Green tea, soy, antioxidants, young… So many foods, substances or eating practices to which anti-cancer virtues are attributed. If some of these assertions are unfounded, others are supported by the results of numerous studies, and validated by national and international collective expertises. Unfortunately, distinguishing between true and false is not always easy.
For two decades, the NACRe network (National Food Cancer Research network) has been advancing knowledge on the links between nutrition and cancer. It also makes available to the public the latest research results in this area.
Fruits and vegetables, dietary fibers, dairy products: on the occasion of its twentieth anniversary, here is a presentation of main nutritional factors recognized as reducing the risk of cancer.
Fruits and vegetables
Consumption of fruits and vegetables is associated with a reduced risk of aerodigestive cancers (cancers of the mouth, pharynx, larynx, nasopharynx, esophagus, lung, stomach, and colon-rectum), with a level of evidence considered probable.
Remember that there are three levels of proof (in descending order): convincing, probable, suggested / limited. They depend on the number, quality and consistency of the studies available, as well as the existence of underlying mechanisms making it possible to explain the observed effects.
It is better to favor whole fruits than fruit juices, which are too sweet and less rich in fiber.Jo Sonn / Unsplash
Low in calories, fruits and vegetables contain fibers and micronutrients (vitamins, minerals) as well as many micro-constituents (polyphenols, carotenoids, sulfur molecules, etc.). The latter can influence carcinogenesis through numerous biological mechanisms, such as antioxidant or antiproliferative activities or modulations of the metabolism of molecules foreign to the organism.
It is recommended to consume at least five servings of 80-100 g per day of fruits and vegetables, in all possible forms: fresh, frozen, canned, raw or cooked. On the other hand, it is better to limit your consumption of fruit juice to one glass per day at most. They contain high amounts of sugar, and less fiber than fruits.
It should also be noted that starchy foods such as potatoes are excluded from this “fruits and vegetables” category …
Consumption of dietary fiber is associated with a reduced risk of colorectal cancer, with a level of evidence considered probable.
This protective effect is explained by various biological effects: reduction of insulin levels in the blood, insulin resistance, circulating steroid hormone concentrations, intestinal transit time and cell exposure. colon to carcinogenic substances present in the lumen of the large intestine (the internal space of the organ, circumscribed by its walls).
Lentils and pulses are also sources of dietary fiber.Betty Subrizi / Unsplash
It is recommended that you eat foods high in fiber such as pulses like lentils or beans at least twice a week. The daily consumption of a whole grain product such as wholemeal bread is also recommended.
The five daily servings of fruits and vegetables mentioned above also provide their share of dietary fiber.
Consumption of dairy products is associated with a reduced risk of colorectal cancer (level of evidence considered probable).
Their protective effect comes from the calcium they contain, as well as the lactic acid bacteria they provide. It is therefore currently recommended to consume two dairy products per day such as milk, unsweetened yogurt, or cheese.
Note that a high consumption of dairy products is associated with an increased risk of prostate cancer, however the level of evidence is limited.
In addition to these dietary factors, research has also shown that practicing physical activity, even moderate, can also limit the risk of developing cancer.
Physical activity, an important protective factor
To exercise is associated with a decreased risk of colon cancer (convincing level of evidence), as well as a decreased risk of postmenopausal breast and endometrial cancer (probable level of evidence).
These results are valid for all types of physical activity and all intensity levels. In contrast, the reduction in the risk of breast cancer before menopause is only established for high intensity physical activity.
Several mechanisms can explain the importance of physical activity in the fight against cancer. Exercise lowers blood levels of hormones and growth factors, and affects insulin resistance and inflammation. It also stimulates immunity and accelerates intestinal transit, thus limiting the exposure of the intestine to carcinogenic substances being eliminated by the stool.
It is recommended get at least the equivalent of 30 minutes per day of dynamic physical activity , that is to say of an intensity at least equivalent to that of brisk walking. It is also advisable to reduce your sedentary lifestyle: do not sit still for too long, and take the time to walk a little every two hours.
Fruits and vegetables and physical activity also help reduce the risk of overweight and obesity, a factor involved in the occurrence of several cancers.
Avoid risk factors
The conclusions of the collective expert appraisals are clear: acting effectively in cancer prevention means above all avoiding exposure to risk factors. These are well known today: they are mainly tobacco, alcohol, an unbalanced diet and overweight.
According to International Agency for Research on Cancer, 346,000 new cases of cancer were diagnosed in 2015 in France in adults aged 30 and over. Among them, 142,000 cases are attributed to lifestyle and the environment, or 41% of all new cancer cases.
It is considered that in France, 16% of new cancer cases in men and 20% in women are attributable to nutritional factors. Indeed, while tobacco is the top four preventable causes of cancer (20% of attributable cancers), the other three relate to food. These are alcohol (8%), unbalanced diet (5.4%) and finally overweight and obesity (5.4%).
Nutrition and cancer: risk factors and protection. Inrae / DR
Insufficient physical activity is responsible for 0.9% of new cancer cases. Finally, an insufficient duration of breastfeeding would be involved in 0.5% of new cases of breast cancer.
To limit the risk of cancer, the first priorities are therefore to reduce the consumption of alcoholic beverages, to ensure that you have a balanced and diversified diet, as well as to maintain a healthy weight and to practice regular physical activity.
For further :
- the collection “Eat, drink, move… How can you reduce your risk of cancer? “ ;
- the collection “Decrypt & Understand” ;
- the collection “Fasting and cancer”.
Paule Latino-Martel, Research director. Coordinator of the National Food Cancer Research Network (NACRe network) from January 2000 to September 2020, Inrae and Bernard Srour, Coordinator of the National Food Cancer Research Network (NACRe network) – Scientist at the Divison of Cancer Epidemiology, German Cancer Research Center DKFZ, Heidelberg, Inserm This article is republished from The Conversation under a Creative Commons license. Read the original article.