Eating More Organic Food Tied to Lower Cancer Risk

Nick Mulcahy

October 22, 2018

A higher frequency of eating organic food was associated with a reduced risk for cancer, according to results from a large population-based observational study published online October 22 in JAMA Internal Medicine.

"Promoting organic food consumption in the general population could be a promising preventive strategy against cancer," conclude the authors, led by Julia Baudry, PhD, of the Center of Research in Epidemiology and Statistics Sorbonne Paris Cité.

The study results need confirming, they add. However, such data would likely also be observational and only show correlation, not causation.

The French investigators hypothesized that consuming high levels of organic foods may be associated with lower cancer risk because of reduced exposure to possibly carcinogenic pesticide residues. So they enrolled 68,946 participants in the NutriNet-Santé Study online and then classified them into four quartiles according to their self-reported consumption of 16 groups of organic products. The team followed the participants for a mean of 5 years.

Participants with the highest frequency of organic food intake had a 25% lower relative risk for a cancer diagnosis during follow-up compared with those with the lowest frequency (hazard ratio for quartile 4 vs 1, 0.75; P for trend = .001).

However, the absolute cancer risk reduction between these outlying quartiles was less eye-catching, at 0.6%.

The study participants were mostly female (78%); the mean age at baseline was 44 years.

During follow-up, 1340 first-incident cancer cases were identified; the most common were breast cancers (34.3%), prostate cancers (13.4%), skin cancers (melanoma and spinocellular carcinoma; 10.1%), colorectal cancers (7.4%), non-Hodgkin's lymphoma (3.5%), and other lymphomas (1.1%).

Notably, the French team also reported that the inverse association between organic food consumption and cancer risk was limited to two types of cancer: postmenopausal breast cancer and lymphomas.

Overall Link Is "Uncertain"

The overall link is "uncertain" between cancer risk and organic food consumption, say a trio of researchers from the Department of Nutrition at the Harvard T. H. Chan School of Public Health in Boston in an accompanying editorial.

They point to the United Kingdom's Million Women Study. That study found that organic food consumption was linked to a slightly increased breast cancer risk, which "raises questions about the meaning of these [French] findings," write Elena Hemler, BS, Jorge Chavarro, MD, ScD, and Frank Hu, MD, PhD.

On the other hand, the new French lymphoma findings are consistent with multiple other studies, including those that have found that occupational exposure to pesticides was associated with different cancers, most strongly, non-Hodgkin lymphoma.

The editorialists also say the new French study has multiple limitations, the most notable of which is that the online questionnaire was not validated.

And they add these strong words: "Organic food intake is notoriously difficult to assess, and its self-report is highly susceptible to confounding by positive health behaviors and socioeconomic factors."

The editorialists suggest that the authors failed to minimize these biases by not determining, in their online survey, the reasons behind not buying and eating organic foods (eg, price, availability, or lack of interest).

"Prospective cohort studies that use validated exposure assessments and carefully control for confounders are necessary [to assess any true association]," they add.

Such research is "urgently needed" because conventionally produced foods that contain pesticide residues are widely consumed, say the editorialists.

They observe that a number of pesticides have been associated with different cancers. Also, diet crossover trials have shown that switching from conventionally grown to organic foods decreases urinary concentrations of pesticides.

High Cost of Organic Food

There will probably never be a randomized trial comparing organic food with conventionally produced food, owing to the long follow-up period needed to detect cancers and the high cost of organic food, say the editorialists.

They offer some general advice on nutrition.

"For overall health, current evidence indicates that the benefits of consuming conventionally grown produce are likely to outweigh the possible risks from pesticide exposure. 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," they write.

In addition, they endorse the American Cancer Society's recommendation to consume a diet that "limits red and processed meat and added sugars, replaces refined grains with whole grains, and increases consumption of fruits and vegetables."

The NutriNet-Santé Study is supported by the French Ministry of Health, the French Institute for Health Surveillance, the National Institute for Prevention and Health Education, the National Institute for Health and Medical Research, the National Institute for Agricultural Research, the National Conservatory of Arts and Crafts, and Paris 13 University. The authors have disclosed no relevant financial relationships. Dr Hu has received research support from the California Walnut Commission.

JAMA Intern Med. Published online October 22, 2018. Full text, Editorial

Follow Medscape senior journalist Nick Mulcahy on Twitter: @MulcahyNick

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