Diet and cancer: what do we know?

Diet and cancer: what do we know?
Diet and cancer: what do we know?

We hear a lot about cancer and diet. But what do we really know about the scientific validity of the statements we are presented with? A recent report conducted by the National Cancer Institute helps us to see more clearly.

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This is the subject where all thrive and plague the new food gurus : the cancer. They can heal everything through the way of life. To fight them, only one weapon at our disposal: science and its method. Certainly, it is less encouraging because it does not have all the answers. Also, it does not necessarily tell us what we want or need to hear. But make no mistake about it: to fight against the sometimes pitiless nature of reality, deluding yourself is useless. In order to fight such serious diseases, you have to get to know them. We need to carefully study the data we have to find out what we know and what we don’t know. This in order to guide us, according to our objectives, towards what we want and what we do not want to do.

A recent report published by the National Cancer Institute (Inca) helps us to see more clearly on the questions concerning the different types of cancer and the impact of certain nutritional factors during and after the disease.

The purpose of the report

This analysis is based on recommendations from of a report dating from 2012, written by theAmerican Cancer Society (ACS). The aim of the latter was to formulate lifestyle guidelines for cancer patients.

Having published several critically important reports on cancer and physical activity, the tobacco, fasting and restrictive diets, it is quite naturally and in the continuity of its approach that the Inca looked into the question of nutritional factors and their influence during and after the onset of cancer. The final objective was to update the recommendations of the ACS and guide healthcare professionals in the management of their patients.

What science tells us

After Sisyphus’s work in the scientific literature, the experts managed to bring together 63 meta-analyzes, 22 pooled analyzes, 65 intervention trials and 93 studies of cohort. Each of these articles was relevant given the inclusion criteria (only studying people after diagnostic cancer and only the following parameters: overall and specific mortality, recidivism, second primary cancer, progression and quality of life) that had been determined by upstream scientists. The investigators then began an analysis of each factor cancer by cancer with the development of an associated level of evidence. Here’s what to remember.

Overweight and undernutrition

Obesity is a risk factor concerning:

  • the overall and specific mortality, the risk of recurrence and the occurrence of a second primary cancer in the context of a breast cancer (convincing level of evidence).
  • overall mortality and risk of recurrence of a Colon Cancer and / or rectum (convincing level of evidence). Conversely, the overweight does not increase or decrease the risk of this type of cancer coming back.
  • the overall and specific mortality of kidney cancer (probable level of proof).

Overweight,obesity and weight gain reduce the risks:

  • overall and specific mortality in the context of lung cancer (convincing level of evidence). For cancer ofesophagus, it also reduces overall mortality only (probable level of evidence).
  • specific mortality for stomach cancer (suggested level of proof). For kidney cancer, being overweight increases the risk of overall mortality (probable level of evidence).

Being underweight, on the other hand, is harmful in all cases. It increases the risks:

  • overall mortality, recurrence and tumor progression for colon and rectal cancers (probable level of evidence).
  • overall mortality (probable level of evidence) and specific mortality (suggested level of evidence) for lung cancer.
  • overall mortality and progression of Cervical cancer and hematologic cancers (suggested level of evidence).

Sarcopenia – the loss of mass lean – increases the risk of overall mortality for cancers of the esophagus, pancreas, of foie (and recurrence for the latter), stomach (and specific mortality and recurrence for the latter). The level of proof is probable for each of these statements.

The alcohol

Surprisingly, very little conclusive data is available for consumption of alcoholic beverages. What the report concludes from data in the literature is an increased risk (probable level of evidence) of second primary cancer for cancers of the upper aerodigestive tract.

Foods and macro-nutrients alone

Of protein to fibers, Soy dairy products, many foods and nutrients have been studied in relation to cancer. Results are available for cancer of the breast, colon and rectum, prostate, head and neck, lung and all cancers combined.

Let’s start with the big question soy and breast cancer. The report mentions a reduction in risk (level of evidence suggested) in Asian, American, Canadian and Australian populations. However, in the recommendations, the experts do not encourage the consumption of soya in the absence of medical indication, in particular because of the lack of precision on the dosage and the frequency of consumption.

The consumption of fruits and vegetables, touted for their juice by the gurus new age, is not associated with any reduction breast cancer risk and cancer all locations combined. However, fiber consumption is beneficial (probable level of evidence) in breast cancer and in cancer colorectal. For the Prostate cancer, we must retain only the possibility of a protective nature of vegetable fats (level of evidence suggested) and aggravating for saturated fats (level of evidence suggested) given the concordance of the results of observational studies. Coffee consumption may help reduce overall mortality from colon and rectal cancer, but the level of evidence is only suggested.

In conclusion, serious results between diet during and after cancer are sorely lacking. But does it really make sense to study the impact food by food ? Indeed, we do not eat isolated foods. A new practice then developed: the study on styles food.

Global diet

A plethora of food styles exist depending on cultures, location, access to food, etc. and some of them have been conceptualized so that they can be studied scientifically. We then know the mediterranean diet, low in fat, anti-inflammatory (or conversely pro-inflammatory), adheres to nutritional recommendations or to low glycemic index / load.

Regarding breast cancer, limiting the amount of fat in the diet would decrease the risk of overall mortality and recurrence (probable level of evidence). For other cancers, the studies are too poor or too few to conclude anything empirically. Follow as much as possible nutritional recommendations is nevertheless recommended.

Nutritional advice

The only nutritional advice with a suggested level of evidence is that which aims to limit weight loss, especially for the risk of specific mortality and recurrence in colon and rectal cancers.

Mushrooms, plants and food supplements

We are praised for them, often for the wrong reasons. A deficiency imaginary diagnosed by obsolete criteria, ” booster »Our metabolism for’winter, protect us from infections, etc. This sneaky marketing rides between wellness rhetoric and low-quality scientific evidence. We must therefore be careful.

Nevertheless, we do know things. Supplementation in vitamin C, for example, has a probable level of evidence in reducing the risk of overall and specific mortality in breast cancer. Supplementation in vitamin D and E has a suggested level of evidence for protection against recurrence of this cancer. Supplementation in amino acids branched-chain would reduce the risk of overall mortality from liver cancer (suggested level of proof).

Taking Coriolus versicolor in extract form would reduce the risk of overall mortality from breast cancer, colon and rectal cancer and stomach cancer (level of evidence suggested). Decoctions of Jianpi Qushi and Jianpi Jiedu improve the quality of life of patients with or remission colon and rectal cancer (suggested level of evidence). As with soy in the context of breast cancer, experts do not encourage the consumption of these products in the absence of medical indication, in particular because of the lack of precision on the dosage and frequency of consumption.

Towards research and beyond

Research conducted so far has struggled to obtain conclusive results on all nutritional factors and cancer. We need more quality research. Report authors call for more directed studies at the time cancer diagnosis, with precise time frames, to really know what to do and when. Some factors have only been studied in one type of population. It would be good to replicate the experiments around the world so that we can have robust results for the whole world. Also, mechanistic evidence has been ignored in the report when it can be used in developing the level of evidence.

This report gives healthcare professionals valuable information about what we know and what we don’t know. If one is aware of the scientific approach, the latter will be able to participate in countering the rhetoric of people claiming to have all the answers. It also teaches everyone how science works, moreover medical science. In medical science, there is rarely an absolute. We rarely hear it working (absolutely) or it does not (absolutely, except for homeopathic granules). This does not mean that there is no absolute answer. It may simply be the consequence of measuring our ignorance. Current claims are being built via a body of evidence comprising controlled trials attempting to identify causal relationships and observational studies attempting to identify complex reality with its variables and various observation conditions.

What to do in “real life”?

The scientific process is very nice, but what if cancer touches me, here and now? What will I do with a suggested level of proof or a lack of sufficient data to conclude? We believe it is, in part, this distress in diagnosing disease that the new food gurus are exploiting. It is therefore all the more important to adapt his speech and his advice to the patient’s request. Obviously, you should not say anything to him. But thanks to this type of report, it is possible to guide the patient so that he becomes an actor in his care. Better a patient actor of his care within the medical community than between the clutches of individuals with nauseating and dangerous speeches.

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