Nutrition plays an important role because it forms the basis for a healthy lifestyle. Through food, the body receives the necessary energy and is supplied with vitamins, minerals and trace elements that are essential for many of the body's functions. If the body is weakened by cancer or chemotherapy, for example, a healthy and balanced diet is even more important to support the body in the healing process.
The type of diet that is beneficial to health is influenced, among other things, by the cancer and the therapy. Accordingly, there is no standardized cancer diet, although there are many myths surrounding this topic.
This article dispels some myths and presents general nutritional recommendations. The following content is intended to provide an overview of important facts and serve as an initial guide. It does not replace individual medical or nutritional advice.
Cancer diet myths
The optimal cancer diet does not exist. Foods or dietary supplements that advertise this general promise currently do so without sufficient evidence, and many myths also harbor serious dangers, which are discussed below:
Antioxidants: cell protection vs. therapeutic influence
Antioxidants offer protection against so-called free radicals. Free radicals are formed by the body itself during various metabolic processes, but are also caused by harmful external influences such as cigarette smoke, UV radiation from the sun or environmental toxins. Antioxidants protect cells through their antioxidant effect and thus fundamentally help to keep cells healthy and prevent diseases.
Antioxidants include vitamins B2, C, E, selenium and zinc, as well as secondary plant substances such as beta-carotene and reveratrol.
However, they can also have negative effects in cancer therapy:
Free radicals can cause DNA damage, which can trigger cancer. In high concentrations, however, free radicals can also kill tumor cells, which presumably contributes to the therapeutic effect of cyostatics and radiotherapy. Antioxidants protect cells from oxidative stress caused by free radicals, which is desirable in healthy cells but undesirable in tumor cells.
The scientific findings to date are the result of basic research. Whether antioxidants increase the risk of metastasis has not yet been conclusively clarified, as clinical studies are lacking.
In addition to the type of cancer, the stage of the disease and the treatment method, the antioxidant substance taken and the concentration of the substance also play a role. For example, it cannot currently be ruled out that vitamin C, E and beta-carotene may influence chemotherapy or radiotherapy. Some vitamins can also interact with cancer drugs [1-6].
For this reason, various professional societies advise against taking dietary supplements with high doses of antioxidants during tumor therapy. In any case, inform your doctor if you still want to take dietary supplements.
Sugar: health vs. cancer growth
In the vernacular, sugar often refers to the industrially produced, sweet energy supplier. In other contexts, this term is used in a broader sense: in a nutritional context, it also refers to carbohydrates, and in a medical context to glycans. Sugar in its broadest sense describes the fourth large biomolecule group that occurs in all living organisms. Sugars in their various forms are fundamental to health because
- they are a main source of energy,
- have an influence on protein structures (folding) and
- the transport of proteins,
- signal transmission and
- on numerous other biological processes in the human body.
These sugar functions also play a role for various cancer cells.
- Sugar and cancer risk
Scientists have not yet been able to establish a direct link between sugar consumption and cancer. Indirectly, however, a diet high in sugar can lead to overweight and obesity, which can increase the risk of various types of cancer. A balanced diet rich in fruits, vegetables, whole grains and lean proteins is recommended to promote overall health and minimize the risk of cancer.
- Sugar and cancer growth
Cancer cells need energy to multiply. They can also obtain this energy from carbohydrates such as sugar. However, so far there is no scientific evidence that a sugar-free diet curbs the growth of cancer cells. Instead, a sugar-free diet can lead to malnutrition and weight loss, which can be detrimental to therapy and the healing process.
Cancer societies such as the American Cancer Society and the German Cancer Research Center recommend a balanced and healthy diet during and after cancer treatment. They generally recommend reducing the consumption of refined sugar and highly processed foods, as these often contain fewer nutrients.
Supportive diet
A balanced and healthy diet is fundamentally important for health - this also applies to cancer. Although there is no single optimal diet for cancer, nutrition can support cancer therapy.
A light wholefood diet, also known as a general light diet or basic diet, is generally recommended. In the light whole food diet, foods that often lead to intolerances are avoided. Instead, more foods are included in the diet that are easy to digest and therefore less stressful. Which foods are suitable for a light wholefood diet depends on the individual, as tendencies towards food intolerances are influenced both genetically and by lifestyle. They therefore vary from person to person.
One form of nutrition that can be considered according to the German Cancer Aid, but is currently not officially recommended due to a lack of results, is a metabolically adapted diet. Studies have shown that a diet with a higher proportion of fats and proteins and a lower proportion of carbohydrates can be beneficial in the context of cancer. This is based on the fact that energy from fats can be better utilized than from carbohydrates. Fats that are often avoided in general “healthy” cuisine are recommended here: e.g. meat, cocoa fat, coconut fat and fish oil. Healthy people should get 30% of their energy from fats; according to the experts, this is too little for cancer patients. With regard to proteins, the recommendation is to consume 1.2-2g per kilogram of body weight per day. Foods with a particularly high protein content include meat, fish, eggs, cheese, pulses, nuts and cereals.
Diets such as an exclusively alkaline or ketogenic diet, which are increasingly mentioned in the context of nutrition for cancer patients, are not included in the professional recommendations considered here.
The German Nutrition Society (DGE) recommends the following for a healthy and wholesome diet:
- Eat a varied diet
A varied diet ensures an adequate supply of all the different nutrients.
- Vegetables and fruit 5 times a day
Three portions of vegetables and two portions of fruit a day are recommended.
- The whole grain
Whole grain products fill you up for longer and contain more nutrients, such as fiber, than white flour products. About 30g of fiber should be consumed per day.
- Animal products
As fish provides important nutrients such as iodine and omega-3 fatty acids, it is advisable to include it 1-2 times a week. Milk and dairy products can also be consumed daily as a source of calcium. However, meat and eggs should only be eaten in moderation. Although meat also provides iron and vitamins, the International Agency for Research on Cancer classifies red and processed meat as probably carcinogenic. The type and quantity of meat should therefore be taken into account.
- Healthy fats
The focus here should be on vegetable rather than animal fats (e.g. olive oil). These provide important fatty acids, but are also very high in energy and can lead to obesity. A conscious dosage is therefore also necessary here.
- Reduce sugar and salt
Watch out for hidden sugar, e.g. in sweet drinks. Also make sure that your daily intake of salt does not exceed 6g/1 tsp per day.
- Water supply
You should drink about 1.5 liters of liquid per day. Preferably unsweetened drinks such as water or tea. Alcohol should only be consumed occasionally and in moderation.
- Gentle preparation
To preserve the nutrients, we recommend cooking at a low temperature with little water and fat.
- Time and enjoyment
Conscious, mindful eating with sufficient time promotes a feeling of satiety.
- Weight and exercise
A combination of sufficient physical activity and a balanced diet can help maintain a healthy body weight.
The topic of nutrition can raise many questions in the context of cancer. As nutritional requirements can vary depending on the type and stage of cancer, the therapies used and the individual's state of health, it is advisable to consult a nutritionist or doctor to develop a nutritional strategy tailored to individual needs.
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