The topic of nutrition and cancer has been the subject of intensive scientific research for decades. According to the German Cancer Research Center (DKFZ), around 40 percent of all new cancer cases are due to factors that we can influence: unhealthy diet, being overweight, regular alcohol consumption, lack of physical activity and smoking.
On the other hand, a balanced diet, a normal weight and the lowest possible consumption of alcoholic beverages reduce the risk of developing cancer. Although a healthy lifestyle and avoiding risk factors for cancer are no guarantee, up to 200,000 people in Germany could in principle avoid a cancer diagnosis every year, the DKFZ says.
What are the biggest risk factors?
Experts rank smoking as the leading risk factor that we can influence, according to the German public broadcaster ARD. This is confirmed, for example, by a study by the American Cancer Society published in 2024.
This causal relationship is already well known, but many other risk factors often remain in the background in public consciousness. In particular, alcohol consumption and obesity increase the risk of several types of cancer and are considered the most important factors related to nutrition - worldwide. With 10 grams of alcohol consumed daily, the risk of liver cancer increases by 4%, and the probability of developing squamous cell carcinoma of the esophagus increases by as much as 25 percent, the publication further states.
In addition, the risk of various types of cancer increases with each increase in body mass index, for example by 5% for colon cancer and up to 50% for endometrial cancer. High-calorie food and obesity can cause chronic inflammation, which is a key factor in the development of cancer, according to the authors of the study in question. The International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) classified unprocessed red meat as "probably carcinogenic to humans" in 2015, and processed meat as – even as – – as "carcinogenic". Even with the consumption of 50 grams of processed meat per day, the risk of colon cancer increases.
Are there any foods that protect against cancer?
In general, there is now a broad consensus that a varied diet rich in plant foods is best suited to reducing the risk of cancer, says another conclusion from the DKFZ. But a healthy diet must go hand in hand with physical activity. Energy balance and body weight also play an important role.
There are also indications that green tea may reduce the risk of cancer. A 2020 analysis, for example, found that it reduces the risk of endometrial cancer, lung cancer, oral cancer and ovarian cancer, as well as the risk of developing Hodgkin lymphoma. However, for many other types of cancer, only unclear or no links have been found.
The European Code Against Cancer recommends a generally balanced diet, rich in plant foods and low in highly processed, calorie-dense foods. Here are some tips:
Eat whole grains, legumes, vegetables, and fruits often;
Eat low-calorie foods high in fat and sugar;
Avoid sugary drinks;
Avoid processed meats;
Eat little red meat and foods high in salt;
Drink alcohol a little and not every day;
Pay attention to a healthy body weight.
Can we cure cancer through proper nutrition?
Good nutrition can help patients overcome cancer more easily and improve their quality of life. But according to the German Cancer Research Center (DKFZ), there is no evidence to date that cancer can be cured with certain forms of nutrition.
Which diet is suitable for an existing cancer depends on the type of tumor and the stage of the disease, but also on the age and general health of the patient. Therefore, those affected should discuss with their doctors what they should pay attention to in their diet, the ARD publication also says.