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Washington, USA .- A large study published this week showed that the largest consumers of organic foods in France were developing fewer cancers than those who had never used them, which illustrates the difficulty of establishing a causal link between food and health.
It is impossible to categorically prove in the laboratory that this or that foodstuff reduces the risk of contracting a disease as complex as cancer.
Researchers have to follow a large number of people for a while. and observe which of them develop cancer, in the hope of documenting the specific post hoc behavior of sick people
Thousands of studies on diet and various diseases have been conducted for decades. Even the biggest ones are sometimes questioned, as is the famous work that showed in 2013 the beneficial effects of the Mediterranean diet against heart disease and the withdrawal this year of a prestigious medical journal due to methodological problems. organic food, only one large study had previously evaluated its effect on cancer, the Million Women Study, with 600,000 Britons, in 2014.
This reveals no difference between consumers and non-consumers of organic products in terms of general cancer risk, but decreased risk of cancer in particular: non-Hodgkin's lymphoma.
New French study badociating in particular the University of the Sorbonne, the National Institute of agronomic research and the National Institute. Health and Medical Research, is more detailed, although it has fewer participants, about 69,000, mostly women. [19659003] Their results were published Monday in the Jama American magazine.
The hypothesis is that consumers of organic products ingest less synthetic pesticides in fruits, vegetables and cereals and thus reduce their risk, while some suspected to be carcinogenic.
After their inclusion, volunteers from the NutriNet-Santé study completed a questionnaire (income, physical activity, smoking or non-smoking, body mbad index, etc.) and reported having consumed organic food 24 hours
The study divided participants into four groups according to the type of ingested organic food. Then, the number of cancer cases in each group was counted on average over four and a half years.
Of a quarter of those who reported eating a majority of organic foods, the risk of cancer was 25% lower in the fourth part, he never ate them. In absolute terms, the increase is only 0.6 percentage points, or six additional patients per 1,000 population.
– "Complex" –
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The study found a statistically significant correlation only for bad cancer in postmenopausal women and for lymphoma, including non-Hodgkin's lymphoma.
The authors feared correcting their results, considering that consumers of organic products were on average richer, less obese and less smokers.
But other invisible, environmental or lifestyle factors can also have an impact. This is the typical problem of these studies.
"People who deliberately consume organic products, to the point of declaring them, are probably different from others in many other aspects," said Nigel Brockton, research director of the American Institute for Research Against cancer (AICR).
This expert recommends, instead of a particular type of food, a set of practices aimed at reducing cancer risks: normal weight, physical activity, healthy eating, not too much red meat …
"The diet is a complex thing," he says. "We would never make a recommendation based on a single study, even if it is statistically significant," he adds.
Other aspects of the study were also questioned: pesticide traces were not measured in participants, which prompted criticism from Harvard experts. in the same issue of Jama. Co-author Julia Baudry told AFP that this was only done in a small sub-sample.
The declarative aspect of the study is also a problem for John Ioannidis, professor emeritus of medicine at Stanford, known to have claimed that most of the published studies were untrue.
"Most people, including myself, can not say exactly how much organic food they eat," he told AFP. "The study has a 3% chance of finding something important and 97% spreading absurd and ridiculous results."
As in the case of the consumption of red meat or cigarettes, many other studies will be needed in the same state. speech to conclude on the effect of biological nutrition.
The American Cancer Society continues to advocate the consumption of fruits and vegetables, organic or not. AFP
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