Hot chocolate can cause cancer

Food and cancer: what protects, what harms?

Cancer feeds on sugar - almost exclusively. The knowledge comes from a famous doctor: Otto Warburg. As early as 1924, the later Nobel Prize winner found out that the metabolism of cancer cells differs from that of healthy cells. In order to reproduce, cancer cells depend on glucose, i.e. sugar.

Warburg's finding is still correct. The diet recommendations that some derive from it, on the other hand, are not only wrong - they are dangerous. "Cancer cannot be starved by giving up sugar," explains Dr. Tilman Kühn, nutrition expert at the German Cancer Research Center (DKFZ) in Heidelberg. Instead, fasting regulations promote a threatening malnutrition from which many cancer patients suffer.

Less is more

The Warburg example stands for numerous dietary rules that haunt the internet and advice literature and want to conquer cancer with tea and raspberries. Findings from the Petri dish are all too quickly transferred to the organism, observations from the mouse to humans.

"Diet definitely has an impact on the development and course of cancer," says Kühn. However, different from what many think. As a rule, the most significant danger posed by food is completely overlooked: whether schnitzel or chocolate - those who eat too much of them increase the risk of cancer in particular.

"If the development continues as before, obesity will overtake smoking as a risk factor," predicts Professor Hartmut Bertz, nutritionist at the Freiburg University Medical Center. Experts have identified at least 13 types of cancer that too many pounds increase your risk of, including some of the most common such as colon, breast, and prostate cancers.

Belly fat hazard

"A woman with a body mass index of 30 doubles her risk of gynecological tumors," says Bertz. This BMI corresponds, for example, to 82 kilos with a height of 1.65 meters. The DKFZ estimates that around six percent of tumor diseases are currently due to obesity.

"Above all, the organ fat in the abdomen has an influence," explains Bertz. It affects the metabolism unfavorably in different ways. In addition to growth factors that allow tumor cells to thrive, the fat cells also produce the hormone estrogen. This can promote the development of hormone-dependent tumors in the female genital organs - hence the increased risk of breast cancer. In addition, messenger substances are released that lead to constant subliminal inflammation in overweight people. This, too, probably favors the development of malignant tumors.

Cancer from alcohol, red meat, and mold

In addition, researchers have unmasked some foods or ingredients that are most likely to promote cancer. First and foremost is alcohol, which has been shown to increase the risk of some common types of tumors. Grilling, roasting and deep-frying produce substances such as acrylamide and nitrosamines, which are also considered to be carcinogenic. Red meat and processed meat products increase the risk of developing colon cancer. Eating moldy foods is also a bad idea. At least if you don't grill or eat salami every day, the influence of all these dishes is rather small, according to Kühn.

But what about the opposite approach? Is there a diet that protects against tumors? Are there any anti-cancer foods? In fact, scientists have tracked down some ingredients that inhibit cancer growth in the laboratory, especially phytochemicals such as mustard oil glycosides and polyphenols. Research is being carried out into whether these can be isolated and used in high doses. "But we are completely gone from the hope that individual foods have an almost pharmacological effect against cancer," emphasizes DKFZ expert Kühn.

How to feed properly?

So eating broccoli, beetroot juice and lemons to prevent or fight cancer makes little sense - even if such myths are circulating on the Internet. One problem in nutritional research, according to Kühn: individual studies have shown spectacular results for certain foods, but these could never be repeated afterwards. In the meantime, scientists are systematically checking the entirety of the study situation in so-called meta-analyzes, which slowly makes errors and incorrect conclusions disappear.

Experts would like more studies, especially for the situation in which the question of the right diet arises: when people are confronted with the diagnosis of cancer.

So diet influences the risk of relapse. A current overview study by Munich researchers shows, for example: a menu that contains a lot of fruit, vegetables, whole grain products, legumes, poultry and fish improves the prognosis for breast cancer patients. However, those who consume a lot of fine flour products, red and processed meat as well as dairy products with a lot of fat have poorer healing prospects.

"Every cancer patient should receive nutritional therapy," urges Dr. Dagmar Hauner, nutritionist at the Munich University Hospital on the right of the Isar. And not just because it can improve the prognosis. "It also protects patients from falling into the hands of charlatans." Because the field of dubious nutrition gurus is huge. In addition, many patients have a strong desire to actively contribute to their healing. "You are highly motivated to do something yourself," is Hauner's experience. Also to change their diet.

Lose excess pounds after therapy

Which diet is the right one after a cancer diagnosis cannot be said in general terms. Age, disease stage, comorbidities and the type of cancer play a role. "Some tumors quickly lead to severe weight loss," said Hauner.

Since cancer increases the need for protein, enough foods should be on the menu to balance it. As a rule, patients are also allowed to eat high-fat. Although being overweight is unfavorable in the long term, the expert strongly advises against weight loss after diagnosis. Only when the therapy has ended and the cancer has been overcome for the time being should one begin to lose weight moderately and slowly.

Another important goal is to avoid a common side effect of a tumor disease: malnutrition. Depending on the type of cancer and therapy, the risk is very different, which is why care should always be taken. According to Kühn, one should take countermeasures at an early stage and use energy, protein and nutrient preparations under medical supervision. "The potential is completely untapped."

Trending diets

Feeding instead of withdrawing is the motto. As a result, cancer diets are usually poorly viewed by experts. "Every few years a new nutritional method pops up that promises miracles," says Professor Andreas Michalsen, chief physician of the Naturopathy Department at the Immanuel Hospital in Berlin.

The latest fad: ketogenic diet, a low-carbohydrate, high-fat diet. Many experts are critical of this. In a study that nutritionist Bertz carried out on healthy people, for example, there was a slight decrease in muscle mass - a problem that cancer patients suffer from anyway.

"If you get the fat and protein mainly from animal sources, it is definitely harmful," adds Michalsen. And expert Hauner also emphasizes: "So far it has not been scientifically proven that the ketogenic diet improves the prognosis."

However, there are initial positive results for another method: short-term fasting during chemotherapy, i.e. about 48 hours before and 24 hours after. In a study by Michalsen with 34 patients suffering from breast or ovarian cancer, this led to an improved quality of life. "Above all, tiredness, but also other side effects, were reduced," reports the expert in naturopathy.

Lent during chemo

Doctors explain the effect as follows: healthy body cells can adapt to times of hunger. "You basically go into hibernation," says Michalsen. They shut down their activity and split less often. The cancer cells remain highly active. The active ingredients of chemotherapy, which damage cells especially during division, then mainly hit the tumor cells.

However, further studies have to show whether short-term fasting is really recommended and to whom. For the time being, physician Michalsen warns cancer patients against fasting on their own: "You can do a lot of things wrong." So far, short-term fasting should only be carried out in specialized centers, ideally under study conditions.

Diet and cancer