Can you eat organic food lower your cancer risk? Hard to prove

WASHINGTON: A new, much-ballyhooed study showing that the most important causes of cancer have been diagnosed.

It is effectively impossible to prove beyond a doubt in a laboratory that it is possible to reduce the risk of developing cancer.

"Diet is complex," Nigel Brockton, the director of research at the American Institute for Cancer Research (AICR), told AFP.

"We would never make a recommendation based on one study, even though it's statistically significant."

Researchers, like the French team behind Monday's study, must then follow a large test group and wait for cancers to develop in some of the subjects.

They then hope that after the fact, they can isolate a specific behavior among all those who are sick that made the difference.

Thousands of studies on diet and illness have been conducted for decades.

Even the findings of the largest are sometimes disputed, such as the one in which the purportedly displayed the sweeping benefits of the so-called Mediterranean diet in fighting heart ailments.

This study was retracted from the prestigious New England Journal of Medicine this year over criticism of the methods used.

Only one major study on the nexus between organic food and cancer has been published in the Journal of the American Medical Association (JAMA) Internal Medicine.

That 2014 research, known as the Million Women Study, used a test group of 600,000 British women. It did not matter what kind of cancer and who did not.

It was found that organic food lovers had a reduced risk of developing non-Hodgkin's lymphoma.

QUESTIONNAIRES AND SELF-REPORTING

So then, how does the new team study?

It is certainly more detailed than the Million Women Study, though it looked at 69,000 women – roughly 10 percent of the sample size.

The hypothesis is that the organic food enthusiasts consume fewer pesticides in their fruit, vegetables and grains, thus reducing their risk of cancer, as some pesticides are suspected of being carcinogenic.

After being recruited for the NutriNet-Health study, volunteers filled out a questionnaire on a variety of issues (income, physical activity, smoking habits, body mass index …).

They also reported how much organic food they had eaten in the preceding 24-hour period.

Researchers separated participants in four groups, based on their consumption of organic food. They then counted the numbers of cancers in each group, over an average period of four and a half years.

In the quarter of people who said they were the most organic products, the risk of cancer was 25%.

In absolute terms, that means increasing incidence of 0.6 percentage points – or six more sick people out of 1,000.

"ONE STUDY AT A TIME"

The only statistically significant correlations were in breast cancer among postmenopausal women, and in the incidence of lymphomas.

The study authors were careful in their assessment of the fact that they were less likely than those who did not.

But other invisible factors, which may also have played a role – the usual problem with studies on diet and exercise.

"People who deliberately eat organic food, to the point that they report it, are likely to be different," Brockton noted.

The AICR suggests a range of behaviors to reduce cancer risk – a healthy weight, exercise, healthy diet, and not too much.

Other problems were raised on Monday's study: traces of pesticide in the subjects were measured, which sparkled criticism from experts at Harvard University in the same issue of the JAMA, who urged caution.

The study's co-author Julia Baudry told AFP that such measurements were only taken for a small sub-sample group.

John Ioannidis, a professor of disease prevention at Stanford University, said that this is the case.

"Most people, including myself (a professor of disease prevention)," Ioannidis told AFP.

"The study has a three percent chance of having found something important and has a 97 percent chance of propagating ridiculous nonsense."

For Brockton, "research moves forward one study at a time."

"When we look at these things, or when we look at a lot of people in different populations, then we have a lot more confidence," he said.

In the meantime, the American Cancer Society continues to eat more fruits and vegetables – organic or not.