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Cancer and nutrition

Nutrition plays an important role in our lives and forms the basis for a healthy lifestyle. Through food, the body receives the necessary energy and is supplied with vitamins, minerals and trace elements, which are essential for the body's functions.

If the body is weakened by cancer, for example, a healthy diet is particularly important. However, many patients face questions and uncertainties: Special diets are recommended for some types of cancer. Some chemotherapy also requires a change in diet. In addition to the complexity of the disease and treatment, there are many myths about nutrition in cancer, especially in the digital space.

This article dispels some myths and presents general dietary recommendations. The following content is intended to provide an overview of important facts and serve as an initial orientation. They do not replace individual, medical or even nutritional therapy advice.

Cancer diet myths

The optimal cancer diet does not exist. Foods or dietary supplements that advertise this general promise are currently doing so without sufficient evidence.
Many myths also pose serious dangers, which are discussed below:


Antioxidants provide protection against so-called free radicals. Free radicals are produced 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 contribute to keeping cells healthy and preventing 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 during cancer treatment:

On the one hand, free radicals can cause damage to DNA, which can trigger cancer. In high concentrations, free radicals can kill cells, including tumor cells, which presumably also contributes to the therapeutic effect of zyostatic drugs and radiotherapy. On the other hand, antioxidants protect against oxidative stress triggered by free radicals. This effect is certainly desirable for healthy cells, but not for tumour cells. Existing scientific findings result from basic research. Whether antioxidants increase the risk of metastasis has not yet been conclusively clarified, as clinical studies are missing.
In addition to the type of cancer, the stage of the disease and the method of treatment, it also plays a role which antioxidant substance is taken in which concentration. For example, it cannot currently be ruled out that vitamins C, E and beta-carotene influence chemotherapy or radiotherapy. Some vitamins may also interact with anticancer drugs [1-6]

Overall, cancer patients are advised by various professional associations against taking dietary supplements containing high-dose antioxidants during tumour therapy. In any case, tell your treating doctor if you still want to take dietary supplements.


Sugar is not just a sweet source of energy. In the nutritional context, carbohydrates are usually referred to, but in a medical context, glycans. Sugars are the fourth major group of biomolecules found in all living organisms. Sugars are essential for health. They play a role in energy balance, but also influence protein structures (folding) and the transport of proteins, signal transmission and numerous other biological processes in the human body. These functions of sugar also play a role in various cancer cells.

Attention should be paid to sugar as an energy supplier, as there are some myths circulating in this context:

Cancer cells need energy to reproduce. They can also obtain this energy from carbohydrates such as sugar. To date, however, 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 harm therapy and the healing process.

Supportive diet

In principle, a balanced and healthy diet is important for health — this also applies to cancer. Although there is no optimal diet for cancer, nutrition can support cancer treatment.

A light whole diet, also known as a general light diet or basic diet, is generally recommended. In light whole foods, foods that often lead to intolerances are avoided. Instead, more foods are being included in the diet that are easy to digest and therefore less stressful. Which foods are suitable for light whole foods is individual, as tendencies towards food intolerances are influenced both genetically and by lifestyle. They are therefore different from person to person.

A diet that can be considered according to German Cancer Aid, but currently due to lack of results not officially recommended Will, is the metabolically adapted diet. Studies have shown that a diet with an increased 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 are recommended here, which are often avoided in general “healthy” cuisine: e.g. meat, cocoa fat, coconut oil and fish oil. Healthy people should get 30% of their energy from fats, which, according to experts, is not enough for cancer patients. With regard to egg whites If the recommendation is available 1.2-2g per kilogram of body weight per day to eat. Foods with a particularly high protein content include meat, fish, eggs, cheese, legumes, nuts or grains.

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.

For a healthy and wholesome diet, the German Nutrition Society (DGE) recommends:

  1. Eat in a variety of ways: A varied diet ensures an adequate supply of all different nutrients.
  2. Vegetables and fruit 5x a day: Three portions of vegetables and two portions of fruit a day are recommended.
  3. The whole grain: Whole grains saturate longer and contain more nutrients, such as fiber than white flour products. Around 30g of fiber should be consumed per day.
  4. Animal products: Since fish provides important nutrients such as iodine and omega-3 fatty acids, it is advisable to incorporate them 1-2 times a week. Milk and dairy products can also be eaten daily as sources of calcium. However, meat and eggs should only be eaten in doses. Although meat also contains iron and vitamins, the International Agency for Research on Cancer classifies red and processed meat as likely to be carcinogenic. The type and quantity of meat should therefore be considered here.
  5. Health-promoting fats: Here, the focus should be on vegetable and not 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.
  6. Save sugar and salt: Be careful when it comes to hidden sugar, e.g. in sweet drinks! Also note that your daily intake of salt does not exceed 6g/1 tsp per day.
  7. Drink: You should drink around 1.5 liters of liquid per day. Prefer unsweetened drinks, such as water or teas. Alcohol should only be drunk occasionally and in moderation.
  8. Gentle preparation: In order to preserve the nutrients, it is recommended to cook at a low temperature with little water and fat.
  9. Time and enjoyment: Eating consciously with enough time promotes satiety.
  10. Weight and exercise: A combination of adequate physical activity and a balanced diet can enable a healthy body weight.

[1] Gorrini, C.; Harris, I.; Mak T.: Modulation of oxidative stress as an anticancer strategy. Nat Rev Drug Discov 2013; 12:931-947

[2] Holch, JW; Michl, M; Heinemann, V;, Erickson, N.: Vitamins and trace elements in oncology. German Med Weekly 2017; 142 (12) :896-902

[3] Martinovic, LS; Persuric, Ž; Pavelić, K: Nutraceuticals and Metastasis Development. Molecules. 2020; 25 (9): E2222. Published 2020 May 8.

[4] Obrador, E; Liu-Smith, F; Dellinger, RW et al.: Oxidative Stress and Antioxidants in the Pathophysiology of Malignant Melanoma. Biol Chem. 2019 Apr 24; 400 (5): 589-612

[5] Le Gal, K; Ibrahim, MX; Wiel, C et al.: Antioxidants can increase melanoma metastasis in mice. Sci Transl Med. 2015; 7 (308): 308re8.

[6] Piskounova, E; Agathocleous, M; Murphy, MM et al.: Oxidative stress inhibits distant metastasis by human melanoma cells. Nature. 2015; 527 (7577): 186—191