A new epidemiological study published in the prestigious journal JAMA Internal Medicine has found that people who eat a high volume of organic food were 25 percent less likely to be diagnosed with cancer compared to those who eat little to no organic food. Many experts have questioned the study's conclusions, pointing out that a variety of other factors that could influence a person's cancer risk weren't taken into account.
The new study tracked nearly 69,000 French subjects, with an average follow-up duration of five years. Homing in on specific types of cancers the study found organic food conferred a reduced risk most prominently in postmenopausal breast cancer and non-hodgkin lymphoma, with little effect seen in other cancers such as prostate cancer and colorectal cancer.
The researchers hypothesize the lower risk of cancer seen in high organic food consumers can be attributed to a reduced exposure to common pesticide residues in non-organic food. Although the study does note its implicit limitations, such as a short follow-up time and potential influence of other lifestyle factors, it still suggests promoting organic food consumption as a preventive strategy against cancer.
The general response to the newly published study has, perhaps unsurprisingly, been reasonably critical, with many experts suggesting it is virtually impossible to account for the variety of social and lifestyle factors that go along with high organic food consumption. Raj Eri, head of Biomedical Sciences at the University of Tasmania, notes the study has several methodological issues making it difficult to generate any firm conclusion.
"As would be expected, participants who used organic foods, were on average better educated, had higher incomes and also otherwise healthier lifestyles," says Eri. "The key problem with this type of study is that regardless of statistical approaches or adjustments, it is practically impossible to say whether it is the use of organic foods, or some other correlated aspect, that led to the observed protective association."
Another significant limitation in the study noted by many experts is the lack of definition in measures of organic food exposure. Sixteen separate organic food categories were included in questionnaires offered to participants, but the final results seemed to be simplified into an overall "organic food score," meaning there was no distinction between different eating habits, such as vegetarians, or those consuming sugar and meat-heavy diets.
Tom Sanders from King's College London suggests the overall conclusion from the study, that promotion of organic food may be a beneficial anti-cancer preventative strategy, is overblown. "The participants who reported eating organic food most frequently were more likely to be non-smokers, had a lower body mass index (less obesity) and drank less alcohol – all factors that would be expected to result in fewer cases of cancer in this group," says Sanders.
Another concern raised is that the study's conclusions could lead to some people consuming less non-organic fruits and vegetables over fears they could enhance their cancer risks. An accompanying commentary, published alongside the new study, authored by scientists from the Harvard T.H. Chan School of Public Health and Brigham and Women's Hospital, solidifies these concerns, reminding people that factors such as body weight, physical activity, and general diet are still the most proven ways to lower individual cancer risk.
"For overall health, current evidence indicates that the benefits of consuming conventionally grown produce are likely to outweigh the possible risks from pesticide exposure," the authors affirm in the accompanying commentary. "Concerns over pesticide risks should not discourage intake of conventional fruits and vegetables, especially because organic produce is often expensive and inaccessible to many populations."
Ultimately, the limitations in these kinds of observational studies are profoundly frustrating when trying to reach any generalizable conclusion. While levels of herbicides and pesticides in food is undeniably a major health concern, it is impossible to draw the conclusion that organic food reduces cancer risks from the data this research has generated. Raj Eri sums up the results, suggesting people should remember that, "Overall fruit and vegetable consumption is good for you, organic or not."
The new study was published in the journal JAMA Internal Medicine.
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