Anti-cancer diets, foods or nutrients: what are we talking about? – Afis Science

ΛCancer affects us: it can affect us personally or our loved ones. The fear of cancer or the diagnosis itself is often accompanied by the search for information in various media and through the Internet. In this search for information, the role of food plays an important role. Since we need to eat every day, food is a well-known area where we can act immediately and make choices on a daily basis.

Is there a link between diet and cancer? Are there “anti-cancer” foods?

For the past 20 years or so, claims about anti-cancer diets, foods, or nutrients have been made regularly, and have been made or discussed by successful book authors. These claims are available in various media (articles, books, etc.), products (diet diets, dietary supplements) or services (conferences, internships, consultations), which are charged and represent a real market.

However, at the same time, French or international institutions that are officially responsible for evaluating knowledge in the field of food and cancer, and the experts themselves, are trying to inform the public and patients about proven relationships between diet and cancer and the fact that There is no specific food, diet or miraculous nutrient that alone can prevent or cure cancer.

Between scientifically validated public health messages and information circulating, there is a significant gap in which we propose to shed light.

Proven links between diet and cancer risk

The Collective Assessment Project for Experts of the National Cancer Institute (INCa) [1], by the International Agency for Research on Cancer (IARC) [2], the World Cancer Research Fund (WCRF) and the American Cancer Research Institute (AICR) [3] evaluation and updating of data levels (see box) of nutritional / nutritional and cancer relationships. Thus, convincing or possible levels of evidence for various nutrients, beneficial or harmful factors have been demonstrated. Here the diet includes food, but also dietary supplements, drinks (including alcohol), physical activity and diet (including body building).

We now know that in France, 40% of cancers are linked to lifestyle and the environment. [2]. Among the four main causes of cancer that can be prevented, after smoking, three concern diet: alcohol, unbalanced diet and overweight (overweight and obesity).

When it comes to diet, it is recommended that you eat a balanced diet (see Figure 1). These recommendations are compatible and consistent with the new dietary recommendations of the National Health and Nutrition Program for French adults, which aim to improve the nutritional prevention of chronic diseases as a whole (cardiovascular disease, cancer, diabetes, etc.). [4]. They are broadcast by the NACRe Network (National Food Cancer Research Network, made up of public research teams and experts) which currently plays an important role in informing the public (the general public, patients, health professionals, the media, etc.). ) [5].

Food during illness

The number of available scientific studies on the role of food in people already suffering from cancer is much more limited than for primary prevention of these cancers (before the onset of the disease). However, we know that the nutritional status of cancer patients affects the quality of life, tolerance to anti-cancer therapies and the prognosis of the disease. It varies depending on the type of cancer, the stage of the disease and the side effects of the treatments and also depends on previous illnesses. Many patients find it difficult to eat during treatments. Some suffer from malnutrition, others, on the contrary, gain too much weight. Therefore, recommendations have been developed specifically for these different situations [6]. Prevention of malnutrition (resulting in weight loss or muscle), control and treatment are therefore major issues in the care of cancer patients [7].

Food and Cancer Links: Criteria for Determining Levels of Evidence

For several decades, traditional medicine based on passive information transmission and mainly based on physiopathological observations and personal experience of physicians has given way to evidence-based medicine. This is now based on a critical reading of the scientific literature, taking into account the “level of evidence” and provides a permanent reassessment of knowledge. [1]. This approach applies to the role of food during illness, which can lead to recommendations for dietary cancer management. It is also necessary to determine or approach a causal relationship between the nutritional factor being considered and the risk of disease, which may lead to recommendations for dietary cancer prevention.

The published scientific studies are considered to be of declining importance:

Intervention tests 1

  • meta-analyzes or aggregate analyzes 2 human intervention tests;
  • Otherwise, individual intervention tests.

Note: intervention studies are not feasible for ethical reasons. Diet intervention studies are yours

air difficult to apply, the intervention cannot be long-term, nor can it be performed blindly.

The studies

epidemiological observation

  • meta-analyzes or aggregate analyzes of cohort studies (perspectives, ie by monitoring participants’ time).
  • Otherwise, individual cohort studies;
  • Otherwise, post-analyzes or aggregate analyzes of epidemiological case studies;
  • Otherwise, individual case studies.

Mechanical studies in animals or in cultured cells.

Note: Experimental studies performed on animal models or cells in culture are useful for analyzing the biological rationality of the relationship between a studied factor and cancer risk. When their effects are encouraging and consistent, they can serve as a starting point for conducting epidemiological studies or clinical trials in humans, but they are not sufficient to determine levels of evidence in humans.

Report

1 | Latino-Martel P et al., “How to move from the level of evidence to recommendations for public health”, French Food and Health Fund, Scientific Letter no. 2, September 2001. On alimentation-sante.org

Unsubstantiated and misleading allegations of cancer

Figure 1: Recommendations for dietary cancer prevention.

Consumers today are waiting for a lot of food to improve their health and well-being. Instead of changing their eating habits, some people choose to take antioxidants in the form of supplements. Others, sensitive to the promises they make, are looking for superfoods whose main feature is the abundant presence of certain antioxidants. Still others are dealing with restrictive regimes.

Anticancer claims, such as those shown in Figure 2, suggest results only from experimental studies performed on experimental animals or cells in culture. In the absence of convincing studies in humans, these claims are unfounded.

In prevention, the perception of anti-cancer foods or nutrients is misleading because cancers have a multifactorial origin and no specific food or nutrient can serve as an “antidote”. For 90 to 95% of cancers, there is an interaction between genetic inheritance and the risks and protective factors to which the body is exposed throughout life. [8]. The effective action in cancer prevention is to start by avoiding exposure to important risk factors such as tobacco, alcohol, nutritional imbalance and overweight. Believing that someone can get away with cancer thanks to a food or a dietary supplement, or avoiding a particular food while continuing to be exposed to these risk factors is a bait!

As for the antioxidants (polyphenols, vitamin C …) provided by the so-called “anti-cancer superfoods” such as turmeric, ginger, soursop, pomegranate juice, green tea, frozen lemon …, it is necessary to take the main research courses in this area [9].

What scientific research has taught us

Figure 2: The most common anti-cancer claims.

The so-called “antioxidant” substances 3 are able to exert multiple biological effects that may prove protective or harmful depending on the pathophysiological condition [10]. At high doses, they can be treated as pre-oxidants and pro-carcinogenic in people exposed to risk factors. [11]. This has been shown, for example, in dietary supplements that contain high doses of beta carotene, which increase the risk of lung and stomach cancer, especially in smokers and people exposed to asbestos.

In advanced stages of tumor growth (preclinical cancer), oxidative stress (which antioxidants aim to prevent) can even act as a brake on tumor progression. Thus, in the treatment of cancer, certain chemotherapeutic agents are used because they destroy cancer cells by creating oxidative stress. In these two cases, swallowing large amounts of antioxidants may therefore be harmful. [12].

In France, we are watching the madness of the public and cancer patients for the practice of fasting. Many books for the general public, clinics and hiking organizers [13] Promoting fasting in relation to health for a preventive or therapeutic purpose testifies to this enthusiasm and strengthens it. Some people claim beneficial effects on cancer, such as better tolerance and effectiveness of treatments. These claims raise new expectations for cancer patients. Some seek the services of oncology health professionals to fast during their treatment. Others do it without informing the health professionals involved in the treatment process.

In this context, the NACRe network conducted a systematic review of the scientific literature and published a collective evaluation report. [14] who rejects these allegations:

  • Most of the available scientific data comes from animal studies, which have significant limitations and do not allow for human extensions. Human data from epidemiological studies or clinical trials

they are not much. Clinical trials are of low quality because most of the time they do not have a control group and include a small number of individuals.

  • At present, there is no evidence in humans of the protective effect of fasting on primary prevention (in relation to cancer development) or during disease (if it is a therapeutic effect or interaction with cancer treatments).
  • In the treatment of cancer, the practice of fasting carries a risk of worsening malnutrition or sarcopenia (loss of muscle mass), two factors that have a negative impact on the prognosis of the disease.

Public perceptions and perceptions of patients

Husband of the tea merchant, Boris Koustoviev (1878-1927)

According to the Cancer Barometer (survey of a sample of 4,000 people, a representative of the French population) [15], French adults are relatively numerous who do not know the effect of dietary factors on cancer risk (in 2015, between 38% and 88% depending on the dietary factor under consideration).

However, an anthropological study shows that in the absence of information and advice on food, people with cancer turn to people who offer complementary non-conventional and non-validated treatment practices (naturopathy, homeopathy …) [16].

Recent epidemiological work using data from the large French NutriNet-Santé [17] provides new and more accurate information on food collection practices and views on food:

  • Among the 42,000 people surveyed, 85% said they used the Internet to receive health and nutrition information and 23% to read or post messages on a health / nutrition forum. Only 16% of participants discuss information obtained online with a healthcare professional. Institutional sites account for only 13% of the 8,000 sites listed by participants as the preferred source of information in the health and nutrition sectors. Only one institutional site (mangerbouger.fr) was present on the 10 most popular nutrition / health sites. Older participants, with lower levels of education and less knowledge of formal dietary recommendations, were more likely to visit non-institutional sites. [18].
  • Among the 2,000 people who were suspected of having or had cancer, 30% reported the media as the main source of information on nutrition, 21% health professionals, 21% Internet, 15% books, 11% favorite, 1% patient correlation. Overall, patients who attribute properties (protective or at risk) that are not scientifically based on nutritional factors (dietary supplements, organic products, dairy products, etc.) more often report the Internet as a source of information about nutrition. [19].

Conclusions

Breakfast, Amalia Lindegren (1814-1891)

Even if, in general, foods that contain antioxidants, especially fruits and vegetables, contribute to a healthy, balanced and varied diet and help reduce the risk of chronic disease, the “higher” interest of the supposedly super to be anti-cancer food to be prooved.

Similarly, there is no evidence that antioxidants are universal antidotes to the disease. In well-nourished populations, therefore at low risk of antioxidant deficiencies, dietary supplements could even present some risks and their long-term effects are still well known. Above all, in the current state of knowledge, the scientific community does not recommend taking long-term dietary supplements. a fortiori the combination of dietary supplements, especially in the case of the present or previous exposure to risk factors.

Fasting, on the other hand, is a social event that the medical world and health services cannot ignore, although its healing properties have not been proven. Patients have high hopes for unconventional practices. Healthcare professionals must therefore listen to their patients’ expectations and allow for dialogue, taking into account the current state of scientific knowledge and potential risks. Training programs for complementary medicine and restrictive diets such as fasting could be offered to health professionals, including caregivers in oncology services.

Finally, in this cacophonous context where formal recommendations coexist with contradictory or unfounded messages, it is important to develop strategies aimed at more effectively transmitting key messages to the general public and patients.

Paule Latino-Martel, Julie Ginhac, Juliette Bigey, Philippine Fassier, Mathilde Touvier

Reports

1 | INCa / NACRe, “Nutrition and Prevention of Primary Cancer: Data Update”, INCa Report, 2015. On inra.fr/nacre
2 | CIRC / INCa, “Cancers due to lifestyle and environment in metropolitan France”, CIRC report, 2018. On inra.fr/nacre
3 | WCRF / AICR “Nutrition, Nutrition, Physical Activity and Cancer: A Global Perspective. Summary of the third expert report “, WCRF Report, 2018. On inra.fr/nacre
4 | Public Health France, “Recommendations for diet, physical activity and sedentary lifestyle for adults”, 2019. On inra.fr/nacre
5 | NACRe Network, “Eat, Drink, Move: How to reduce your risk of cancer? », 2018. In inra.fr/nacre
6 | SFNEP / NACRe Network, Summary of Recommendations “Diet in Adult Cancer Patients”, 2012. On inra.fr/nacre
7 | Δίκτυο NACRe, Εστίαση στο “Υποσιτισμός, οι συνέπειές του και οι θεραπείες του”, 2016. On inra.fr/nacre
8 | INCa, “Παράγοντες κινδύνου”, φάκελος “Τι είναι ο καρκίνος; ” Στο e-cancer.fr
9 | Latino-Martel P et al., «Τι απομένει από τα αντιοξειδωτικά και τις επιπτώσεις τους; “, Αναθεώρηση ιατρού, 2017, 8: 831-4.
10 | ANSES, «Διατροφή και καρκίνος. Νομιμότητα των διατροφικών συστάσεων στο πλαίσιο της πρόληψης του καρκίνου », 2011. On anses.fr
11 | INCa, “Διατροφή και πρόληψη του πρωτογενούς καρκίνου: ενημέρωση των δεδομένων”, 2015. Στο e-cancer.fr
12 | Latino-Martel P et al., “Διατροφή σε ενήλικες ασθενείς που πάσχουν από καρκίνο: αντιοξειδωτικά συμπληρώματα διατροφής κατά τη διάρκεια και μετά τη θεραπεία του καρκίνου”, Nutr Clin Metabol, 2012, 26: 238-246.
13 | Γαλλική Ομοσπονδία νηστείας και πεζοπορίας.
14 | Δίκτυο NACRe, «νηστεία, περιοριστικές δίαιτες και καρκίνος: συστηματική ανασκόπηση επιστημονικών δεδομένων και κοινωνικο-ανθρωπολογική ανάλυση σχετικά με τον τόπο νηστείας στη Γαλλία», 2017. Onra.fr/nacre
15 | INCa, “Cancer Barometer 2015”, 2019. Στο e-cancer.fr
16 | Cohen P, Legrand E, «Τροφή και καρκίνος. Πρόσωπα που επηρεάζονται και εναλλακτικές αρχές », Ανθρωπολογία & Υγεία, 2011, doi: 10.4000 / ανθρωπολογίαante.629
17 | etude-nutrinet-sante.fr
18 | Fassier P et al, «Αναζήτηση πληροφοριών σχετικά με την υγεία και τη διατροφή στο Διαδίκτυο σε μεγάλο πληθυσμό Γάλλων ενηλίκων: αποτελέσματα της μελέτης NutriNet-Santé», Br J Nutr., 2016, 115: 2039-46.
19 | Fassier P, “Τροφή, κατανάλωση αλκοόλ, σωματική δραστηριότητα, πρόσληψη συμπληρωμάτων διατροφής, διακύμανση βάρους και διατροφικές αναπαραστάσεις: εξέλιξη πριν / μετά τη διάγνωση του καρκίνου”, Διδακτορική διατριβή, Πανεπιστήμιο του Παρισιού 13, 2017.

Διατροφή: καρκίνοι που οφείλονται

Ο Διεθνής Οργανισμός Έρευνας για τον Καρκίνο (IARC) συντόνισε μια μελέτη για τις αιτίες του καρκίνου στη Γαλλία, στην οποία συμμετείχαν περισσότεροι από 80 ερευνητές [1] . Το 2015, υπήρχαν 350.000 νέες περιπτώσεις καρκίνου, συμπεριλαμβανομένων 140.000 (41%) που σχετίζονται με τον τρόπο ζωής και το περιβάλλον. Η πρώτη αποτρέψιμη αιτία καρκίνου στη Γαλλία είναι ο καπνός, στον οποίο 69.000 καρκίνοι οφείλονται το 2015 ή το 20% των καρκίνων. Αλλά η διατροφή, εάν συμπεριλαμβάνετε αλκοόλ, παχυσαρκία και υπερβολικό βάρος, είναι επίσης μια πολύ σημαντική αιτία καρκίνου: 28.000 καρκίνοι οφείλονται σε

κατανάλωση αλκοολούχων ποτών (η δεύτερη κύρια αιτία καρκίνου στη Γαλλία), 19.000 με μη βέλτιστη διατροφή, 19.000 με παχυσαρκία και υπέρβαρο1. Επιπλέον, υπάρχουν 3.000 νέες περιπτώσεις καρκίνου κάθε χρόνο λόγω έλλειψης σωματικής άσκησης.

Σε αυτή τη μελέτη, μια μη βέλτιστη διατροφή ορίζεται από την κατανάλωση λιγότερο από 300 γραμμάρια φρούτων την ημέρα, λιγότερο από 25 γραμμάρια ινών την ημέρα, επεξεργασμένα κρέατα (ζαμπόν, πατέ, λουκάνικο κ.λπ.), περισσότερα από 300 γραμμάρια κρέατος. κόκκινο την εβδομάδα, λιγότερο από 300 γραμμάρια μη αμυλούχων λαχανικών την ημέρα και λιγότερο από δύο μερίδες γαλακτοκομικών προϊόντων (15 cl γάλα, 30 g τυρί, γιαούρτι) την ημέρα.

Ο πίνακας παρουσιάζει τις εκτιμήσεις των κλασμάτων που οφείλονται στη διατροφή κατά τη θέση του καρκίνου. Στα τρόφιμα, αυτό που συμβάλλει περισσότερο στον κίνδυνο καρκίνου στον πληθυσμό είναι η ανεπαρκής κατανάλωση φρούτων (4.900 καρκίνοι) και ινών (4.700 καρκίνοι), η κατανάλωση μεταποιημένου κρέατος (4.400 καρκίνοι), πάρα πολύ κόκκινο κρέας (2.000 καρκίνοι), όχι αρκετά λαχανικά (1.800 καρκίνοι) και όχι αρκετά γαλακτοκομικά προϊόντα (850 καρκίνοι). Περίπου το 69% των ενηλίκων δεν τρώνε τη συνιστώμενη ποσότητα φρούτων, το 85% δεν τρώνε αρκετές φυτικές ίνες, το 69% δεν τρώνε αρκετά λαχανικά και το 39% δεν τρώνε αρκετά γαλακτοκομικά προϊόντα. Επιπλέον, το 62% των ενηλίκων καταναλώνουν ποσότητες κόκκινου κρέατος μεγαλύτερες από αυτές που συνιστώνται και το 84% των ενηλίκων καταναλώνουν μεταποιημένα κρέατα.

Και το 58% του πληθυσμού δεν ασκεί μέτρια σωματική δραστηριότητα για 30 λεπτά την ημέρα (όπως ηλεκτρική σκούπα ή ποδηλασία ήσυχα).

Εκτίμηση του κλάσματος των καρκίνων που αποδίδεται στη διατροφή και του συνολικού αριθμού των καρκίνων το 2015 ανά τοποθεσία των καρκίνων, με σειρά μειωμένης συχνότητας 1


1 * Ο αριθμός που αποδίδεται στο σύνολο είναι μικρότερος από το άθροισμα, επειδή πολλές αιτίες μπορούν να συμβάλουν στον ίδιο καρκίνο. Το κλάσμα που αποδίδεται σε ένα σύνολο δύο παραγόντων είναι ίσο με το άθροισμα μείον το προϊόν των δύο αποδόσιμων κλασμάτων.

Κάθριν Χιλ (επιδημιολόγος)

Αναφορές

1 | Διεθνές Κέντρο Έρευνας για τον Καρκίνο, “Καρκίνοι που οφείλονται στον τρόπο ζωής και το περιβάλλον στη μητροπολιτική Γαλλία”, 2018. On gco.iarc.fr

1 Για να είναι καλής ποιότητας, οι δοκιμές παρέμβασης πρέπει να περιλαμβάνουν δύο ομάδες (παρέμβαση και έλεγχος), να σχετίζονται με μεγάλο αριθμό θεμάτων που κατανέμονται τυχαία στις δύο ομάδες και να πραγματοποιούνται σε διπλά τυφλά (κατά τη διάρκεια της παρέμβασης, Οι αρχηγοί της μελέτης και τα άτομα δεν γνωρίζουν ποιος επηρεάζεται σε κάθε ομάδα).

2 Στατιστικές αναλύσεις που συνδυάζουν και συνθέτουν τα αποτελέσματα πολλών μελετών.

3 Ένα αντιοξειδωτικό είναι ένα μόριο ικανό να εξουδετερώνει τις ελεύθερες ρίζες (χημικά είδη με ένα ή περισσότερα ζεύγη ηλεκτρόνια, που χαρακτηρίζεται από πολύ υψηλή αντιδραστικότητα και οξειδωτική ισχύ), και επομένως προστατεύει το κύτταρο από βλάβες που προκαλούνται από αυτές τις ελεύθερες ρίζες. Τα αντιοξειδωτικά μπορούν να παρέχονται από τρόφιμα (βιταμίνες Ε και C, καροτενοειδή, ορισμένες πολυφαινόλες …). Ορισμένα υψηλής δόσης αντιοξειδωτικά (καταναλώνονται με τη μορφή συμπληρωμάτων διατροφής ή εμπλουτισμένων τροφίμων) συμπεριφέρονται ως προ-οξειδωτικά, δηλαδή ότι, σε αντίθεση με το αναμενόμενο αποτέλεσμα, οδηγούν στο σχηματισμό ελεύθερων ριζών.

Anti-cancer diets, foods or nutrients: what are we talking about? – Afis Science
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