between 1 and 3 portions of dairy products a day (250 ml of milk, 125 gr of yoghurt, 30 gr of cheese). If you eat less than 250 ml a day make sure you get enough of other sources of protein and calcium (green vegetables, oleaginous fruits, etc.)
Vary the fats you use for cooking and seasoning and be careful not to use them to excess.
- Oleaginous fruits
Eat 15 to 25 gr of nuts (unsalted and unsweetened). Be careful not to overconsume as nuts contain high quality fats that are a major source of energy.
Reduce salt consumption and favour aromatic spices and herbs to add taste to your food.
During treatment, nutritional advice must be personalised to take into account the individual patient (age, other health problems, psychological condition), type of cancer and type of treatment prescribed. Nutritional advice is always adapted in line with the overall treatment plan.
Apart from genetic factors that may predispose to a risk of cancer, a number of environmental factors can increase the risk of cancer: smoking (lungs, ENT, etc.), exposure to sun (skin), pollution, virus/bacteria (hepatitis B/C for the liver, Helicobacter pylori for the stomach, for example), chemical substances (asbestos for the lungs, etc.) and certain foods or unbalanced diets.
Scientific bodies are agreed on the following recommendations:
- Some foods can have a positive impact on certain types of cancer: the fibres present in fruit and vegetables in particular but also in certain whole grains and legumes (colon, breast cancer), a regular but moderate consumption of dairy products (colon cancer), also breast feeding (breast cancer) and the regular practice of a physical activity (all cancers).
- On the other hand, the following factors can have a negative impact: excessive alcohol consumption (ENT, liver, bladder, colon, breast cancer), excessive consumption of meat and charcuterie (colon cancer and, to a lesser extent, breast cancer), excessive salt consumption (stomach cancer) and obesity (all cancers but especially colon and breast cancer).
The nutritional assessment must be included from the outset, that is, from the moment of diagnosis. A frequent re-evaluation is then needed given the likely change in symptoms associated with the treatment. Depending on the result of this evaluation and the cancer treatment programmed (surgery and/or chemotherapy and/or radiotherapy), a consultation will be requested.
In all cases the nutritional recommendations will be adapted depending on the type of cancer and treatment plan.
It is also important for the patient to be weighed on each visit or on hospitalisation
Specific supplements are essential if a blood test shows deficiencies (of vitamin B12, iron, magnesium, for example).
As a vitamin D deficiency is common, supplements are recommended and could help avoid the cancer returning, especially in the case of breast cancer.
Anti-oxidant supplements (vitamins E, A, C, selenium, etc.) are not only ineffective but could also be contra-indicated.
A varied and balanced diet is sufficient to meet vitamin, oligo element and mineral needs.
Probiotics are living microorganisms, bacteria or yeast. Naturally present in the body, probiotics boost health and the immune system. They are found in our diet in yoghurts, kefir, soya derivatives (miso, tempeh, etc.) as well as in sourdough bread. Probiotic supplements can be useful in restoring the intestinal flora (microbiota), especially after a course of antibiotic treatment. There is no proof that probiotics reduce the risk of cancer. However, in the case of neutropenia (reduction in white blood corpuscles) consult your oncologist for advice before taking probiotics.
For patients who are undernourished or who are taking insufficient food, we recommend oral nutritional supplements (ONS) in the form of drinks, creams, biscuits, etc. The advantage of these ONS is that they provide a major source of calories and protein in a small unit. This enables patients suffering from anorexia, for example, to consume small portions with a high calorific density. Of course these must be taken as a supplement to a normal diet. In addition, they also contain micronutrients without being overdosed.
For many patients the diet has to be adapted due to the effects of the treatment. In case of gastric surgery, for example, a reduced diet will be recommended while for a patient suffering from an ENT cancer the food texture is a factor.
In general, it is always recommended to follow a varied and balanced diet, consisting of fruit and vegetables, proteins (of animal or plant origin), and an adequate calorific content. In the case of cancer it is important to meet nutritional needs (nutriments and vitamins) so as to maintain a sufficient weight, combat the disease and have better treatment tolerance.
For patients with a normal IMC or BMI (between 20 and 25, maximum 27), we recommend the avoidance of any weight increase that could be induced by hormone treatment.
For patients who are overweight or obese, we recommend dietary monitoring to avoid any additional weight increase and if possible achieve a weight reduction.
A balanced diet must be combined with regular physical activity of at least 3 x 30 minutes a week (fast walking, cycling, swimming, etc.). The physical activity must be adapted to each patient and take into account age, pathology and other health problems. It must also be compatible with the treatment followed.
These recommendations remain valid for patients whose cancer is in remission. In the particular case of breast cancer it is important to avoid excessive weight gain.
Eating soya does not increase the risk of breast cancer. On the contrary, a consumption of 50 gr a day of soya in the form of whole soya such as plain beans (edamame) or tofu is recommended to prevent breast cancer. Also, soya does not present a problem during or after breast cancer. Soya is a source of good quality plant protein and can be included in a balanced and varied diet.
This must be qualified somewhat in regard to soya-based food supplements. These can be presented as a natural alternative to hormone replacement therapy to treat symptoms of the menopause. Soya-based supplements can contain a high concentration of phyto-oestrogens. However, there is considerable controversy about their potential effect on the development of breast cancer. Soya-based supplements can contain a high concentration of phyto-oestrogens. This concentration could influence and increase the risk of hormone-dependent breast cancer. We therefore advise against taking soya-based food supplements.
Studies show that vitamin D supplements, or at least the correction of a vitamin D deficiency, can have a favourable effect on preventing the return of breast cancer.
To put it simply, the concept of these diets is to make the cancer cells more sensitive to chemotherapy by "starving" them. As all body cells, tumour cells feed on sugar (glucose) and even excessively so. Studies dating back a century show that the cancer cell uses sugar differently than a normal cell (the "Warburgh" effect). It was these discoveries that gave rise to the notion that sugar deprivation could weaken the tumour cell. Hence the concept of fasting and the so-called "keto" diet.
- Fasting is defined as the total cessation of the consumption of nutritious food during several hours or days. This causes the body to draw on its energy reserves so as to maintain the functioning of vital organs (heart, brain, lungs, etc.) and leads to weight loss and loss of muscle mass in particular.
- Intermittent fasting, which has become fashionable in recent years to encourage weight loss and improve health problems associated with excess weight (diabetes, high blood pressure, high cholesterol, etc.). There are three types of intermittent fasting
- Reduction in period during which meals are taken (example: first meal of the day at midday and the last at around 8 pm, which means a fast of 16 hours).
- The 5:2 diet (5 days of "standard" diet and 2 days of fasting).
- The 1:1 diet (fasting every other day). Intermittent fasting is based on the same principle that fasting causes the body to draw on its energy reserves, producing ketone bodies as an energy substrates and thereby favouring the loss of fat mass.
- The KETO diet involves reducing the consumption of glucidic nutrients but without any reduction in the total calorific intake that must be 100% of the recommended intake. As a result, the body will initially convert fats into "ketone bodies" to nourish the cells. A normal cell can use these ketone cells but that is not the case of tumour cells. In this case too, these dietary restrictions can contribute to a weight loss that is already very common in cancer patients and especially so during treatment.
Today, the findings of all studies of these restrictive diets in humans are unanimous. Despite some data obtained in animals, there is at present no proof that such diets are effective in combating cancer in humans. Studies are continuing for certain types of cancer and certain types of chemotherapy. It is not therefore recommended to follow these diets during cancer treatment or following a cancer cure. Our role is to warn patients by alerting them to risks of negative effects. If patients nevertheless wish to follow such diets, an even more regular nutrition monitoring is then essential so as to best guide them in their action.
All sugar consumption of whatever kind: complex (flour, pasta, rice, etc.) or simple (sweets, juices, sugar, etc.) is converted into glucose (the smallest unit of sugar) in the blood. This glucose is used by the cancer cells but also by the body.
Unfortunately, to function correctly our body has a vital need of a source of sugar. If you try to "weaken" the cancer cells you will also be weakening yourself and will be less able to tolerate treatment. In addition, recent studies have shown that cancer cells have the ability to find other energy substrates through the intermediary of proteins and lipids.
To conclude, it is therefore more advisable to focus attention on the quantity and quality of food intake as part of a balanced diet.
Yes, regular physical activity is recommended. It must be accompanied by a healthy diet. This can play a part in prevention but can also help improve the effectiveness and tolerance of treatment. Physical activity plays a role in achieving a good recovery following a cancer cure.
Physical activity must be regular and adapted to each individual. The advice of a physiotherapist can be useful.