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WASHINGTON • A new study showing that the most greedy consumers of organic foods have fewer cancers than those who never eat them illustrates the difficulty of establishing a cause-and-effect relationship when of the badessment of food and health.
It is actually impossible to prove unequivocally in a laboratory that a given food reduces the risk of developing a disease as complex as cancer.
"The diet is complex," said Dr. Nigel Brockton, director of research at the American Institute for Cancer Research (AICR).
"We will never make a recommendation based on a study, even if it is statistically significant."
The researchers, like the French team at the head of the study last Monday, must then follow a large test group and wait for the cancer to occur. develop in some of the subjects.
They hope then, after the fact, to isolate a specific behavior among all those who are sick and who made the difference.
When we see a very consistent obse Rvations or badociations with things like alcohol and red meat and body weight – when many studies show these things again and again, in different populations – then we have much more confidence.
DR NIGEL BROCKTON, American Institute for Director of Cancer Research, Cancer Research
Thousands of studies on diet and disease have been conducted for decades.
Even the most important conclusions are sometimes disputed, as in 2013 a study that showed the considerable benefits of the so-called Mediterranean Diet in the fight against heart disease.
This study was removed from the prestigious New England Journal of Medicine earlier this year on reviews of the methods used.
Only one major study on the link between organic foods and cancer was conducted. before the last publication published in the Journal of the American Medical Association (Jama) Internal Medicine.
This 2014 research, known as the Million Women Study, has a test group of 600,000 Britons. He found no overall difference in cancer risk between those who ate organic foods and those who did not eat them.
He only found that lovers of organic foods were less likely to develop non-Hodgkin's lymphoma.
So, how
It is certainly more detailed than the Million Women study, although it involved 69,000 women – about 10% of the sample size.
The hypothesis is that organic food enthusiasts consume fewer pesticides in their fruits, vegetables and cereals, which reduces their risk of cancer as some pesticides are suspected to be carcinogens.
After being recruited for the NutriNet-Sante study, volunteers completed a questionnaire on various issues such as income, physical activity, smoking habits, and body mbad index.
They also reported three times the amount of organic food they had eaten during the previous 24-hour period.
The researchers divided the participants into four. groups, according to their consumption of organic foods. They then counted the number of cancers in each group over an average period of 41.5 years.
In the quarter of people who reported consuming the most organic products, the risk of cancer was 25% lower than in the previous group.
In absolute terms, the incidence of cancer increased by 0.6 percentage points – an additional six out of every 1,000 patients.
The only statistically significant correlation was a reduction in the number of bad cancers in postmenopausal women and marked decline in the incidence of lymphoma
The study authors were careful to correct their findings to account for the fact that organic food consumers were on average more rich, less overweight and smoked less than others.
But other invisible factors, whether related to the environment or to lifestyle habits, could also have played a role – the usual problem of studies on diet and exercise.
"People who deliberately consume organic foods emphasize the report, which they are probably different in many other ways as well," noted Dr. Brockton.
The AICR offers a range of behaviors designed to reduce the risk of cancer – maintaining a healthy weight, exercise, healthy diet, not too much red meat – but does not recommend a specific type of food.
Other problems were raised about last Monday's study – pesticide traces in the subjects were not measured, which sparked criticisms of the fact. experts from Harvard University in the same issue of Jama,
Julia Baudry, co-author of the study, told Agence France-Presse that such measures were only taken for a small group subsamples.
Dr. John Ioannidis, Professor of Disease Prevention at Stanford University, renowned for claiming that most published studies are false, self-reporting could be a problem in this case.
"Most people, including myself, would not be able to say exactly if I eat organic foods and how often / how often," he added. [19659002] "The study has a 3% chance of having found something important and 97% of spreading ridiculous nonsense."
For Dr. Brockton, "research advances from one study at a time".
"When we observe very consistent observations or badociations with elements such as alcohol, red meat and body weight – when many studies show these phenomena over and over, within different populations – we have a lot more confidence, "he said.
Meanwhile, the American Cancer Society urges people to eat more fruits and vegetables, whether they are organic or not.
FRANCE-PRESS AGENCY
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